Extrusion processing of raw food materials and by-products: A review

Extrusion cooking of protein-based products: potentials and challenges

Extrusion cooking is receiving increasing attention as technology applied for the production of protein-based products. Researchers in this field showed that proteins from several sources are barely consumed because of their poor functionality and lack of acceptability related to the presence of some antinutritional factors. In this regard, extrusion is becoming of key importance thanks to its ability to improve protein functional properties. Based on this remarkable advantage, several studies have been published so far providing evidence of the enhanced functional, physicochemical and sensory properties of protein-based extruded products. The objective of the present review is to give a detailed overview of the potential of extrusion for the production of protein-based products. More specifically, the work describes all the studies published so far on vegetable and animal proteins including those recently released applying the technology on insect proteins. The aspects related to the functional properties of the extrudates together with the quality changes occurring during the process are also described to highlight the potential of the technology for future applications.

Influence of extrusion cooking on physicochemical properties and starch digestion kinetics of Sphenostylis stenocarpa, Cajanus cajan, and Vigna subterranean grains

Thermal degradation of sugars and amino acids, and depolymerization of macromolecules such as starch, proteins and fibre occasioned by high-temperature short-time extrusion cooking modify the physicochemical and functional properties of raw materials. High-temperature short-time extrusion cooking holds promise for the expanded use of non-conventional ingredients as food/feed due to its practicality, increased productivity and efficiency, and ability to retain thermally degradable nutrients during cooking. However, little is known about the effect of the high-temperature short-time extrusion cooking process on the physicochemical properties and starch digestibility of lesser-known grain legumes such as African yam beans (Sphenostylis stenocarpa), Pigeon pea (Cajanus cajan), and Bambara peanut (Vigna subterranean). In this study, we investigate the effect of high-temperature short-time extrusion cooking and extrusion cooking temperature; low (100°C) vs high (140°C) temperatures in a single screw extruder, on hydration characteristics, viscoamylolytic properties, in vitro starch digestibility and digestion kinetics of these grain legumes. We show that water holding capacity and swelling power increased (p < 0.05) with increasing extrusion temperature for Sphenostylis stenocarpa and Vigna subterranean but not Cajanus cajan extrudates. Significant effects of extrusion cooking (i.e unextruded vs 100°C and unextruded vs 140°C) and extrusion temperatures (i.e. 100°C vs 140°C) were observed in peak, trough, final and setback viscosities of all extrudates. Starch digestibility and digestion characteristics were modified with increase in extrusion temperature, however, no effect of extrusion temperatures (i.e. 100°C vs 140°C) on starch digestion kinetics was observed for Sphenostylis stenocarpa and Vigna subterranean except for hydrolysis index (34.77 vs 40.77%). Nutritional and physiological implications of extruded grain legumes in monogastric animal feeding were also highlighted. The Information presented herein will influence expanded use of extruded grain legumes as feed ingredients for intensive monogastric animal feeding.

Effect of drying methods on the gastrointestinal fate and bioactivity of phytochemicals from cocoa pod husk: In vitro and in silico approaches

Cocoa pod husk (CPH) contains many nutraceutical phytochemicals whose gastrointestinal fate and bioactivity can be affected by drying methods. Microwave (MW), forced-air drying (AF), and AF plus extrusion (AF-E) dried CPH samples were chemically characterized, and their phenolic and theobromine (THB) contents were evaluated under oral-gastric-intestinal (in vitro) and colonic fermentation (ex vivo). Absorption, distribution, metabolism, excretion, and toxicity (ADEMT) properties of CPH's small molecules were evaluated in silico. The chemical composition of CPH [mostly carbohydrates/insoluble dietary fiber], polyphenol [total polyphenols > condensed tannin (CT) > monomeric flavonoids] differed minimally among samples, except for THB content (AF/AF-E > MW) and antioxidant capacity (MW > AF/AF-E). Time- trend gastrointestinal (X³ behavior) and colonic bioaccessibility were AF/AF-E > MW, but phenolic acids, procyanidins, and THB fluctuated in a sample-specific fashion. In silico modeling showed that bioactives of CPH easily crossed the intestinal epithelium illustrating their bioaccessibility and, permeability. These bioactives can act as receptor ligands in a structure-dependent manner, suggesting their use as a functional ingredient.

Kinetics of Starch Degradation during Extrusion Cooking of Steady State Flow Konjac (Amorphophallus oncophyllus) Tuber Flour in a Single Screw Extruder

The presence of glucomannan in Konjac (Amorphophallus oncophyllus) tuber flour has promoted its various applications, especially in the food, drink, drug delivery and cosmetics. Starch is the main impurity of Konjac tuber flour. Although the common wet refining method may result in a high purity Konjac tuber flour, it is very tedious, time consuming and costly. This research aimed to study the kinetics of starch degradation in the extrusion cooking process of dry refining method to produce high quality Konjac tuber flour. In this research, Konjac tuber flour with 20% (w/w) moisture was extruded in a single screw extruder by varying screw speeds (50, 75, 100, 125, 150 and 175 rpm) and barrel temperatures (353, 373, 393, 413 and 433 K). The results showed that the starch extrusion cooking obeys the first reaction order. The reaction rate constant could be satisfactorily fitted by Arrhenius correlation with total activation energy of 6191 J.mol−1 and pre-exponential factor of 2.8728×10−1 s−1. Accordingly, thermal degradation was found to be the primary cause of starch degradation, which shared more than 99% of the energy used for starch degradation. Based on mass Biot number and Thiele modulus evaluations, chemical reaction was the controlling mechanism of the process. The results of this research offer potential application in Konjac tuber flour refining process to obtain high quality flour product. Copyright © 2020 by Authors, Published by BCREC Group. This is an open access article under the CC BY-SA License (https://creativecommons.org/licenses/by-sa/4.0).  

Use of Legumes in Extrusion Cooking: A Review

The traditional perception that legumes would not be suitable for extrusion cooking is now completely outdated. In recent years, an increasing number of studies have been conducted to assess the behavior of various types of legume flours in extrusion cooking, proving that legumes have excellent potential for the production of extruded ready-to-eat foods by partially or totally replacing cereals. This review identifies the optimal processing conditions for legume-based and legume-added extruded foods, which allow the improvement of the expansion ratio and give the extrudates the spongy and crisp structure expected by consumers. In particular, the effect of the individual processing parameters on the physical-chemical and nutritional properties of the final product is highlighted. The extrusion cooking process, indeed, has a positive effect on nutritional characteristics, because it induces important modifications on starch and proteins, enhancing their digestibility, and reduces the content of trypsin inhibitors, lectins, phytic acid, and tannins, typically present in legumes. Therefore, the extrusion of legume flours is a viable strategy to improve their nutritional features while reducing home preparation time, so as to increase the consumption of these sustainable crops.

Development of ternary nanoadsorbent composites of graphene oxide, activated carbon, and zero-valent iron nanoparticles for food applications

In this study, a ternary nanocomposite comprising graphene oxide and carbon loaded with zero-valent iron nanoparticles was developed as a promising nanoadsorbent, especially for polyphenols available in food industry by-products. The fabricated nanoadsorbents were characterized in terms of structural, morphological, and chemical attributes. Zero-valent iron nanoparticles (nZVI) were produced by a modified method leading to the formation of nanoparticles below 50 nm. Also, active carbon was transformed to a needle-like shape instead of its native shape so that the active surface area was drastically increased which favors the higher adsorption process. Moreover, the space between graphene oxide sheets was enhanced by ultrasonication so that more active carbon and nZVIs could be oriented between these sheets. Finally, the FTIR and Raman data demonstrated the formation of O-H stretching groups and a D/G value of 0.85 corresponding to the maintenance of a desired structure of the graphene oxide sheets, respectively. To summarize, the developed nanocomposites can be employed as a promising tool for the adsorbance of food and beverage industry by-products, especially polyphenols.