Location: Functional Foods Research2021 Annual Report
Objective 1: Develop innovative processes for pulses, pulse fractions, and pulse byproducts to enable increased commercial use of pulse-based ingredients. Sub-objective 1.1: Enhance the nutritional and functional properties of pulse flours, fractions and byproducts by thermomechanical processing treatments alone or in combination with other physical treatments to obtain new pulse-based components and ingredients. Sub-objective 1.2: Enhance the nutritional and functional properties of pulse flours, fractions and byproducts by germination or fermentation in combination with thermomechanical processing treatments and/or chemical modification. Sub-objective 1.3: Enhance the nutritional and functional properties of pulse flours, fractions and byproducts by addition of fats and oils for composite formation, ligands for starch complex formation, or proteins and hydrocolloid gums for flavor, texture, or structure improvement. Objective 2: Resolve the unknown physical and nutritional properties for foods and functional properties for non-foods prepared with increased levels of modified or concentrated pulse ingredients to enable the development of new products. Sub-objective 2.1: Develop food applications from pulse components. Sub-objective 2.2: Develop non-food applications from pulse components.
The dietary benefits of pulses are well established and are increasingly recognized as valuable sources of protein, fiber, antioxidants, and other nutrients. Although the production of pea, bean, and lentil flours and their protein products is increasing, there exist both (1) barriers to more widespread consumer acceptance and (2) a growing need to find uses for pulse processing byproducts such as a starch-rich milling fraction and hulls. Previous studies have shown effects of individual processing methods on pulse seeds, but very little is known about combinations of methods such as combining thermomechanical processing with biological and chemical treatments. The goal of this research is to develop innovative processing methods for pulses and pulse fractions involving combinations of either steam jet-cooking or extrusion with (1) germination and fermentation, and (2) with the strategic addition of exogenous proteins, hydrocolloids, lipids, and functional food ingredients. Research will focus on identifying synergistic treatment effects and utilizing component interactions to enhance the nutritional, structural and functional properties of pulse-based foods and food ingredient products. These new materials will be added to standard food formulations with the goal of maximizing the content of pulse-based ingredients or make totally pulse-based food products with marketable organoleptic properties. Non-food applications will also be investigated for selected pulse fractions based on their physical properties. The results of this research will enable expanded markets for pulse crops and therefore contribute to the sustainability of the pulse-based economy.
Bean cooking water has been used to create edible foams to replace egg whites, as consumer preference for plant-based foods is increasing. For Objective 1, to improve the performance of plant-based foams, navy bean flour was jet-cooked and then sodium palmitate was added prior to centrifuging to obtain a water-soluble fraction containing amylose-sodium palmitate complexes. These fractions were freeze-dried so that the effect of complexes on foaming capacity and foam stability can be determined when compared with freeze-dried water-soluble fractions without added sodium palmitate. Although pulse and cereal flours contain many bioactive components, some are not readily absorbed because they are bound to cellular components and tissue structures. The heat and shear of thermomechanical processing methods can open up the tissue structure and enable the release of nutritional components in the diet. For Objective 1, as a prelude to determining the effects of steam explosion on pulse flours, the technology for laboratory-scale steam explosion was explored in a collaborative project that investigated buckwheat flour. Whole buckwheat flour was steam exploded at 120, 140, and 160 °C with holding times of 0, 15, and 30 minutes. The degree of structural breakdown, uniformity of the processed material, and darkening color of the flour dispersions increased with temperature and holding times. Analysis of structure, antioxidant, phenolic, dietary fiber, color, and water solubility compared to control buckwheat flour obtained after conventional cooking revealed differences between the control and treated samples. Soluble fiber was shown to increase slightly upon 120 and 140 °C treatment relative to the control while the soluble fiber of the 160 °C treatment decreased likely due to degradation. Antioxidant activities of the treated samples were all shown to improve over the control sample. Water solubility of the flour increased at 120 °C while at 140 and 160 °C a significant decrease was observed. The unusual physical properties of processed buckwheat flour reconstituted from the freeze-dried state required modifications to the procedures for analyzing water holding capacity and protein for fiber analysis. Steam explosion treatment could provide potential advantages for food applications such as increased antioxidant ability and soluble fiber and controlling reaction temperatures and times may be useful to modify the flour for specific applications. This collaborative study with buckwheat flour enabled processing methodology development for experiments with pulse flours which are currently underway. Plant essential oils have flavor and insect repellent properties that can be used in food and repellent applications, respectively. However, these oils are generally volatile which prevents them from providing acceptable long-term levels of flavor retention or repellent protection. Therefore, the ability to diminish their volatility and prolong their efficacy is needed. Our research on Objective 1 has demonstrated jet cooked navy bean starch or corn starch can effectively complex 2-undecanone, a volatile oil, to form stable starch inclusion complexes that were spectroscopically characterized. Preliminary experiments show the complexed oil is released more slowly than either the neat oil or a noncomplexed physical mixture of starch and oil. Ongoing research is focused on improving and quantifying the complexes release rates. Fatty acids possessing one carboxylic acid group are well known to complex starch and produce inclusion complexes. In contrast, dicarboxylic acids (contain two carboxylic acid groups) which can serve as potential lipid substrates in parenteral nutrition have different solubility and polarity characteristics than fatty acids and their ability to produce and modify starch inclusion complexes are not well studied or understood. As part of Objective 1, starch inclusion complexes using the 12-, 14-, and 16-carbon alkyl chain dicarboxylic acids were simply prepared in good yield from aqueous media using steam jet cooking technology while the shorter 10-carbon diacid gave low yields of inclusion complexes due to its high water solubility. For comparison, inclusion complexes were also prepared via a traditional laboratory bench-scale alkaline potassium hydroxide method. Both types of complex preparations were characterized using X-ray diffraction data, infrared spectroscopy, differential scanning calorimetry, and extraction techniques to show the dicarboxylic acids were efficiently complexed by starch. Complexes with the 16-carbon ligand formed abundant toroidal spherulites on cooling, which would make the starch more slowly digestible. Characterization of the properties of these novel complexes could provide new opportunities for improving pulse-derived food ingredients. Development of oleogels is necessary to replace food products previously containing trans-fats. Small amounts of natural waxes have been shown to form stable oleogels with soybean oil. Currently combinations of different wax mixtures are being examined to improve oleogel properties. Phase contrast and polarized light microscopy has revealed novel crystalline structure in these gels suggesting specific interaction of wax components during gelation. Hot stage experiments revealed multiple stages of crystal formation during cooling. These structural changes reveal a scaffolding mechanism that contributes to the gel stability and firmness. Since most pulse flours contain very little oil, oleogels may serve as useful additives to pulse components to achieve desirable flavor and texture properties in functional food formulations as proposed in Objective 1.
1. Effect of particle size and cooking method on digestibility of pulse flours. The particle size of pulse flours is known to affect the digestion-resistant starch content, since larger particles contain intact cells that inhibit starch digestion. However, the effect of particle size on protein digestibility and raffinose family oligosaccharides, which are sugars associated with flatulence, has not been studied. ARS researchers at Peoria, Illinois, examined the digestibility of navy bean flours with different particle sizes processed under different moisture conditions. The starch and protein digestibility both decreased by about half in the flour with the largest particle size compared to the smallest particle size. The digestibility was highest in flours cooked in excess water, decreased slightly in baked flours and was much lower in roasted flours. However, neither the particle size nor the cooking method affected the extractability of raffinose family oligosaccharides. These results suggest that reducing pulse flour particle size, which can be addressed by applying various milling technologies, could improve starch and protein digestibility depending on the cooking method used.
2. Pulse processing affects gas production by gut bacteria during in vitro fecal fermentation. Pulses are known to be nutritious and health-promoting, but the perception of pulse consumption causing flatulence and bloating for many people is a barrier to increasing pulse consumption for many people in the U.S. ARS scientists at Peoria, Illinois, in collaboration with University of Nebraska researchers, determined the effect of three types of pulses and seven processing methods on the concentration of gas-producing constituents (raffinose family oligosaccharides, or RFO) in pulses and investigated the production of gas in the large intestine. Processing can be an effective strategy to reduce total gas production by the microbiome in some, but not all, types of pulses, but the reduction of gas-producing components had negative impacts on the gut microbiome due to less carbohydrates available for fermentation. Germination (sprouting) is a processing method that was found to reduce RFO concentrations in Pardina lentils and green peas but not Navy beans. This decreased the abundance of certain bacteria leading to reduced gas production. These results suggest that inclusion of germination in pulse processing is a useful approach for developing food ingredients with less risk of flatulence.
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