Thermal processing effects on the functional properties and microstructure of lentil, chickpea, and pea flours

Comparative study of the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours as affected by pH

The demand for products of high nutritional value from sustainable sources is growing rapidly in the global food market. In this study, the effect of pH on the functional properties of lupin, green pea, fava bean, hemp, and buckwheat flours was investigated and compared with wheat flour. Functional properties included solubility, emulsifying and foaming properties, gelling ability, and water holding capacity (WHC). All flours had minimal solubility at pH 4 and their corresponding values increased with increasing pH. Emulsifying properties were improved at pH 10 for all samples and emulsion stability showed a similar trend. Increasing pH in the range 4-10 enhanced the foaming properties of the flours, particularly buckwheat and hemp. Wheat, green pea, buckwheat, and fava bean were more capable of forming firm gels compared with lupin and hemp, as indicated by least gelling concentrations (LGCs). The ranking of the water binding properties of the different types of flours were lupin>hemp>fava bean>buckwheat>green pea>wheat. Results indicate that underutilized flours from sustainable plant sources could be exploited by the food industry as functional food ingredients or as replacements of wheat flour for various food applications. Depending on the application, flour functionality may be effectively tailored by pH adjustment.

Effect of thermal treatments on anti-nutritional factors and antioxidant capabilities in yellow soybeans and green-cotyledon small black soybeans

BACKGROUND

The effects of different thermal processes on the anti-nutritional factors (tannins, phytic acids and trypsin inhibitors) and antioxidant capacity of yellow soybeans (YS) and green-cotyledon small black soybeans (GCSBS) were investigated. The soybean samples were subjected to roasting, microwaving and boiling as the thermal treatments.

RESULTS

Sixty-minute boiling was most effective for eliminating the tannins in both YS and GCSBS, and also resulted in the maximal reduction of phytic acids. Trypsin inhibitors were most effectively reduced (76.92-97.91%) by microwaving, and boiling was least favourable for retaining total phenolic content. The total flavonoid content was significantly (P < 0.05) decreased by all thermal processes, and particularly by employing 60-min boiling. The total anthocyanin content of GCSBS was higher than that of YS, but significantly declined upon boiling (P < 0.05). Roasting did not significantly affect the DPPH free radical scavenging activity of GCSBS (P > 0.05). Microwaving increased the FRAP (ferric reducing antioxidant power) of GCSBS up to 6.07%.

CONCLUSION

Our raw GCSBS possesses much better antioxidant capacity than raw YS. Microwaving resulted in a substantial reduction of the trypsin inhibitors of our soybean samples. Dry thermal treatments caused slight increase of FRAP in GCSBS.

Physicochemical, pasting, and functional properties of amaranth seed flours: effects of lipids removal

The present work was carried out to evaluate physicochemical (composition, hunter color, and sodium dodecyl sulfate-polyacrylamide gel electrophoresis [SDS-PAGE]), pasting, and functional properties (foaming, emulsification, water, and fat absorption capacity) of amaranth full-fat flours from 6 lines/cultivars (AFs), and to see the effects of lipid removal/defatting on these properties. Protein, ash, and lipid content of AFs ranged between 12.5% to 15.2%, 3.0% to 3.5%, and 7.1% to 8.0%, respectively. The flours showed a number of bands between 97 and 7 kDa, with main subunits of approximately 58, 37, 33, 31, 23, and 16 kDa in the SDS-PAGE profiles. The protein content and L* value increased, while b* values decreased following defatting for most of the lines/cultivars. The defatted flours (DAFs) had higher final viscosity and stability (lower breakdown viscosity) as compared to counterpart AFs. The protein profiling of the flours was not affected with the lipid removal/defatting. However, water absorption capacity and foam stability of the flours improved upon defatting. Principal component analysis revealed that pasting temperature was positively related to lipid content, while breakdown viscosity was negatively related to protein content. Foaming properties (capacity and stability) showed negative relationship with lipid content, and positive with protein content, ash content, water, and fat absorption capacity.

PRACTICAL APPLICATION

Amaranth grains are known to have higher amount of proteins and lipids than cereals. Amaranth lipids are rich in unsaturated fatty acids, which are prone to oxidative rancidity. Removal of lipids or defatting of flours may be carried out to enhance product shelf life by preventing undesirable oxidative chain reactions. Therefore, this research was undertaken to see the effects of defatting on the functional properties of amaranth flours. The defatting was a value addition process as it improved the functional properties of the flours.

In vitro gastrointestinal digestion of glabrous canaryseed proteins as affected by variety and thermal treatment

Glabrous or hairless canaryseed is a nutritional grain that could be a good addition to the diet if approved as a novel food. To assess the impact of thermal treatment on its digestibility; raw, roasted or boiled flours prepared from three different varieties of glabrous canaryseed were subjected to in vitro gastrointestinal digestion conditions and the effect on protein electrophoretic profiles was examined using sodium dodecyl sulphate polyacrylamide gel electrophoresis (SDS-PAGE). Roasting was done by dry-heat in an oven at 176 °C for 12 min whereas boiling was done in water at 98 °C for 12 min. SDS-PAGE showed approximately twenty-five protein bands in the undigested raw flour with molecular masses (MM) ranging from <14 kDa to >97 kDa. The dominant proteins had low MM, between the ranges of ~57 to 12 kDa. Roasting markedly altered the protein electrophoretic profile with the appearance of large molecular weight aggregates. Canaryseed proteins were more easily digested after thermal treatment and under sequential gastric-duodenal conditions than under gastric or duodenal conditions alone. Furthermore, roasting appeared to have a greater impact on in vitro protein digestibility than boiling.

Nutritional Profile and Carbohydrate Characterization of Spray-Dried Lentil, Pea and Chickpea Ingredients

Although many consumers know that pulses are nutritious, long preparation times are frequently a barrier to consumption of lentils, dried peas and chickpeas. Therefore, a product has been developed which can be used as an ingredient in a wide variety of dishes without presoaking or precooking. Dried green peas, chickpeas or lentils were soaked, cooked, homogenized and spray-dried. Proximate analyses were conducted on the pulse powders and compared to an instant mashed potato product. Because the health benefits of pulses may be due in part to their carbohydrate content, a detailed carbohydrate analysis was carried out on the pulse powders. Pulse powders were higher in protein and total dietary fibre and lower in starch than potato flakes. After processing, the pulse powders maintained appreciable amounts of resistant starch (4.4%–5.2%). Total dietary fibre was higher in chickpeas and peas (26.2% and 27.1% respectively) than lentils (21.9%), whereas lentils had the highest protein content (22.7%). Pulse carbohydrates were rich in glucose, arabinose, galactose and uronic acids. Stachyose, a fermentable fibre, was the most abundant oligosaccharide, making up 1.5%–2.4% of the dried pulse powders. Spray-drying of cooked, homogenized pulses produces an easy to use ingredient with strong nutritional profile.