Process Development and Product Characterization of a Fermented Rice-Based Baby Food

Abstract

Oryza glaberrima is a local rice variety that is native to West Africa. Its tough texture and robustness produces milled rice with a large quantity of broken grains when dehusked (polished) accounting for the huge gap in quality. Consequently, imported rice is much more consumed in Ghana than locally cultivated and milled rice. The objective of this study was to add value to local rice by developing and characterizing a rice-based baby food from low grade locally milled and parboiled rice by using simple traditional food processing technologies of fermentation and size reduction. A 2χ 4 factorial design for a local rice cultivar (milled and parboiled) and fermentation time (0, 12, 24 and 48 hours) was used to develop drum dried, pre-cooked fermented rice product as baby food. The physico-chemical, functional and sensory characteristics of the drum dried fermented rice product were evaluated. The drum dried products had moisture content of 5.88 -7.84 % and 5.12 - 11.2 % for milled and parboiled rice respectively. Fermentation time and milling method influenced the physical characteristics of the final products. Parboiled products were lighter in colour (ΔE= 4.27 - 2.69) and showed significantly lower pH values (4.13-3.38) with corresponding higher total acidity values (0.046-0.150)% lactic acid as fermentation time increased. Lower water absorption index (WAI) values and corresponding higher water solubility index (WSI) values were recorded for parboiled products as fermentation progressed due to the incidence of degraded starch molecules. The SDS-PAGE patterns of rice proteins showed three bands corresponding to proteins of molecular weights 14kDa, 30kDa and 45kDa respectively in both milled and parboiled rice samples in all three buffer systems. Protein solubility increased with fermentation time until twelve hours then it decreased through to 48 hours fermentation time. Parboiling and increasing fermentation time also significantly favoured the formation of accessible protein thiols. Pasting profiles of products indicated that milled products had a higher tendency to disintegrate as well as undergo retrogradation and thus were more likely to give thinner gruels when hot water was used for re-constitution than parboiled rice. The 48-hour fermented products from both milled and parboiled rice exhibited the highest protein and starch digestibilities. Sensory profiles revealed altering intensities of sensory attributes of appearance, aroma, flavour, aftertaste and texture (mouth feel and touch sensation) using powdered and re-constituted forms of the eight fermented milled and parboiled rice-based products. Parboiled samples were described as more fermented, rich, sour with sour after-taste as fermentation time progressed by the quantitative descriptive analysis (QDA). Principal component analysis (PCA) scores were used to classify baby food products based on aroma and flavour from quantitative descriptive analysis (QDA) data as well as e-sensing measurements(electronic nose and tongue). These findings suggest that local rice would be very useful as a baby food product and demonstrates the function of quantitative descriptive analysis and e-sensing in evaluating and identifying product attributes that could be essential to consumers and food processors.