High moisture extrusion of plant proteins: advances, challenges, and opportunities.

High moisture extrusion is a widely used technology for producing fibrous meat analogues in an efficient and scalable manner. Extrusion of soy, wheat gluten, and pea is well-documented and related products are already available in the market. There has been growing interest to diversify the protein sources used for meat analogues due to concerns over food waste, monocropping and allergenicity. Optimizing the extrusion process for plant proteins (e.g., hemp, mung bean, fava bean) tends to be time consuming and relies on the operators' intuition and experience to control the process well. Simulating the extrusion process has been challenging so far due to the diverse inputs and configurations involved during extrusion. This review details the mechanism for fibrous structure formation and provides an overview of the extrusion parameters used for texturizing a broad range of plant protein sources. Referring to these data reduces the resources needed for optimizing the extrusion process for novel proteins and may be useful for future extrusion modeling efforts. The review also highlights potential challenges and opportunities for extruding plant proteins, which may help to accelerate the development and commercialization of related products.

Texture, sensory properties and functionality of extruded snacks from pulses and pseudocereal proteins.

BACKGROUND: The protein-rich fractions of pulses and pseudocereals exhibit a well-balanced amino acid profile, particularly when combined in different portions, and are therefore high-value ingredients for the production of extruded snacks. However, the impact of a combination of pulses and pseudocereals on the physical and sensory qualities of extruded snacks has not been investigated up to now. Native or preconditioned protein isolates and concentrates from pulses - as single ingredients or in combination with protein-rich flours of pseudocereals - were analyzed regarding their thermal and functional properties in relation to extrusion characteristics. Low moisture extrusion cooking was used to investigate the impact of protein source (lentil, lupin, faba bean), pseudocereal source (quinoa, amaranth, buckwheat) and protein content (30%, 50%, 70%) on sectional expansion, specific hardness, density and sensory properties of the snacks. RESULTS: With increasing protein content from 30% to 50%, the sectional expansion decreased and the density and specific hardness of the extrudates increased, which could be counteracted by preconditioning of the protein-rich ingredients. Lupin protein-based extrudates exhibited satisfactory texture and sensory properties. Extruded mixtures of pulses and pseudocereals (70% protein) exhibited a smaller sectional expansion compared to pulses as single ingredients (30%, 50%), regardless of pseudocereal type. However, the texture and sensory properties of the extruded blends were satisfactory. CONCLUSIONS: We show for the first time that protein-rich fractions of pulses and pseudocereals can be processed into expanded snacks with favorable texture and nutritional properties such as increased protein contents (70%) and balanced amino acid profiles. © 2020 The Authors. Journal of The Science of Food and Agriculture published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Significance of Fermentation in Plant-Based Meat Analogs: A Critical Review of Nutrition, and Safety-Related Aspects.

Plant-based meat analogs have been shown to cause less harm for both human health and the environment compared to real meat, especially processed meat. However, the intense pressure to enhance the sensory qualities of plant-based meat alternatives has caused their nutritional and safety aspects to be overlooked. This paper reviews our current understanding of the nutrition and safety behind plant-based meat alternatives, proposing fermentation as a potential way of overcoming limitations in these aspects. Plant protein blends, fortification, and preservatives have been the main methods for enhancing the nutritional content and stability of plant-based meat alternatives, but concerns that include safety, nutrient deficiencies, low digestibility, high allergenicity, and high costs have been raised in their use. Fermentation with microorganisms such as Bacillus subtilis, Lactiplantibacillus plantarum, Neurospora intermedia, and Rhizopus oryzae improves digestibility and reduces allergenicity and antinutritive factors more effectively. At the same time, microbial metabolites can boost the final product's safety, nutrition, and sensory quality, although some concerns regarding their toxicity remain. Designing a single starter culture or microbial consortium for plant-based meat alternatives can be a novel solution for advancing the health benefits of the final product while still fulfilling the demands of an expanding and sustainable economy.

The potentials and challenges of using fermentation to improve the sensory quality of plant-based meat analogs.

Despite the advancements made in improving the quality of plant-based meat substitutes, more work needs to be done to match the texture, appearance, and flavor of real meat. This review aims to cover the sensory quality constraints of plant-based meat analogs and provides fermentation as a sustainable approach to push these boundaries. Plant-based meat analogs have been observed to have weak and soft textural quality, poor mouth feel, an unstable color, and unpleasant and beany flavors in some cases, necessitating the search for efficient novel technologies. A wide range of microorganisms, including bacteria such as Lactobacillus acidophilus and Lactiplantibacillus plantarum, as well as fungi like Fusarium venenatum and Neurospora intermedia, have improved the product texture to mimic fibrous meat structures. Additionally, the chewiness and hardness of the resulting meat analogs have been further improved through the use of Bacillus subtilis. However, excessive fermentation may result in a decrease in the final product's firmness and produce a slimy texture. Similarly, several microbial metabolites can mimic the color and flavor of meat, with some concerns. It appears that fermentation is a promising approach to modulating the sensory profiles of plant-derived meat ingredients without adverse consequences. In addition, the technology of starter cultures can be optimized and introduced as a new strategy to enhance the organoleptic properties of plant-based meat while still meeting the needs of an expanding and sustainable economy.

Mathematical optimisation of extruded mixed plant protein-based meat analogues based on amino acid compositions.

Developing meat analogues of superior amino acid (AA) profiles in the food industry is a challenge as plant proteins contain less of some essential AA than animal proteins. Mathematical optimisation models such as linear/non-linear programming models were used to overcome this challenge and create high-moisture meat analogues (HMMA) with AA profiles as close as possible to chicken breast meat. The effect on the physiochemical properties and specific mechanical energy (SME) of the HMMA was investigated. The AA content of HMMA was generally lower than chicken. Strong intermolecular bonds present in the globulin fraction could hinder protein acid hydrolysis of HMMA. Plant proteins also affect the HMMA colour as certain AA forms Maillard reaction products with higher browning intensity. Lastly, different characteristics of plant proteins resulted in different SME values under the same extrusion conditions. While mathematical programming can optimise plant protein combinations, fortification is required to match the AA profile of HMMA to an animal source.

Impact of Rapeseed Press Cake on the Rheological Properties and Expansion Dynamics of Extruded Maize Starch.

Rapeseed press cake (RPC), an oil pressing side product rich in protein and fiber, can be combined with starch and valorized into directly expanded products using extrusion technology. The mechanism of starch expansion has been studied in detail, but the impact of RPC on expansion behavior is poorly understood. However, it can be linked to rheological and physicochemical properties and is a key product quality parameter. Blends with different amounts of RPC (0, 10, 40 g/100 g) were extruded at different barrel temperatures (100, 120, 140 °C) and moisture contents (24 or 29 g/100 g). The initial, intermediate and final sectional, longitudinal and volumetric expansion indices (SEI, LEI, VEI) were monitored directly, 10 s and 24 h after die exit to measure extrudate growth and shrinkage. The viscous and elastic properties of the extruded blends were investigated in a closed cavity rheometer. Starch and blends with 10 g/100 g RPC achieved a high initial SEI followed by significant short-term shrinkage. Blends containing 40 g/100 g RPC did not show any initial expansion. With increasing RPC content, the intermediate SEI decreased, but all samples reached a similar final SEI due to time-dependent swelling of the RPC blends. With increasing RPC content, the elasticity of the starch-based extruded samples significantly increased. Our study shows that comprehensive control and understanding of expansion mechanisms can be achieved only by investigating all stages of extrudate growth and shrinkage. We also found that the closed cavity rheometer is a powerful tool to correlate the rheological properties and expansion mechanisms of biopolymers.

Linking Expansion Behaviour of Extruded Potato Starch/Rapeseed Press Cake Blends to Rheological and Technofunctional Properties.

In order to valorise food by-products into healthy and sustainable products, extrusion technology can be used. Thereby, a high expansion rate is often a targeted product property. Rapeseed press cake (RPC) is a protein- and fibre-rich side product of oil pressing. Although there is detailed knowledge about the expansion mechanism of starch, only a few studies describe the influence of press cake addition on the expansion and the physical quality of the extruded products. This study assessed the effect of RPC inclusion on the physical and technofunctional properties of starch-containing directly expanded products. The effect of starch type (native and waxy), RPC level (10, 40, 70 g/100 g), extrusion moisture content (24, 29 g/100 g) and barrel temperature (20-140 °C) on expansion, hardness, water absorption, and solubility of the extrudates and extruder response was evaluated. At temperatures above 120 °C, 70 g/100 g of RPC increased the sectional and volumetric expansion of extrudates, irrespective of starch type. Since expansion correlates with the rheological properties of the melt, RPC and RPC/starch blends were investigated pre- and postextrusion in a closed cavity rheometer at extrusion-like conditions. It was shown that with increasing RPC level the complex viscosity |ƞ*| of extruded starch/RPC blends increased, which could be linked to expansion behaviour.

Extrusion Processing of Rapeseed Press Cake-Starch Blends: Effect of Starch Type and Treatment Temperature on Protein, Fiber and Starch Solubility.

For the valorization of oilseed press cakes into food products, extrusion can be used. A common way of applying the protein- and fiber-rich press cakes in directly expanded products is the combination thereof with starch, since starch gives a favourable texture, which correlates directly to expansion. To control product properties like expansion of protein and fiber-rich extruded products, the underlying physicochemical changes of proteins, fibers and starch due to thermomechanical input need to be comprehensively described. In this study, rapeseed press cake (RPC) was extruded and treated under defined thermomechanical conditions in a closed-cavity rheometer, pure and in combination with four starches. The impact of starch type (potato PS, waxy potato WPS, maize MS, high-amylose maize HAMS) and temperature (20/25, 80, 100, 120, 140 °C) on protein solubility, starch gelatinization (Dgel), starch hydrolysis (SH) and fiber solubility of the blends was evaluated. The extrusion process conditions were significantly affected by the starch type. In the extruded blends, the starch type had a significant impact on the protein solubility which decreased with increasing barrel temperature. Increasing barrel temperatures significantly increased the amount of soluble fiber fractions in the blends. At defined thermomechanical conditions, the starch type showed no significant impact on the protein solubility of the blends. Therefore, the observed effects of starch type on the protein solubility of extruded blends could be attributed to the indistinct process conditions due to differences in the rheological properties of the starches rather than to molecular interactions of the starches with the rapeseed proteins in the blends.

Extrusion texturization of cricket flour and soy protein isolate: Influence of insect content, extrusion temperature, and moisture-level variation on textural properties.

Due to the increasing global population and unsustainable meat production, the future supply of animal-derived protein is predicted to be insufficient. Currently, edible insects are considered as a potential and "novel" source of protein in the development of palatable meat analogues. This research used high moisture extrusion cooking (HMEC), at a screw speed of 150 rpm, to produce meat analogues using full- or low-fat cricket flours (CF) and soy protein isolate (SPI). Effects of water flow rate (WFR), cooking temperature (9 and 10 ml/min; 120, 140, and 160°C, respectively), and CF inclusions levels of 0, 15, 30, and 45% were analyzed. Cooking temperature and CF inclusion had a significant effect (p < .05) on both tensile stress in parallel and perpendicular directions, while WFR had no significant effect (p = .3357 and 0.7700), respectively. The tensile stress increased with temperature but decreased with CF inclusion at both WFRs. Comparatively, the tensile stress was stronger at WFR of 9 ml/min than at 10 ml/min; however, the tensile stress in parallel was mostly greater than tensile stress in perpendicular directions. Fibrous meat analogues with high anisotropic indices (AIs) of up to 2.80 were obtained, particularly at WFR of 10 ml/min and at inclusions of 30% low-fat CF. By controlling HMEC conditions, full-/low-fat cricket flours at 15% and 30% inclusions can offer an opportunity to partially substitute SPI in manufacturing of fibrous meat analogues.

Influence of the Isolation Method on the Technofunctional Properties of Protein Isolates from Lupinus angustifolius L.

The technofunctional properties of 2 protein isolates from Lupinus angustifolius L. Vitabor isolated by different procedures were investigated. The lupin protein isolate prepared by aqueous alkaline extraction with subsequent isoelectric precipitation (ILP) showed a significantly higher degree of protein denaturation and lower denaturation temperatures than the one obtained by aqueous salt-induced extraction followed by dilutive precipitation (MLP) as determined by differential scanning calorimetry. Rheological investigations revealed higher firmness and a viscoelastic solid-like behavior of ILP, in contrast to MLP that showed viscoelastic, liquid-like properties. Protein solubility of MLP was higher compared to ILP and solubility minima were slightly different for both lupin protein isolates. The protein isolates exhibited different technofunctional properties with ILP showing higher water binding capacity, lower oil binding capacity and lower emulsifying capacity than MLP. This reflects the different putative application of both lupin protein isolates as food ingredients, for example for ILP as a moisture enhancer and for MLP as a "natural" emulsifier in mixed food systems.