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The mulberry fruit is edible and medicinal, and it is commonly referred to as the "best health product of the 21st century". The purpose of this study was to find out whether different drying methods affect the quality of mulberry fruits and the main nature of the volatile organic compounds (VOCs) they contain. This study used vacuum freeze-drying (VFD), vacuum drying (VD), sun drying (SD), hot-air drying (HAD), and microwave drying (MD) to treat fresh mulberry fruits. Gas-phase ion mobility spectrometry (GC-IMS) was used to detect and analyze the VOCs in mulberry fruit samples treated with the different drying methods. There were 47 VOCs detected, with aldehydes and alcohols dominating. The obtained data were subjected to principal component analysis (PCA), cluster analysis (CA), nearest neighbor fingerprint analysis, and partial least-squares regression analysis (PLS-DA). The conclusion was drawn that fresh mulberry fruits contain abundant VOCs, and mulberry fruits after VD contain many aldehydes; thus, VD promoted the synthesis of phellandrene and other compounds widely used in the preparation of cosmetics such as perfume and soap. HAD promoted the synthesis of esters commonly used in the preparation of fruit flavor and wine essence. The higher (E)-2-heptenal content with SD was conducive to the Maillard reaction. MD promoted the synthesis of heptanal and valeraldehyde with aroma characteristics such as fatty, green, fruity, grassy, and floral. According to the VIP results, VOCs (E)-2-heptenal, pentanal D, cyclohexanone, and 2-hexanone D influenced the VOCs in most of the mulberry fruit samples. The findings of this study provide an important reference for drying mulberry fruits, which, in turn, will help to ensure the safety and effectiveness of processed mulberry fruit products. [ABSTRACT FROM AUTHOR]

Cauliflower (Brassica oleraceae L. var. Botrytis Linnaeus) has various health benefits due to its rich bioactive compound content. However, this fresh vegetable faces challenges related to its perishability and short shelf life. This study explores the effect of five drying methods, namely vacuum drying (VD), convective drying (CD), infrared drying (IRD), low-temperature vacuum drying (LTVD) and vacuum freeze-drying (VFD), on the bioactive compounds and health-promoting properties of cauliflower. Analyses of amino acids, hydroxycinnamic acid and its derivatives, glucosinolates, and isothiocyanates, as well as evaluations of their anti-inflammatory, antiproliferative, and neuroprotective properties, were conducted based on these five drying methods. The results revealed that samples treated with VFD and IRD had a higher content of amino acids involved in GSL anabolism. Moreover, VFD samples retained hydroxycinnamic acid derivatives and glucosinolates to a greater extent than other methods. Nonetheless, the CD and VD samples exhibited higher antiproliferative and neuroprotective effects, which were correlated with their high sulforaphane content. Overall, considering the retention of most bioactive compounds from cauliflower and the topical inflammation amelioration induced in mice, VFD emerges as a more satisfactory option. [ABSTRACT FROM AUTHOR]

Mulberry perishes easily due to its high water content and thin skin. It is important to extend the shelf life of mulberry by proper processing methods. In the present study, the influence of three drying techniques, including hot air drying (HAD), vacuum drying (VD), and vacuum freeze-drying (VFD) on the quality maintenance of mulberry was comprehensively evaluated. Bioactive compounds, antioxidant activity, and the sensory and volatile flavor compounds of mulberry have been researched. The results showed that VFD treatment maintained the highest anthocyanins (6.99 mg/g), total flavones (3.18 mg/g), and soluble sugars (2.94 mg/g), and exhibited the best DPPH· (81.2%) and ABTS+· (79.9%) scavenging ability. Mulberry also presented the lowest hardness and the greatest brittleness after VFD. Additionally, VFD maintained the optimal color and presented the best sensory attributes. Furthermore, 30, 20, and 32 kinds of volatile flavor compounds were detected in HAD, VD, and VFD, respectively, among which aldehydes, esters, and ketones were the most abundant compounds. This study indicated the potential application value of VFD for the drying of fruit and vegetable foodstuffs. [ABSTRACT FROM AUTHOR]

This article systematically reviews the advancements in processing litchi peel (Litchi chinensis), emphasizing drying, extraction, purification methods, and the potential of bioactive compounds obtained from litchi peel. This work also highlights the impact of various drying techniques on phytochemical profiles, focusing on how methods such as hot air and freeze-drying affect the preservation of bioactive compounds. The study delves into extraction methods, detailing how different solvents and techniques influence the efficiency of extracting bioactive compounds from litchi peel. Furthermore, the purification and characterization of active compounds, showcasing the role of chromatographic techniques in isolating specific bioactive molecules, is discussed. Biological properties and mechanisms of action, such as antioxidant, antihyperglycemic, cardioprotective, hepatoprotective, anti-atherosclerotic, and anticancer activities, are reviewed, providing insight into the potential health benefits of litchi peel compounds. This review highlights the importance of optimizing and selecting accurate drying and extraction methods to maximize the therapeutic effects of litchi peel and its bioactive compounds. This review also reveals the broad pharmacological potential of the isolated compounds, underscoring the need for further research to discover their specific actions and health benefits. [ABSTRACT FROM AUTHOR]

The mulberry fruit is edible and medicinal, and it is commonly referred to as the “best health product of the 21st century”. The purpose of this study was to find out whether different drying methods affect the quality of mulberry fruits and the main nature of the volatile organic compounds (VOCs) they contain. This study used vacuum freeze-drying (VFD), vacuum drying (VD), sun drying (SD), hot-air drying (HAD), and microwave drying (MD) to treat fresh mulberry fruits. Gas-phase ion mobility spectrometry (GC-IMS) was used to detect and analyze the VOCs in mulberry fruit samples treated with the different drying methods. There were 47 VOCs detected, with aldehydes and alcohols dominating. The obtained data were subjected to principal component analysis (PCA), cluster analysis (CA), nearest neighbor fingerprint analysis, and partial least-squares regression analysis (PLS-DA). The conclusion was drawn that fresh mulberry fruits contain abundant VOCs, and mulberry fruits after VD contain many aldehydes; thus, VD promoted the synthesis of phellandrene and other compounds widely used in the preparation of cosmetics such as perfume and soap. HAD promoted the synthesis of esters commonly used in the preparation of fruit flavor and wine essence. The higher (E)-2-heptenal content with SD was conducive to the Maillard reaction. MD promoted the synthesis of heptanal and valeraldehyde with aroma characteristics such as fatty, green, fruity, grassy, and floral. According to the VIP results, VOCs (E)-2-heptenal, pentanal D, cyclohexanone, and 2-hexanone D influenced the VOCs in most of the mulberry fruit samples. The findings of this study provide an important reference for drying mulberry fruits, which, in turn, will help to ensure the safety and effectiveness of processed mulberry fruit products.

This study evaluated the effects of different drying techniques on the physicochemical properties of Pleurotus citrinopileatus Singer (P. citrinopileatus), focusing on the ergothioneine (EGT) contents. The P. citrinopileatus was subjected to natural ventilation drying (ND), freeze-drying (FD), and hot-air drying (HD). EGT was extracted using high-hydrostatic-pressure extraction (HHPE), and response surface methodology (RSM) was employed with four variables to optimize the extraction parameters. The crude EGT extract was purified by ultrafiltration and anion resin purification, and its antioxidant activity was investigated. The results showed that the ND method effectively disrupted mushroom tissues, promoting amino acid anabolism, thereby increasing the EGT content of mushrooms. Based on RSM, the optimum extracting conditions were pressure of 250 MPa, extraction time of 52 min, distilled water (dH2O) as the extraction solvent, and a 1:10 liquid–solid ratio, which yielded the highest EGT content of 4.03 ± 0.01 mg/g d.w. UPLC-Q-TOF-MSE was performed to assess the purity of the samples (purity: 86.34 ± 3.52%), and MS2 information of the main peak showed primary ions (m/z 230.1) and secondary cations (m/z 186.1050, m/z 127.0323) consistent with standard products. In addition, compared with ascorbic acid (VC), EGT showed strong free radical scavenging ability, especially for hydroxyl and ATBS radicals, at more than 5 mmol/L. These findings indicate that the extraction and purification methods used were optimal and suggest a possible synthetic path of EGT in P. citrinopileatus, which will help better explore the application of EGT. [ABSTRACT FROM AUTHOR]

Cauliflower (Brassica oleraceae L. var. Botrytis Linnaeus) has various health benefits due to its rich bioactive compound content. However, this fresh vegetable faces challenges related to its perishability and short shelf life. This study explores the effect of five drying methods, namely vacuum drying (VD), convective drying (CD), infrared drying (IRD), low-temperature vacuum drying (LTVD) and vacuum freeze-drying (VFD), on the bioactive compounds and health-promoting properties of cauliflower. Analyses of amino acids, hydroxycinnamic acid and its derivatives, glucosinolates, and isothiocyanates, as well as evaluations of their anti-inflammatory, antiproliferative, and neuroprotective properties, were conducted based on these five drying methods. The results revealed that samples treated with VFD and IRD had a higher content of amino acids involved in GSL anabolism. Moreover, VFD samples retained hydroxycinnamic acid derivatives and glucosinolates to a greater extent than other methods. Nonetheless, the CD and VD samples exhibited higher antiproliferative and neuroprotective effects, which were correlated with their high sulforaphane content. Overall, considering the retention of most bioactive compounds from cauliflower and the topical inflammation amelioration induced in mice, VFD emerges as a more satisfactory option.

Mulberry perishes easily due to its high water content and thin skin. It is important to extend the shelf life of mulberry by proper processing methods. In the present study, the influence of three drying techniques, including hot air drying (HAD), vacuum drying (VD), and vacuum freeze-drying (VFD) on the quality maintenance of mulberry was comprehensively evaluated. Bioactive compounds, antioxidant activity, and the sensory and volatile flavor compounds of mulberry have been researched. The results showed that VFD treatment maintained the highest anthocyanins (6.99 mg/g), total flavones (3.18 mg/g), and soluble sugars (2.94 mg/g), and exhibited the best DPPH· (81.2%) and ABTS+· (79.9%) scavenging ability. Mulberry also presented the lowest hardness and the greatest brittleness after VFD. Additionally, VFD maintained the optimal color and presented the best sensory attributes. Furthermore, 30, 20, and 32 kinds of volatile flavor compounds were detected in HAD, VD, and VFD, respectively, among which aldehydes, esters, and ketones were the most abundant compounds. This study indicated the potential application value of VFD for the drying of fruit and vegetable foodstuffs.

This article systematically reviews the advancements in processing litchi peel (Litchi chinensis), emphasizing drying, extraction, purification methods, and the potential of bioactive compounds obtained from litchi peel. This work also highlights the impact of various drying techniques on phytochemical profiles, focusing on how methods such as hot air and freeze-drying affect the preservation of bioactive compounds. The study delves into extraction methods, detailing how different solvents and techniques influence the efficiency of extracting bioactive compounds from litchi peel. Furthermore, the purification and characterization of active compounds, showcasing the role of chromatographic techniques in isolating specific bioactive molecules, is discussed. Biological properties and mechanisms of action, such as antioxidant, antihyperglycemic, cardioprotective, hepatoprotective, anti-atherosclerotic, and anticancer activities, are reviewed, providing insight into the potential health benefits of litchi peel compounds. This review highlights the importance of optimizing and selecting accurate drying and extraction methods to maximize the therapeutic effects of litchi peel and its bioactive compounds. This review also reveals the broad pharmacological potential of the isolated compounds, underscoring the need for further research to discover their specific actions and health benefits.

This study aimed to examine the differences in the nutrients and volatile compounds of Stropharia rugoso-annulata after undergoing three different drying treatments. The fresh mushrooms were dried using hot air drying (HAD), vacuum freeze drying (VFD), and natural air drying (NAD), respectively. After that, the nutrients, volatile components, and sensory evaluation of the treated mushrooms were comparably analyzed. Nutrients analysis included proximate compositions, free amino acids, fatty acids, mineral elements, bioactive compositions, and antioxidant activity. Volatile components were identified by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and analyzed with principal component analysis (PCA). Finally, sensory evaluation was conducted by ten volunteers for five sensory properties. The results showed that the HAD group had the highest vitamin D2 content (4.00 μg/g) and antioxidant activity. Compared with other treatments, the VFD group had higher overall nutrient contents, as well as being more preferred by consumers. Additionally, there were 79 volatile compounds identified by HS-SPME-GC-MS, while the NAD group showed the highest contents of volatile compounds (1931.75 μg/g) and volatile flavor compounds (1307.21 μg/g). PCA analysis suggested the volatile flavor compositions were different among the three groups. In summary, it is recommended that one uses VFD for obtaining higher overall nutritional values, while NAD treatment increased the production of volatile flavor components of the mushroom. [ABSTRACT FROM AUTHOR]

This study investigated the effects of different drying methods on the drying characteristics, three-dimensional (3D) appearance, color, total polysaccharide content (TPC), antioxidant activity, and microstructure of Pleurotus eryngii slices. The drying methods included hot air drying (HAD), infrared drying (ID), and microwave drying (MD). The results showed that the drying method and conditions significantly influenced the drying time, with MD having a significant advantage in reducing the drying time. The 3D appearance of P. eryngii slices was evaluated based on shrinkage and roughness as quantitative indexes, and the best appearance was obtained by hot air drying at 55 and 65 °C. HAD and ID at lower drying temperatures obtained better color, TPC, and antioxidant activity, but MD significantly damaged the color and nutritional quality of P. eryngii. The microstructure of dried P. eryngii slices was observed using scanning electron microscopy, and the results showed that drying methods and conditions had an obvious effect on the microstructure of P. eryngii slices. Scattered mycelia were clearly observed in P. eryngii samples dried by HAD and ID at lower drying temperatures, while high drying temperatures led to the cross-linking and aggregation of mycelia. This study offers scientific and technical support for choosing appropriate drying methods to achieve a desirable appearance and quality of dried P. eryngii. [ABSTRACT FROM AUTHOR]

This study evaluated the effects of different drying techniques on the physicochemical properties of Pleurotus citrinopileatus Singer (P. citrinopileatus), focusing on the ergothioneine (EGT) contents. The P. citrinopileatus was subjected to natural ventilation drying (ND), freeze-drying (FD), and hot-air drying (HD). EGT was extracted using high-hydrostatic-pressure extraction (HHPE), and response surface methodology (RSM) was employed with four variables to optimize the extraction parameters. The crude EGT extract was purified by ultrafiltration and anion resin purification, and its antioxidant activity was investigated. The results showed that the ND method effectively disrupted mushroom tissues, promoting amino acid anabolism, thereby increasing the EGT content of mushrooms. Based on RSM, the optimum extracting conditions were pressure of 250 MPa, extraction time of 52 min, distilled water (dH2O) as the extraction solvent, and a 1:10 liquid–solid ratio, which yielded the highest EGT content of 4.03 ± 0.01 mg/g d.w. UPLC-Q-TOF-MSE was performed to assess the purity of the samples (purity: 86.34 ± 3.52%), and MS2 information of the main peak showed primary ions (m/z 230.1) and secondary cations (m/z 186.1050, m/z 127.0323) consistent with standard products. In addition, compared with ascorbic acid (VC), EGT showed strong free radical scavenging ability, especially for hydroxyl and ATBS radicals, at more than 5 mmol/L. These findings indicate that the extraction and purification methods used were optimal and suggest a possible synthetic path of EGT in P. citrinopileatus, which will help better explore the application of EGT.

Large amounts of waste result from licorice mold rot; moreover, prompt drying directly influences product quality and value. This study compared various glycyrrhiza drying methods (Hot air drying (HAD), infrared combined hot air drying (IR-HAD), vacuum freeze drying (VFD), microwave vacuum drying (MVD), and vacuum pulsation drying (VPD)) that are used in the processing of traditional Chinese medicine. To investigate the effects of various drying methods on the drying characteristics and internal quality of licorice slices, their color, browning, total phenol, total flavonoid, and active components (liquiritin and glycyrrhizic acid) were chosen as qualitative and quantitative evaluation indices. Our results revealed that VFD had the longest drying time, but it could effectively maintain the contents of total phenol, total flavonoid, and liquiritin and glycyrrhizic acid. The results also showed that VFD samples had the best color and the lowest degree of browning, followed by HAD, IR-HAD, and VPD. We think that VFD is the best approach to ensure that licorice is dry. [ABSTRACT FROM AUTHOR]

Maya nut (Brosimum alicastrum) is a novel food with high nutritional value. This research aimed to evaluate the nutritional and antioxidant properties of Maya nut flour (MNF) made from seeds dried by different methods (sun-dried and using hot air at 45 °C and 60 °C) to explore its incorporation into cookies and evaluate its nutritional and functional properties. The naturally sun-dried flour (NF) had the highest content of ash (3.64 ± 0.11 g/100 g), protein (6.35 ± 0.44 g/100 g), crude fiber (6.75 ± 0.29 g/100 g), and functional properties (water and oil absorption). The color of the flour was affected by the different drying methods. While the drying methods influenced the total polyphenolic content (TPC) and antioxidant activity (AA) of MNF, they did not affect the morphology of the native starch or generated important molecular-structural changes. The substitution of 60% of wheat flour with NF in the cookie's formula increased the protein and fiber content, whereas 20% substitution increased its AA. MNF is a source of protein, dietary fiber, micronutrients, and functional compounds that can enrich cookie formulations. [ABSTRACT FROM AUTHOR]

The present study aimed to investigate the effect of rotary microwave vacuum drying (RMVD), radio frequency vacuum drying (RFVD), vacuum far infrared drying (VFID), vacuum drying (VD), hot air drying (HD) and natural drying (ND) on the drying characteristics, active ingredients and microstructure of Codonopsis pilosulae slices. Compared with the fitting results of the four models, the Weibull model is the most suitable drying model for Codonopsis. The RFVD and HD color difference values were smaller compared to ND. The effective moisture diffusivity (Deff) under different drying methods was between 0.06 × 10−8 m2/s and 3.95 × 10−8 m2/s. RMVD-dried products had the shortest drying time and retained more active ingredients. The microstructure analysis revealed that the porous structure of RMVD is more favorable for water migration. RMVD is a promising dehydration method for obtaining high-value-added dried Codonopsis products. [ABSTRACT FROM AUTHOR]

Understanding the effects of drying on the selenium (Se) content and Se bioaccessibility of Se-rich plants is critical to dietary supplementation of Se. The effects of five common drying methods (far-infrared drying (FIRD), vacuum drying (VD), microwave vacuum drying (MVD), hot air drying (HD), and freeze vacuum drying (FD)) on the content and bioaccessibility of Se and Se species in Cardamine violifolia leaves (CVLs) were studied. The content of SeCys2 in fresh CVLs was the highest (5060.50 μg/g of dry weight (DW)); after FIRD, it had the lowest selenium loss, with a loss rate of less than 19%. Among all of the drying processes, FD and VD samples had the lowest Se retention and bioaccessibility. FIRD, VD, and FD samples have similar effects on antioxidant activity. [ABSTRACT FROM AUTHOR]

Different drying methods affect the quality of foods. The aim of this study is to explore the effects of seven drying methods, including hot air drying at 60 °C and 80 °C, ultrasound-assisted hot air drying at 60 °C and 80 °C, microwave drying, vacuum microwave drying, and vacuum freeze-drying, on the quality and nonvolatile flavor components of Oudemansiella raphanipes. The vacuum freeze-drying resulted in minimal collapse, mild shrinkage at the macroscopic level, and the formation of uniform pores at the microscopic level on the surfaces of O. raphanipes mushrooms. In addition, vacuum freeze-drying can improve the color attributes of the mushrooms. Therefore, the appearance and shape of vacuum freeze-drying treated O. raphanipes were closest to those of fresh mushrooms. We found that ultrasound-assisted treatment can effectively shorten the drying time of O. raphanipes. The drying time of ultrasound-assisted hot air drying at 60 °C was 20% shorter than that of hot air drying at 60 °C, and the drying time of ultrasound-assisted hot air drying at 80 °C was 37.5% shorter than that of hot air drying at 80 °C. The analysis of the nonvolatile flavor components showed that the ultrasound-assisted hot air drying at 60 °C of the O. raphanipes sample had the highest content of free amino acids (83.78 mg/g) and an equivalent umami concentration value (1491.33 monosodium glutamate/100 g). The vacuum freeze-drying treated O. raphanipes had the highest 5′-nucleotide content of 2.44 mg/g. Therefore, vacuum freeze-drying and ultrasound-assisted hot air drying at 60 °C, followed by vacuum microwave drying, might protect the flavor components of O. raphanipes to the greatest extent. However, microwave drying, hot air drying at 80 °C, and ultrasound-assisted hot air drying at 80 °C could destroy the flavor components of O. raphanipes during drying. The results of this study provided data support for the industrial production of dried O. raphanipes. [ABSTRACT FROM AUTHOR]

The influences of four drying methods (hot air drying (HAD), vacuum freeze drying (VFD), vacuum drying (VD) and intermittent microwave combined with hot air drying (MW-HAD)) on the taste profile and flavor characteristic of Cordyceps militaris were investigated. MW-HAD samples had the highest levels of umami taste 5′-nucleotides, bitter taste amino acids, and equivalent umami concentration (EUC) value. The aroma fingerprints and differences of dried Cordyceps militaris were established by GC-MS with odor activity values (OAVs) and GC-IMS with principal component analysis (PCA). GC-MS data showed that the predominant volatiles of dried samples were aldehydes, alcohols, and ketones. VFD samples had the highest amount of total aroma compounds and C8 compounds. Moreover, 21 aroma-active components (OAVs ≥ 1) were the main contributors to the flavor of dried Cordyceps militaris. The OAVs of 1-octen-3-one and 3-octanone associated with mushroom-like odor in VFD were significantly higher than other samples. Furthermore, a significant difference in flavor compounds of four dried samples was also clearly demonstrated by GC-IMS analysis with PCA. GC-IMS analysis revealed that VFD samples had the most abundant flavor compounds. Overall, MW-HAD was an effective drying method to promote umami taste, and VFD could superiorly preserve volatiles and characteristic aroma compounds in dried Cordyceps militaris. [ABSTRACT FROM AUTHOR]

In this study, fresh Lyophyllum decastes was dried using hot air drying (HAD), hot air combined with vacuum drying (HAVD), and vacuum freeze drying (VFD). Additionally, the quality and volatile compounds were analyzed. VFD achieved the best color retention, the highest rehydration capacity, and the slightest damaged tissue structure; however, it recorded the longest drying time and the highest energy consumption. HAD was the most energy-efficient of the three methods. Furthermore, the products with more hardness and elasticity were obtained by HAD and HAVD—this finding was convenient for transportation. In addition, GC-IMS demonstrated that the flavor components had significantly changed after drying. A total of 57 volatile flavor compounds was identified, and the aldehyde, alcohol, and ketone compounds were the primary ingredient of the L. decastes flavor component, whereby the relative content of the HAD sample was apparently higher than HAVD and VFD. Taken together, VFD was better at preserving the color and shape of fresh L. decastes, but HAD was more appropriate for drying L. decastes because of the lower energy consumption, and was more economical. Meanwhile, HAD could be used to produce a more intense aroma. [ABSTRACT FROM AUTHOR]

This study investigated the effects of different drying methods on the drying characteristics, three-dimensional (3D) appearance, color, total polysaccharide content (TPC), antioxidant activity, and microstructure of Pleurotus eryngii slices. The drying methods included hot air drying (HAD), infrared drying (ID), and microwave drying (MD). The results showed that the drying method and conditions significantly influenced the drying time, with MD having a significant advantage in reducing the drying time. The 3D appearance of P. eryngii slices was evaluated based on shrinkage and roughness as quantitative indexes, and the best appearance was obtained by hot air drying at 55 and 65 °C. HAD and ID at lower drying temperatures obtained better color, TPC, and antioxidant activity, but MD significantly damaged the color and nutritional quality of P. eryngii. The microstructure of dried P. eryngii slices was observed using scanning electron microscopy, and the results showed that drying methods and conditions had an obvious effect on the microstructure of P. eryngii slices. Scattered mycelia were clearly observed in P. eryngii samples dried by HAD and ID at lower drying temperatures, while high drying temperatures led to the cross-linking and aggregation of mycelia. This study offers scientific and technical support for choosing appropriate drying methods to achieve a desirable appearance and quality of dried P. eryngii.

This study aimed to examine the differences in the nutrients and volatile compounds of Stropharia rugoso-annulata after undergoing three different drying treatments. The fresh mushrooms were dried using hot air drying (HAD), vacuum freeze drying (VFD), and natural air drying (NAD), respectively. After that, the nutrients, volatile components, and sensory evaluation of the treated mushrooms were comparably analyzed. Nutrients analysis included proximate compositions, free amino acids, fatty acids, mineral elements, bioactive compositions, and antioxidant activity. Volatile components were identified by headspace-solid phase microextraction-gas chromatography-mass spectrometry (HS-SPME-GC-MS) and analyzed with principal component analysis (PCA). Finally, sensory evaluation was conducted by ten volunteers for five sensory properties. The results showed that the HAD group had the highest vitamin D2 content (4.00 μg/g) and antioxidant activity. Compared with other treatments, the VFD group had higher overall nutrient contents, as well as being more preferred by consumers. Additionally, there were 79 volatile compounds identified by HS-SPME-GC-MS, while the NAD group showed the highest contents of volatile compounds (1931.75 μg/g) and volatile flavor compounds (1307.21 μg/g). PCA analysis suggested the volatile flavor compositions were different among the three groups. In summary, it is recommended that one uses VFD for obtaining higher overall nutritional values, while NAD treatment increased the production of volatile flavor components of the mushroom.

Allium mongolicum Regel (AMR) is a traditional Mongolian food. Various drying methods play an important role in foodstuff flavor. However, the effect of different drying methods on AMR is limited. In this study, freeze drying (FD), vacuum drying (VD), and hot-air drying (HAD) were applied to dry fresh AMR to a moisture content of 8% (wet basis); headspace gas chromatography mass spectrometry was adopted to identify volatile compounds in AMR; and principal component analysis and fingerprint similarity analysis based on the Euclidean distance was used to distinguish the fresh and three dried treatments. In total, 113 peaks were detected and 102 volatile compounds were identified. Drying causes significant changes to the amounts of volatile compounds in AMR, and the drying method plays a key role in determining which volatile compounds appear. Compared to FD, VD and HAD were more appropriate for drying AMR because the volatile compounds after VD and HAD were closer to those of fresh AMR. These findings can provide a scientific basis to help to preserve future seasonal functional food and aid in Mongolian medicine production. [ABSTRACT FROM AUTHOR]

Ginger (Zingiber officinale Roscoe) is one of the most popular spices in the world, with its unique odor. Due to its health benefits, ginger is also widely used as a dietary supplement and herbal medicine. In this study, the main flavor components of gingers processed by different drying methods including hot air drying, vacuum drying, sun-drying, and vacuum-freeze drying, were identified on the basis of headspace-gas chromatography coupled with mass spectrometry (HS-GC-MS) and fast gas chromatography electronic-nose (fast GC e-nose) techniques. The results showed that the ginger dried by hot air drying exhibited high contents of volatile compounds and retained the richest odor in comparison with those dried by other methods, which indicated that hot air drying is more suitable for the production of dried ginger. Sensory description by fast GC e-nose exhibited that ginger flavor was mainly concentrated in the spicy, sweet, minty, fruity, and herbaceous odor. The relative content of the zingiberene was significantly higher in the hot air drying sample than those by other methods, suggesting that dried ginger by hot air drying can retain more unique spicy and pungent odorants. Furthermore, the results of chemometrics analyses showed that the main variance components among the samples by different drying methods were α-naginatene, (+)-cyclosativene, and sulcatone in HS-GC-MS analysis, and α-terpinen-7-al, dimethyl sulfide, and citronellal in fast GC e-nose analysis. For comparison of fresh and dried gingers, terpinolene, terpinen-4-ol, 2,4-decadienal, (E, Z)-, and linalool were considered the main variance components. This study generated a better understanding of the flavor characteristics of gingers by different drying methods and could provide a guide for drying and processing of ginger. [ABSTRACT FROM AUTHOR]

Edible herbs are widely used in the human diet due to their pleasant flavors and countless health benefits associated with their components having, mainly, antioxidant and anti-inflammatory therapeutic functions. Since herbs are highly perishable materials because of their high water content, to guarantee products are safe and stable over time, it is necessary that they undergo stabilization operations. The application of microwave-assisted drying, a promising technique in terms of process sustainability, for the stabilization of the aromatic herb, Ocimum basilicum L., was investigated. The activities were carried out by applying different operating conditions in order to evaluate the impact of the time/temperature combination on the final quality of dried basil. The latter was investigated via the chemical characterization of extracted essential oils and tissue damages. Conventional convective processes were also applied to perform comparisons between dried basil products both under production and the quality preservation points of view. Results showed that microwave heating is suitable as a drying method, as expected, due to the well-known interaction between vegetable tissue (rich in water) and the electromagnetic field; and that drying methods have a different influence on the chemical composition of the essential oils extracted from dried products, in terms of the number (ranging from 41 to 18 components in different dried samples) and percentage (until 67% in linalool and 21% in α-trans-bergamotene in different dried samples) of its' constituents. [ABSTRACT FROM AUTHOR]

Large amounts of waste result from licorice mold rot; moreover, prompt drying directly influences product quality and value. This study compared various glycyrrhiza drying methods (Hot air drying (HAD), infrared combined hot air drying (IR-HAD), vacuum freeze drying (VFD), microwave vacuum drying (MVD), and vacuum pulsation drying (VPD)) that are used in the processing of traditional Chinese medicine. To investigate the effects of various drying methods on the drying characteristics and internal quality of licorice slices, their color, browning, total phenol, total flavonoid, and active components (liquiritin and glycyrrhizic acid) were chosen as qualitative and quantitative evaluation indices. Our results revealed that VFD had the longest drying time, but it could effectively maintain the contents of total phenol, total flavonoid, and liquiritin and glycyrrhizic acid. The results also showed that VFD samples had the best color and the lowest degree of browning, followed by HAD, IR-HAD, and VPD. We think that VFD is the best approach to ensure that licorice is dry.

The present study aimed to investigate the effect of rotary microwave vacuum drying (RMVD), radio frequency vacuum drying (RFVD), vacuum far infrared drying (VFID), vacuum drying (VD), hot air drying (HD) and natural drying (ND) on the drying characteristics, active ingredients and microstructure of Codonopsis pilosulae slices. Compared with the fitting results of the four models, the Weibull model is the most suitable drying model for Codonopsis. The RFVD and HD color difference values were smaller compared to ND. The effective moisture diffusivity (Deff) under different drying methods was between 0.06 × 10−8 m2/s and 3.95 × 10−8 m2/s. RMVD-dried products had the shortest drying time and retained more active ingredients. The microstructure analysis revealed that the porous structure of RMVD is more favorable for water migration. RMVD is a promising dehydration method for obtaining high-value-added dried Codonopsis products.

Maya nut (Brosimum alicastrum) is a novel food with high nutritional value. This research aimed to evaluate the nutritional and antioxidant properties of Maya nut flour (MNF) made from seeds dried by different methods (sun-dried and using hot air at 45 °C and 60 °C) to explore its incorporation into cookies and evaluate its nutritional and functional properties. The naturally sun-dried flour (NF) had the highest content of ash (3.64 ± 0.11 g/100 g), protein (6.35 ± 0.44 g/100 g), crude fiber (6.75 ± 0.29 g/100 g), and functional properties (water and oil absorption). The color of the flour was affected by the different drying methods. While the drying methods influenced the total polyphenolic content (TPC) and antioxidant activity (AA) of MNF, they did not affect the morphology of the native starch or generated important molecular-structural changes. The substitution of 60% of wheat flour with NF in the cookie’s formula increased the protein and fiber content, whereas 20% substitution increased its AA. MNF is a source of protein, dietary fiber, micronutrients, and functional compounds that can enrich cookie formulations.

Different drying methods affect the quality of foods. The aim of this study is to explore the effects of seven drying methods, including hot air drying at 60 °C and 80 °C, ultrasound-assisted hot air drying at 60 °C and 80 °C, microwave drying, vacuum microwave drying, and vacuum freeze-drying, on the quality and nonvolatile flavor components of Oudemansiella raphanipes. The vacuum freeze-drying resulted in minimal collapse, mild shrinkage at the macroscopic level, and the formation of uniform pores at the microscopic level on the surfaces of O. raphanipes mushrooms. In addition, vacuum freeze-drying can improve the color attributes of the mushrooms. Therefore, the appearance and shape of vacuum freeze-drying treated O. raphanipes were closest to those of fresh mushrooms. We found that ultrasound-assisted treatment can effectively shorten the drying time of O. raphanipes. The drying time of ultrasound-assisted hot air drying at 60 °C was 20% shorter than that of hot air drying at 60 °C, and the drying time of ultrasound-assisted hot air drying at 80 °C was 37.5% shorter than that of hot air drying at 80 °C. The analysis of the nonvolatile flavor components showed that the ultrasound-assisted hot air drying at 60 °C of the O. raphanipes sample had the highest content of free amino acids (83.78 mg/g) and an equivalent umami concentration value (1491.33 monosodium glutamate/100 g). The vacuum freeze-drying treated O. raphanipes had the highest 5′-nucleotide content of 2.44 mg/g. Therefore, vacuum freeze-drying and ultrasound-assisted hot air drying at 60 °C, followed by vacuum microwave drying, might protect the flavor components of O. raphanipes to the greatest extent. However, microwave drying, hot air drying at 80 °C, and ultrasound-assisted hot air drying at 80 °C could destroy the flavor components of O. raphanipes during drying. The results of this study provided data support for the industrial production of dried O. raphanipes.

Understanding the effects of drying on the selenium (Se) content and Se bioaccessibility of Se-rich plants is critical to dietary supplementation of Se. The effects of five common drying methods (far-infrared drying (FIRD), vacuum drying (VD), microwave vacuum drying (MVD), hot air drying (HD), and freeze vacuum drying (FD)) on the content and bioaccessibility of Se and Se species in Cardamine violifolia leaves (CVLs) were studied. The content of SeCys2 in fresh CVLs was the highest (5060.50 μg/g of dry weight (DW)); after FIRD, it had the lowest selenium loss, with a loss rate of less than 19%. Among all of the drying processes, FD and VD samples had the lowest Se retention and bioaccessibility. FIRD, VD, and FD samples have similar effects on antioxidant activity.

The influences of four drying methods (hot air drying (HAD), vacuum freeze drying (VFD), vacuum drying (VD) and intermittent microwave combined with hot air drying (MW-HAD)) on the taste profile and flavor characteristic of Cordyceps militaris were investigated. MW-HAD samples had the highest levels of umami taste 5′-nucleotides, bitter taste amino acids, and equivalent umami concentration (EUC) value. The aroma fingerprints and differences of dried Cordyceps militaris were established by GC-MS with odor activity values (OAVs) and GC-IMS with principal component analysis (PCA). GC-MS data showed that the predominant volatiles of dried samples were aldehydes, alcohols, and ketones. VFD samples had the highest amount of total aroma compounds and C8 compounds. Moreover, 21 aroma-active components (OAVs ≥ 1) were the main contributors to the flavor of dried Cordyceps militaris. The OAVs of 1-octen-3-one and 3-octanone associated with mushroom-like odor in VFD were significantly higher than other samples. Furthermore, a significant difference in flavor compounds of four dried samples was also clearly demonstrated by GC-IMS analysis with PCA. GC-IMS analysis revealed that VFD samples had the most abundant flavor compounds. Overall, MW-HAD was an effective drying method to promote umami taste, and VFD could superiorly preserve volatiles and characteristic aroma compounds in dried Cordyceps militaris.

In this study, fresh Lyophyllum decastes was dried using hot air drying (HAD), hot air combined with vacuum drying (HAVD), and vacuum freeze drying (VFD). Additionally, the quality and volatile compounds were analyzed. VFD achieved the best color retention, the highest rehydration capacity, and the slightest damaged tissue structure; however, it recorded the longest drying time and the highest energy consumption. HAD was the most energy-efficient of the three methods. Furthermore, the products with more hardness and elasticity were obtained by HAD and HAVD—this finding was convenient for transportation. In addition, GC-IMS demonstrated that the flavor components had significantly changed after drying. A total of 57 volatile flavor compounds was identified, and the aldehyde, alcohol, and ketone compounds were the primary ingredient of the L. decastes flavor component, whereby the relative content of the HAD sample was apparently higher than HAVD and VFD. Taken together, VFD was better at preserving the color and shape of fresh L. decastes, but HAD was more appropriate for drying L. decastes because of the lower energy consumption, and was more economical. Meanwhile, HAD could be used to produce a more intense aroma.

Allium mongolicum Regel (AMR) is a traditional Mongolian food. Various drying methods play an important role in foodstuff flavor. However, the effect of different drying methods on AMR is limited. In this study, freeze drying (FD), vacuum drying (VD), and hot-air drying (HAD) were applied to dry fresh AMR to a moisture content of 8% (wet basis); headspace gas chromatography mass spectrometry was adopted to identify volatile compounds in AMR; and principal component analysis and fingerprint similarity analysis based on the Euclidean distance was used to distinguish the fresh and three dried treatments. In total, 113 peaks were detected and 102 volatile compounds were identified. Drying causes significant changes to the amounts of volatile compounds in AMR, and the drying method plays a key role in determining which volatile compounds appear. Compared to FD, VD and HAD were more appropriate for drying AMR because the volatile compounds after VD and HAD were closer to those of fresh AMR. These findings can provide a scientific basis to help to preserve future seasonal functional food and aid in Mongolian medicine production.

Ginger (Zingiber officinale Roscoe) is one of the most popular spices in the world, with its unique odor. Due to its health benefits, ginger is also widely used as a dietary supplement and herbal medicine. In this study, the main flavor components of gingers processed by different drying methods including hot air drying, vacuum drying, sun-drying, and vacuum-freeze drying, were identified on the basis of headspace-gas chromatography coupled with mass spectrometry (HS-GC-MS) and fast gas chromatography electronic-nose (fast GC e-nose) techniques. The results showed that the ginger dried by hot air drying exhibited high contents of volatile compounds and retained the richest odor in comparison with those dried by other methods, which indicated that hot air drying is more suitable for the production of dried ginger. Sensory description by fast GC e-nose exhibited that ginger flavor was mainly concentrated in the spicy, sweet, minty, fruity, and herbaceous odor. The relative content of the zingiberene was significantly higher in the hot air drying sample than those by other methods, suggesting that dried ginger by hot air drying can retain more unique spicy and pungent odorants. Furthermore, the results of chemometrics analyses showed that the main variance components among the samples by different drying methods were α-naginatene, (+)-cyclosativene, and sulcatone in HS-GC-MS analysis, and α-terpinen-7-al, dimethyl sulfide, and citronellal in fast GC e-nose analysis. For comparison of fresh and dried gingers, terpinolene, terpinen-4-ol, 2,4-decadienal, (E, Z)-, and linalool were considered the main variance components. This study generated a better understanding of the flavor characteristics of gingers by different drying methods and could provide a guide for drying and processing of ginger.

Edible herbs are widely used in the human diet due to their pleasant flavors and countless health benefits associated with their components having, mainly, antioxidant and anti-inflammatory therapeutic functions. Since herbs are highly perishable materials because of their high water content, to guarantee products are safe and stable over time, it is necessary that they undergo stabilization operations. The application of microwave-assisted drying, a promising technique in terms of process sustainability, for the stabilization of the aromatic herb, Ocimum basilicum L., was investigated. The activities were carried out by applying different operating conditions in order to evaluate the impact of the time/temperature combination on the final quality of dried basil. The latter was investigated via the chemical characterization of extracted essential oils and tissue damages. Conventional convective processes were also applied to perform comparisons between dried basil products both under production and the quality preservation points of view. Results showed that microwave heating is suitable as a drying method, as expected, due to the well-known interaction between vegetable tissue (rich in water) and the electromagnetic field; and that drying methods have a different influence on the chemical composition of the essential oils extracted from dried products, in terms of the number (ranging from 41 to 18 components in different dried samples) and percentage (until 67% in linalool and 21% in α-trans-bergamotene in different dried samples) of its’ constituents.

This study evaluated the effects of pretreatments (blanching (60 and 95 °C) and boiling) and drying methods (freeze-drying and oven drying) on the quality characteristics of potato flour derived from three potato varieties, namely, Shangi, Unica, and Dutch Robjin. The percentage flour yield, color, particle size distribution, flow characteristics, microstructural and functional properties of the potato flour were determined. Unica recorded the least peeling loss, while the Dutch Robjin variety had the highest. Color parameters were significantly affected (p < 0.05) by the pretreatments and drying methods. Freeze drying produced lighter potato flour (L* = 92.86) compared to the other methods. Boiling and blanching at 95 °C followed by oven drying recorded a low angle of repose and compressibility index, indicating better flow characteristics. The smallest particle size (56.5 µm) was recorded for the freeze-drying treatment, while boiling followed by oven drying had the largest particle size (307.5 µm). Microstructural results indicate that boiling and blanching at 95 °C, followed by oven drying resulted in damaged starch granules, while freeze-drying and low-temperature blanching (60 °C) maintained the native starch granule. Particle size and the solubility index of potato flour showed strong positive correlation. This study revealed that the pretreatments and drying methods affected potato flour’s physical and microstructural parameters differently, resulting in changes in their functionality.

In this study, fresh Lentinula edodes was dehydrated using freeze-drying (FD), hot-air drying (HAD), and natural drying (ND), and the volatile and non-volatile flavor compounds were analyzed. The drying process changed the contents of eight-carbon compounds and resulted in a weaker “mushroom flavor” for dried L. edodes. HAD mushrooms had higher levels of cyclic sulfur compounds (56.55 μg/g) and showed a stronger typical shiitake mushroom aroma than those of fresh (7.24 μg/g), ND (0.04 μg/g), and FD mushrooms (3.90 μg/g). The levels of 5′-nucleotide increased, whereas the levels of organic acids and free amino acids decreased after the drying process. The dried L. edodes treated with FD had the lowest levels of total free amino acids (29.13 mg/g). However, it had the highest levels of umami taste amino acids (3.97 mg/g), bitter taste amino acids (6.28 mg/g) and equivalent umami concentration (EUC) value (29.88 g monosodium glutamate (MSG) per 100 g). The results indicated that FD was an effective drying method to produce umami flavor in dried mushrooms. Meanwhile, HAD can be used to produce a typical shiitake mushroom aroma. Our results provide a theoretical basis to manufacture L. edodes products with a desirable flavor for daily cuisine or in a processed form.

Research on the processing of yam (Dioscorea spp.) into flour is aimed at optimizing techniques to obtain a material with high physicochemical and functional properties. The present study investigates the effect of the processing techniques on the levels of inulin, organic acids, total phenolics (TP), antioxidant capacity, and polyphenol oxidase (PPO) and peroxidase (POD) activities, as well as on the physicochemical properties of flour derived from two yam species—Dioscorea esculenta and Dioscorea bulbifera. All tubers were peeled and sliced, then subjected to different processing techniques through blanching, soaking, and drying. The results revealed that freeze-drying appears to be the best technique in achieving the highest whiteness index of yam flour. This coincided well with the low phenolics content and POD activity, which suggests a reduced enzymatic browning reaction in the freeze-dried yam flour. On the other hand, chemical analyses showed that D. esculenta and D. bulbifera flours have the highest levels of inulin (23.0 and 27.8 g/100 g DW, respectively) and succinic acid (7.96 and 7.65 g/100 g DW, respectively) in the samples subjected to direct oven-drying. Oven drying without pretreatment neither blanching nor water steeping maintained antioxidant activity in the flour derived from both D. esculenta and D. bulbifera.

Burdock (Arctium lappa L.) is one of the nutritional foods widely planted in many countries. Dried burdock root (BR) is available as a herbal tincture and tea in many Asian countries with good flavor and taste. In this study, the volatile components in dried BR were identified and the effects of different drying methods on the volatile components were investigated by HS-GC-MS method. A total of 49 compounds were identified. Different drying methods including hot-air drying (HD, at 50, 60, 70, and 80 °C), vacuum drying (VD, at 50, 60, 70, and 80 °C), sunlight drying (SD), natural drying (ND), and vacuum freeze drying (VFD) were evaluated by HS-GC-MS-based metabolomics method. Results showed that different drying methods produced different effects on the volatile compounds. It was observed that 2,3-pentanedione, 1-(1H-pyrrol-2-yl)-ethanone, furfural, and heptanal were detected at higher concentrations in HD 80 and VD 70. The traditional HD and SD methods produced more flavor substances than VFD. The BR treated by the VFD method could maintain the shape of the fresh BR pieces while HD50 and VD80 methods could maintain the color of fresh BR pieces. These findings could help better understand the flavor of the corresponding processed BR and provide a guide for the drying and processing of BR tea.

There is a need and great interest among food producers in obtaining powders from fruit and vegetables of both high nutritional value and sensory qualities superior to those hitherto obtained by convection drying (CD) and spray drying methods and cheaper to prepare than the sublimation method. This study is focused on whether powders can be obtained from fruit berries with a sticky structure, using the chokeberry (Aronia melanocarpa) as a test example, by a combined fluidized-bed jet milling and drying (FBJD) of pre-dried fruit by CD to an adequate water activity (aw). The pre-drying step reduced sticking between fruit particles during the simultaneous drying and grinding processes of the FBJD method in order to obtain powders of desired granulation. Three different pre-drying temperatures of 50, 60, and 70 °C were tested for levels of microorganisms in chokeberries at a water activity of 0.4. Vitamin C content and antioxidant properties were also examined along with polyphenol separation. Fruit pre-dried at 60–70 °C had significantly higher vitamin C and polyphenolic content and greater antioxidant properties than those pre-dried at 50 °C. Further studies were thus undertaken on powders pre-dried at 70 °C in which antioxidant properties, vitamin C, and polyphenols content were also compared with CD obtained powders. The FBJD method combined with CD pre-drying proved superior to just using the CD method, where powders had a greater preservation of vitamin C at 84% (CD powders 35%), a 12% higher total polyphenol content, and a 10% higher antioxidant activity. The test method also uses a much shorter drying time than the CD method, because the grinding of the hard-textured material takes only few minutes.

Flowers of hemp (Cannabis sativa L.) are widely used in cosmetics, food, and in the pharmaceutical industry. The drying process plays a key role in retention of aroma and also in the quality of products. Seven variants of hemp flower drying, including convection drying (CD), vacuum–microwave drying (VMD), and combined drying consisting of convective pre-drying followed by vacuum–microwave finishing drying (CPD-VMFD) were checked in this study. For each process, we applied the two-term model. Dried material was submitted to color and chromatographical assessments. Analyses of obtained essential oil showed the presence of 93 volatile compounds, predominantly β-myrcene, limonene, and β-(E)-caryophyllene, as well as α-humulene. Application of 240 W during VMD and 50 °C during CD gave the highest retention of aroma compounds, amounting to 85 and 76%, respectively, but with huge color changes. Additionally, sensory analysis proved that drying with a microwave power of 240 W provides a product most similar to fresh material.

This study evaluated the effects of pretreatments (blanching (60 and 95 °C) and boiling) and drying methods (freeze-drying and oven drying) on the quality characteristics of potato flour derived from three potato varieties, namely, Shangi, Unica, and Dutch Robjin. The percentage flour yield, color, particle size distribution, flow characteristics, microstructural and functional properties of the potato flour were determined. Unica recorded the least peeling loss, while the Dutch Robjin variety had the highest. Color parameters were significantly affected (p < 0.05) by the pretreatments and drying methods. Freeze drying produced lighter potato flour (L* = 92.86) compared to the other methods. Boiling and blanching at 95 °C followed by oven drying recorded a low angle of repose and compressibility index, indicating better flow characteristics. The smallest particle size (56.5 µm) was recorded for the freeze-drying treatment, while boiling followed by oven drying had the largest particle size (307.5 µm). Microstructural results indicate that boiling and blanching at 95 °C, followed by oven drying resulted in damaged starch granules, while freeze-drying and low-temperature blanching (60 °C) maintained the native starch granule. Particle size and the solubility index of potato flour showed strong positive correlation. This study revealed that the pretreatments and drying methods affected potato flour's physical and microstructural parameters differently, resulting in changes in their functionality. [ABSTRACT FROM AUTHOR]

In this study, fresh Lentinula edodes was dehydrated using freeze-drying (FD), hot-air drying (HAD), and natural drying (ND), and the volatile and non-volatile flavor compounds were analyzed. The drying process changed the contents of eight-carbon compounds and resulted in a weaker "mushroom flavor" for dried L. edodes. HAD mushrooms had higher levels of cyclic sulfur compounds (56.55 μg/g) and showed a stronger typical shiitake mushroom aroma than those of fresh (7.24 μg/g), ND (0.04 μg/g), and FD mushrooms (3.90 μg/g). The levels of 5′-nucleotide increased, whereas the levels of organic acids and free amino acids decreased after the drying process. The dried L. edodes treated with FD had the lowest levels of total free amino acids (29.13 mg/g). However, it had the highest levels of umami taste amino acids (3.97 mg/g), bitter taste amino acids (6.28 mg/g) and equivalent umami concentration (EUC) value (29.88 g monosodium glutamate (MSG) per 100 g). The results indicated that FD was an effective drying method to produce umami flavor in dried mushrooms. Meanwhile, HAD can be used to produce a typical shiitake mushroom aroma. Our results provide a theoretical basis to manufacture L. edodes products with a desirable flavor for daily cuisine or in a processed form. [ABSTRACT FROM AUTHOR]

Research on the processing of yam (Dioscorea spp.) into flour is aimed at optimizing techniques to obtain a material with high physicochemical and functional properties. The present study investigates the effect of the processing techniques on the levels of inulin, organic acids, total phenolics (TP), antioxidant capacity, and polyphenol oxidase (PPO) and peroxidase (POD) activities, as well as on the physicochemical properties of flour derived from two yam species—Dioscorea esculenta and Dioscorea bulbifera. All tubers were peeled and sliced, then subjected to different processing techniques through blanching, soaking, and drying. The results revealed that freeze-drying appears to be the best technique in achieving the highest whiteness index of yam flour. This coincided well with the low phenolics content and POD activity, which suggests a reduced enzymatic browning reaction in the freeze-dried yam flour. On the other hand, chemical analyses showed that D. esculenta and D. bulbifera flours have the highest levels of inulin (23.0 and 27.8 g/100 g DW, respectively) and succinic acid (7.96 and 7.65 g/100 g DW, respectively) in the samples subjected to direct oven-drying. Oven drying without pretreatment neither blanching nor water steeping maintained antioxidant activity in the flour derived from both D. esculenta and D. bulbifera. [ABSTRACT FROM AUTHOR]

Burdock (Arctium lappa L.) is one of the nutritional foods widely planted in many countries. Dried burdock root (BR) is available as a herbal tincture and tea in many Asian countries with good flavor and taste. In this study, the volatile components in dried BR were identified and the effects of different drying methods on the volatile components were investigated by HS-GC-MS method. A total of 49 compounds were identified. Different drying methods including hot-air drying (HD, at 50, 60, 70, and 80 °C), vacuum drying (VD, at 50, 60, 70, and 80 °C), sunlight drying (SD), natural drying (ND), and vacuum freeze drying (VFD) were evaluated by HS-GC-MS-based metabolomics method. Results showed that different drying methods produced different effects on the volatile compounds. It was observed that 2,3-pentanedione, 1-(1H-pyrrol-2-yl)-ethanone, furfural, and heptanal were detected at higher concentrations in HD 80 and VD 70. The traditional HD and SD methods produced more flavor substances than VFD. The BR treated by the VFD method could maintain the shape of the fresh BR pieces while HD50 and VD80 methods could maintain the color of fresh BR pieces. These findings could help better understand the flavor of the corresponding processed BR and provide a guide for the drying and processing of BR tea. [ABSTRACT FROM AUTHOR]

There is a need and great interest among food producers in obtaining powders from fruit and vegetables of both high nutritional value and sensory qualities superior to those hitherto obtained by convection drying (CD) and spray drying methods and cheaper to prepare than the sublimation method. This study is focused on whether powders can be obtained from fruit berries with a sticky structure, using the chokeberry (Aronia melanocarpa) as a test example, by a combined fluidized-bed jet milling and drying (FBJD) of pre-dried fruit by CD to an adequate water activity (aw). The pre-drying step reduced sticking between fruit particles during the simultaneous drying and grinding processes of the FBJD method in order to obtain powders of desired granulation. Three different pre-drying temperatures of 50, 60, and 70 °C were tested for levels of microorganisms in chokeberries at a water activity of 0.4. Vitamin C content and antioxidant properties were also examined along with polyphenol separation. Fruit pre-dried at 60–70 °C had significantly higher vitamin C and polyphenolic content and greater antioxidant properties than those pre-dried at 50 °C. Further studies were thus undertaken on powders pre-dried at 70 °C in which antioxidant properties, vitamin C, and polyphenols content were also compared with CD obtained powders. The FBJD method combined with CD pre-drying proved superior to just using the CD method, where powders had a greater preservation of vitamin C at 84% (CD powders 35%), a 12% higher total polyphenol content, and a 10% higher antioxidant activity. The test method also uses a much shorter drying time than the CD method, because the grinding of the hard-textured material takes only few minutes. [ABSTRACT FROM AUTHOR]

Flowers of hemp (Cannabis sativa L.) are widely used in cosmetics, food, and in the pharmaceutical industry. The drying process plays a key role in retention of aroma and also in the quality of products. Seven variants of hemp flower drying, including convection drying (CD), vacuum–microwave drying (VMD), and combined drying consisting of convective pre-drying followed by vacuum–microwave finishing drying (CPD-VMFD) were checked in this study. For each process, we applied the two-term model. Dried material was submitted to color and chromatographical assessments. Analyses of obtained essential oil showed the presence of 93 volatile compounds, predominantly β-myrcene, limonene, and β-(E)-caryophyllene, as well as α-humulene. Application of 240 W during VMD and 50 °C during CD gave the highest retention of aroma compounds, amounting to 85 and 76%, respectively, but with huge color changes. Additionally, sensory analysis proved that drying with a microwave power of 240 W provides a product most similar to fresh material. [ABSTRACT FROM AUTHOR]