Evaluating technological quality of okara flours obtained by different drying processes

Influence of weevil on the physicochemical characteristics, functional properties, and nutritional value of rice (Oryza sativa L.) produced at Yagoua (far-north Cameroon)

The infestation of rice by pests during the post-harvest phase is one of the consequences of the deterioration of its technological and nutritional quality. Therefore, the present study was carried out to determine the physico-chemical characteristics, functional properties and nutritional value of uninfested and weevil-infested rice during storage. To this end, rice samples were collected from a rice production unit in the Far North Region of Cameroon. The physico-chemical and functional properties of uninfested and infested rice flours were determined using standard methods. The results showed that among the functional properties, only porosity showed a significant difference (p˂0.05) between infested (13.88 %) and uninfested (17.30 %) rice flours. Concerning the proximate composition, except for the carbohydrate content, where a significant decrease (p˂0.05) was observed between infested (68.15 %) and non-infested (58.43 %) rice flours, no significant difference (p > 0.05) was observed for the other nutrients evaluated. It was also observed that weevil infestation had a significant (p < 0.05) effect on the mineral content of the rice samples. Furthermore, scanning electron microscopy analysis revealed the presence of smaller granules with imprecise shapes in non-infested rice flour. Thus, this study showed that weevil infestation had a significant negative impact on the nutritional quality of rice and that good practices must be adopted by producers to ensure the quality of rice grains during storage.

High-Pressure Pasteurization of Soy Okara

Okara is a by-product from the production of soy beverages, which has a high content of protein and fiber. Even though it has a high nutritional value, it is generally discarded or used as animal feed or compost. The problem is its short shelf life due to its high water content and high water activity. The aim of this study was to investigate the effect of high-pressure pasteurization at 200 MPa, 400 MPa, and 600 MPa on the shelf life of soy okara. Microbiological growth, as well as thermal properties, viscosity, water holding capacity, and oil holding capacity, was evaluated after the pressure treatments. Treatment at 600 MPa significantly reduced (p < 0.05) the growth of total aerobic count, yeast and mold, and lactic acid bacteria for up to four weeks of storage at 4 °C. The pasting properties were increased while the water and oil holding capacities of the soy okara did not significantly change (p > 0.05) after high-pressure pasteurization at 400 MPa and 600 MPa. High-pressure pasteurization is therefore a potential application technique for soy okara to produce a microbiologically safe product with maintained functional properties. However, more research is needed to optimize the process and to further investigate the microbiological species present in untreated soy okara to exclude any potential food safety risks.

Modeling the Influence of Okara Flour Supplementation from Time-Temperature Drying Treatment on the Quality of Gluten-Free Roll Produced from Rice Flour

Okara, an unassuming residue, is emerging as a notable reservoir of essential nutrients, encompassing an abundant supply of protein, dietary fiber, and potent antioxidant components. Hence, the incorporation of okara as an ingredient in the production of rice flour-based rolls held a considerable interest in nutritional and functional aspects. Okara flour supplement was prepared by drying at 100 °C for 2 h and selected based on the highest antioxidant level. Gluten-free rolls were prepared containing 0, 5, and 10% okara flour dried at 100 °C for 2 h, and their physicochemical properties were analyzed. Okara flour addition reduced the deformation of gluten-free batter roll by improving solid and liquid-like behavior, as evaluated with rheological measurements. Rolls containing okara flour processed at 100 °C for 2 h had increased firmness and decreased specific volume compared to the control. However, there were no significant differences in the sensory evaluation scores, suggesting that the consumers' acceptance of the control and the Okara rolls was similar. Okara flour supplement at 10% addition led to the nutritional improvement of the gluten-free rolls (increase of 2.4% protein and 1.32 times dietary fiber, dry basis). In contrast, there were no significant differences in the antioxidant level compared to the control. Okara flour is a functional ingredient with potential use in gluten-free products and a variety of novel products where enrichment is desirable.

Almond okara as a valuable ingredient in biscuit preparation

BACKGROUND

The okara is the water-insoluble residue derived from the production of plant-based beverages, including almond milk. Information on almond okara is scarce, with no scientific references. In the present study, the almond okara was characterized and used to replace wheat flour at 15%, 25% and 35% for biscuit preparation.

RESULTS

The contents of protein, lipid and dietary fiber of almond okara were 140.08, 421.16 and 407.90 g kg^-1 dry matter, respectively. The lipid fraction of almond okara showed contents of triacylglycerol oligopolymers and oxidized triacylglycerols of 0.12 and 5.14 g kg^-1 , respectively, which were significantly lower than the levels observed in the sunflower oil used in the formulation of biscuits. Consequently, the biscuits containing okara showed a content of triacylglycerol oligopolymers lower than that of control biscuits. The texture analysis revealed that the addition of the okara at 25% and 35% caused a significant increase in biscuit hardness and a reduction of the brittleness, compared to the control. The sensory evaluation confirmed these data, highlighting the slight impact of the almond okara on the almond odor, taste and flavor attributes.

CONCLUSION

Almond okara is a valuable by-product that can be easily used as an ingredient for biscuit preparation, exploiting its fiber, protein and lipid content to improve the nutritional value of food, with a limited impact on the sensory properties. © 2022 Society of Chemical Industry.

Profile and content of isoflavones on flaked and extruded soybeans and okara submitted to different drying methods

Isoflavones (IFs) are biocompounds found in considerable amounts in soybean grains. However, to originate soybean-based materials, the grains must be subjected to numerous thermal and mechanical treatments, which can impair the IFs content. The influence of these treatments was investigated and a protocol for IFs extraction and quantification is proposed. Sequential extractions were performed on industrially pretreated soybean samples (broken, flakes, and collets), on okara submitted to different drying methods (freeze-drying, forced convection, and under vacuum), and on soybean oils extracted with hexane and ethanol. β-glucosides levels were decreased by the thermal processes of lamination, expansion, and drying, while the aglycone forms were not affected. Lyophilization was identified as the most viable drying method for the quantification of IFs in okara. Soybean oils extracted with ethanol presented significant amounts of aglycone. Furthermore, two stages of extraction were sufficient for the recovery of the IFs from different matrices.

Soybean processing wastes and their potential in the generation of high value added products

Soybean and its derivatives are rich sources of nutrients and bioactive compounds with antioxidant properties, however, the wastes with high nutritional value are discarded by the industry. This study aimed to evaluate centesimal composition, microbial safety and antioxidant activity of soybean processing wastes (okara and okara flour) and soymilk. High fiber, carbohydrate, energy and lipids contents were found. Antioxidant activity by spectrophotometric and Electron Paramagnetic Resonance assays showed values for soybean (72.4% and 83.5%), okara (9.6% and 7.7%), okara flour (30.7% and 11.5%) and soymilk (28.4% and 36.5%). The total phenolic content was an average of 3.33 mg of gallic acid equivalent.g-1. Infrared spectra revealed no significant changes in the absorption bands, guaranteeing non-alteration in the compounds composition after processing. Microbiological assays indicated that soybean derivatives are safe for consumption. These results reinforce that these wastes contain bioactive compounds of interest with great potential to generate high value added products.

Physicochemical Properties, Antioxidant Capacity, Prebiotic Activity and Anticancer Potential in Human Cells of Jackfruit (Artocarpus heterophyllus) Seed Flour

The general aim of this study was to evaluate physicochemical properties, prebiotic activity and anticancer potential of jackfruit (Artocarpus heterophyllus) seed flour. The drying processes of jackfruit seeds were performed at 50, 60 and 70 °C in order to choose the optimal temperature for obtaining the flour based on drying time, polyphenol content and antioxidant capacity. The experimental values of the moisture ratio during jackfruit seed drying at different temperatures were obtained using Page's equation to establish the drying time for the required moisture between 5 and 7% in the flour. The temperature of 60 °C was considered adequate for obtaining good flour and for performing its characterization. The chemical composition, total dietary fiber, functional properties and antioxidant capacity were then examined in the flour. The seed flour contains carbohydrates (73.87 g/100 g), dietary fiber (31 g/100 g), protein (14 g/100 g) and lipids (1 g/100 g). The lipid profile showed that the flour contained monounsaturated (4 g/100 g) and polyunsaturated (46 g/100 g) fatty acids. Sucrose, glucose, and fructose were found to be the predominant soluble sugars, and non-digestible oligosaccharides like 1-kestose were also found. The total polyphenol content was 2.42 mg of gallic acid/g of the sample; furthermore, the antioxidant capacity obtained by ferric reducing antioxidant power (FRAP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) was 901.45 µmol Trolox/100 g and 1607.87 µmol Trolox/100 g, respectively. The obtained flour exhibited good functional properties, such as water and oil absorption capacity, swelling power and emulsifier capacity. Additionally, this flour had a protective and preventive effect which is associated with the potential prebiotic activity in Lactobacillus casei and Bifidobacterium longum. These results demonstrate that jackfruit seed flour has good nutritional value and antioxidant and prebiotic activity, as well as potential protective effects and functional properties, making it an attractive food or ingredient in developing innovative functional products.

Development and Characterization of Novel Composite Films Based on Soy Protein Isolate and Oilseed Flours

The possibility of using oilseed flours as a waste source for film-forming materials with a combination of soy protein isolate in preparation of edible films was evaluated. Physical, mechanical and barrier properties were determined as a function of the oilseed type: hemp, evening primrose, flax, pumpkin, sesame and sunflower. It was observed that the addition of oilseed flours increased the refraction and thus the opacity of the obtained films from 1.27 to 9.57 A mm⁻¹. Depending on the type of flours used, the edible films took on various colors. Lightness (L*) was lowest for the evening primrose film (L* = 34.91) and highest for the soy protein film (L* = 91.84). Parameter a* was lowest for the sunflower film (a* = −5.13) and highest for the flax film (a* = 13.62). Edible films made of pumpkin seed flour had the highest value of the b* color parameter (b* = 34.40), while films made of evening primrose flour had the lowest value (b* = 1.35). All analyzed films had relatively low mechanical resistance, with tensile strength from 0.60 to 3.09 MPa. Films made of flour containing the highest amount of protein, pumpkin and sesame, had the highest water vapor permeability, 2.41 and 2.70 × 10⁻⁹ g·m⁻¹ s⁻¹ Pa⁻¹, respectively. All the edible films obtained had high water swelling values from 131.10 to 362.16%, and the microstructure of the films changed after adding the flour, from homogeneous and smooth to rough. All blended soy protein isolate–oilseed flour films showed lower thermal stability which was better observed at the first and second stages of thermogravimetric analysis when degradation occurred at lower temperatures. The oilseed flours blended with soy protein isolate show the possibility of using them in the development of biodegradable films which can find practical application in the food industry.

Effect of Drying Methods on Volatile Compounds of Burdock (Arctium lappa L.) Root Tea as Revealed by Gas Chromatography Mass Spectrometry-Based Metabolomics

Burdock (Arctium lappa L.) is one of the nutritional foods widely planted in many countries. Dried burdock root (BR) is available as a herbal tincture and tea in many Asian countries with good flavor and taste. In this study, the volatile components in dried BR were identified and the effects of different drying methods on the volatile components were investigated by HS-GC-MS method. A total of 49 compounds were identified. Different drying methods including hot-air drying (HD, at 50, 60, 70, and 80 °C), vacuum drying (VD, at 50, 60, 70, and 80 °C), sunlight drying (SD), natural drying (ND), and vacuum freeze drying (VFD) were evaluated by HS-GC-MS-based metabolomics method. Results showed that different drying methods produced different effects on the volatile compounds. It was observed that 2,3-pentanedione, 1-(1H-pyrrol-2-yl)-ethanone, furfural, and heptanal were detected at higher concentrations in HD 80 and VD 70. The traditional HD and SD methods produced more flavor substances than VFD. The BR treated by the VFD method could maintain the shape of the fresh BR pieces while HD50 and VD80 methods could maintain the color of fresh BR pieces. These findings could help better understand the flavor of the corresponding processed BR and provide a guide for the drying and processing of BR tea.

Microwave Drying for Production of Rehydrated Foods: A Case Study of Stink Bean (Parkia speciosa) Seed

The potential of microwave drying in the production of rehydrated foods is demonstrated with stink beans (Parkia speciosa), smelly legumes of Africa and Asia. Compared to stink beans dehydrated by convective drying and freeze drying, the microwave products exhibit higher moisture contents, but the distribution of microscopic pores leads to good rehydration characteristics. Dehydration by microwave drying is also achieved within a much shorter period than that commonly used in freeze drying. The dehydration time can be further reduced to 6 h comparable to convective drying, and the moisture content is dropped to 11% by decreasing the pressure during microwave drying. However, the rehydration time remains around 65 min for products from both ambient and low-pressure (400 Pa) microwave drying. In rehydration, the period is successfully reduced to 30 min by increasing the water temperature to 70 °C. The results indicate that microwave drying does not affect the value of crude protein and rehydrated products are comparable to fresh stink beans. From these findings, the microwave drying technique is an applicable technology for both manufacturers and consumers, with acceptable drying time and rehydration characteristics.

Prebiotic Impacts of Soybean Residue (Okara) on Eubiosis/Dysbiosis Condition of the Gut and the Possible Effects on Liver and Kidney Functions

Okara is a white-yellow fibrous residue consisting of the insoluble fraction of the soybean seeds remaining after extraction of the aqueous fraction during the production of tofu and soymilk, and is generally considered a waste product. It is packed with a significant number of proteins, isoflavones, soluble and insoluble fibers, soyasaponins, and other mineral elements, which are all attributed with health merits. With the increasing production of soy beverages, huge quantities of this by-product are produced annually, which poses significant disposal problems and financial issues for producers. Extensive studies have been done on the biological activities, nutritional values, and chemical composition of okara as well as its potential utilization. Owing to its peculiar rich fiber composition and low cost of production, okara might be potentially useful in the food industry as a functional ingredient or good raw material and could be used as a dietary supplement to prevent varied ailments such as prevention of diabetes, hyperlipidemia, obesity, as well as to stimulate the growth of intestinal microbes and production of microbe-derived metabolites (xenometabolites), since gut dysbiosis (imbalanced microbiota) has been implicated in the progression of several complex diseases. This review seeks to compile scientific research on the bioactive compounds in soybean residue (okara) and discuss the possible prebiotic impact of this fiber-rich residue as a functional diet on eubiosis/dysbiosis condition of the gut, as well as the consequential influence on liver and kidney functions, to facilitate a detailed knowledge base for further exploration, implementation, and development.