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

Unlocking the potential of enzyme engineering via rational computational design strategies

Enzymes play a pivotal role in various industries by enabling efficient, eco-friendly, and sustainable chemical processes. However, the low turnover rates and poor substrate selectivity of enzymes limit their large-scale applications. Rational computational enzyme design, facilitated by computational algorithms, offers a more targeted and less labor-intensive approach. There has been notable advancement in employing rational computational protein engineering strategies to overcome these issues, it has not been comprehensively reviewed so far. This article reviews recent developments in rational computational enzyme design, categorizing them into three types: structure-based, sequence-based, and data-driven machine learning computational design. Case studies are presented to demonstrate successful enhancements in catalytic activity, stability, and substrate selectivity. Lastly, the article provides a thorough analysis of these approaches, highlights existing challenges and potential solutions, and offers insights into future development directions.

Understanding the multi-scale structure, physicochemical and digestive properties of extruded yam starch with plasma-activated water

In this study, the synergistic effect of plasma-activated water (PAW) combined with twin-screw extrusion (TSE) on multi-scale structure, physicochemical and digestive properties of yam starch (YS) was studied. PAW-TSE resulted in higher amylose content in YS than TSE alone. Compared with single TSE, the relative crystallinity, short-range ordered degree, and gelatinization enthalpy of YS were increased by PAW-TSE according to the results of X-ray diffraction, Fourier transform infrared, Raman spectroscopy, and differential scanning calorimetry. Furthermore, rapid viscosity and dynamic rheological analysis showed that the peak and breakdown viscosity of PAW-TSE treated YS paste were considerably reduced, and the storage modulus and loss modulus were significantly increased, indicating that the gel strength and thermal stability were improved. In addition, the resistant starch (RS) content of YS treated by PAW-TSE increased from 6.04 % to 21.21 %. Notably, the effect of PAW-TSE on YS enhanced with the preparation time of PAW increased. Finally, correlation analysis indicated that the characteristic indexes of PAW had a significant impact on the long or short-range ordered structure, thermal properties, and in vitro digestibility of YS during extrusion. Therefore, PAW-TSE, as an emerging dual modification technology, will greatly expand the application of extrusion technology.

Advances in Starch Nanoparticle for Emulsion Stabilization

Starch nanoparticles (SNPs) are generally defined as starch grains smaller than 600-1000 nm produced from a series of physical, chemical, or biologically modified starches. Many studies have reported the preparation and modification of SNPs, which are mostly based on the traditional "top-down" strategy. The preparation process generally has problems with process complexity, long reaction periods, low yield, high energy consumption, poor repeatability, etc. A "bottom-up" strategy, such as an anti-solvent method, is proven to be suitable for the preparation of SNPs, and they are synthesized with small particle size, good repeatability, a low requirement on equipment, simple operation, and great development potential. The surface of raw starch contains a large amount of hydroxyl and has a high degree of hydrophilicity, while SNP is a potential emulsifier for food and non-food applications.

Application of transglutaminase modifications for improving protein fibrous structures from different sources by high-moisture extruding

Plant proteins can be extruded under high moisture content (above 40 %) to form meat-like fibrous structures, which is the basis for meat-like substitute products. However, the proteins' extrudability from various sources remain challenging in terms of generating fibrous structures under combinations of high-moisture extrusion with transglutaminase (TGase) modifications. In this study, proteins from soy (soy protein isolate, SPI, and soy protein concentrate, SPC), pea (pea protein isolate, PPI), peanut (peanut protein powder, PPP), wheat (wheat gluten, WG), and rice (rice protein isolate, RPI) were texturized using high-moisture extrusion combined with transglutaminase (TGase) modifications to enact changes in protein structure and extrusion capabilities. The results showed that soy proteins (SPI or SPC) responsed to torque, die pressure and temperature during extrusion, and this phenomenon was more pronounced at a higher protein content (SPI). In contrast, rice protein exhibited poor extrudability, leading to large losses of thermomechanical energy. TGase significantly affects the orientation of protein fibrous structures along the extrusion direction by impacting the rate of protein gelation during the high-moisture extrusion process, with the impact mainly occurring in the cooling die. Globulins (mainly 11S) played a major role in forming fibrous structures and the aggregation of globulins or reduction of gliadins under TGase modification impacted the orientation of the fibrous structure along the extrusion direction. Some thermomechanical treatment during high-moisture extrusion results in protein conversion from compact structure into more extended or stretched state, and the increase of random coil structures for proteins derived from wheat and rice would lead to these looser structures in the extrudates. Thus, TGase can be combined with high-moisture extrusion to regulate the formation of plant protein fibrous structures, dependent on the specific protein source and content.

Improving the Yield of Feruloyl Oligosaccharides from Rice Bran through Enzymatic Extrusion and Its Mechanism

Rice bran, rich in feruloyl arabinoxylan, is a good source of feruloyl oligosaccharides (FOs). To prepare FOs, bran was often hydrolyzed by amylase and protease to remove starch and protein and then hydrolyzed by xylanase, which was time-consuming and had a low yield. To solve the above problems, enzymatic extrusion was used to treat rice bran, and the effects of traditional hydrolysis, a combination of traditional extrusion and hydrolysis (extrusion-hydrolysis) and enzymatic extrusion on the yield of FOs were investigated and compared in this study. It was found that traditional extrusion and enzymatic extrusion significantly increased the yield of FOs. Particularly, the yield of FOs resulting from enzymatic extrusion was increased to 5.78%, while the yield from traditional hydrolysis was 4.23%. Microscopy analysis showed that extrusion damaged the cell wall of bran, which might increase the accessibility of xylanase to arabinoxylan and the yield of FOs. Spectroscopy analysis suggested that FOs obtained by different pretreatments had similar structures. It was obvious that enzymatic extrusion saved the time for removal of starch and protein and increased the yield of FOs. In addition, the highest yield of FOs was found at the moisture content of 30% and the screw speed of 50 rpm. This study provided an efficient method for the preparation of FOs that is suitable for industrial production.

Fabrication of starch-based packaging materials

This chapter aims to provide the reader with some information about the possibility of starch as a suitable substitute for synthetic polymers in biodegradable food packaging. This is due to the starch has good characteristics which are great biodegradability, low cost and also easy to gain from natural resources. However, some of technical challenges are also introduced before starch-based polymers can be used in more applications. These technical challenges involved preparation methods and incorporation of additives and these are being summarized in this topic. Hence, the enhancement of starch can be done in order to prepare innovative starch-based biodegradable materials.

Designing liquefaction and saccharification processes of highly concentrated starch slurry: Challenges and recent advances

Starch-based sugars are an important group of starch derivatives used in food, medicine, chemistry, and other fields. The production of starch sugars involves starch liquefaction and saccharification processes. The production cost of starch sugars can be reduced by increasing the initial concentration of starch slurry. However, the usage of the highly concentrated starch slurry is characterized by challenges such as low reaction efficiency and poor product performance during the liquefaction and saccharification processes. In this study, we endeavored to provide a reference guide for improving high-concentration starch sugar production. Thus, we reviewed the effects of substrate concentration on the starch sugar production process and summarized several potential strategies. These regulation strategies, such as physical field pretreatment, complex enzyme-assisted, and temperature control, can significantly increase the starch concentration and mitigate the challenges of using highly concentrated starch slurry. We believe that highly concentrated starch sugar production will achieve a qualitative leap in the future. This review provides theoretical guidance and highlights the importance of high concentration in starch-based sugar production. Further studies are needed to explore the fine structure and enzyme attack mode during the liquefaction and saccharification processes to regulate the production of more targeted products.

Food extrusion: An advanced process for innovation and novel product development

Extrusion is a versatile process capable of producing a variety of new and novel foods and ingredients, thus increasing manufacturing opportunities. Further, it could provide nutritious, safe, sustainable, and affordable foods, especially directed at individualized consumer needs. In addition to past research efforts, more investigations should be conducted in order to refine, redesign, or develop new extrusion processing technologies. The present review highlights the current advances made in new and novel food product development by considering the extrusion process, the influencing parameters, and product characteristics and properties; the most promising extrusion processes that can be used in novel food product and ingredient development, such as extrusion cooking, hot-melt extrusion, reactive extrusion, and extrusion-based 3D printing; the possibilities of using various raw materials in relation to process and product development; and the needs for product development modeling along with extrusion process design and modeling. In correlation with extruded product development, topics that merit further investigation may include structure formation, plant and animal biopolymers functionalization, biopolymer reactions, process simulation, modeling and control, engineering and mechanical aspects of extruders, analysis of pre-processing treatments, as well as prototyping, risk analysis, safety, sensory and consumer acceptance.

The Effect of Soybean Peptides on Improving Quality and the ACE Inhibitory Bioactivity of Extruded Rice

It is crucial to address the dietary problems of hypertensive patients. The effect and mechanism of different contents of soybean protein on cooking quality and angiotensin-converting enzyme (ACE) inhibitory action in the extruded rice were firstly investigated. The results showed that the extruded rice with soybean protein possessed the higher taste value (90.32 ± 2.31), hardness (2.65 ± 0.01 g), and good pasting quality (p ≤ 0.05). Meanwhile, the soybean protein notably retarded the starch digestibility; the sample with 6% soybean protein showed the fewest rapidly digestible starch (RDS) content (78.82 ± 0.01 mg g−1) and the most slowly digestible starch (SDS) content (8.97 ± 0.45 mg g−1). Importantly, the ACE inhibition rate improved from 17.09 ± 0.01% to 74.02 ± 0.65% in the 6% soybean protein sample because of the production of peptides. The peptide composition of samples were compared, which showed that the effective ACE-inhibitory peptides usually contain 2~20 amino acids, and Pro, Leu, Ile, Val, Phe, and Ala were the main components. Overall, moderate soybean protein would give a good quality and lower ACE activity in extruded food.

Intravitreal Injectable Hydrogels for Sustained Drug Delivery in Glaucoma Treatment and Therapy

Glaucoma is extensively treated with topical eye drops containing drugs. However, the retention time of the loaded drugs and the in vivo bioavailability of the drugs are highly influenced before reaching the targeted area sufficiently, due to physiological and anatomical barriers of the eye, such as rapid nasolacrimal drainage. Poor intraocular penetration and frequent administration may also cause ocular cytotoxicity. A novel approach to overcome these drawbacks is the use of injectable hydrogels administered intravitreously for sustained drug delivery to the target site. These injectable hydrogels are used as nanocarriers to intimately interact with specific diseased ocular tissues to increase the therapeutic efficacy and drug bioavailability of the anti-glaucomic drugs. The human eye is very delicate, and is sensitive to contact with any foreign body material. However, natural biopolymers are non-reactive, biocompatible, biodegradable, and lack immunogenic and inflammatory responses to the host whenever they are incorporated in drug delivery systems. These favorable biomaterial properties have made them widely applicable in biomedical applications, with minimal adversity. This review highlights the importance of using natural biopolymer-based intravitreal hydrogel drug delivery systems for glaucoma treatment over conventional methods.

Mechanoenzymatic Reactions Involving Polymeric Substrates or Products

Mechanoenzymology is an emerging field in which mechanical mixing is used to sustain enzymatic reactions in low-solvent or solvent-free mixtures. Many enzymes have been reported that thrive under such conditions. Considering the central role of biopolymers and synthetic polymers in our society, this minireview highlights the use of mechanoenzymology for the synthesis or depolymerization of oligomeric or polymeric materials. In contrast to traditional in-solution reactions, solvent-free mechanoenzymology has the advantages of avoiding solubility issues, proceeding in a minimal volume, and reducing solvent waste while potentially improving the reaction efficiency and accessing new reactivity. It is expected that this strategy will continue to gain popularity and find more applications.

Heat-induced conversion of multiscale molecular structure of natural food nutrients: A review

Thermal process is the most important way of treating foods. Heat energy inputted into the natural food system induces the depolymerization of multi-scale structures of matrix, and causes the intramolecular and intermolecular interactions of different nutrients. It attacks and breaks the original polymeric molecule structures and the functional properties of macronutrients such as carbohydrates, proteins and lipids. Micronutrients such as vitamins and other novel functional ingredients are also thermally converted. The heat-induced conversions of nutrients are slightly or totally with discrepancy in simple-, simulated- and real-food systems, respectively. Thus, this review aims to extensively summarize the heat-induced structural characteristics, thermal conversion pathways and pyrolysis mechanism of nutrients both in simple and complex food matrices. The structural change of each nutrient and its thermal reaction kinetics depend on the molecule structure and polymeric characteristic of the unit substances in the system.

Mechanical force-induced dispersion of starch nanoparticles and nanoemulsion: Size control, dispersion behaviour, and emulsified stability

High amylose starch nanoparticles (HS-SNPs) were rapidly synthesised by high-speed circumferential force of homogenisation (3000 and 15,000 rpm) during nanoprecipitation. Morphology and dynamic light scattering analyses showed that HS-SNPs fabricated by stronger circumferential shearing were excellent stabilisers in smaller sizes (20-50 nm). Their aggregates were liable to separate in the aqueous phase with the nano effect under either homogenisation over 6 min or ultrasonication in 2 min. SNP-based nanoemulsion (<200 nm) of high-water fraction was achieved, though the high hydrophilicity of the SNPs were identified by the contact angle. For homogenisation (with 100-2000 nm emulsion size), only time prolongation led to a better dispersion of SNP aggregates. Ultrasonication with periodic cavitation could disintegrate SNP aggregates into micro-aggregates for a stable emulsion system in a short period. In contrast, long-term ultrasound caused simultaneous re-agglomeration and solubilisation of the SNPs, leading to weakened interface barriers and decreased storage stability.

Bifunctional Fe3O4 nanoparticles as magnet and inducer in bioextruded fabrication of starch-based composite with hierarchical pore architecture

Starch (St) was used as green and renewable matrix (> 80%, db) for the preparation of Zn-St-MOCP/nFe₃O₄ composite via bioextrusion. Bifunction of Fe₃O₄ NPs as magnet and pore-inducer was confirmed and could be more homogeneously embedded in the St-based framework with hierarchical porous structure via SEM-EDS mapping. For the nFe₃O₄-induced microstructure of Zn-St-MOCP/nFe₃O₄ composite, submicronic pores and nanopores were observed with Fe₃O₄ NPs onto the inner surface of micron channels. According to the XPS, XRD, FTIR, TGA analyses, it is probably due to the coordination between Fe^3+/2+ and Zn²⁺/hydroxy groups and the recombination of St chains in crystalline/amorphous zones interfered by Fe₃O₄ NPs. Saturation magnetization value was measured with an excellent separation behavior. Seven kinetic equations were conducted for the fitting of dye adsorption data. Overall, the nFe₃O₄-assisted bioextrusion strategy is developed for the continuous fabrication of bio-based materials with rapid magnetic separation and hierarchical-pore architecture promising in practical adsorption.

Keratin-inorganic hybrid nanoflowers decorated with Fe3O4 nanoparticles as enzyme mimics for colorimetric detection of glucose

Fe₃O₄ magnetic nanoparticles (MNPs) are highly active enzyme-like catalysts. However, low stability is still a big challenge for Fe₃O₄-based enzyme mimics because the Fe₃O₄ MNPs can be easily dissolved when exposed to acidic conditions. Inspired by the numerous catalytic sites of a flower-like structure and the biological functions of amino acids in structural proteins, herein, by employing keratin as a protein component, stable Fe₃O₄-based MNP embedded keratin-Cu₃(PO₄)₂ nanoflowers were constructed, from which hierarchical nanostructures with a three-dimensional petal-like morphology were selected for subsequent studies owing to their excellent enzymic catalytic activity. The keratin-nanoflower@Fe₃O₄ exhibited significantly enhanced catalytic activity compared with that of keratin-Cu₃(PO₄)₂ nanoflowers and individual Fe₃O₄ MNPs. Remarkably, keratin-nanoflower@Fe₃O₄ exhibited superior long-term stability to Fe₃O₄ MNPs under more acidic conditions and favorable reusability. This method has been successfully exploited for the colorimetric determination of glucose in human serum with satisfactory sensitivity and specificity, offering a novel approach for glucose detection.

Recent advances in utilization of pectins in biomedical applications: a review focusing on molecular structure-directing health-promoting properties

The numerous health benefits of pectins justify their inclusion in human diets and biomedical products. This review provides an overview of pectin extraction and modification methods, their physico-chemical characteristics, health-promoting properties, and pharmaceutical/biomedical applications. Pectins, as readily available and versatile biomolecules, can be tailored to possess specific functionalities for food, pharmaceutical and biomedical applications, through judicious selection of appropriate extraction and modification technologies/processes based on green chemistry principles. Pectin's structural and physicochemical characteristics dictate their effects on digestion and bioavailability of nutrients, as well as health-promoting properties including anticancer, immunomodulatory, anti-inflammatory, intestinal microflora-regulating, immune barrier-strengthening, hypercholesterolemia-/arteriosclerosis-preventing, anti-diabetic, anti-obesity, antitussive, analgesic, anticoagulant, and wound healing effects. HG, RG-I, RG-II, molecular weight, side chain pattern, and degrees of methylation, acetylation, amidation and branching are critical structural elements responsible for optimizing these health benefits. The physicochemical characteristics, health functionalities, biocompatibility and biodegradability of pectins enable the construction of pectin-based composites with distinct properties for targeted applications in bioactive/drug delivery, edible films/coatings, nano-/micro-encapsulation, wound dressings and biological tissue engineering. Achieving beneficial synergies among the green extraction and modification processes during pectin production, and between pectin and other composite components in biomedical products, should be key foci for future research.

Advances in bio food packaging - An overview

In recent years, there has been an increase in demand for bioactive techniques in the food packaging industry. Although edible packaging is popular, it has yet to be effectively implemented into the market. Packaging made of plastics and chemicals is widely employed in the market today, posing a threat to the environment and living creatures. This research attempts to show current breakthroughs and progress in the field of biodegradable packaging. When compared to ancient packaging materials, bio-based packaging materials are safer. Sustainable biodegradable packaging materials can be made from edible films, coatings, and other bio food packaging techniques made from various biological resources. This paper discusses the important qualities and advantages of several bio-based packing materials. It is highlighted the advantages of bio-based packaging materials over synthetic packaging materials. It has been debated the importance of employing bio-based packaging to mitigate the environmental risks associated with traditional packaging technologies. Many researchers may be prompted by this study to focus on packaging reformulation options. Thus, we can attain food packing materials by considering customer's economic and sustainability aspects.

Stability and bioaccessibility of curcumin emulsions stabilized by casein hydrolysates after maleic anhydride acylation and pullulan glycation

The effects of maleic anhydride (MA) acylation and pullulan glycation on casein hydrolysates (CH) and the physicochemical stability of modified or unmodified CH-stabilized emulsions were explored. Compared with casein, the solubility of CH was improved, and CH₁ (hydrolysis degree 4%) exhibited the optimal emulsifying properties. After the acylation of MA, degrees of acylation (DA) increased with increasing addition of MA. Fourier-transform infrared spectroscopy revealed that a covalent bond was formed between MA and CH₁. The results of pullulan glycation indicated that the degree of glycation decreased with increasing DA. Acylation combined with glycation effectively reduced the surface hydrophobicity of CH. Results of analysis of physicochemical stability and gastrointestinal fate of curcumin in emulsions revealed that CH modified by MA acylation and pullulan glycation played a positive role in enhancing the stability and bioaccessibility of curcumin loaded in emulsions.

A comprehensive review of cereal germ and its lipids: Chemical composition, multi-objective process and functional application

Cereal germ (CG), a by-product of grain milling, has drawn much attention in the food industry because of its nutritional and functional advantages. Nowadays, the utilization of cereal germ from animal feeds to foodstuff is a popular trend. CGs have high content of polyunsaturated fatty acids in their lipids (43.9-64.9% of total fatty acids), but they are also induced to oxidative rancidity under the catalytic reaction of enzymes. Chemical and structural properties of lipids in CGs are affected by different treatments. Thermal and non-thermal effects prevent lipid oxidation or promote lipid combination with starch/protein in CG. Thus, the functional properties and final quality of CG are directly changed. In this review, the chemical composition and application of CGs especially the endogenous lipids are summarized and the effects of various processes on CG lipids/matrices are discussed for CG future development.

Investigation of the Formation Mechanism and Curcumin Bioaccessibility of Emulsion Gels Based on Sugar Beet Pectin and Laccase Catalysis

In this study, modified whey protein hydrolysates (WPH) were obtained after succinic anhydride succinylation and linear dextrin glycation, and emulsion gels were prepared on the basis of unmodified/modified WPH stabilized emulsions with sugar beet pectin (SBP) addition and laccase-catalyzed cross-linking. The influences of emulsifier types and SBP contents on the texture of emulsion gels were estimated. The texture and rheological properties of emulsion gels were characterized. An ideal gel emulsion was formed when the SBP content was 3% (w/w). A uniform network was observed in emulsion gels stabilized by W-L, W-L-S, and W-S-L. In addition, the effect of the emulsifier type on the bioaccessibility of curcumin encapsulated in emulsion gels was investigated and the W-S-L stabilized emulsion gel exhibited the highest curcumin bioaccessibility (65.57%). This study provides a theoretical basis for the development of emulsion gels with different textures by SBP addition and laccase cross-linking as encapsulation delivery systems.

Sono- and mechanochemical technologies in the catalytic conversion of biomass

This tutorial review focuses on the valorisation of biomass by sonochemical and mechanochemical activation.

Preparation and characterization of zein/carboxymethyl dextrin nanoparticles to encapsulate curcumin: Physicochemical stability, antioxidant activity and controlled release properties

In this work, zein/carboxymethyl dextrin nanoparticles were successfully fabricated at different zein to carboxymethyl dextrin (CMD) mass ratios. Zein/CMD nanoparticles with the negative charge and the smallest size (212 nm) were formed when the mass ratio of zein to CMD was 2:1, exhibiting improved encapsulation efficiency of curcumin (85.5%). Electrostatic interactions, hydrogen bonding and hydrophobic interactions were main driven forces for nanoparticles formulation and curcumin encapsulation. Fourier transform infrared spectroscopy determined curcumin might be partially embedded in CMD during encapsulation. The spherical structures of zein/CMD nanoparticles and curcumin-loaded zein/CMD nanoparticles were observed by transmission electron microscopy. The photothermal stability and antioxidant activity of curcumin were significantly enhanced after be loaded in zein/CMD nanoparticles. Furthermore, encapsulation of curcumin in zein/CMD nanoparticles significantly delayed the release of curcumin in simulated gastrointestinal fluids. These results indicated that zein/CMD nanoparticles could be effective encapsulating materials for bioactive compounds in food industry.

Effect of anion type on enzymatic hydrolysis of starch-(thermostable α-amylase)-calcium system in a low-moisture solid microenvironment of bioextrusion

The effect of six anions (Cl-, OH-, NO₃-, SO₄²-, C₆H₁₀O₆²- and PO₄³-) on a starch (St)-enzyme (thermostable α-amylase, TαA)-calcium (Ca) system was investigated in a low-moisture solid state. Two levels of Ca salts (1 and 10 mmol/100 g St) added to potato starch with and without TαA were analyzed by FT-IR, DSC and SEM. The surface morphologies of the St-Ca complexes were different in the presence of various anions, and the residual Ca salts around the St granules might decrease the enzymatic action. For bioextrusion, TαA (0.5‰ and 1.5‰) were introduced for a relatively low Ca content (1 mmol/100 g). Significant differences in enzyme activity were observed, increasing the activity of TαA by SO₄²- (146.54 %) > C₆H₁₀O₆²- > Cl- > control > NO₃- > OH- ≈ PO₄³- and C₆H₁₀O₆²- (123.20 %) ≈ Cl- ≈ SO₄²- > control > PO₄³ > OH- > NO₃- for the low and high enzyme levels, respectively.