Search

Aflatoxin contamination of maize in Rwanda and underlying causes are poorly documented. This study aimed to address this gap where maize samples for aflatoxins analysis were collected from two different agro-ecological zones and the temperature and relative humidity conditions during the time preceding sample collection were monitored to determine the conditions conducive to this contamination. Maize was analysed for moisture content and aflatoxin contamination and the temperature and humidity data were used to estimate the saturation deficit of the ambient air as an indicator of risk of contamination, which is high when the saturation deficit is low. Results showed an average lower saturation deficit of 0.0018 kg H₂O kg−1 in the high-altitude Volcanic region compared to the 0.00095 kg H₂O kg−1 recorded in the lower altitude region of the Eastern Savannah. Given the high moisture content in most of the analysed samples, this meant that it is more challenging to dry maize to the safe storage moisture content in the Volcanic region compared to the Eastern Savannah. The mean aflatoxin contamination was 40.45 μg kg−1 in the Volcanic region significantly higher than 4.66 μg kg−1 in the Eastern Savannah. Aflatoxin G1 was predominant among the contaminated samples. Affordable drying technologies that use renewable sources of energy should be developed and made accessible to farmer cooperatives. • Aflatoxins contamination in maize during storage is influenced by temperature and humidity conditions. • Low temperature drying of maize relies on temperature and humidity conditions in the environment. • Saturation deficit of air can be based on to assess the suitability of air to dry maize to the desired moisture content. • Low saturation deficit means prolonged drying time and thus increased risk of contamination. [ABSTRACT FROM AUTHOR]

Response surface methodology was used to optimise pyrolysis conditions to produce biochar from maize residues (cobs, husks, leaves and stalks). The aim was to obtain biochar with good potential as an additive for composting. Mathematical models were developed to explain the experimental responses of volatile matter content (VM), ash content (AC), pH and electrical conductivity (EC) to the operating parameters such as temperature, heating rate and holding time. The temperature had the most significant influence on biochar properties. AC, pH and EC significantly increased ( p  < 0.05) with increasing temperature, while the VM decreased. The holding time showed less effect on the responses, while the heating rate had insubstantial effect. Under the optimal conditions, the husk and leaf biochar had higher AC (11.42 and 26.55%), pH (10.96 and 11.51), and EC (12.37 and 6.79 mS/cm), but lower VM (7.38 and 8.39%) than those of cob and stalk biochar. [ABSTRACT FROM AUTHOR]

In this study, biochar was produced from maize residues (cobs, husks, leaves) in a lab-scale pyrolysis reactor without using a purging gas. The physicochemical properties of biomass and biochar were analysed. Box–Behnken design was used to optimise operational conditions for biochar yields. Multivariate correlations of biochar yields were established using reduced quadratic models with R 2 = 0.9949, 0.9801 and 0.9876 for cobs, husks and leaves, respectively. Biochar yields were negatively correlated with the temperature, which was significantly influenced by the exothermic reactions during the pyrolysis of maize residues. The heating rate was found to have the least effect on biochar yields. Under optimal conditions, the maximum biochar yields from cobs, husks and leaves were 33.42, 30.69 and 37.91%, respectively. The highest biochar yield from maize leaves was obtained at a temperature of 300 °C, a heating rate of 15 °C/min and a holding time of 30 min. [ABSTRACT FROM AUTHOR]

Polyphenol-rich purple rice has been shown to exhibit a wide range of health properties including antioxidant activity. This study aimed to determine the impact that gastrointestinal digestion of purple rice had on its phenolic bioaccessibility and antioxidant activity. Our results demonstrated a significant difference (p < 0.01) in bioaccessible phenolic content level and antioxidant activity between simulated gastric and intestinal digestion. However, mass spectrometry and ultra-high-performance liquid chromatography (UHPLC) coupled with online ABTS•+ scavenging activity demonstrated a significant loss in the number of polyphenols that were bioaccessible after digestion. Interestingly, substantial free radical scavenging activity was retained after digestion due to the bioaccessibility of bioactive compounds such as tryptophan and protocatechuic acid. Hence, purple rice may be considered as a source of bioaccessible phenolic and antioxidant compounds. • Bioaccessible rice polyphenols evaluated using UHPLC-online ABTS.•+ system. • Significant phenolic content and antioxidant activity retained after digestion. • Anthocyanins extracted in the gastric phase but degraded in the intestinal phase. • PCA and tryptophan had significant bioaccessible content and antioxidant activity. [ABSTRACT FROM AUTHOR]

Cassava is mainly grown for its roots whereas leaves are mostly considered as a byproduct. Cassava leaves are a rich source of protein, minerals, and vitamins. However, the presence of antinutrients and cyanogenic glucosides are the major drawbacks in cassava leaves which limit its human consumption. These antinutrients and toxic compounds of cassava leaves cause various diseases depending on the consumption level. Hence these antinutrients and toxic potential of cassava leaves should be addressed during cassava leaf processing (CLP) before human consumption. Several CLP methods have been developed but every method has its own limitations. Some CLP methods successfully detoxify cassava leaves but simultaneously destroy the nutrients. Efforts have also been made for cassava leaf protein extraction in the form of cassava leaf protein concentrate (CLPC) but protein recovery was very low. This review summarizes the nutrient, antinutrient and toxic composition of cassava leaves, CLPC, different CLP methods, human consumption and diseases caused by cassava leaves. Furthermore, recommendations have been made in order to encourage cassava leaves consumption as an important source of protein and micronutrients. [ABSTRACT FROM AUTHOR]

• Cultivar, leaf position, and plant age affected cassava leaves qualities. • The middle leaves of Rayong 5 cultivar at 6-months-old provided the highest contents of nutrients. • Cassava leaves provide high protein, glutamine, aspartic acid, and leucine but show a lack in methionine and cysteine. • Cassava leave is a good source of bioactive compounds. • The total cyanide contents in all cassava leaves were high. The variation of proximate compositions, amino acids, carotenoids, chlorophyll, and total cyanide contents in cassava leaves was studied to identify the most suitable leaves for human consumption. The cassava leaves from 4 cultivars were analysed at 3 leaf positions as well as at 2 plant ages. The leaves of 'Rayong 5' cultivar from the middle position at 6 months after planting contained the highest crude protein, amino acids, carotenoids, and chlorophyll. The total cyanide content was high and therefore, an effective detoxification method is needed. Protein from the cassava leaves was rich in glutamine, aspartic acid, and leucine, but low in methionine and cysteine. Additionally, cassava leaves were found to be a rich source of carotenoids and chlorophyll. This study provided the evidences that cassava leaves can be an alternative source as protein supplement and for carotenoids and chlorophyll extraction and paves the way to valorise this abundant agricultural by-product. [ABSTRACT FROM AUTHOR]

Abstract: In the present work we evaluated five enzyme-mixtures (Protex 7L, Alcalase 2.4L, Viscozyme L, Natuzyme, and Kemzyme) for their effectiveness in extracting the oil and protein recovery from sesame seeds during an enzyme-assisted aqueous extraction (EAAE) process. Alcalase 2.4L was found to be the best for attaining a high oil yield (57.4% of the total oil content in the seed), whereas, the maximum amount of protein (87.1% of the total seed protein), was recovered in the aqueous phase with Protex 7L. The quality attributes such as fatty acids profile, density, refractive index, free fatty acid contents, iodine value, colour, saponification number and unsaponifiable matter of the sesame oil, extracted by aqueous enzymatic process, were comparable with that of the control (oil extracted without enzyme treatment) and hexane-extracted oil (HEO), revealing no significant (p> 0.05) variations among oils, produced by either of the methods. The oxidative stability state of the enzyme-extracted oil (EEO) was noted to be considerably improved relative to the control and HEO. The amount of tocopherols for the oils, produced by the enzyme–adjuvant was found to be higher than the control and HEO. An appreciable increase in the antioxidant activity as assessed by determinations of total phenolic contents, DPPH radical scavenging capacity, and inhibition of linoleic acid oxidation of EEO was also established. Overall, the present results revealed improvement in the quality of the EEO while a major portion of the food grade protein was also extracted in the aqueous phase. [ABSTRACT FROM AUTHOR]

Cassava foam, another form in which cassava may potentially be used as food, was produced from the pulp of yellow-flesh and white-flesh cassava varieties by whipping with foaming agent (20 %w/w glycerol monostearate colloid, GMS) and stabilizer (sodium carboxymethyl cellulose, NaCMC). Cassava foaming was optimized for concentration of foaming agent, stabilizer and whipping time. Using Box-Behnken experimental design, two responses were measured: foam expansion (FE, %) and foam density (FD, g/mL). White-flesh cassava pulp required 14.97% GMS, 0.51% NaCMC and 2.07 min to give a foam of 52.63% expansion and density of 0.75 g/mL. Yellow-flesh cassava pulp required 14.29% GMS, 0.6% NaCMC and 2 min to yield a foam of 48.25% expansion and density of 0.76 g/mL. Predicted optimal FE and FD were 54.9% and 0.73 g/mL for white-flesh cassava foam, and 49.86% and 0.73 g/mL for yellow-flesh cassava foam, respectively, and are close to validated values. The optimal foams were quite stable after 4 h at 25 ± 2 °C, with low volume collapse of 1.79% and 1.26% for white and yellow cassava foams, respectively. The optimal cassava foams were dried into foam powder. There was significant difference in color values (L*, a*, b*, C*, E*, H*, % W, Δ E y e l l o w − w h i t e ∗ ) and total carotenoids content of pulp, optimal foam, and powder of both varieties. Microstructure analysis of the optimal foams revealed round air bubbles and positive skewed distribution of bubble sizes. Foaming and drying significantly reduced total cyanogenic potential in cassava, and may be considered as processing operations capable of reducing cyanogenic potential in cassava considerably. Image 1 • Process variables for foaming of cassava were optimized and experimentally validated. • A comparison of the properties of cassava pulp, foam and foam powder were evaluated. • The cyanogenic potential of cassava was significantly reduced by foaming and drying. [ABSTRACT FROM AUTHOR]

This study focused on the optimization of enzymatic treatments of cassava tuber peels to enhance hydrolysis and therefore improve the peeling process. A commercial enzyme was applied on the cassava peels. The parameters of the enzymatic treatments comprising temperature, pH, incubation time, and dose of enzyme were varied using the response surface methodology by the central composite design to optimize the enzymatic treatment of cassava peels. The glucose content and total soluble solids were determined as response factors for screening the enzymatic treatment efficacy. After 30 runs of enzyme treatments in the central composite design, multivariate correlation of the glucose content was established with R 2 at 0.956 and MAPE at 1.14 %. Results show that glucose content and total soluble solids were significantly (p < 0.05) affected by the enzyme dose and incubation time. Under optimal conditions the maximum glucose content, the maximum soluble solids and the loss in peel thickness were 21.2 %, 2.5 °Bx and 1.74 ± 0.2 mm, respectively, at a pH of 4.5, a temperature of 49.8 °C, an incubation time of 3.9 h and the addition of 1.25 mL enzyme per 1 g of cassava peels. Further investigation of enzyme treatment efficiency on peeling of cassava tuber was conducted under optimum conditions. Results showed that enzyme treatment can improve the peeling process of cassava tuber, with a reduction of peeling time to 75.0 ± 21.5 s and an increase of peeling yield to 82.0 ± 1.9 %. Image 1 • Optimal conditions of enzyme treatment were identified for hydrolysis of cassava peels. • Hydrolysis of cassava peels was optimized by maximizing glucose content to 21.2 %. • SEM study verified structural alteration of cell walls by enzyme treatment. • Enzyme treatment shows potential to facilitate the peeling of cassava tubers. • Enzyme treatment did not influence the texture of cassava tubers. [ABSTRACT FROM AUTHOR]

Jatropha curcas L. shelled seeds (kernels) have been gaining attention as protein source due to their high protein content. However, due to the soft texture, screw pressing the kernels resulted in a low performance, which was indicated by high residual oil content in the press cake. In order to overcome the low oil recovery from the extraction process, J. curcas kernels blended with rapeseed, maize or soybean as additives were studied. The blending effects on the performance of mechanical oil extraction, along with the quality of oil and press cake were evaluated. To achieve the maximum oil recovery, blending ratio, nozzle diameter and screw speed were optimised using response surface methodology. Higher blending ratio showed significantly higher oil recovery ( p < 0.05). Soybean blend exhibited highest oil recovery of 91.0%. Specific energy requirement and oil recovery were negatively correlated with throughput. Oil from maize blend generated the highest acid value and free fatty acid of 8.39 mg KOH/g and 4.19%, respectively. Carbon residue of the sedimented oil from all material blends fulfilled the standard threshold of German Institute for Standardization (DIN 51605). The highest press head temperature of 104.6 °C was observed from soybean blend. The ash content of the press cake from pure J. curcas kernels was lower than the other material blends. Press cake from soybean blend revealed low pepsin insoluble nitrogen and high crude protein content, pepsin plus trypsin digestibility and available lysine. Regarding the antinutritional factors, press cake from rapeseed blend showed highest phytate and trypsin inhibitors of 4.1% and 22.7 mg trypsin inhibited/100 mg sample, respectively. In terms of oil recovery and press cake quality, soybean appears to be the most suitable additive compared with rapeseed and maize. [ABSTRACT FROM AUTHOR]

Since drought stress and low WUE both influence fruit quality, the corresponding relationship between water supply and synthesis of bioactive compounds requires investigation. In this study, the effect of regulated deficit irrigation (RDI) and partial root-zone drying irrigation (PRD) techniques on the lycopene, β-carotene, vitamin C, and total phenolic (TPC) contents in two tomato cultivars ( Matina and Cochoro ) were investigated. Antioxidant activity was evaluated using DPPH, FRAP and TEAC assays. Deficit irrigation treatments affected plant growth as well as yield, quality, and antioxidant contents of fruits. However, the effects on content of antioxidants were cultivar-dependent. Vitamin C and lycopene contents in Matina significantly increased, while values decreased in Cochoro under both PRD and RDI. TPC and β-carotene contents increased in both cultivars, but a greater increment of TPC (+88.1%fw) was recorded in Cochoro . Overall, vitamin C and TPC were found to be the main contributors to the total antioxidant activity in fruits. The study suggested that choice of appropriate cultivars subjected to deficit irrigation strategies can significantly influence the bioactive compounds, particularly vitamin C, lycopene, and TPC. [ABSTRACT FROM AUTHOR]

The aim of the study was to investigate quality and shelf life of beef meat cooked under sous vide conditions then extended refrigerated storage for 10 weeks. Biceps femoris (n = 6) from six to seven year old cows were treated with 2 g/L ginger powder (GP) containing zingibain or control (no injection) and were then cooked in sous vide conditions at 65 °C for 1 h or 8 h. Cooked samples were evaluated for physicochemical (pH, total water content, cooking loss, Warner-Bratzler shear force (WBSF), texture profile analysis (TPA), L *, a* , b * properties and thiobarbituric acid reactive substance (TBARS)), microstructure (scanning electron microscopy) and microbiological (Brochothrix thermospacta, Clostridium perfringens , Lactic acid bacteria, Listeria monocytogenes, Salmonella spp , and yeasts and moulds) quality after vacuum packing, cooking, then refrigerated storage at 4 °C for 0, 2, 4, 8 or 10 weeks. Physicochemical parameters were improved by GP treatment (P < 0.05) while there was no effect of storage time on WBSF, TPA or microstructure. The microbial quality of sous vide cooked meat in refrigerated storage appeared to be four weeks and oxidation shelf life of the cooked meat was found to be two weeks under refrigerated storage. [ABSTRACT FROM AUTHOR]

Papaya has been identified as a valuable source of nutrients and antioxidants, which are beneficial for human health. To preserve the nutritional properties after drying, appropriate storage specifications should be considered. This study aimed to investigate the quality and stability of air-dried papaya in terms of quality dynamics and behavior of bio-active compounds during storage for up to 9 months in two packaging materials: aluminum laminated polyethylene and polyamide/polyethylene. Samples with moisture content (MC) of 0.1328 g g −1 and water activity ( a w ) of 0.5 were stored at 30 °C and relative humidity (RH) of 40–50%. The MC, a w , degree of browning (DB) and 5-hydroxymethylfurfural (HMF) content were found to notably increase as storage progressed. On the contrary, there was a significant decrease in antioxidant capacity (DPPH, FRAP and ABTS), total phenolic (TP) and ascorbic acid (AA) contents. Packaging in aluminum laminated polyethylene under ambient conditions was found to better preserve bio-active compounds and retard increases in MC, a w and DB, when compared to polyamide/polyethylene. [ABSTRACT FROM AUTHOR]