Improved storage and eat-ripe quality of avocados using a plant protein-based coating formulation

Coating comprising the plant protein, kafirin, propylene glycol (PG) and glucono-delta-lactone (GDL) have been shown to extend the quality of ‘Packham’s Triumph’ pears. In this study, both of these coating treatments considerably extended the shelf-life and the time that the eat-ripe quality of ‘Hass’ avocados was maintained when compared to uncoated fruit. To determine the roles of the additives, PG and GDL in the functionality of kafirin edible coatings, different kafirin coatings were applied to ‘Hass’ avocados prior to storage under ripening conditions of 18 °C for up to 21 days. All the kafirin coatings were effective at extending and maintaining the shelf-life quality of avocados compared to uncoated fruit due to reduced respiration rate, 102 ml CO2/kg/h for kafirin-PG+GDL compared to 115 ml CO2/kg/h uncoated avocados on day 14 and consequently reduced ethylene production of the coated fruit. Kafirin-PG+GDL coated avocados lost less weight and remained firmer than uncoated fruit. Descriptive sensory analysis showed kafirin-PG+GDL coatings were most effective, extending the quality of the avocados 7 days beyond the untreated control due to improved kafirin solvation facilitated by the GDL. Thus kafirin-PG+GDL coatings are an effective method of increasing shelf-life and extending the eat-ripe quality of climacteric fruit.South African National Research Foundation.http://www.wageningenacademic.com/loi/qashb2016Food Scienc

Effect of micronisation temperature (130 and 170 °C) on functional properties of cowpea flour

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Effects of gamma irradiation and stearic acid, alone and in combination, on functional, structural, and molecular characteristics of high amylose maize starch

The effects of gamma irradiation and stearic acid, alone and in combination, on functional, structural, and molecular characteristics of high amylose maize starch (Hylon VII, 60% amylose) were studied. Stearic acid (0, 1.5, and 5%) was added to Hylon VII starch, and then irradiated at 0, 30, and 60 kGy. Gamma irradiation significantly (p 0.05) increased solubility, water absorption capacity, and oil absorption capacity as well as decreased swelling power (at 90 and 95°C) of Hylon VII starch. These changes related well with increased amylose and decreased amylopectin content, decreased MW, and decreased transition endotherms of the starches due to gamma irradiation. Stearic acid addition significantly increased (p 0.05) water and oil absorption capacities, relative crystallinity as well as decreased solubility and swelling power of Hylon VII. Gamma irradiation had more effect on the molecular structure of Hylon VII compared with stearic acid. Gamma irradiation alone and with stearic acid did not seem to change the XRD pattern and microstructure of Hylon VII. The similar XRD pattern and morphology observed for irradiated and non-irradiated Hylon VII suggests that gamma irradiation depolymerizes amylose, and amylopectin mostly in the amorphous region of the starch to produce less branched or unbranched amylopectin. Gamma irradiation with stearic acid has potential in Hylon VII modification.This research was funded in part under the International Atomic Energy Agency (IAEA) Technical Cooperation (TC) project and Ghana Atomic Energy Commission (GHA/0/010, Government of Ghana).http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1521-379Xhb201

Relating physico-chemical properties of frozen green peas (Pisum sativum L.) to sensory quality

BACKGROUND : The acceptability of frozen green peas depends on their sensory quality. There is a need to relate physico-chemical parameters to sensory quality. In this research, six brands of frozen green peas representing product sold for retail and caterer’s markets were purchased and subjected to descriptive sensory evaluation and physico-chemical analyses (including dry matter content, alcohol insoluble solids content, starch content, °Brix, residual peroxidase activity, size sorting, hardness using texture analysis and colour measurements) to assess and explain product quality. RESULTS : The sensory quality of frozen green peas, particularly texture properties, were well explained using physico-chemical methods of analysis notably alcohol insoluble solids, starch content, hardness and °Brix. Generally, retail class peas were of superior sensory quality to caterer’s class peas although one caterer’s brand was comparable to the retail brands. Retail class peas were sweeter, smaller, greener, more moist and more tender than the caterer’s peas. Retail class peas also had higher °Brix, a*, hue and chroma values; lower starch, alcohol insoluble solids, dry matter content and hardness measured. CONCLUSIONS : The sensory quality of frozen green peas can be partially predicted by measuring physico-chemical parameters particularly °Brix and to a lesser extent hardness by texture analyser, alcohol insoluble solids, dry matter and starch content.NRF Technology and Human Resources for Industry (THRIP) Programme TP2010071400011http://onlinelibrary.wiley.com/journal/10.1002/(ISSN)1097-0010hb201

Novel in situ evaluation of the role minerals play in the development of the hard-to-cook (HTC) defect of cowpeas and its effect on the in vitro mineral bioaccessibility

Cowpea is a nutritionally important drought-resistant legume in sub-Saharan Africa. It is, however, underutilised, in part due to the hard-to-cook (HTC) defect caused by adverse storage conditions resulting in seeds not softening during cooking. This study introduced a novel evaluation of the potential role that minerals play in the development of the HTC defect. The mineral distribution in the cotyledons of normal and HTC cowpeas were analysed by Proton Induced X-ray Emission (PIXE) spectrometry. The phytate, tannin and total phenolic contents were analysed together with in vitro mineral bioaccessibility. In HTC cowpeas, Ca and Mg were more concentrated in the cell wall-middle lamella area of the parenchyma cells. This, together with the reduction in phytate content, confirmed the ‘phytase–phytate–mineral’ hypothesis as a mechanism for development of the HTC defect. Despite the phytate reduction in stored cowpeas, the HTC defect decreased the bioaccessibility of Ca, Fe and Zn in cowpeas.http://www.elsevier.com/locate/foodchem2016-05-31hb201

Effect of attachment time followed by chlorine washing on the survival of inoculated listeria monocytogenes on tomatoes and spinach

The effect of attachment time (30 min, 24, 48 & 72 h) followed by chlorine washing (200 ppm) on the survival of inoculated Listeria monocytogenes on the surface and sub-surface of tomatoes and spinach were studied. The work was done to determine the efficacy of chlorine to decontaminate surface and sub-surface pathogens that may have come into contact with produce during pre-harvest. Tomatoes and spinach leaves were inoculated with a 6 log cfu/ml 18 h culture of L. monocytogenes ATCC 7644 (LM) on the surface and sub-surface and incubated at 20 oC for either, 30 min, 24, 48 or 72 h. LM attached and survived on the surface and sub-surface structures of both control and chlorine washed vegetables after each attachment time, up to 72 h. Higher levels of LM attachment and survival was however noticed on the sub-surface structures. Chlorine had a greater effect on the LM on the surface structures compared to those in the sub-surface structures, possibly because chlorine was not able to access the sub-surface structures where the pathogens were located. Chlorine was not effective in totally inactivating the surface LM on spinach and tomato. This research indicated that LM could attach to both surface and sub-surface structures of both tomatoes and spinach, within 30 min, and that even after 72 h, it still remained viable.http://www.blackwell-synergy.com

Effect of kafirin protein coating on sensory quality and shelf-life of 'Packham's Triumph' pears during ripening

BACKGROUND: Pears are exported in large quantities from South Africa resulting in large revenues. Minimisation of quality losses once the fruit has reached the export destination is as important as following strict export and distribution protocols. Kafirin can form edible films. An edible coating, made from a 2 % (w/w) kafirin coating solution was applied as a post-havest treatment to retard quality deterioration of ‘Packham’s Triumph’ pears during storage at the typical ripening temperature (20° C). The changes in physic-chemical and sensory quality were studied over a period of 24 days. RESULTS: The kafirin coating was unable to retard the onset of ripening but decreased the respiration rate and retarded the progression of senescence. However, moisture loss was exacerbated in the kafirin-coated fruit during ripening at 20° C especially towards the end of the shelf-life. CONCLUSION: The coating extended the eat-ripe quality of the pears between one and two weeks. However, appearance of the fruit was unacceptable after 14 days of storage in terms of wrinkled skin. Further work is needed to improve the water barrier properties of the kafirin coating by incorporating a wax or triglyceride into the coating formulation or more simply by applying a kafirin coating to waxed fruit.The European Commission (Enviropak project, INCO2: ICA4-CT-2001-10062) and CSIR Biosciences.http://www.soci.or

Microstructure of protein bodies in marama bean species

Marama bean is an underutilised indigenous legume from Southern Africa. The understanding of the microstructure of marama protein bodies, the organelles of protein storage, is an important step towards the characterisation and utilisation of its protein. The protein body structures of two species of marama bean (Tylosema esculentrum and Tylosema fassoglense) were determined in comparison with soya bean (Glycine max). T. fassoglense seemed to have higher protein content than soya. Marama showed clustered spherical protein bodies surrounded by lipid bodies similar to soya bean. T. esculemtum seemed to contain smaller sized (4 ± 2 µm) protein bodies per cell as compared with T. fassoglense (7 ± 4 µm), Marama protein bodies contained spherical globoid and druse crystal inclusions, which were absent in soya. P, K, Mg and Ca were the major minerals in marama, which probably originated mainly from storage protein sites. The protein body structure of marama is similar to soya in terms of spherical shape and localisation within the parenchyma cells.EU MARAMA II PROJECT (Contract no.: 032059)http://www.elsevier.com/locate/lwtnf201

Nutritional quality and antioxidant activity of marama–sorghum composite flours and porridges

Marama bean, an underutilised legume in southern Africa, is a good source of protein, fat and phenolic compounds, the latter known to have potential health benefits. Marama flours, sorghum meal, marama– sorghum composite flours and porridges were analysed for proximate composition, amino acid composition, energy value, fatty acid composition, total phenolic content and antioxidant activity. Compositing sorghum meal (70%) with marama flours (30%) significantly increased the protein and fat contents in flours and porridges. Energy values of marama–sorghum composite porridges were 11– 24% higher than sorghum porridge. Lysine content was 3–4 times higher in marama–sorghum porridges than in sorghum porridge. There was an increase in oleic acid as sorghum meal was composited with marama flour. There was a positive correlation between the total phenolic content and antioxidant activity in all samples. Use of marama flour in sorghum composite flours and porridges improved the nutritional quality and antioxidant activity.This research was sponsored by the EU MARAMA II PROJECT.http://www.elsevier.com/locate/foodchemnf201

Sensory and physicochemical analyses of roasted marama beans [Tylosema esculentum (Burchell) A. Schreiber] with specific focus on compounds that may contribute to bitterness

The role of phenolics and saponins in contributing to bitterness in marama beans, an underutilized legume, especially when roasted, was investigated. Marama beans were roasted at 150 C for 20, 25 or 30 min, then dehulled to separate cotyledons, and pastes were prepared from these. Water extracts were prepared from full fat and defatted flours from roasted and unroasted marama cotyledons. A sensory panel evaluated the sensory attributes of marama pastes and water extracts. Marama water extracts were analysed for total phenolic content, phenolic composition and saponin content. Roasting of marama beans for more than 20 min resulted in negative properties, such as bitterness. The major extractable phenolic acids present in marama water extracts were gallic and protocatechuic acids which increased as a function of roasting time. Saponin content of the water extracts was in the range of 55–63 mg/l. The identified phenolic acids, saponins and other as yet unidentified compounds may contribute to the perceived bitterness.http://www.elsevier.com/locate/foodchemhb201