Substitution of whey protein by pea protein is facilitated by specific fractionation routes

Characterizations of emulsion gel formed with the mixture of whey and soy protein and its protein digestion under in vitro gastric conditions

Partially replacing animal proteins with plant proteins to develop new products has much attention. To get knowledge of their application in emulsion gels, heat-induced composite protein emulsion gels were fabricated using the mixtures of whey protein isolate (WPI) and soy protein isolate (SPI) with the final total protein concentration of 10% (w/w). The water holding capacity (WHC), mechanical and rheological properties and microstructure of mixed protein emulsion gels prepared at different WPI to SPI ratios (100:0, 90:10, 70:30, 50:50, 30:70, 10:90, 0:100, w/w) were investigated. The ratios of WPI to SPI showed little effect on the WHC of the mixed protein emulsion gels (p > 0.05). Increasing the ratio of SPI decreased the hardness and storage modulus (G') of mixed protein emulsion gels, whereas the porosity of mixed protein emulsion gels in the microstructure increased, as shown by CLSM. Both β-lactoglobulin and α-lactalbumin from WPI and 7 S and 11 S from SPI participated in forming the gel matrix of mixed protein emulsion gels. More protein aggregates existed as the gel matrix filler at the high soy protein levels. Interestingly, the G' of mixed protein emulsion gels at the WPI to SPI ratio of 50:50 was higher than the sum of G' of individual WPI and SPI emulsion gels. The whey protein network predominated the gel matrix, while soy protein predominated in the active filling effect. When subjected to an in vitro dynamic gastric digestion model, soy protein in the gels (WPI:SPI = 50:50) degraded faster than whey protein during gastric digestion. This study provided new information on the characteristics of composite protein emulsion gel fabricated with the WPI and SPI mixture.

Dry fractionation process operations in the production of protein concentrates: A review

The market for plant proteins is expanding rapidly as the negative impacts of animal agriculture on the environment and resources become more evident. Plant proteins offer competitive advantages in production costs, energy requirements, and sustainability. Conventional plant-protein extraction is water and chemical-intensive, posing environmental concerns. Dry fractionation is an energy-efficient and environmentally friendly process for protein separation, preserving protein's native functionality. Cereals and pulses are excellent sources of plant proteins as they are widely grown worldwide. This paper provides a comprehensive review of the dry fractionation process utilized for different seeds to obtain protein-rich fractions with high purity and functionality. Pretreatments, such as dehulling and defatting, are known to enhance the protein separation efficiency. Factors, such as milling speed, mill classifier speed, feed rate, seed type, and hardness, were crucial for obtaining parent flour of desired particle size distribution during milling. The air classification or electrostatic separation settings are crucial in determining the quality of the separated protein. The cut point in air classification is targeted based on the starch granule size of the seed material. Optimization of these operations, applied to different pulses and seeds, led to higher yields of proteins with higher purity. Dual techniques, such as air classification and electrostatic separation, enhance protein purity. The yield of the protein concentrates can be increased by recycling the coarse fractions. Further research is necessary to improve the quality, purity, and yield of protein concentrates to enable more efficient use of plant proteins to meet global protein demands.

Quantifying the effects of pre-roasting on structural and functional properties of yellow pea proteins

Roasting could modify the protein structure/conformation, contributing to changes in functional properties. Here we investigated the effects of pre-roasting on the extraction efficiency, structural and functional properties of pea protein concentrates and isolates (PPC and PPI) produced from yellow split peas. The shorter roasting times (150 °C, 10 and 20 min) had little effect on protein yields and could increase the solubility of PPC or PPI by ∼ 12% at pH 7 and enhance the solubility of PPI by ∼ 12% (10-min roasting) and ∼ 24% (20-min roasting) at pH 3. However, a longer duration of pre-roasting (150 °C, 30 min) significantly reduced the extraction efficiency of PPC and PPI by ∼ 30% and ∼ 61%, respectively. Meanwhile, pre-roasting had minor effects on SDS-PAGE profiles and the secondary structures of pea proteins but significantly altered tertiary structures by reducing free sulfhydryl groups, increasing disulfide bonds and surface hydrophobicity. As for the emulsifying properties, pre-roasting improved the emulsion ability index (EAI) of PPC and PPI but decreased the emulsion stability index (ESI) of PPC and had no significant effect on PPI. Moreover, PPC and PPI with shorter pre-roasting duration (10 and 20 min) had endothermic peaks and showed a slight decrease in the denaturation temperature (Td) and the onset temperature (To), respectively. Overall, the study demonstrated that controlled pre-roasting at 150 °C for 10 min and 20 min altered protein structures (mainly tertiary structures), improving the solubility and EAI of pea proteins at pH 7, while retaining their thermal properties in comparison to unroasted samples.

Thermal Behavior of Pea and Egg White Protein Mixtures

The partial substitution of animal protein by plant protein is a new opportunity to produce sustainable food. Hence, to control the heat treatment of a composite protein ingredient, this work investigated the thermal behavior of mixtures of raw egg white (EW) and a laboratory-prepared pea protein isolate (PPI). Ten-percentage-by-weight protein suspensions prepared with different PPI/EW weight ratios (100/0, 75/25, 50/50, 25/75, 0/100) at pH 7.5 and 9.0 were analyzed by differential scanning calorimetry (DSC) and dynamic rheology in temperature sweep mode (T < 100 °C). The DSC data revealed changes in the thermal denaturation temperatures (Td) of ovotransferrin, lysozyme, and pea legumin, supposing interactions between proteins. Denaturation enthalpy (∆H) showed a high pH dependence related to pea protein unfolding in alkaline conditions and solubility loss of some proteins in admixture. Upon temperature sweeps (25-95 °C), the elastic modulus (G') of the mixtures increased significantly with the EW content, indicating that the gel formation was governed by the EW protein. Two thermal sol-gel transitions were found in EW-containing systems. In particular, the first sol-gel transition shifted by approximately +2-3 °C at pH 9.0, probably by a steric hindering effect due to the presence of denatured and non-associated pea globulins at this pH.

Comparative study on molecular and higher-order structures of legume seed protein isolates: Lentil, mungbean and yellow pea

Lentils and mungbean proteins are under-researched compared to pea and soybean. Lentils (green, red and black-lentils), mungbean and yellow pea protein isolates were obtained by alkaline extraction (pH 9)-isoelectric precipitation (pH 4.5) and investigated for molecular and higher-order structures using complementary and novel approaches. These extracted isolates showed comparable protein content but significantly greater nitrogen solubility index (NSI > 85 %) than commercial pea and soy protein isolates (NSI < 60 %). Based on molecular weight estimations from sodium dodecyl sulphate-polyacrylamide gel electrophoresis analysis, the soluble proteins of lentils and yellow pea were identified as legumin-like and vicilin-like, while mungbean was dominated by vicilin-like proteins. The soluble extracts were confirmed to be in native structural condition by size exclusion chromatography and nano-differential scanning calorimetry, unlike commercial extracts. Further differences in secondary structure were evident on circular dichroism spectra of the soluble extracts and deconvolution of the Amide I region (1700-1600 cm-1) from Fourier Transform Infrared of the total protein.

Effects of ultrasonic treatment on the structural and functional properties of cactus (Opuntia ficus-indica) seed protein

With the steady increase in the consumption of ultra-processed foods, there is growing interest in sustainable diets that include more plant protein. However, little information is available regarding the structural and functional properties of cactus (Opuntia ficus-indica) seed protein (CSP), a by-product of the cactus seed food-processing chain. This study aimed to explore the composition and nutritional value of CSP and reveal the effects of ultrasound treatment on protein quality. Protein chemical structure analysis showed that an appropriate intensity of ultrasound treatment (450 W) could significantly increase protein solubility (96.46 ± 2.07%) and surface hydrophobicity (13.76 ± 0.85 μg), decrease the content of T-SH (50.25 ± 0.79 μmol/g) and free-SH (8.60 ± 0.30 μmol/g), and enhance emulsification characteristics. Circular dichroism analysis further confirmed that the ultrasonic treatment increased the α-helix and random coil content. Amino acid analysis also suggested that ultrasound treatment (450 W) increased the hydrophobic amino acid content. To evaluate the impact of changes in the chemical structure, its digestion behavior was studied. The results showed that ultrasound treatment increased the release rate of free amino acids. Furthermore, nutritional analysis showed that the digestive products of CSP by ultrasound treatment can significantly enhance the intestinal permeability, increase the expression of ZO-1, Occludin and Claudin-1, thus repairing LPS induced intestinal barrier disfunction. Hence, CSP is a functional protein with high value, and ultrasound treatment is recommended. These findings provide new insights into the comprehensive utilization of cactus fruits.

Membrane Emulsification as an Emerging Method for Lacticaseibacillus rhamnosus GG® Encapsulation

Techniques capable of producing small-sized probiotic microcapsules with high encapsulation yields are of industrial and scientific interest. In this study, an innovative membrane emulsification system was investigated in the production of microcapsules containing Lacticaseibacillus rhamnosus GG® (Lr), sodium alginate (ALG), and whey protein (WPI), rice protein (RPC), or pea protein (PPC) as encapsulating agents. The microcapsules were characterized by particle size distribution, optical microscopy, encapsulation yield, morphology, water activity, hygroscopicity, thermal properties, Fourier-transform infrared spectroscopy (FTIR), and probiotic survival during in vitro simulation of gastrointestinal conditions. The innovative encapsulation technique resulted in microcapsules with diameters varying between 18 and 29 μm, and encapsulation yields > 93%. Combining alginate and whey, rice, or pea protein improved encapsulation efficiency and thermal properties. The encapsulation provided resistance to gastrointestinal fluids, resulting in high probiotic viability at the end of the intestinal phase (> 7.18 log CFU g-1). The proposed encapsulation technology represents an attractive alternative to developing probiotic microcapsules for future food applications.

Graphical Abstract

Supplementary Information

The online version contains supplementary material available at 10.1007/s11947-023-03099-w.

In vitro gastro-small intestinal digestion of conventional and mildly processed pea protein ingredients

We report on the effect of processing, particularly heating, on the digestion dynamics of pea proteins using the standardised semi-dynamic in vitro digestion method. Fractions with native proteins were obtained by mild aqueous fractionation of pea flour. A commercial pea protein isolate was chosen as a benchmark. Heating dispersions of pea flour and mild protein fractions reduced the trypsin inhibitory activity to levels similar to that of the protein isolate. Protein-rich and non-soluble protein fractions were up to 18% better hydrolysed after being thermally denatured, particularly for proteins emptied later in the gastric phase. The degree of hydrolysis throughout the digestion was similar for these heated fractions and the conventional isolate. Further heating of the protein isolate reduced its digestibility as much as 9%. Protein solubility enhances the digestibility of native proteins, while heating aggregates the proteins, which ultimately reduces the achieved extent of hydrolysis from gastro-small intestinal enzymes.

Plant Proteins for Future Foods: A Roadmap

Protein calories consumed by people all over the world approximate 15-20% of their energy intake. This makes protein a major nutritional imperative. Today, we are facing an unprecedented challenge to produce and distribute adequate protein to feed over nine billion people by 2050, in an environmentally sustainable and affordable way. Plant-based proteins present a promising solution to our nutritional needs due to their long history of crop use and cultivation, lower cost of production, and easy access in many parts of the world. However, plant proteins have comparatively poor functionality, defined as poor solubility, foaming, emulsifying, and gelling properties, limiting their use in food products. Relative to animal proteins, including dairy products, plant protein technology is still in its infancy. To bridge this gap, advances in plant protein ingredient development and the knowledge to construct plant-based foods are sorely needed. This review focuses on some salient features in the science and technology of plant proteins, providing the current state of the art and highlighting new research directions. It focuses on how manipulating plant protein structures during protein extraction, fractionation, and modification can considerably enhance protein functionality. To create novel plant-based foods, important considerations such as protein-polysaccharide interactions, the inclusion of plant protein-generated flavors, and some novel techniques to structure plant proteins are discussed. Finally, the attention to nutrition as a compass to navigate the plant protein roadmap is also considered.