Characterization of ready-to-eat baby foods based on fermented African rice

Rice is a staple in most West African countries and an attractive ingredient for a number of food products as a result of its bland taste, hypoallergenicity, availability, and high digestibility. In this frame, this project aimed at the characterization of a ready-to-eat baby food, based on either milled or parboiled local Togo Marshall rice that was fermented for various times (0, 12, 24, and 48 hours) in the presence of alpha-amylase. The properties of the resulting products were addressed by instrumental sensory analysis and by a combination of physico-chemical, rheological and molecular approaches. Electronic nose gave significantly different responses only in the case of milled rice-based sample fermented for 48 hours, whereas electronic tongue discriminated between samples from either milled or parboiled rice, being these latter more astringent and bitter. An effect of the rice parboiling and of the fermentation time on the baby food properties was also highlighted by the WAI and the WSI. As expected, pH and titratable acidity correlated well with the fermentation time. As for the pasting properties, investigated by microviscoamylograph, parboiled rice-based products show a lower viscosity both when heated-up and cooled-down, as a result of the starch gelatinization occurred during the parboiling process. A viscosity increase during fermentation - most likely due to the synthesis of exopolysaccharides by lactic acid bacteria - was evident only in milled rice-based samples. As for molecular approaches, protein aggregation studies indicate that the amount of soluble proteins clearly decreases at higher fermentation times, suggesting the degradation of proteins into peptides. In particular, most of protein hydrolysis events are completed after 12 hours fermentation in the case of milled rice, whereas peptide release is much slower in parboiled rice-based samples. Fermentation also resulted in a slight decrease in the amount of accessible thiols only in the case of milled rice-based samples. Rice parboiling resulted also in significant differences as for the free sugars content in the various products during fermentation. However, pre-treatments had no peculiar influence on the predicted glycemic index. The application of a multidisciplinary approach to the characterization of differently fermented rice-based food contributed to address the quality parameters of the samples. Differences among samples can be related to rice pretreatment before fermentation, that was carried out in the presence of enzymes. This information can offer some guidelines as for designing specific African low-grade rice- based baby foods with peculiar nutritional properties.