Protease-induced gelation of unheated and heated whey proteins: effects of pH, temperature, and concentrations of protein, enzyme and salts

Rheological and microstructural characterisation of heat-induced whey protein isolate gels affected by the addition of caseinomacropeptide

Caseinomacropeptide (CMP) is derived from the chymosin cleavage of κ-casein during cheese production. This study developed gels from CMPs, which were isolated by different ultrafiltration systems, and whey protein isolate (WPI), and studied their rheological and ultrastructural characteristics. The 30% WPI gel showed high elastic modulus (G') values and stronger structure than the other samples with CMP. Another gel, with 50% protein, 30% WPI and 20% CMP sample isolated from the 30 kDa retentate, had a weaker structure and lower G' value. The third gel, with 30% WPI and 20% CMP sample from the 5 kDa retentate derived from the 30 kDa retentate, presented intermediate structural strength. Despite the increase in protein concentration from the addition of CMP, there was a decrease in the strength of the gel network. Different CMP isolation processes also contributed to differences in the microscopic analysis of gel structures with the same protein content.

The effect of composition, microfluidization and process parameters on formation of oleogels for ice cream applications

The use of oleogels is an innovative and economical option for the technological development of some food products, among them ice creams. The aim of this study was to establish the best processing conditions to obtain an emulsion which form oleogels with the lowest ζ-potential and average droplet size (ADS) for use as ice cream base. Using surface response methodology (SRM), the effects of three numerical factors (microfluidization pressure, oil and whey protein concentration, WP) and four categorical factors (oil type, temperature, surfactant, and type of WP) on formation of emulsions were assessed. The response variables were ζ, ADS, polydispersity index (PDI), viscosity (η), hardness, cohesiveness and springiness. Additionally, a numerical optimization was performed. Two ice creams containing milk cream and oleogel, respectively were compared under the optimization conditions. Results suggest oleogels obtained from the microfluidization of whey and high oleic palm oil are viable for the replacement of cream in the production of ice cream.

Protein-Based Nanostructures for Food Applications

Proteins are receiving significant attention for the production of structures for the encapsulation of active compounds, aimed at their use in food products. Proteins are one of the most used biomaterials in the food industry due to their nutritional value, non-toxicity, biodegradability, and ability to create new textures, in particular, their ability to form gel particles that can go from macro- to nanoscale. This review points out the different techniques to obtain protein-based nanostructures and their use to encapsulate and release bioactive compounds, while also presenting some examples of food grade proteins, the mechanism of formation of the nanostructures, and the behavior under different conditions, such as in the gastrointestinal tract.

Effect of type and quality of milk on heat induced protein-protein interactions in khoa

The present study was carried out to evaluate the effect of developed acidity and subsequent neutralization of milk (cow/buffalo) on heat induced protein-protein interactions occurring at various stages during khoa preparation. Protein-protein interactions were studied in terms of surface hydrophobicity (Fmax), sulfhydryl (-SH) group and SDS PAGE. As milk progressed to boiling stage, increase in Fmax and decrease in -SH content was observed. Khoa prepared from cow milk had comparatively higher values for Fmax and lower values for -SH group. Fmax was observed to be highest in acidic samples followed by neutralized and fresh samples. While considering -SH group, maximum values were observed in neutralized samples followed by acidic and fresh samples of both milk and khoa. However, no visible difference was observed in SDS PAGE patterns of casein fractions isolated from different types of samples. The bands of β-lg and α-la did not resolve clearly in the khoa samples due to high heat treatment involved in its preparation, indicating intense denaturation of whey proteins especially in neutralized samples where an alkaline medium resulted in strong binding between casein and whey proteins. The quality of milk also resulted in altered heat induced protein-protein interactions in khoa.

Design of whey protein nanostructures for incorporation and release of nutraceutical compounds in food

Whey proteins are widely used as nutritional and functional ingredients in formulated foods because they are relatively inexpensive, generally recognized as safe (GRAS) ingredient, and possess important biological, physical, and chemical functionalities. Denaturation and aggregation behavior of these proteins is of particular relevance toward manufacture of novel nanostructures with a number of potential uses. When these processes are properly engineered and controlled, whey proteins may be formed into nanohydrogels, nanofibrils, or nanotubes and be used as carrier of bioactive compounds. This review intends to discuss the latest understandings of nanoscale phenomena of whey protein denaturation and aggregation that may contribute for the design of protein nanostructures. Whey protein aggregation and gelation pathways under different processing and environmental conditions such as microwave heating, high voltage, and moderate electrical fields, high pressure, temperature, pH, and ionic strength were critically assessed. Moreover, several potential applications of nanohydrogels, nanofibrils, and nanotubes for controlled release of nutraceutical compounds (e.g. probiotics, vitamins, antioxidants, and peptides) were also included. Controlling the size of protein networks at nanoscale through application of different processing and environmental conditions can open perspectives for development of nanostructures with new or improved functionalities for incorporation and release of nutraceuticals in food matrices.

Improved Functional Characteristics of Whey Protein Hydrolysates in Food Industry

This review focuses on the enhanced functional characteristics of enzymatic hydrolysates of whey proteins (WPHs) in food applications compared to intact whey proteins (WPs). WPs are applied in foods as whey protein concentrates (WPCs), whey protein isolates (WPIs), and WPHs. WPs are byproducts of cheese production, used in a wide range of food applications due to their nutritional validity, functional activities, and cost effectiveness. Enzymatic hydrolysis yields improved functional and nutritional benefits in contrast to heat denaturation or native applications. WPHs improve solubility over a wide range of pH, create viscosity through water binding, and promote cohesion, adhesion, and elasticity. WPHs form stronger but more flexible edible films than WPC or WPI. WPHs enhance emulsification, bind fat, and facilitate whipping, compared to intact WPs. Extensive hydrolyzed WPHs with proper heat applications are the best emulsifiers and addition of polysaccharides improves the emulsification ability of WPHs. Also, WPHs improve the sensorial properties like color, flavor, and texture but impart a bitter taste in case where extensive hydrolysis (degree of hydrolysis greater than 8%). It is important to consider the type of enzyme, hydrolysis conditions, and WPHs production method based on the nature of food application.

Effect of pretreatment on enzymatic hydrolysis of bovine collagen and formation of ACE-inhibitory peptides

Bovine collagen was pre-treated (boiled or high pressure (HP)-treated) and then hydrolysed by 6 proteases. The degree of hydrolysis (DH) and the angiotensin-converting enzyme (ACE)-inhibitory activity of hydrolysates were measured. All enzymes used were able to partly degrade collagen and release ACE-inhibitory peptides. The highest ACE-inhibitory activity was obtained with Alcalase. Pretreatment significantly influenced the DH and ACE-inhibition. For most enzymes, boiling for 5 min resulted in a significantly higher DH and ACE-inhibitory activity. With Alcalase and collagenase, hydrolysis and release of ACE-inhibitory peptides occurred without any pretreatment, but HP-treatment significantly improved the DH and ACE-inhibitory activity. HP did not markedly affect the hydrolysis with the other enzymes. The major peptides obtained with Alcalase were identified; all were released from the triple helix structure of collagen. Many of these peptides had C-terminal sequences similar to known ACE-inhibitory peptides. The present results suggest that collagen-rich food materials are good substrates for the release of potent ACE-inhibitory peptides, when proper pre-treatment and enzymatic treatment is applied.

Physicochemical characteristics and functional properties of vitabosa (mucuna deeringiana) and soybean (glycine max)

Physicochemical characteristics and functional properties of vitabosa flour (Mucuna deeringiana) and soybean flour (Glycine max) were determined. Oil absorption capacity was higher in vitabosa. Water absorption capacity was higher in soy and it was affected by the change in the ionic strength of the medium. Emulsifying Activity (EA) decreased with increasing concentration of flour, while Emulsifying Stability (ES) showed an increased. EA and ES of flours have more ionic strength in the range between 0.0 and 0.4 M, but it is reduced afterwards with the higher concentration of NaCl. Foaming stability varied with the concentration of flour solution reaching maximum values of 39 and 33% for vitabosa and soybean, respectively at 10% flour concentration.Vitabosa had the best foaming capacity (56% to 0.6 M) compared with soybeans (47% to 0.4 M). Maximum capacity of gelation was observed in vitabosa at 10% flour concentration. Increases in ionic strength of the flour solution, at low salt concentrations (<0.4 M), improved the gelation of flours.

In vitro digestion of beta-lactoglobulin fibrils formed by heat treatment at low pH

Extensive studies have been done on beta-lactoglobulin (beta-Lg) fibrils in the past decade due to their potential as functional food ingredients, gelling agents, and encapsulation devices etc. (van der Goot, A. J.; Peighambardoust, S. H.; Akkermans, C.; van Oosten-Manski, J. M. Creating novel structures in food materials: The role of well-defined shear flow. Food Biophys. 2008, 3(2), 120-125 and Loveday, S. M.; Rao, M. A.; Creamer, L. K.; Singh, H. Factors affecting rheological characteristics of fibril gels: The case of beta-lactoglobulin and alpha-lactalbumin. J. Food Sci. 2009, 74 (3), R47-R55). However, most of the studies focus on the formation and mechanism of the fibrils. Little is known about fibril digestibility to date. In this work, in vitro pepsin digestion of bovine beta-lactoglobulin (beta-Lg) fibrils in simulated gastric fluid was investigated using thioflavin T fluorescence photometry, sodium dodecyl sulfate-polyacrylamide gel electrophoresis, size-exclusion chromatography, matrix-assisted laser desorption/ionization mass spectrometry, and transmission electron microscopy (TEM). The fibrils were formed by heating beta-Lg solutions at 80 degrees C and pH 2.0 for 20 h. The fibrils were found to be digested completely by pepsin within 2 min, when long, straight fibrils were no longer observed by TEM. The peptides in the fibrils (2000-8000 Da) could be digested to smaller peptides (mostly <2000 Da) by pepsin. The peptides in the fibrils were believed to be more susceptible for pepsin to access and attack because of their hydrophobic nature. For comparison purposes, solutions of beta-Lg heated at neutral pH (pH 7.4) were also studied under the same conditions.

Influence of Processing on Functionality of Milk and Dairy Proteins

The inherent physical functionality of dairy ingredients makes them useful in a range of food applications. These functionalities include their solubility, water binding, viscosity, gelation, heat stability, renneting, foaming, and emulsifying properties. The suitability of dairy ingredients for an application can be further tailored by altering the structure of the proteins using appropriate processes. The processes discussed include physical modification (heat treatment, acidification, addition of mineral slats, homogenization, and shear), enzymatic modification (renneting, hydrolysis, and transglutamination), and chemical modification (use of chemical agents and the Maillard reaction). Emerging food processes (high pressure and ultrasound) are also discussed. The challenges for using dairy ingredients for the delivery of nutrients and bioactive components, while maintaining physical functionality, are also highlighted. There is a need for continued research into the fundamental aspects of milk proteins and their responses to various stresses for further differentiation of milk products and for the delivery of ingredients with consistent quality for target applications.

The influence of kosmotropic and chaotropic salts on the functional properties of Mucuna pruriens protein isolate

The influence of chaotropic and kosmotropic salts on Mucuna pruriens protein isolates was investigated. Protein solubility profile indicated that solubility was minimal at the isoelectric point of the protein isolate (4.0) while the solubility was maximal at pH 10.0 in all salt solutions. Chaotropes (I(-), ClO(4)(-) and SCN(-)) exhibit better protein solubility than the kosmotropes (SO(4)(2-), Cl(-) and Br(-)). Increase in protein solubility follows the Hofmeister series: NaSO(4)<NaCl<NaBr<NaI<NaClO(4)<NaSCN. Maximal water absorption capacity was recorded at low concentration of all the salts (0.1M). The water absorption capacity reduced as the concentration of the salts was increased to 2.0M. Kosmotropic salts exhibited better water absorption capacity than chaotropic salts. Both foaming capacity and stability were better in chaotropic salts compared with kosmotopic salts. Maximal foam capacities and stability were observed in protein solutions at 0.1M concentration. However the foam capacity and stability decreased as the concentration was increased further to 2.0M. The result indicates that emulsion activity index (EAI) and emulsion stability index (ESI) was reduced as the concentration of salts in each protein solution was increased. Protein solutions which contained NaSCN exhibited the highest emulsifying properties while those in Na(2)SO(4) recorded the lowest emulsifying properties. In addition, chaotropic salts had better emulsifying properties compared with kosmotropic salts. Increase in emulsifying activity follows the Hofmeister series. The least gelation concentration increased as the concentration of the salts increased. However chaotropic salts exhibited better gelation properties than kosmotropic salts.

Gel Formation of Peptides Produced by Extensive Enzymatic Hydrolysis of β-Lactoglobulin

The purpose of the present study was to identify which peptides were responsible for enzyme-induced gelation of extensively hydrolyzed beta-lactoglobulin with Alcalase in order to gain insight into the mechanism of gelation. Dynamic rheology, aggregation measurements, isoelectrofocusing as well as chromatography and mass spectrometry were used to understand the gel formation. A transparent gel was formed above a critical concentration of peptides while noncovalently linked aggregates appear with increasing time of hydrolysis. Extensive hydrolysis was needed for gelation to occur as indicated by the small size of the peptides. Isoelectrofocusing was successful at separating the complex mixture, and 19 main peptides were identified with molecular weight ranging from 265 to 1485 Da. Only one fragment came from a beta-sheet rich region of the beta-lactoglobulin molecule, and a high proportion of peptides had proline residues in their sequence.