Extrusion processing: A strategy for improving the functional components, physicochemical properties, and health benefits of whole grains

Extrusion puffing as a pretreatment method to change the surface structure, physicochemical properties and in vitro protein digestibility of distillers dried grains with solubles

BACKGROUND

Distillers dried grains with solubles (DDGS) are rich in nutrition, and they are potential protein feed raw material. However, the existence of cellulose, hemicellulose and lignin hinders animals' digestion and absorption of DDGS. Making full use of unconventional feed resources such as DDGS can alleviate the shortage of feed resources to a certain extent. This research investigated the effects of twin-screw extrusion on the macromolecular composition, physical and chemical properties, surface structure and in vitro protein digestibility (IVPD) of DDGS.

RESULTS

The findings showed that extrusion puffing significantly increased the protein solubility, bulk density, water holding capacity, and swelling capacity, while significantly decreased hemicellulose and crude protein content, particle size and zeta potential of DDGS. The structure damage of DDGS induced by the extrusion was characterized by scanning electron microscopy (SEM), Fourier-transform infrared (FITR) spectroscopy and X-ray diffraction (XRD) analysis. Interestingly, no random coil was observed in the analysis of the secondary structure, and extrusion promoted the transformation of α-helix and β-turn to β-sheet, which led to significant increases in protein solubility and IVPD of DDGS (P < 0.05). Additionally, correlation analysis revealed that IVPD and PS had a positive relationship.

CONCLUSION

Extrusion puffing was an ideal pretreatment method for DDGS modification to improve in vitro protein digestibility. © 2023 Society of Chemical Industry.

Mechanism of feed moisture levels in extrusion treatment to improve the instant properties of Chinese yam (Dioscorea opposita Thunb.) flour

Extruded yam flour was prepared at different feed moisture to improve its instant properties. The water solubility index (WSI) and water absorption index (WAI) were used to compare the instant properties of yam flour. Their chemical compositions, particle size distribution, crystalline structure, and microscopic forms were also analyzed to assess the effects of feed moisture on the instant properties of yam flour. We found that extrusion significantly improved the instant properties of yam flour, while the WSI value increased from 29.50% to 71.86% and the WAI value decreased from 387.88% to 228.06% with decreased feed moisture. Extrusion led to the degradation of total starch and amylopectin, and the contents of soluble substances increased markedly. Extrusion destroyed the granular and crystalline structures, which were reconstituted as amylose-lipid complexes with a significant decrease in relative crystallinity. Increasing the feed moisture was beneficial to the flow and color retention, while lower feed moisture was more favorable to enhance the instant properties.

Sustainable production of naturally colored extruded breakfast cereals from blends of broken rice and vegetable flours

There is a growing demand for practical and healthy food products. Obtaining naturally colored breakfast cereals with the incorporation of functional ingredients is a promising alternative for consumers that are looking for healthiness. This study aimed to evaluate the feasibility of using vegetable flours, rich in pigments, to obtain naturally colored breakfast cereals through thermoplastic extrusion. Vegetables considered "unsuitable for the retail market", classified as "type B", were used to prepare different flours from carrot (CF), spinach (SF) and beetroot (BF). Extrudates were produced from a mixture of 90% broken rice (BR) and 10% vegetable flour (CF, SF or BF). Besides giving the extrudates a natural color, the use of vegetable flours also provided nutritional and functional enrichment due to increased mineral, protein, lipid, fiber and phenolic compound contents, and greater antioxidant capacity. However, some of these components, such as fibers, affect extrudate physical structure and technological characteristics, evidenced by reduced expansion, hardness, paste viscosity and greater interaction with water present in milk under consumption conditions. In general, the evaluated flours proved to be an alternative for imparting a natural color to extruded breakfast cereals, in addition to positively contributing to their nutritional and functional value.

A Review of the Changes Produced by Extrusion Cooking on the Bioactive Compounds from Vegetal Sources

The demand for healthy ready-to-eat foods like snacks is increasing. Physical modification of vegetal food matrices through extrusion generates significant changes in the chemical composition of the final product. There is a great variety of food matrices that can be used in extrusion, most of them being based on cereals, legumes, fruits, vegetables, or seeds. The aim of this review was to summarize the main effects of the extrusion process on the bioactive compounds content, namely phenolics, terpenes, vitamins, minerals, and fibers of vegetal mixes, as well as on their biological activity. The literature reported contradictory results regarding the changes in bioactive compounds after extrusion, mainly due to the differences in the processing conditions, chemical composition, physicochemical properties, and nutritional value of the extruded material and quantification methods. The thermolabile phenolics and vitamins were negatively affected by extrusion, while the fiber content was proved to be enhanced. Further research is needed regarding the interactions between bioactive components during extrusion, as well as a more detailed analysis of the impact of extrusion on the terpenes since there are few papers dealing with this aspect.

Changes in the cocoa shell dietary fiber and phenolic compounds after extrusion determine its functional and physiological properties

The influence of different extrusion conditions on the cocoa shell (CS) dietary fiber, phenolic compounds, and antioxidant and functional properties was evaluated. Extrusion produced losses in the CS dietary fiber (3-26%), especially in the insoluble fraction, being more accentuated at higher temperatures (160 °C) and lower moisture feed (15-20%). The soluble fiber fraction significantly increased at 135 °C because of the solubilization of galactose- and glucose-containing insoluble polysaccharides. The extruded CS treated at 160 °C-25% of feed moisture showed the highest increase of total (27%) and free (58%) phenolic compounds, accompanied by an increase of indirect (10%) and direct (77%) antioxidant capacity. However, more promising results relative to the phenolic compounds' bioaccessibility after in vitro simulated digestion were observed for 135°C-15% of feed moisture extrusion conditions. The CS' physicochemical and techno-functional properties were affected by extrusion, producing extrudates with higher bulk density, a diminished capacity to hold oil (22-28%) and water (18-65%), and improved swelling properties (14-35%). The extruded CS exhibited increased glucose adsorption capacity (up to 2.1-fold, at 135 °C-15% of feed moisture) and α-amylase in vitro inhibitory capacity (29-54%), accompanied by an increase in their glucose diffusion delaying ability (73-91%) and their starch digestion retardation capacity (up to 2.8-fold, at 135 °C-15% of feed moisture). Moreover, the extruded CS preserved its cholesterol and bile salts binding capacity and pancreatic lipase inhibitory properties. These findings generated knowledge of the CS valorization through extrusion to produce foods rich in dietary fiber with improved health-promoting properties due to the extrusion-triggered fiber solubilization.

Kidney Bean Substitution Ameliorates the Nutritional Quality of Extruded Purple Sweet Potatoes: Evaluation of Chemical Composition, Glycemic Index, and Antioxidant Capacity

The extrusion process may influence the nutritional profiles of carbohydrate-rich food ingredients, including the glycemic index (GI) and antioxidant capacity. This study aimed to evaluate the nutritional profile of extruded purple sweet potato (EPSP) substituted with kidney bean flour (KBF) (0, 30, and 40%). These foods were further characterized by their proximate composition, resistant starch, polyphenols, GI, and antioxidant capacities. The 40% KBF substitution enhanced the protein and fiber contents of the EPSP by up to 8% and 6%, respectively. Moreover, it also revealed that EPSP with 40% KBF substitution had a low-GI category (53.1), while the 0 and 30% substitution levels had a high-GI category, i.e., 77.4 and 74.7, respectively. However, the extrusion processing reduced the anthocyanin content and antioxidant capacity of purple sweet potato flour containing 40% KBF by 48% and 19%, respectively. There was a significant relationship between the GI values of proteins, fats, and fibers (p < 0.05). The insignificant effect of resistant starch and phenol contents on GI value was recorded due to the low concentrations of those components. KBF substitution could ameliorate the profile of protein, fiber, and GI, but not for antioxidant capacity. The other innovative processes for preserving antioxidant capacity might improve the product quality.

Andean Sprouted Pseudocereals to Produce Healthier Extrudates: Impact in Nutritional and Physicochemical Properties

The tailored formulation of raw materials and the combination of grain germination and extrusion processes could be a promising strategy to achieve the desired goal of developing healthier expanded extrudates without compromising sensory properties. In this study, modifications in the nutritional, bioactive profile and physicochemical properties of corn extrudates as influenced by the complete or partial replacement by sprouted quinoa (Chenopodium quinoa Willd) and cañihua (Chenopodium pallidicaule Aellen) were investigated. A simplex centroid mixture design was used to study the effects of formulation on nutritional and physicochemical properties of extrudates, and a desirability function was applied to identify the optimal ingredient ratio in flour blends to achieve desired nutritional, texture and color goals. Partial incorporation of sprouted quinoa flour (SQF) and cañihua flour (SCF) in corn grits (CG)-based extrudates increased phytic acid (PA), total soluble phenolic compounds (TSPC), γ-aminobutyric acid (GABA) and oxygen radical antioxidant activity (ORAC) of the extrudates. Sprouted grain flour usually results in an deleterious effect physicochemical properties of extrudates, but the partial mixture of CG with SQF and SCF circumvented the negative effect of germinated flours, improving technological properties, favoring the expansion index and bulk density and increasing water solubility. Two optimal formulations were identified: 0% CG, 14% SQF and 86% SCF (OPM1) and 24% CG, 17% SQF and 59% SCF (OPM2). The optimized extrudates showed a reduced amount of starch and remarkably higher content of total dietary fiber, protein, lipids, ash, PA, TSPC, GABA and ORAC as compared to those in 100% CG extrudates. During digestion, PA, TSPC, GABA and ORAC showed good stability in physiological conditions. Higher antioxidant activity and amounts of bioaccessible TSPC and GABA were found in OPM1 and OPM2 digestates as compared to those in 100% CG extrudates.