In vivo protein quality of selected cereal-based staple foods enriched with soybean proteins
Sammanfattning
Background: One way to diminish protein malnutrition in children is by enriching cereal-based flours for the
manufacturing of maize tortillas, wheat flour tortillas, and yeast-leavened breads, which are widely consumed
among low socio-economic groups.
Objective: The aim was to determine and compare the essential amino acid (EAA) scores, protein digestibility
corrected amino acid scores (PDCAAS), and in vivo protein quality (protein digestibility, protein efficiency
ratio (PER), biological values (BV), and net protein utilization (NPU) values) of regular versus soybeanfortified
maize tortillas, yeast-leavened bread, and wheat flour tortillas.
Design: To comparatively assess differences in protein quality among maize tortillas, wheat flour tortillas,
and yeast-leavened breads, EAA compositions and in vivo studies with weanling rats were performed. The
experimental diets based on regular or soybean-fortified food products were compared with a casein-based
diet. Food intake, weight gains, PER, dry matter and protein digestibility, BV, NPU, and PDCAAS were
assessed. The soybean-fortified tortillas contained 6% of defatted soybean flour, whereas the yeast-leavened
bread flour contained 4.5% of soybean concentrate.
Results: The soybean-fortified tortillas and bread contained higher amounts of lysine and tryptophan, which
improved their EAA scores and PDCAAS. Rats fed diets based on soybean-fortified maize or wheat tortillas
gained considerably more weight and had better BV and NPU values compared with counterparts fed with
respective regular products. As a result, fortified maize tortillas and wheat flour tortillas improved PER from
0.73 to 1.64 and 0.69 to 1.77, respectively. The PER improvement was not as evident in rats fed the enriched
yeast-leavened bread because the formulation contained sugar that decreased lysine availability possibly to
Maillard reactions.
Conclusions: The proposed enrichment of cereal-based foods with soybean proteins greatly improved
PDCAAS, animal growth, nitrogen retention, and PER primarily in both maize and wheat flour tortillas.
Therefore, these foods can help to diminish protein malnutrition among children who greatly depend on
cereals as the main protein dietary source.