Search

Nano-fibrillated cellulose (NFC) is of interest in several fields due to its unique physical properties derived from its nanoscale dimensions. NFC has potential use in food systems as a dietary fiber that increases viscosity and limit diffusion of glucose. This study focused on the effects of added NFC on solution viscosity, starch digestion and glucose absorption. NFC did not affect α-amylase and α-glucosidase activity, but significantly retarded glucose diffusion, delayed amylolysis and reduced the amount of glucose released during in vitro digestion of starch. Specifically, 1% NFC retarded ∼26.6% of glucose released during the amylolysis process. The greatly increased viscosity of NFC at concentrations >0.5% was thought to be the main mechanism for its potential hypoglycemic effects. NFC suspensions also had higher glucose adsorption capacity than those containing cellulose. In addition, NFC bound 35.6% of the glucose when the initial glucose level was within the range of 5–200 mM. These results suggest that NFC may be useful for building viscosity in food products and serving to inhibit glucose absorption in vivo in starch-containing products. [ABSTRACT FROM AUTHOR]

The glass transition temperature (T g ) is an important property that influences the processing and textural characteristics of candy. Measurement of T g is done by comparably expensive and complex instruments. In this study, we tested a new system which uses capacitance thermal analysis (CTA) of candy trapped between stainless plates, as the system is caused to heat at an uncontrolled rate. The data of capacitance as a function of temperature were processed by a genetic algorithm (GA), and fitted to a three-section model to determine T g . T g of the candies were independently measured by DSC as a reference. The results showed that when the T g of the candy was below ∼15 °C, the measurement from the GA-CTA was higher (2–3 °C) than that from DSC. However, if T g of the candy was higher than 15 °C, the two methods gave similar values. GA based CTA provides a feasible new way to measure phase transitions in candies with relatively inexpensive equipment, and with less need for user interpretation of data. [ABSTRACT FROM AUTHOR]

Highlights: [•] We fortify peanut butters (PBs) with ground peanut skins to increase the level of bioactives. [•] We examine changes in the levels of phenolics and fibre contents as well as antioxidant capacity in PBs. [•] We identify the proanthocyanidins in the peanut skins responsible for the increase in PB phenolics. [•] Addition of 5% peanut skins to PBs can permit a “good source of fibre” claim to be made on the label. [•] Better by-product utilisation can improve an existing product and allow diversification of a brand. [ABSTRACT FROM AUTHOR]

Abstract: The combined effects of dough freezing rate, storage temperature and time on bread quality were studied. Yeasted bread dough was frozen using four freezing rates, and stored between −10°C and −35°C for up to 180 days. Dough stored at −10°C or −20°C and frozen at 18–39°C/h resulted in higher specific volume and softer bread, but higher rates of staling, and was related to relatively high yeast activity. NMR studies showed that while frozen dough stored at −30°C or −35°C produced bread with lower volume, it also had reduced staling rates. Crust color was lighter and more uniform for slower frozen dough stored at −10°C or −20°C. Longer frozen dough storage produced darker, less uniform colored crust. Increased understanding of the combined effects of processing conditions is essential for producing better quality dough and bread. This research demonstrated that specific combinations of freezing rates and storage conditions contribute to better bread quality and staling. [Copyright &y& Elsevier]

Lettuce and spinach inoculated with Escherichia coli O157:H7 were processed and handled in ways that might occur in commercial situations, including variations in holding times before and after product cooling, transportation conditions and temperatures, wash treatments, and product storage temperatures and times. Populations of background microflora and E. coli O157:H7 were enumerated after each step in the system. Data analysis was done to predict response variables with a combination of independent categorical variables. Field temperature, time before cooling, and wash treatment significantly affected E. coli O157:H7 populations on both products. The lowest populations of E. coli O157:H7 were encountered when precool time was minimal, lettuce was washed with chlorine, and storage temperature was 4°C. For lettuce, field and transportation temperature were not important once the storage period started, whereas after 2 days E. coli O157:H7 populations on packaged baby spinach were not affected by field temperature. On chopped iceberg lettuce and whole leaf spinach that was packaged and stored at 4°C, E. co.li O157:H7 contamination could still be detected after typical handling practices, although populations decreased from initial levels in many cases by at least 1.5 log units. In abusive cases, where populations increased, the product quality quickly deteriorated. Although E. coli O157:H7 levels decreased on products handled and stored under recommended conditions, survivors persisted. This study highlights practices that may or may not affect the populations of E. coli O157:H7 on the final product. [ABSTRACT FROM AUTHOR]

Abstract: The relationship between microstructural and physical properties of dried foods is difficult to quantify. This study uses artificial neural network analysis (ANN) to predict shrinkage and rehydration of dried carrots, based on inputs of moisture content and normalized fractal dimension analysis (ΔD/D 0) of the cell wall structure. Several drying techniques were used including conventional hot air (HAD), low pressure superheated steam (LPSSD), and freeze drying (FD). Dried carrot sections were examined by light microscopy and the fractal dimension (D) determined using a box counting technique. Optimized ANN models were developed for HAD, LPSSD, HAD+LPSSD, and HAD+LPSSD+FD, based on 1–10 hidden layers and neurons per hidden layer. ANN models were then tested against an independent dataset. Measured values of shrinkage and rehydration were predicted with an R 2 >0.95 in all cases. [Copyright &y& Elsevier]

This study was undertaken to determine the influence of storage time and temperature on the volume, weight, and pH of egg albumen, the physical strength of vitelline membrane, and the fate of Salmonella Enteritidis artificially inoculated into egg albumen. A fiber-optic probe was used for inoculation with Salmonella Enteritidis at 10², 104, or 106 cells per egg. Both fresh and inoculated eggs were stored at 4, 10, and 22°C for 6 weeks. Five fresh uninoculated eggs from each storage group were collected each week, and the weight, volume, and pH of the egg albumen were measured. The forces, energies, and degrees of membrane deformation required to rupture the vitelline membranes also were determined from either albumen-free yolks or yolks surrounded by albumen. In separate experiments, five inoculated eggs were evaluated each week for populations of Salmonella Enteritidis. When the eggs were stored at 4°C, the albumen retained significantly more volume and weight and had a relatively lower pH. The vitelline membranes from eggs stored at 4 and 10°C required more force and energy for rupture. Salmonellae flourished at 22°C, even in the albumen with the lowest initial population, 10² cells per egg. Storage at 4 and 10°C inhibited the growth of salmonellae in the albumen of eggs with initial populations of 10², 104, or 106 cells per egg. In eggs with initial Salmonella populations of 106 cells per egg that were stored at 22°C, the populations of reached as high as 1010 cells per egg after 4 weeks of storage. Storage at 4 and perhaps 10°C postponed the aging process of chicken eggs, preserved the antimicrobial agents of the albumen, and maintained the integrity of vitelline membrane. Low-temperature storage therefore had a significant impact on the safety and overall quality of the eggs. [ABSTRACT FROM AUTHOR]

Pulsed 1H NMR was used to determine moisture content and molecular mobility of wheat starch suspensions at water activity (aw) values between 0 and 0.93. Moisture determination by NMR agreed well with gravimetric determinations (R2=0.99). Transverse proton relaxation (T2) of the systems were identified using single pulse and CPMG experiments. T2 associated with starch molecules increased linearly from 7.1 to 10.1 μs as aw increased from 0 to 0.93, due to plasticizing effects of water. T2 associated with water molecules showed a linear increase up to aw of 0.69. Results indicated that 1H NMR could be employed to determine moisture content of starch suspension and to identify and quantify the molecular motion of starch chains and water molecules of starch suspensions at low moisture levels. [Copyright &y& Elsevier]

Nut kernel color is a crucial quality indicator affecting the consumers first impression of the product. While growing evidence suggests that plant phenolics and their derivatives are linked to nut kernel color, the compounds (biomarkers) responsible for kernel color stability during storage remain elusive. Here, pathway-based metabolomics with machine learning algorithms were employed to identify key metabolites of postharvest pecan color stability. Metabolites in phenylpropanoid, flavonoid, and anthocyanin biosynthetic pathways were analyzed in the testa of nine pecan cultivars using liquid chromatography–mass spectrometry. With color measurements, different machine learning models were compared to find relevant biomarkers of pecan color phenotypes. Results revealed potential marker compounds that included flavonoid precursors and anthocyanidins as well as anthocyanins (e.g., peonidin, delphinidin-3- O -glucoside). Our findings provide a foundation for future research in the area, and will help select genes/proteins for the breeding of pecans with stable and desirable kernel color. [Display omitted] • Metabolomics with machine learning (ML) identified markers for pecan color stability. • Lasso regression and SVM-RFE were the most effective ML models for marker selection. • Selected markers included anthocyanidins, anthocyanins, and flavonoid precursors. • Collected information will help pecan breeding with desirable kernel color. [ABSTRACT FROM AUTHOR]

The effect of heating in the absence or presence of oxygen on the enzyme activity and nutritional quality of apple puree were investigated. Using designed equipment, apples were vacuum-ground, packaged, and heated under vacuum (2.67 kPa, 90 °C for 30 min) to limit exposure to oxygen, and compared to those heated in open air. All thermal treatments led to complete inactivation of oxidative enzymes. Heating without oxygen effectively maintained color, antioxidant activity, phenolic compounds, and ascorbic acid, as compared to fresh apples. In contrast, heating with oxygen led to considerable browning and degradation of antioxidant activities, phenolics, and ascorbic acid. The results indicate that thermal processing without oxygen can help preserve the nutritional value and retard changes in phenolic-related quality of fruits and vegetables. This study suggests that browning and nutritional loss during thermal treatment of apple may be attributed to oxidation, which is accelerated by the elevated temperature. Image 1 • Apple puree was heated in the presence or absence of oxygen at 90 °C for 30 min. • Both heat treatments with or without oxygen led to enzyme inactivation. • Oxygen-free conditions can help maintain phenolic-related quality during heating. • Browning and nutritional loss during heating may be attributed to oxidation. • The oxidation during heating may be accelerated by the elevated temperature. [ABSTRACT FROM AUTHOR]

Abstract Salmonella enterica is a major food safety issue for the spice industry. Slow-releasing chlorine dioxide (ClO 2) gas from self-contained sachets, which can be employed in a small-scale operation, was evaluated for its effectiveness in reducing Salmonella contamination on black pepper, cumin, and sesame seed. Three levels of chlorine dioxide gas (100, 200, or 500 mg ClO 2 /kg spice) were applied to Salmonella- inoculated spices. Spices were sampled immediately after treatment, and at 1, 10, and 30-days post-treatment. The combined effect of ClO 2 gas treatment and storage time on Salmonella numbers on spices was evaluated. Salmonella reductions on black pepper, cumin, and sesame seed samples ranged from 0.81 to 2.74 log CFU/g after ClO 2 treatment. Storage time also had a significant impact on Salmonella numbers, as numbers decreased by up to 2.50 log CFU/g over 30 days of storage. Self-contained ClO 2 releasing sachets could provide small food processors a post-lethality treatment alternative for spices. Highlights • The reduction capabilities of chlorine dioxide gas versus Salmonella on spices was tested. • Chlorine dioxide gas reduced Salmonella numbers by 0.81 to 2.74 log CFU/g. • Salmonella numbers on treated spices decreased by up to 2.50 log CFU/g over 30 days of storage. • Slow-release chlorine dioxide gas has the potential to provide processors with an alternative safeguard. [ABSTRACT FROM AUTHOR]

The purpose of this study was to evaluate the effect of grinding at different vacuum levels (2.67, 6.67, 13.33, 19.99, and 101.33 kPa) on key quality factors of apple. In the control apple, ground at atmospheric pressure of 101.33 kPa, the antioxidant activities rapidly decreased within the first 30 min, then plateaued thereafter, while enzymatic browning increased. When apples were ground and held under vacuum, changes in color and antioxidant activity were much less, and the least change was measured in samples prepared at the lowest pressure. Model fitting of the data showed that antioxidant activity decreased as a function of the logarithm of the absolute pressure. The results from analysis for key phenolic compounds including chlorogenic acid, procyanidin B2, and epicatechin indicated that these compounds were least changed at vacuum grinding at 2.67 kPa, compared to atmospheric grinding. [ABSTRACT FROM AUTHOR]

Highlights: [•] Gum arabic microcapsules have fast-release phenolics and antioxidant activity. [•] Whey protein microcapsules sustain release of phenolics and antioxidant activity. [•] Alcohol extracts of anthocyanins retain antioxidant activity better than acetone. [ABSTRACT FROM AUTHOR]

Abstract: Konjac glucomannan was extruded and subsequently ground under four conditions denoted: KGM1 (33% solids, 90°C), KGM2 (24% solids, 90°C), KGM3 (24% solids, 90°C, die restriction), and KGM4 (24% solids, 110°C). SEM and particle size analysis showed that extruded KGM had slightly larger and rougher particles. The water absorption index was decreased to 47.92–128.80, as compared to 153.64 for the control (KGMC). The crystallinity index increased to 2.97 and 3.42 for KGM3 and KGM4 samples, as compared to 1.72 for the control. Zero-shear viscosity of 0.5% solutions decreased to 0.36–3.01Pas. All samples were shear-thinning and data were best fitted by the Cross model. Based on capillary viscometry, molecular weights were decreased to 2.7×105–9.9×105, as compared to 1.2×106 for the control. In most cases, properties were most altered by higher temperature and shear, and to a lesser extent by lower solids in the feed. [Copyright &y& Elsevier]

Abstract: The development of a relationship between microstructural changes of model food products (carrot and potato cubes) and their physical changes during conventional hot air drying (HAD) using combined fractal and image analysis was performed in this study. Dried carrot and potato sections were examined by light microscopy and the fractal dimension (FD) of the microscopic images was determined using a box counting technique. The apparent physical changes of the samples undergoing HAD were represented in terms of the percentage of shrinkage and rehydration ratio. These apparent changes correlated well with their microstructural changes represented by the normalized changes of fractal dimension (ΔFD/FD0) of the microstructural images. Although the microstructural changes of the samples undergoing HAD were quite different, the changes of ΔFD/FD0 of the samples undergoing drying were in the same trend. FD has thus proved to be a good indicator of microstructural changes of products undergoing drying. [Copyright &y& Elsevier]

• Blueberry purees were consecutively ground, packaged, and heated without oxygen. • Heating both with and without oxygen led to inactivation of oxidative enzymes. • Glycosylated glucose was more thermal-stable than glycosylated arabinose. • Delphinidin had the highest oxygen sensitivity, followed by petunidin and malvidin. • Oxygen-free conditions during heating can maintain anthocyanin-related quality. The effect of thermal treatment of blueberry was investigated using a designed grinding and continuous packaging system under oxygen–free conditions. The grinding, packaging, and heating at 90 °C for 30 min under anaerobic condition were compared to heating under aerobic conditions, showing complete inactivation of oxidative enzymes. Heating without oxygen retained anthocyanins and ascorbic acid whereas heating in atmospheric air does not. Delphinidin glycoside was mostly influenced by oxygen deficiency during heating, followed by petunidin and malvidin glycosides. The differences in oxygen sensitivity may be closely associated with the number of hydroxylation in the B ring. The result of anthocyanin led to higher antioxidant activity and redness values of purees heated without oxygen than purees heated with oxygen. Consequently, thermal processing under oxygen–free condition can prevent oxidation of anthocyanin, resulting in higher retention of color and nutritional values of blueberry products. [ABSTRACT FROM AUTHOR]