Casein Degradation of Fynbo Cheese Salted with NaCl/KCl Brine and Ripened at Various Temperatures

ABSTRACT: Effect of temperature and salt substitution on casein degradation of Fynbo cheese was studied. Fynbo cheeses, salted in solutions of 190 g NaCl/L and of 100 g NaCl/L and 100 g KCl/L and ripened at 5, 12, and 16 °C, were sampled at 1, 5, 10, 20, 30, 60, and 90 d of ripening, at central and external zones. Samples were analyzed for moisture and chloride contents, maturation index, and casein degradation by urea‐polyacrylamide gel electrophoresis. NaCl replacement by KCl did not affect any of the parameters studied. Total salt concentration and ripening temperature affected proteolysis significantly. First‐order kinetics constants for α_s1‐casein degradation were in the range of 0.002 to 0.016 day^‐1 and the activation energy of the reaction was approximately 26 kcal/gmol.     

Secondary proteolysis of Fynbo cheese salted with NaCl/KCl brine and ripened at various temperatures

Effects of temperature and salt substitution on secondary proteolysis of Fynbo cheese were studied and different peaks of the chromatographic profiles were examined. Cheeses, salted in solutions of NaCl (190 g l⁻¹) and NaCl/KCl (100 g l⁻¹/100 g l⁻¹) and ripened at 5, 12, and 16 °C, were sampled during 90 days at two different zones. Samples were analysed by RP-HPLC of the trichloroacetic acid-soluble fraction. The information was successfully summarized in 2 dimensions, accounting for 86.5% of data variation using principal component analysis. The source of variation explained by PC1 (77.1% VAR) was related to the ripening time. Two groups of chromatographic peaks were distinguished according to the sign of PC2 loading. Total salt concentration and ripening temperature affected secondary proteolysis significantly, while NaCl replacement by KCl had no affect. An important peptide produced during cheese ripening (α_s1-casein (f1-23)) was tentatively identified, taking into account the chromatographic profile and the amino acid composition of the peak isolated.     

Whey protein aggregates-alginate composite gel for astaxanthin-chia oil encapsulation

Chia oil (rich in omega-3 fatty acids) and astaxanthin are associated with various benefits for human health. However, their low solubility and poor stability reduce their direct use as bioactive compounds. Its encapsulation within the appropriate material can be a solution in this case. This work evaluated the effect of whey protein aggregates (WPA) on the storage stability of chia oil-astaxanthin blends encapsulated in alginate gel beads. Bead characteristics and the stability of encapsulated bioactive compounds stored at 25°C for 30 days were evaluated. High values of encapsulation efficiency (>85%) were observed in the cases studied. The addition of WPA affected some characteristics of the beads and improved the stability of the bioactive compounds compared to pure alginate beads. After 30 days of storage, higher preservation of astaxanthin and lower content of lipid oxidation products were observed in beads with WPA compared to alginate beads.     

Influence of the degree of hydrolysis on the bioactive properties of whey protein hydrolysates using Alcalase®

Whey protein concentrate was enzymatically hydrolysed at several time courses using the commercial preparation Alcalase^® 2.4 L, different hydrolysates were achieved, and the effect of degree of hydrolysis (DH) on both technological and biological properties was studied. Results have shown that solubility, antioxidant and ACE inhibition activities were increased as DH was also augmented from about 8 to 17%. RP‐HPLC studies also revealed a decrease in hydrophobicity when samples were hydrolysed in comparison with controls. When the enzyme hydrolytic action was augmented, it stimulated both the bioactivity of whey protein and relevant technological properties, allowing these hydrolysates to be employed as additives in the development of food formulations.     

Characterisation of soluble aggregates from commercial whey protein concentrate suspensions: Effect of protein concentration,pH, and heat treatment conditions

Soluble aggregates obtained from heat‐treated suspensions of commercial whey protein concentrate with 74.4% w/w protein were characterised. The effect of protein concentration (7 and 8% w/w), pH (7.0, 7.5 and 8.0), and heating time (0, 5, 10, 15, 20 and 30 min) at 80 °C were evaluated. Whey protein concentrate suspensions with the highest protein concentration (8% w/w) and the lowest pH (pH 7.0) had the highest steady shear viscosity and absorbance values, indicating the effect of the soluble aggregate content (high concentration) and the aggregate size (at lower pH values). According to principal component analysis, samples with 8% w/w and pH 7.0 were grouped in a plot region that confirmed the behaviour observed by confocal microscopy. Those whey protein concentrate suspensions could have soluble aggregates with a strong probability of interacting with cations (in cold gelation applications such as microencapsulation) and with each other (in film‐formation during coating).     

Influence of technological variables on the functionality of the cell‐free fraction of fermented buttermilk

Buttermilk is a suitable substrate for fermentation with proteolytic strains of Lactobacillus in order to release peptide fractions able to enhance the gut mucosal immune system. We aimed to determine the influence of the degree of proteolysis of buttermilk proteins on their functionality. Animals received for seven consecutive days the cell‐free fraction of 10 or 20% (w/v) buttermilk fermented with Lactobacillus delbrueckii subsp. lactis 210 at pH 6. The pH was controlled either with NaOH or Ca(OH)₂. No significant differences in the number of IgA‐producing cells in the small intestine of mice were found. The functional capacity of the product under study was not affected by the technological variables considered.     

The influence of ripening temperature and sampling site on the proteolysis in Reggianito Argentino cheese

The effects of elevated ripening temperature and sampling site on proteolysis in Reggianito Argentino cheese were evaluated. Cheeses ripened at 12 or 18 °C and 85% relative humidity were analysed at 2, 4 and 6 months in 2 sampling zones (central and external). Samples were analysed to determine the physicochemical and proteolysis parameters through the urea-PAGE of the urea-soluble fraction, RP-HPLC analysis of the water-soluble fraction at pH 4.6, and the free amino acid analysis. Proteolysis was significantly affected by ripening temperature and sampling site. Urea-PAGE analysis showed that elevated temperature increased the degradation of α_s1- and β-casein. The degradation of α_s1-casein was larger in the central zone than in the external one, while β-casein degradation was similar in both zones. The majority peaks detected by RP-HPLC of the water-soluble fraction at pH 4.6 and free amino acids were significantly affected by ripening temperature and sampling site. Glu, His, Val, Leu, and Lys had the higher concentrations. Principal component analysis showed useful groupings when results from chromatograms were studied. In conclusion, the results obtained not only are useful to characterise the ripening of an Argentinean hard cheese, but also to evaluate the effect of an increase of ripening temperature on Reggianito Argentino cheese proteolysis.