An investigation into the composition and nutritional properties of a mixed seed food product
Radhi, Khadija Samir
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Maintaining an adequate food supply remains a global challenge, with hundreds of thousands of lives lost each year because of malnutrition, especially in developing countries. Although malnutrition tends to be more common in these countries, where there are shortages of food, in industrialised countries, more and more people are being diagnosed with malnutrition caused by food allergies. The main approach to managing allergies is to avoid certain foods, which may also lead to inadequate food intake and malnutrition. The first aim of this study was to develop a nutritional, ambient-stable, confectionary product containing seeds, nuts, and treacle with raw materials that are readily available in Middle Eastern and African countries. The second aim was to determine the effect of different thermal processing methods on the product with respect to Maillard reaction products (MRP) and antioxidant properties. The third aim was to measure the effect of different thermal processing methods and additives on the composition, solubility, structure, and immune reactivity of peanut allergens extracted from the product. The fourth aim was to test the effect of additives such as sodium bisulphite and ascorbic acid on the structure and allergenicity of peanut proteins. The second chapter of the thesis addresses product development based on literature-derived information of the proximate composition of various ingredients, including peanuts, sesame seeds, Nigella seeds, and treacle. The composition of the final product, called the black seed mix, was analysed by proximate analysis using approved AOAC methods. The amino acid composition was analysed by HPLC and the fatty acid composition by GC and minerals by atomic absorption spectroscopy. It was demonstrated that the product contains significant quantities of fat, carbohydrate, fibre, linoleic acid, protein and essential amino acids, magnesium, zinc and iron, to meet nutritional requirements for selected age groups. The third chapter deals with shelf stability and sensory analysis of the product. Water activity measurements of the fresh product, combined with knowledge of sugar content, led to categorisation of the product as a chewy, sweet confection. Texture analysis of the fresh product fell within an acceptable range, and the sensory evaluation proved to be acceptable. The vacuum -packed product was stable after one month’s storage under accelerated storage conditions (37°C). However, after 2 month’s storage, the product showed increased water activity, texture hardness, fracturability and cohesion strength, but this was still within an acceptable range according to published criteria. The peroxide value of fats also increased after 2 months accelerated storage, which was regarded as a limiting factor. The fourth chapter addresses the effect of different processing conditions on extracts of the black seed mix on Maillard reaction products (MRP; measured by spectroscopic absorbance and fluorescence), antioxidant activity (radical scavenging, ferric reducing and inhibition of lipid peroxidation measured by DPPH, FRAP, FTC, and TBA methods), and solubility (Bradford and Kjehldahl methods). The roasted product showed increased third stage MRP, which correlated with improved radical scavenging activity, similar ferric reducing activity but reduced inhibition of lipid peroxidation ability compared to the control and boiled sample. The boiled product resulted in higher intermediate-stage MRP, increased radical scavenging ability, reduced ferric reducing ability and increased inhibition of lipid peroxidation ability. The fifth chapter deals with the effect of processing and the addition of additives to the black seed mix on immune reactivity of peanut allergens (peanut-allergic patient sera) using the ELISA, SDS-PAGE, and Western Blot techniques. The results indicate that extract from the roasted product caused increased immune reactivity. I also report the loss of soluble peanut 7S and 11S in extracts from the boiled version, leading to reduced immune reactivity for the soluble fraction (ELISA and Western blot). I demonstrated that the addition of the approved food additive sodium bisulphite to the black seed mix lowers the immune reactivity of peanut allergens by ELISA, which was caused by reduction of disulphide bonds of the 11S peanut allergen as determined by SDS-PAGE. It is concluded that the preferred thermal processing method of the black seed mix would be boiling of the peanuts before addition to the rest of the ingredients and further processing.