Development and evaluation of nutritious rice-based pasta from low grade milled rice
Abstract
Rice-based gluten-free pasta with albumen as a structure building ingredient has not only come to be used as an appropriate nutritional intervention for people with various forms of gluten intolerance, but has the potential to be used in the management of burns in children. The aim of the study was to develop and evaluate nutritious rice-based pasta from low-grade milled rice fortified with soy and orange-fleshed sweetpotato flour. Four different formulations based on pre-gelatinized rice flour and liquid egg albumen, and containing soybean and/or sweet potato (up to 20%) were prepared using a single screw extruder at 25°C and oven-dried for 17 hours at a temperature of 65°C. Biochemical characterisation (Bradford test, SDS-PAGE electrophoresis, in-vitro protein digestibility and accessible thiols), cooking indices (cooking time, cooking loss and water absorption capacity), as well as sensory evaluation using e-nose and tongue were carried out on the developed pasta. The results showed significant differences (p<0.05) in the amount of proteins solubilised using the three different buffer treatments (saline, urea and urea/DTT buffer) for the Bradford test and thiol reactivity an indication of the presence of protein aggregates stabilized by hydrophobic interactions and disulphide bonds in all pasta samples, and a higher network-forming ability in soybean-enriched pasta, that may explain the lower cooking losses of this specific sample. Pasta with rice and soy had the highest protein digestibility, followed by pasta with rice only. Soybean and sweet potato enrichment resulted in a decrease in the pasta consistency and in significant changes in the color of the resulting samples. In particular, soybean clearly affected pasta yellowness, whereas the addition of sweet potato resulted in a significant decrease in lightness and an increase of redness, most likely as a result of Maillard-type browning reactions. Also, significant differences (p<0.05) existed in the cooking loss (9.07-10.50)g/100, water absorption (67.20-72.10)g/100g and firmness (233.61-535.87)N of the pasta samples produced. E-sensing approaches indicated that the sensory profile of the various pasta products strongly depends on the peculiar enrichment. Sweet potato increased the pasta astringency, whereas soybean enrichment resulted in a typical umami taste and a specific electronic nose response. The results from this study indicate that the different treatment/ingredient combinations significantly affect both nutritional and functional properties of the rice-based pasta. These findings will be useful in designing and producing gluten-free snacks that satisfy the consumers’ expectations. The development of innovative enriched rice products is a promising way to exploit low-grade African rice varieties.
Description
A thesis submitted to the School of Graduate Studies, Kwame Nkrumah University of Science and Technology in partial fulfillment of the requirements for the award of the Degree of Master of Philosophy in Human Nutrition and Dietetics.