Changes of soy protein under ultra-high hydraulic pressure

Exploring the effect of high pressure in the denaturation of casein micelles by in-situ SERS

To investigate the structural changes of casein in response to the pressurization process under varying pressure levels, this study carried out both ex-situ and in-situ high-pressure experiments. In the in-situ experiments, the surface-enhanced Raman scattering (SERS) technique was combined with a diamond anvil cell (DAC). The high-pressure experiments indicated that significant dissociation of casein occurred at 200 MPa. Over the range of 0-302 MPa, casein exhibited both dissociation and aggregation behaviors. However, casein tended towards aggregation at pressures of 302-486 MPa, with a further increase observed beyond 486 MPa.

Recent application of protein hydrolysates in food texture modification

The demand for clean labels has increased the importance of natural texture modifying ingredients. Proteins are unique compounds that can impart unique textural and structural changes in food. However, lack of solubility and extensive aggregability of proteins have increased the demand for enzymatically hydrolyzed proteins, to impart functional and structural modifications to food products. The review elaborates the recent application of various proteins, protein hydrolysates, and their role in texture modification. The impact of protein hydrolysates interaction with other food macromolecules, the effect of pretreatments, and dependence of various protein functionalities on textural and structural modification of food products with controlled enzymatic hydrolysis are explained in detail. Many researchers have acknowledged the positive effect of enzymatically hydrolyzed proteins on texture modification over natural protein. With enzymatic hydrolysis, various textural properties including foaming, gelling, emulsifying, water holding capacity have been effectively improved. It is evident that each protein is unique and imparts exceptional structural changes to different food products. Thus, selection of protein requires a fundamental understanding of its structure-substrate property relation. For wider applicability in the industrial sector, more studies on interactions at the molecular level, dosage, functionality changes, and sensorial attributes of protein hydrolysates in food systems are required.

Status of Plant Protein-Based Green Scaffolds for Regenerative Medicine Applications

In recent decades, regenerative medicine has merited substantial attention from scientific and research communities. One of the essential requirements for this new strategy in medicine is the production of biocompatible and biodegradable scaffolds with desirable geometric structures and mechanical properties. Despite such promise, it appears that regenerative medicine is the last field to embrace green, or environmentally-friendly, processes, as many traditional tissue engineering materials employ toxic solvents and polymers that are clearly not environmentally friendly. Scaffolds fabricated from plant proteins (for example, zein, soy protein, and wheat gluten), possess proper mechanical properties, remarkable biocompatibility and aqueous stability which make them appropriate green biomaterials for regenerative medicine applications. The use of plant-derived proteins in regenerative medicine has been especially inspired by green medicine, which is the use of environmentally friendly materials in medicine. In the current review paper, the literature is reviewed and summarized for the applicability of plant proteins as biopolymer materials for several green regenerative medicine and tissue engineering applications.

High hydrostatic pressure (HHP) effects on antigenicity and structural properties of soybean β-conglycinin

In this study, the effect of high hydrostatic pressure (HHP) on antigenicity, free sulfhydryl group (SH) content, hydrophobicity (Ho), fluorescence intensity and circular dichroism data of soybean β-conglycinin was studied. The antigenicity of soybean β-conglycinin was decreased significantly at pressures 200-400 MPa. The antigenicity inhibition rate of β-conglycinin declined from 92.72 to 55.15%, after being treated at 400 MPa for 15 min. Results indicated that free sulphydryl (SH) groups and surface Ho of β-conglycinin were significantly increased at pressures 200-400 MPa and 5-15 min, whereas these properties decreased at the treatments above 400 MPa and 15 min. The maximum fluorescence intensity was noticed at 400 MPa and 15 min. The circular dichroism data analysis revealed that the amount of β-turns and unordered structure significantly increased, while the content of α-helix1 and β-strand1 noticeably decreased. These results provide evidence that HHP-induced the structural modification of β-conglycinin and could alter the antigenicity of β-conglycinin.

Differential Scanning Calorimetry Analysis of the Effects of Heat and Pressure on Protein Denaturation in Soy Flour Mixed with Various Types of Plasticizers

The effects of heat and pressure on protein denaturation in soy flour were explored by an experimental design that used pressure (atmospheric to 600 MPa), temperature (room to 90 °C), time (1 to 60 min), and type of aqueous plasticizer (NaCl, sucrose, betaine, and lactobionic acid (LBA)) as factors. When 50% (w/w) soy flour-water paste was high hydrostatic pressure (HHP)-treated for 20 min at 25 °C, the treatment at 200 MPa showed a small effect on denaturation of only the 7S soy globulin, but the treatment at 600 MPa showed a significant effect on denaturation of both the 7S and 11S soy globulins. The treatment at 60 °C showed a less-pronounced effect on denaturation of the 11S globulin, even at 600 MPa, but that at 90 °C showed a similar extent of denaturation of the 11S globulin at 600 MPa to that at 25 °C. Chaotropic 2N NaCl, 50% sucrose-, 50% betaine-, or 50% LBA-water solutions showed protective effects on protein denaturation during HHP treatment at 25 °C. Although LBA enhanced the extent of thermostability of soy protein less than did 2N NaCl, LBA exhibited better stabilization against pressure. The results from DSC analysis demonstrated that thermostable soy proteins were not always barostable.

Characterization of physicochemical properties and IgE-binding of soybean proteins derived from the HHP-treated seeds

The aim of this work was to evaluate the characterization of physicochemical properties and IgE-binding of soybean proteins derived from the high hydrostatic pressure (HHP) treated seeds. Soybean seeds were treated by HHP at different pressures, and changes in the physicochemical properties of soybean proteins were characterized by proteins solubility, free sulfhydryl (SH) content, surface hydrophobicity, and secondary structures. Sodium dodecyl sulphate-polyacrylamide gel electrophoresis (SDS-PAGE) and enzyme-linked immunoabsorbent assay (ELISA) were used to define the proteins patterns and IgE-binding ability. The results showed that HHP treatment in the ranges of 0 to 500 MPa led to a slight but gradual decline in free SH content. The solubility and hydrophobicity of soybean proteins increased sharply from 100 to 200 MPa, and gradually decreased upon the further increase of pressure. The α-helix and β-sheets contents of soybean proteins decreased, while the random coil content increased. The SDS-PAGE showed that HHP treatment of 100 to 200 MPa could dissociate the proteins, breaking the aggregates into smaller units, while the treatment ranging from 300 to 500 MPa could induce the proteins aggregation into larger units. Moreover, the ELISA revealed that the IgE-binding of soybean proteins after HHP treatment at 200 MPa decreased 61.7% compared to the untreated group. Our findings suggested that HHP processing could not only modify the physicochemical properties of soybean proteins, but also significantly reduce its IgE-binding at an appropriate pressure level.

Opportunities and Challenges in High Pressure Processing of Foods

Consumers increasingly demand convenience foods of the highest quality in terms of natural flavor and taste, and which are free from additives and preservatives. This demand has triggered the need for the development of a number of nonthermal approaches to food processing, of which high-pressure technology has proven to be very valuable. A number of recent publications have demonstrated novel and diverse uses of this technology. Its novel features, which include destruction of microorganisms at room temperature or lower, have made the technology commercially attractive. Enzymes and even spore forming bacteria can be inactivated by the application of pressure-thermal combinations, This review aims to identify the opportunities and challenges associated with this technology. In addition to discussing the effects of high pressure on food components, this review covers the combined effects of high pressure processing with: gamma irradiation, alternating current, ultrasound, and carbon dioxide or anti-microbial treatment. Further, the applications of this technology in various sectors - fruits and vegetables, dairy, and meat processing - have been dealt with extensively. The integration of high-pressure with other matured processing operations such as blanching, dehydration, osmotic dehydration, rehydration, frying, freezing / thawing and solid-liquid extraction has been shown to open up new processing options. The key challenges identified include: heat transfer problems and resulting non-uniformity in processing, obtaining reliable and reproducible data for process validation, lack of detailed knowledge about the interaction between high pressure, and a number of food constituents, packaging and statutory issues.