Quality Evaluation of Custard Produced from Blends of Sweet Potato and Corn Starch Enriched with Defatted Soybean

Custard is a thick, rich, creamy sweet or savory dessert, made mixtures of eggs or egg yolks, milk or cream and commonly consumed in most part of Africa especially Nigeria. This research was carried out to determine the physicochemical properties and sensory characteristics of custard produced from the blends of sweet potato and corn starch enriched with defatted soybean flour. The sweet potato was peeled, washed and diced into small cubes to aid milling while the maize grains were cleaned and soaked in water for 24 hours, and they were separately milled and filtered. The filtrates were allowed to settle for four hours, the starches were obtained and dried at 70°C and 60°C for 8 hours and 5 hours respectively. The soybean was cleaned, soaked, boiled, toasted, dehulled, milled and defatted in petroleum ether. Ten custard samples were then formulated using sweet potato starch, corn starch and defatted soybean flour respectively in the following ratios: 100:0:0; 80:10:10; 70:20:10; 60:30:10; 50:40:10; 40:50:10; 30:60:10; 20:70:10; 10:80:10; 0:100:0. The custard formulations were evaluated for their physicochemical and sensory characteristics, using commercial custard (Checkers custard) as control. The result of the proximate composition showed that moisture, ash, crude fibre, crude protein and carbohydrate content in % ranged from 5.40-18.08, 0.70-3.07, 1.16-6.52, 0.82-5.23, 1.31-9.91 and 68.87-85.25, respectively. The functional properties also showed that least gelation concentration (%), bulk density (g/cm), swelling power and gelatinization temperature (oC) ranged from 4.00-10.00; 0.59-0.83; 6.37-8.02 and 69.2-80.1, respectively. The result showed that the swelling power differed significantly (p<0.05) from each other and some of the samples differed significantly in bulk density, least gelation and gelatinization temperature, respectively. Sensory evaluation carried out on different samples of the custard formulation showed that the control sample (Checkers custard) had the highest score of overall acceptability. The 100% corn starch and 100% sweet potato starch were accepted by the consumers as an alternative to the commercial custard product. The enrichment of custard with soybean contributed to an increase in the nutritional value of the custard.

Tailoring Physical and Sensory Properties of Tofu by the Addition of Jet-Milled, Superfine, Defatted Soybean Flour

The use of defatted soybean flour (DSF) in food as a source of dietary fiber has been limited due to its rough texture and bitter taste. Our previous work indicates that superfine DSF prepared by jet milling could overcome these problems, as it positively affected physical and sensory properties. Therefore, differently sized DSFs were incorporated in tofu, and their impacts on physical and sensory properties were investigated in this study. Coarse DSF (Dv50 = 341.0 µm), fine DSF (Dv50 = 105.3 µm), and superfine DSF (Dv50 = 5.1 µm) were prepared by conventional sifting and jet milling. Tofu was made with a 5% addition of differently sized DSFs and without DSF (control tofu). The quality of tofu was evaluated by scanning electron microscopy, color measurement, texture profile analysis, and quantitative descriptive analysis. The tofu made with coarse and fine DSF showed negative changes in its physical and organoleptic qualities, such as reduced yields, a less pure color, a harder texture, and a rougher mouthfeel. However, the tofu made with superfine DSF showed only minimal changes in its qualities compared to the control. Therefore, superfine DSF is a promising fiber supplement that does not change the physical and sensory properties in the making of high-quality tofu.

The Effect of Thermo-Chemical Treatment on the Water Resistance of Defatted Soybean Flour-Based Wood Adhesive

The aim of this study was to effectively improve the water resistance of a defatted soybean flour (DSF)-based adhesive by subjecting DSF to thermo-chemical treatment in the presence of sodium dodecyl sulfate (SDS), and then the crosslinking with epichlorohydrin-modified polyamide (EMPA). The effect of thermo-chemical treatment on the structures and properties of the DSF and DSF-based adhesive were investigated by plywood evaluation, boiling-water-insoluble content, and acetaldehyde value measurements, as well as FTIR, X-ray photoelectron spectroscopic (XPS), X-ray diffraction spectroscopy (XRD), thermogravimetric analysis (TGA), and rheology analyses. The test results revealed that the water resistance of the DSF-based adhesive was significantly improved, attributed to the formation of a solid three-dimensional crosslinked network structure resulted from the repolymerization of DSF, the Maillard reaction between the protein and carbohydrate, and chemical crosslinking between the crosslinker and DSF. Moreover, SDS destroyed the hydrophobic interactions within protein and inhibited macromolecular aggregations during the thermal treatment. Therefore, more reactive groups buried within the globular structure of the soybean protein component of DSF could be released, which supported the repolymerization, Maillard reaction, and chemical crosslinking of DSF, thereby leading to an improved crosslinking density of the cured DSF-based adhesive. In addition, the adhesive composed of thermo-chemically treated DSF and EMPA exhibited preferable viscosity and viscosity stability suitable for the production of wood composites.