Background The last decade has seen the extensive use of bio-based polymers from renewable resources in many fields, to facilitate a sustainable, effective and diversified development of human activities. However, the natural polymeric matrices have processing difficulties because of their complicated structures. The green method combing reactive extrusion (REX) and enzymatic action has been adopted for the efficient conversion and utilisation of these biomaterials in food, medicine, energy as well as other areas. Scope and approach This review aims to offer a panoramic overview of the development of food-related biopolymers such as starch, protein and the derivatives, using REX and enzyme as powerful and useful processes. The special advantages, critical issues, application cases and future developments of REX–enzyme strategy were thoroughly discussed. Key findings and conclusions New types of REX–enzyme synergies were illustrated with different mechanisms according to the enzyme or extruder type, substrate level and energy intensity in the reaction microenvironment. The multiple REX and enzymatic processes is popular but gradually improved to a simple co-extrusion process of enzymatic reactive extrusion (eREX). It requires a compatible reaction state of both enzyme and substrate for eREX under the same and balanced conditions. Furthermore, starch- and protein-based matrices are usually extruded with strong or limited enzymatic actions for producing general and functional foods.

Advances in conversion of natural biopolymers: A reactive extrusion (REX)–enzyme-combined strategy for starch/protein-based food processing

Rice is a globally important staple consumed by billions of people, and recently there has been considerable interest in promoting the consumption of wholegrain brown rice (WBR) due to its obvious advantages over polished rice in metabolically protective activities. This work highlights the effects of innovative processing technologies on the quality and functional properties of WBR in comparison with traditional approaches; and it is aimed at establishing a quantitative and/or qualitative link between physicochemical changes and high-efficient processing methods. Compared with thermal treatments, applications of innovative nonthermal techniques, such as high hydrostatic pressure (HHP), pulsed electric fields (PEF), ultrasound and cold plasma, are not limited to modifying physicochemical properties of WBR grains, since improvements in nutritional and functional components as well as a reduction in anti-nutritional factors can also be achieved through inducing related biochemical transformation. Much information about processing methods and parameters which influence WBR quality changes has been obtained, but simultaneously achieving the product stabilization and functionality of processed WBR grains requires a comprehensive evaluation of all the quality changes induced by different processing procedures as well as quantitative insights into the relationship between the changes and processing variables.

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Innovative processing techniques for altering the physicochemical properties of wholegrain brown rice (Oryza sativa L.) - opportunities for enhancing food quality and health attributes.

Co-culture submerged fermentation by lactobacillus and yeast more effectively improved the profiles and bioaccessibility of phenolics in extruded brown rice than single-culture fermentation.

This study is aimed at exploring the release of bound polyphenols (BP) from insoluble dietary fiber (IDF) and its mechanism by solid-state fermentation (SSF) via Trichoderma viride. The results indicated that BP released by SSF (5.55 mg GAE/g DW) was significantly higher than by alkaline hydrolysis. In addition, 39 polyphenols and catabolites were detected, and the related biotransformation pathways were speculated. Quantitative analysis showed that SSF released more ferulic acid, p-coumaric acid, and organic acids, which led to advances in antioxidant, α-amylase, and α-glucosidase inhibitory activities. Furthermore, structural characteristics (scanning electron microscopy, X-ray diffraction, thermos gravimetric analysis, and Fourier transform infrared spectroscopy) and dynamic changes of carbohydrate-hydrolyzing enzymes indicated that the destruction of hemicellulose and the secretion of xylanase were vital for releasing BP. Overall, this study demonstrated that SSF was beneficial to release BP from IDF, which could provide insight into utilizing agricultural byproducts in a more natural and economical way.

Bound Polyphenols from Insoluble Dietary Fiber of Defatted Rice Bran by Solid-State Fermentation with Trichoderma viride: Profile, Activity, and Release Mechanism.

A novel “industry-scale microfluidizer system” (ISMS) was used to prepare whole corn slurry (WCS). The impact of processing pressure (0–120 MPa) on the properties of WCS was examined. ISMS preserved the soluble solid content, stabilized the native pH (~7.2), and retained the desirable yellow color of WCS. Moreover, it did not adversely impact the concentration of major nutrients, such as starch (~50 g/100g), protein (~13 g/100g), fat (~8 g/100g) and dietary fiber (~17 g/100g). ISMS also increased the polyphenol content and improved the in vitro antioxidant activity of WCS. Increasing the pressure led to an improvement in the physical stability of WCS, which was linked to the reduction in particle size, increase in viscosity, improved dispersion of the particulate matter and formed network with decreased dimensions. These results suggest that ISMS can be a new processing tool to create whole corn beverages with improved nutritional value, enhanced shelf life, and better functional performance.

The nutritional and physicochemical properties of whole corn slurry prepared by a novel industry-scale microfluidizer system

Based on the results of phenolic retention of brown rice treated by extrusion with thermostable α-amylase (ETA), this work investigated the phenolic retention of brown rice after extrusion with mesophilic α-amylase (EMA). Similarly, EMA significantly increased phenolic retention of brown rice with the increasing enzyme level, and the phenolic retention was positively correlated with reducing sugars. However, brown rice treated by EMA had higher retention rate of free phenolic content, free antioxidant activity, and total identified free phenolic acids than that treated by ETA at different enzyme levels, although the corresponding reducing sugars produced by EMA were lower than by ETA. These results indicated that the extrusion temperature had greater effect on the phenolic retention than enzymatic hydrolysis during enzymatic extrusion. In addition, brown rice treated by EMA with 0.5% enzyme had a high retention of free flavonoids at 72.4%. Therefore, EMA might be a better processing technology for brown rice to improve its nutrition.

Jinyu Miao

Papers

Phenolic retention of brown rice after extrusion with mesophilic α-amylase