Effect of microwave-assisted treatment on proximate, techno-functional, thermal, structural, and storage properties of TGN (Cyperus esculentus L.) flour

BACKGROUND

The use of the emerging technique of microwave-assisted roasting on TGN (TGN) flour was investigated. Tiger nuts were subjected to microwave irradiation at 450, 600, and 900 W each at 5, 10, and 15 min, and milled to flour. The flours were analyzed for proximate, bioactive, techno-functional, morphological, thermal, and storage effects on their composition. An untreated sample was the control.

RESULTS

The results revealed that microwave treatment significantly (P < 0.05) elicited various modifications in the proximate composition and techno-functional properties. The treatment improved the bioactive composition of phenolic content together with the antioxidant activity of the flour. Progressive microwave treatment of TGNs resulted in flours with darker colors and reduced pasting parameters. Structural modification of starch granules, protein denaturation, and starch-protein complexes occasioned by microwave treatment were evidenced in the functional group analysis, including morphological agglomeration, increased particle size, and thermal properties. Treatment also enhanced the microbiological qualities of flour after 8 weeks of storage.

CONCLUSION

This study shows that microwave treatment produces excellent physical modifications that lead to improvements in the nutritional, functional, sensory, and color properties, and safety attributes of TGN flour for food application. This is a development that could present opportunities for novel food formulation by the food industry and related industries. © 2024 Society of Chemical Industry.

Special Issue: Rheology and Quality Research of Cereal-Based Food

New trends in the cereal industry deal with a permanent need to develop new food products that are adjusted to consumer demands and, in the near future, the scarcity of food resources. Sustainable food products as health and wellness promoters can be developed redesigning traditional staple foods, using environmentally friendly ingredients (such as microalgae biomass or pulses) or by-products (e.g., tomato seeds) in accordance with the bioeconomy principles. These are topics that act as driving forces for innovation and will be discussed in the present special issue. Rheology always was the reference discipline to determine dough and bread properties. A routine analysis of cereal grains includes empirical rheology techniques that imply the use of well-known equipment in cereal industries (e.g., alveograph, mixograph, extensograph). Their parameters determine the blending of the grains and are crucial on the technical sheets that determine the use of flours. In addition, the structure of gluten-free cereal-based foods has proven to be a determinant for the appeal and strongly impacts consumers' acceptance. Fundamental rheology has a relevant contribution to help overcome the technological challenges of working with gluten-free flours. These aspects will also be pointed out in order to provide a prospective view of the relevant developments to take place in the area of cereal technology.

High Temperature Rotational Rheology of the Seed Flour to Predict the Texture of Canned Red Kidney Beans (Phaseolus vulgaris)

The pasting profile of starchy tissues is conventionally measured by recording the apparent viscosity (η) in heating/cooling cycles. However, conventional rheometers show critical limitations when the starch is embedded in compact protein-rich cotyledon matrices, as occurs in pulses. In this work, the pasting profile of 13 red kidney beans (Phaseolus vulgaris) from the same cultivar but different growing locations was investigated using a heating/cooling cycle at higher temperature (130 °C) and pressurized conditions, using both water and brine as cooking solvents. It was hypothesized that the continuous measure of η at these conditions of flours from the dry seed would correlate with the texture, as determined by the mini-Kramer cell, of the beans after the entire process of soaking and canning. Furthermore, mechanistic answers were obtained by investigating their composition (starch, protein, and ash content) and physical properties (water holding capacity, seed ratio and weight). Interestingly, as opposed to the pasting profile at 95 °C, pasting indicators at 130 °C, including trough and final viscosity, strongly correlated with starch and protein content, seed coat ratio and, remarkably, with the firmness of the beans after canning when brine was incorporated. These results clearly show that small beans with a high protein content would bring about a more compact matrix that restricts starch from swelling and results in canned beans with a hard texture, which can be predicted by a lower pasting profile of the whole bean flour.

Study of the Effects Induced by Ball Milling Treatment on Different Types of Hydrocolloids in a Corn Starch-Rice Flour System

The effects of ball milling treatment on both the structure and properties of guar gum (GG), tara gum (TG), and methylcellulose (MC) were analyzed prior to assessing their potential interactions with starch components when they are used alone or in blends in a corn starch-rice flour system. X-ray diffraction profiles showed that the ball milling caused a reduction in the crystallin domain and, in turn, a diminished viscosity of the GG aqueous solutions. Despite an increase in its viscosity properties, effects on TG were minimal, while the milled MC exhibited reduced crystallinity, but similar viscosity. When both milled and un-milled hydrocolloids were individually added to the starch-flour system, the pasting properties of the resulting mixtures seemed to be affected by the type of hydrocolloid added rather than the structural changes induced by the treatment. All hydrocolloids increased the peak viscosity of the binary blends (especially pure GG), but only milled and un-milled MC showed values of setback and final viscosity similar to those of the individual starch. Ball milling seemed to be more effective when two combined hydrocolloids (milled GG and MC) were simultaneously used. No significant differences were observed in the viscoelastic properties of the blends, except for un-milled GG/starch, milled TG/starch, and milled MC/milled TG/starch gels.