Starch Modification Differentially Affects the in vivo Protein Quality of Cereal-Based Diets

Abstract

Functional starch modification may help address technical challenges commonly encountered in gluten-free cereals, such as suboptimal texture, reduced volume, and rapid staling, yet it also raises concerns about the protein quality of these grains. This study aimed to evaluate the effects of starch cross-linking and pre-gelatinization on protein quality of gluten-containing (wheat) and gluten-free (corn, millet) cereals in vivo. Eighty-eight weanling Wistar rats were assigned to eleven isocaloric, isonitrogenous dietary groups (8 rats/group): protein-free, casein, and three types of bread flours; wheat, corn, millet, each provided in regular (R), cross-linked (CL), or pregelatinized (PG) forms (10% w/w protein). Over 28 days, body weight gain, nitrogen balance, protein efficiency ratio (PER), true protein digestibility (TPD), and protein digestibility-corrected amino acid score (PDCAAS) as well as serum insulin-like growth factor I (IGF-I) and albumin levels were assessed. Rats fed with cereal-based diets showed significantly (p<0.05) reduced weight gain (40-80%), PER (34-74%), PDCAAS (56-76%), and IGF-I concentrations (25-50%) compared to their casein group counterparts. PER was significantly (p<0.05) decreased in CL and PG wheat (0.52±0.06 and 0.43±0.06) compared to R wheat group (1.09 ±0.03), whereas effects in corn and millet groups were limited. TPD, PDCAAS, and IGF-I tended to decline in CL and PG groups (3-8%, 3-8%, and 22-29% respectively) across all cereals. These results suggest that protein quality in wheat-based diets was reduced by starch cross-linking and pre-gelatinization compared to corn- and millet- based diets. Therefore, starch modification in these gluten-free cereals can enhance industrial applications while preserving protein quality.