Physical characterization and fluidization design parameters of wheat germ

Effect of heat treatments on quinoa germ quality and its storage study

Quinoa is a potential crop to address the situation as it offers a plethora of benefits as it is nutritionally rich and can adapt to extreme climatic and salt conditions. Quinoa germ consists of almost 25-30% of whole grain. Quinoa germ obtained using roller milling has remarkable nutritional properties with high protein, fat and mineral content. Presence higher fat content limits shelf-life of quinoa germ. The objective of the present investigation is to study the effect of different treatment on stabilization of quinoa germ and its storge study. Quinoa germ was subjected to microwave and infrared treatment for shelf-life extension. Colour properties of the germ has not changed drastically by both treatments. Sorption behavior of quinoa germ stored at different RH was studied and results showed typical sigmoid curve for all samples. Sorption studies revealed that treated quinoa germ were stable at 64% RH. The storage study was carried out at accelerated conditions using PET/PE packaging material. Based on the results of the study, it can be inferred that the quinoa germ can be kept up to three months at accelerated conditions. Study demonstrated that microwave treatments of quinoa germ showed highest shelf life of three months at accelerated conditions.

Three thermal treated methods improve physicochemical and functional properties of wheat bran-germ and the bran-germ containing products

BACKGROUND

To fully investigate the effect of different stabilization methods on WBG in the same environment, we studied the effect of microwaving, baking, and extrusion on the nutritional, physicochemical, and processability properties of WBG and whole wheat bran-germ noodle (WBGN). Principal component analysis was used to comprehensively evaluate the qualities of WBG and WBGN. Machine learning-based research was conducted to predict the quality of WBGN based on the features of WBG.

RESULTS

The results showed that three methods improved antioxidant ability, bound flavonoids, bound and total phenolics, and the processing properties in WBG (P < 0.05). Extruded-WBG showed a lower polyphenol oxidase activity, lipase activity (35.02 ± 2.02 U and 20.29 ± 0.47 mg g^-1 ) and particle size (54.08 ± 0.38 μm), and higher water hold capacity (2.60 ± 0.68%) and bound phenolic levels. The enhanced quantity of bound polyphenols had a major role in the increased antioxidant potential of WBGN. Extruded-WBGN showed higher antioxidant ability for 2,2-diphenyl-1-picrylhydrazyl (171.28 ± 3.16 μmol Trolox eq kg^-1 ). The extruded-WBGN had high concentrations of WBG aroma compounds, and low contents of bitterness and raw bran-germ flavor compounds. Next, the enzymatic activity, powder properties, color, and antioxidant capacity of WBG were further utilized to predict the polyphenolic, flavonoids, flavor compounds, and antioxidant capacities of WBGN, where the R² value of the model exceeded 0.90. The best comprehensive quality modification method of the WBG and WBGN was extrusion, followed by baking and microwaving.

CONCLUSION

The present study shows that extrusion is a promising way to improve WBG into a nutritious and flavorful cereal food ingredient. © 2023 Society of Chemical Industry.

Improvement of stability and antioxidant activity of wheat germ by mixed fermentation versus single fermentation

Wheat germ is a high-nutrient by-product from the milling industry with very limited optimal consumption due to its short shelf life. The severe activity of endogenous lipase and lipoxygenase is associated with the release of fatty acids which are responsible for the rancidity and shelf-life deficiency. Reducing these enzymes activity is essential for prolonging the wheat germ shelf-life. For this purpose, the mixed and simple fermentation of different wheat germ concentrations (10, 15 and 20% w/v wheat germ in distilled water) with Lactobacillus plantarum and Lactobacillus acidophilus was investigated to improve the stability of wheat germ by restraining the activity of the enzymes. Fermentation noticeably reduced the activity of the enzymes in all samples (ranges from 50 to 82.15% for lipase and 55.34 to 72 for lipoxygenase in different treatments), but the mixed-fermented wheat germ with the maximum concentration (20%) achieved the highest reduction level in both enzymes inactivation. Fermentation also resulted in an obvious increase in antioxidant activity from 51.18% in raw wheat germ to more than 72.73% in different samples, which mixed fermentation of 20% wheat germ suspension with the value of 89.76 was ranked first.

Effects of low-temperature microwave treatment of wheat germ

BACKGROUND

Wheat germ has a great potential byproduct in food formulations for its outstanding nutritional value. To allow valorization, there is a need to inactivate endogenous enzymes such as lipases to avoid lipid oxidation. In the present study, the effects of microwaves on enzyme activity, as well as on functional and physical properties of wheat germ, were evaluated. Microwave treatments were performed at 50, 60 and 70 °C for 5-20 min.

RESULTS

Lipase activity was severely affected at 60 and 70 °C in contrast to lipoxygenase. Microwave treatment did not cause changes in germ moisture content or color parameters. No significant changes were observed in equilibrium moisture content when comparing the adsorption and desorption processes of raw and microwave-treated wheat germ. The best model to describe sorption process was the Guggenheim-Anderson-De Boer equation. According to the dielectric properties of raw wheat germ, it could be considered as transparent to energy (ε' < 1.87 and ε'' < 0.35). Thermal analysis of proteins showed a low denaturation degree (below 35% to raw material). In addition, some functional properties were enhanced such as oil retention capacity. Conformational changes as a result of microwave treatment were associated with the slight decline observed on the monolayer moisture content.

CONCLUSION

Microwave treatments of wheat germ at 60 and 70 °C were effective for lipase inactivation. Physical properties did not change drastically after the treatments. Microwave-treated wheat germ could be a good source of high-protein ingredient in food product development. © 2021 Society of Chemical Industry.

Effect of microwave and hot air treatment on enzyme activity, oil fraction quality and antioxidant activity of wheat germ

The aim of this work was to study the effects of microwaves (MW) and hot air (HA) treatments on enzyme activities and quality parameters in wheat germ (WG). Both MW and HA were effective at inactivating lipases. MW treatment inactivated lipases more at lower temperatures (60 and 70 °C) than HA (150-200 °C). Peroxide values, acidity, and fatty acid profiles of WG oil remained unaltered after HA and MW treatments. Loss of α-tocopherol contents was observed following HA treatment, but total tocopherol content remained above 77% baselines values in all treated samples. The main antioxidant mechanism of WG extracts was associated with inactivation of radicals, rather than reducing capacity. MW treatment at 60 and 70 °C enhanced radical scavenging activity, while total polyphenol contents and reducing capacities were negatively affected. Therefore, MW treatment is a promising technology to stabilise WG, retaining quality and antioxidant activity.

Microwave-assisted enzymatic hydrolysis of wheat germ albumin to prepare polypeptides and influence on physical and chemical properties

Wheat germ albumin (WGA) is rich in nutrients and contains a number of antioxidant polypeptides. The effects of microwave-assisted alkaline protease, neutral protease, papain and compound protease on the degree of hydrolysis of WGA and the clearance rate of DPPH• were comparatively studied. The results showed that papain had the best proteolytic activity. The functional properties of WGA and its hydrolysis polypeptides were determined. The results showed that the solubility of WGA increased after papain hydrolysis, and the apparent viscosity and foam stability reduced. Compared with the amino acids of WGA, the proportions of proline, histidine, glycine, lysine, and glutamic acid in the enzymatic hydrolysis products increased, while the proportions of leucine, phenylalanine, arginine and isoleucine decreased.  After papain hydrolysis, the surface structure was loose, and the surrounding blocks became more rounded.

Effect of Loading on Wheat Germ Drying in a Batch Fluidized Bed for Industrial Production

A high loading production in the manufacturing process of wheat germ (WG) drying is important for reducing the production costs. From a cost perspective, the drying performance become more effective in a batch process when the loading increases. The objective of this investigation was to evaluate the drying performance of WG with different loadings, from 2 to 9 kg, at 120 °C in a fluidized bed dryer. The moisture content, according to the American Association of Cereal Chemists (AACC) method, and the water activity using a thermal hygrometer were measured. The absolute humidity, diffusivity of moisture, and thermal efficiency were analyzed using a mathematical model. An analysis of the dehydration flux demonstrated a linear relationship between dehydration time and WG loading using a fluidized bed dryer. The kinetics of WG drying were observed with a simple exponential model used to match the experimental observation, indicating that the drying rate constant decreases with an increase in WG loading. A linear relationship was obtained between the WG loading and heating time (heating time = −0.212 + 0.577 × WG loading). On this basis, a process optimization was developed for industrial operation, and for predicting the drying performance of WG for industrial-scale production.