Stability of whey protein hydrolysate powders: Effects of relative humidity and temperature

The Effect of Whey Protein Isolate Hydrolysate on Digestive Properties of Phytosterol

Phytosterol (PS) is a steroid, and its bioavailability can be enhanced by interacting with protein in the C-24 hydroxyl group. The interaction between sterols and amino acid residues in proteins can be enhanced by enzymatic hydrolysis. Phytosterol and whey insulation hydrolysates (WPH1-4) fabricated by the Alcalase enzyme at different enzymatic hydrolysis times were selected as delivery systems to simulate sterol C-24 hydroxyl group interaction with protein. Increasing hydrolysis time can promote the production of β-Lg, which raises the ratio of β-turn in the secondary structure and promotes the formation of interaction between WPH and PS. The correlation coefficient between hydrogen bonds and encapsulation efficiency (EE) and bioaccessibility is 0.91 and 0.88 (P < 0.05), respectively, indicating that hydrogen bonds of two components significantly influenced the combination by concealing the hydrophobic amino acids and some residues, which improved PS EE and bioavailability by 3.03 and 2.84 times after PS was combined with the WPI hydrolysate. These findings are expected to enhance the absorption of PS and other macromolecules by protein enzymatic hydrolysis to broaden their applications for food.

Physicochemical characteristics and antioxidant stability of spray-dried soy peptide fractions

The direct addition of health-promoting peptides to food products is limited due to their physicochemical instability and bitter taste as well as their bio-functionality may be influenced by M_W. In this study, SPI hydrolysate (SPIH) was Alcalase-prepared, size-fractionated (<10, 10-30, and 30-100 kD), and the amino acid composition of peptide fractions determined. The physicochemical properties, morphology, and antioxidant stability of the fractions were also investigated after spray-drying encapsulation in maltodextrin-WPC carrier. The two low M_W peptide fractions (especially, PF < 10) were more active than intact SPI, SPIH, and high M_W peptide fraction in scavenging free radicals and chelating transition metal ions. As compared to the particles containing SPIH, those containing the smallest peptide fraction (PF < 10) had higher solubility and hygroscopicity, lower production yield and wettability, and more wrinkles, indentations and surface roughness. The highest antioxidant stability during spray-drying was observed for the two low M_W peptide fractions, which examined by scavenging of free radicals of DPPH (88%), ABTS (97%), OH (93%) and NO (80%), chelating of iron (88%) and copper (87-90%) ions, reducing power (93%), and total antioxidant activity (90%). This finding reflects more structural and biological stability of the low M_W fractions to shear stress and dehydration during spray-drying, as compared with SPIH. The spray-drying encapsulated soy peptide fractions may be used as nutraceuticals for the development of functional foods.

The enzymatic modification of whey-proteins for spray drying encapsulation of Ginkgo-biloba extract

Ginkgo biloba extract (GBLE) contains many bioactives including flavonoids and terpene trilactones that play some pharmacological roles. These compounds are sensitive to operating conditions; so, encapsulation is a suitable approach to protect them. In this study, different carriers including maltodextrin (MD), and its combination with gum-Arabic (MD-GA), whey protein concentrate (MD-WPC), and whey-protein hydrolysate (MD-HWPC) were used to encapsulate GBLE. Powder production yield, physicochemical/functional characteristics, physical stability and flowability of particles were affected by the type and composition of carriers. FTIR results indicated the placement of phenolic compounds in the carrier matrix. The SEM images also showed the morphological changes of particles (especially the size, indentation and surface shrinkage) under the influence of various carriers. Microencapsulated powders formulated using MD-HWPC showed the highest values of TPC, DPPH, and ABTS and a lighter color which determined the suitability of this wall material (due to the improvement of surface activity and emulsifying properties of protein as a result of partial enzymatic hydrolysis) to protect the antioxidant properties of GBLE during spray-drying, improving the production yield and preserving physical and functional characteristics of the encapsulated powders.

Physicochemical and functional properties of egg white peptide powders under different storage conditions

This study aims to evaluate the effects of different storage conditions (temperature and relative humidity) on the physicochemical and functional properties of egg white peptide powders (EWPPs). The samples (EWPPs) were stored for 28 d under four conditions (4 °C, 50% RH; 4 °C, 75% RH; 25 °C, 50% RH; 25 °C, 75% RH). Results showed that storage temperature and relative humidity had a significant effect on the physicochemical and functional properties of EWPPs. The contents of antioxidant amino acids such as histidine, tyrosine, tryptophan, and lysine were reduced significantly under different storage conditions, which resulted in the decrease of the antioxidant activity of EWPPs. Circular dichroism spectroscopy analysis indicated that the secondary structure of EWPPs changed from the regular structure to the irregular coiled structure during the storage. Additionally, the hydrophobic groups of the EWPPs originally embedded inside the molecules were exposed to the surface of the molecules during the storage, which led to an aggregation of EWPPs molecule and a decrease in solubility of EWPPs. The aggregation of EWPPs molecules resulted in a decrease in emulsification, emulsification stability, foaming ability and foaming stability of the EWPPs. Therefore, different storage conditions do have an impact on the physicochemical and functional properties of EWPPs. Lower temperature and humidity storing conditions were beneficial to retain the functional property of the EWPPs.

Foaming and Physicochemical Properties of Commercial Protein Ingredients Used for Infant Formula Formulation

Protein, as one of the main ingredients for infant formula, may be closely related to the undesirable foam formed during the reconstitution of infant formula. Demineralized whey powder (D70 and D90), whey protein concentrate (WPC), and skimmed milk powder (SMP) are the four protein ingredients commonly used in infant formula formulation. The foaming and physicochemical properties of these four protein ingredients from different manufacturers were analyzed in the present study. Significant differences (p < 0.05) in foaming properties were found between the samples from different manufacturers. SMP showed a highest foaming capacity (FC) and foam stability (FS), followed by D70, D90, and WPC. Although the protein composition was similar based on reducing SDS-PAGE, the aggregates varied based on non-reducing SDS-PAGE, probably resulting in the different foaming properties. Particle size, zeta potential, and solubility of the protein ingredients were assessed. The protein structure was evaluated by circular dichroism, surface hydrophobicity, and free sulfhydryl. Pearson’s correlation analysis demonstrated that FC and FS were positively correlated with random coil (0.55 and 0.74), β-turn (0.53 and 0.73), and zeta potential (0.55 and 0.51) but negatively correlated with β-strand (−0.56 and −0.71), free sulfhydryl (−0.56 and −0.63), particle size (−0.45 and −0.53), and fat content (−0.50 and −0.49). The results of this study could provide a theoretical guidance for reducing formation of foam of infant formula products during reconstitution.

Desorption isotherms and isosteric heat of protein hydrolysate from tilapia slaughtering by-product

Abstract Due to the by-products generated during the processing of meat, biomolecules derived from these by-products, in the form of protein hydrolysates, have been studied for being used as raw materials to produce food. In the present study, the tilapia slaughtering by-products were hydrolyzed, under 60 oC for 2 hours, and spray-dried under 130 oC. After the drying process, equilibrium isotherms of the by-products were obtained through the dynamic method, under temperatures of 20 oC, 35 oC, and 50 oC. All the equilibrium curves presented type III behavior and in the adjustment of the empirical models, the White and Eyring model represented more properly the experimental data of equilibrium. This model presented the highest value of the determination coefficient and lower values of the Sum of the Squares of Residuals (SSR), Relative Mean Error (RME), and Akaike Information Criteria (AIC). The isosteric desorption heat, calculated by the Othmer method, varied from 2395 to 5682 kJ/kg, for equilibrium moisture contents between 0.09 and 0.30 kg/kg. The equation obtained for the calculation of the isosteric desorption heat of the tilapia by-product hydrolysate can be employed in calculations related to the modeling, simulation, optimization, and control of industrial-scale drying processes.

Whey proteins as stabilizers in amorphous solid dispersions

Whey proteins are extensively used as nutritional supplements but have so far not been investigated as co-formers for amorphous solid dispersions (ASD) to enhance the solubility and dissolution rate of poorly water soluble drugs. In this study, whey protein isolate (WPI) and whey protein hydrolysate (WPH) were each mixed with three poorly water soluble drugs (indomethacin: IND, carvedilol: CAR and furosemide: FUR) and prepared as ASDs at 50% (w/w) drug loading using vibrational ball milling. Subsequently, solid state characteristics, dissolution rate and physical stability of the obtained samples were analyzed. All ASDs showed a significant increase in their glass transition temperatures, as well as faster dissolution rates and higher apparent solubilities compared to both the respective pure crystalline and amorphous drugs. The saturation solubility of the drugs was increased in the presence of the whey proteins, and the investigated ASDs showed supersaturation by attaining higher drug concentrations compared to the respective saturation solubilities. Upon storage, ASDs containing IND were found to be physically stable for at least 27 months, whereas, ASDs containing CAR or FUR were stable for about 8 months and 17 months, respectively. This was a tremendous increase in physical stability compared to the pure amorphous drugs which recrystallized within less than one week. Overall, WPI and WPH proved to be promising co-formers and amorphous stabilizers in ASD formulations.

Particle Size of Milk Protein Concentrate Powder Affects the Texture of High-Protein Nutrition Bars During Storage

Milk protein concentrate powder with 85% protein (MPC85) was jet-milled to give 2 particle size distributions (that is, JM-Coarse and JM-Fine) or freeze-dried (FD), in order to improve the functional properties of MPC85 for use in high-protein nutrition (HPN) bars. Volume-weighted mean diameter decreased from 86 μm to 49, 22, and 8 μm in FD, JM-Coarse, and JM-Fine, respectively (P < 0.05). The MPC85 powders modified by jet-milling and freeze-drying were significantly denser than the control MPC85 (P < 0.05). Volume of occluded air in the modified powders decreased (P < 0.05) by an order of magnitude, yet only FD possessed a lower volume of interstitial air (P < 0.05). Particle size reduction and freeze-drying MPC85 decreased its water holding capacity and improved its dispersibility by at least 20%. Contact angle measurements showed that these modifications increased initial hydrophobicity and did not improve wettability. HPN bars made from JM-Fine or FD were firmer by 40 or 17 N, respectively, than the control on day 0 (P < 0.05). HPN bar maximum compressive force increased by 38%, 33%, and 242% after 42 d at 32 °C when formulated with JM-Fine, FD, or control MPC85, respectively. HPN bars prepared with JM-Fine were less crumbly than those formulated with control or FD MPC85. Physically altering the particle structure of MPC85 improved its ability to plasticize within HPN bars and this improved their cohesiveness and textural stability.

Physicochemical Changes and Glycation Reaction in Intermediate-Moisture Protein-Sugar Foods with and without Addition of Resveratrol during Storage

An intermediate-moisture food (IMF) model consisting of whey protein isolate and glucose and an IMF model fortified with resveratrol were used to study the effect of resveratrol on physicochemical changes and glycation of protein-sugar-rich foods during storage. The water activity (aw) of the storage was controlled at 0.75 or 0.56. The browning rate or hardness of fortified IMFs was significantly lower than that of IMFs after 45-day storage. The rate of Maillard reaction in the samples stored at aw 0.56 was higher than that of samples stored at aw 0.75. The fortified IMFs had lower levels of AGEs (advanced glycation end products), CML (N(ε)-(carboxymethyl)-l-lysine), and insoluble protein during storage. The inhibition capability of resveratrol against glycation was also confirmed by using sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), liquid chromatography mass spectrometry (LC-MS), and Fourier transform infrared spectroscopy (FTIR) analysis to monitor glycated proteins and protein aggregation in the samples. The results of this study suggested that resveratrol could be used as an inhibitor to reduce the formation of undesirable AGEs and other Maillard reaction products in foods during storage.

Effect of hydrolyzed whey protein on surface morphology, water sorption, and glass transition temperature of a model infant formula

Physical properties of spray-dried dairy powders depend on their composition and physical characteristics. This study investigated the effect of hydrolyzed whey protein on the microstructure and physical stability of dried model infant formula. Model infant formulas were produced containing either intact (DH 0) or hydrolyzed (DH 12) whey protein, where DH=degree of hydrolysis (%). Before spray drying, apparent viscosities of liquid feeds (at 55°C) at a shear rate of 500 s(-1) were 3.02 and 3.85 mPa·s for intact and hydrolyzed infant formulas, respectively. On reconstitution, powders with hydrolyzed whey protein had a significantly higher fat globule size and lower emulsion stability than intact whey protein powder. Lactose crystallization in powders occurred at higher relative humidity for hydrolyzed formula. The Guggenheim-Anderson-de Boer equation, fitted to sorption isotherms, showed increased monolayer moisture when intact protein was present. As expected, glass transition decreased significantly with increasing water content. Partial hydrolysis of whey protein in model infant formula resulted in altered powder particle surface morphology, lactose crystallization properties, and storage stability.