Evaluation of a low-resource soy protein production method and its products.

Introduction: One key approach to achieve zero hunger in Sub-Saharan Africa (SSA) is to develop sustainable, affordable, and green technologies to process nutritious food products from locally available sources. Soybeans are an inexpensive source of high-quality protein that may help reduce undernutrition, but it is underutilized for human consumption. This research evaluated the feasibility of a low-cost method developed initially at the United States Department of Agriculture to produce soy protein concentrate (SPC) from mechanically pressed soy cake and thus create a more valuable ingredient to improve protein intake in SSA. Methods: The method was initially tested in the bench scale to assess process parameters. Raw ingredients comprised defatted soy flour (DSF), defatted toasted soy flour (DTSF), low-fat soy flour 1 (LFSF1; 8% oil), and LFSF2 (13% oil). Flours were mixed with water (1:10 w/v) at two temperatures (22 or 60°C) for two durations (30 or 60 min). After centrifugation, supernatants were decanted, and pellets were dried at 60°C for 2.5 h. Larger batches (350 g) of LFSF1 were used to examine the scalability of this method. At this level, protein, oil, crude fiber, ash, and phytic acid contents were measured. Thiobarbituric acid reactive substances (TBARS), hexanal concentration and peroxide value were measured in SPC and oil to evaluate oxidative status. Amino acid profiles, in vitro protein digestibility, and protein digestibility corrected amino acid score (PDCAAS) were determined to assess protein quality. Results: Bench scale results showed accumulation of protein (1.5-fold higher) and reduction of oxidative markers and phytic acid to almost half their initial values. Similarly, the large-scale production trials showed high batch-to-batch replicability and 1.3-fold protein increase from initial material (48%). The SPC also showed reductions in peroxide value (53%), TBARS (75%), and hexanal (32%) from the starting material. SPC's in vitro protein digestibility was higher than the starting material. Conclusion: The proposed low-resource method results in an SPC with improved nutritional quality, higher oxidative stability, and lower antinutrient content, which enhances its use in food-to-food fortification for human consumption and is thus amenable to address protein quantity and quality gaps among vulnerable populations in SSA.

Evaluation of Oxidative Stability of Full Fat Soybean Flour in Storage and Sensory Quality of Tuo Zaafi-Enriched with Soy Flour as Influenced by Traditional Processing Methods.

The oxidative stability of pretreated full-fat soybean flour (FFSF) was evaluated under commercial (Experiment I) and accelerated conditions (Experiment II). In Experiment I, soybeans were pretreated using germination, soaking (24 h), or roasting (110-120 °C), and the dried, milled FFSF was stored for 120 days under commercial storage conditions in two cities in Ghana. Acid value (AV) and peroxide value (PV) were determined. The proximate and sensory quality of Tuo Zaafi, a maize-only dish in northern Ghana enriched with 10-30% of the pretreated FFSF, was assessed. Before storage, all samples had similar PV (1.907-4.305 mEq/kg oil); however, the AV of the germinated sample was higher than that of the unprocessed samples (10.83 vs. 3.13 mgKOH/g oil; p < 0.001). After storage, although AV fluctuated, the PV was similar (2.39-3.74 mEq/kg oil; p = 1.00). Storage location showed no significant differences in terms of AV (4.96-4.97 mgKOH/g oil; p = 0.994), unlike PV (2.07-3.55 mEq/kg oil; p < 0.001). Increasing the levels of the pretreated FFSF in Tuo Zaafi resulted in lower consumer preference scores for all sensory attributes. In Experiment II, FFSF samples (dehulled and nondehulled) prepared from germination, soaking (18 h and 24 h) and roasting were evaluated under accelerated conditions (AC) of controlled temperature (45 ± 0.1 °C) and relative humidity (81 ± 1%) for AV, PV, p-anisidine value (pAV), lipoxygenase activity (LOX), color, and moisture. Pretreatment, condition, time, and their interaction affected the oxidative stability of all FFSF samples (p < 0.001). Roasted samples showed the highest increase in AV and pAV in both storage conditions (p < 0.05). Under room temperature conditions (RTC), the roasted and germinated samples had lower LOX activity (p < 0.05) at the end of storage time compared to that of the controls. In conclusion, germination and soaking reduced oxidation of FFSF, while roasting promotes it, despite its common use.