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The roles of sulfhydryl/disulfide interactions and acid/pepsin hydrolysis on β-lactoglobulin (β-lg) thermal aggregation at acidic pH 3.35 and 2 were studied using rheology, sodium dodecyl sulfate-polyacrylamide gel electrophoresis (SDS-PAGE), transmission electron microscopy (TEM), and Western blotting. Pepsin promoted additional hydrolysis compared to the acid-hydrolyzed control sample based on a 12% increase in free amino groups. Hydrolysis with pepsin also resulted in an increase in the apparent viscosity by 2 logs upon heating 8% β-lg solutions at pH 3.35. Seemingly, hydrolysis promoted thermal aggregation of β-lg, correlating well with viscosity increases. Large microgels were observed in heated pepsin hydrolysates using TEM, supporting the increased viscosities of these dispersions. During thermal aggregation (85 °C, 3 h) of β-lg at pH 3.35, beyond the existence of limited disulfide interactions, acid hydrolysis and noncovalent interactions more likely play a crucial role in defining the functionality of acidified powdered modified whey ingredients.

We investigated the possibility of using starter cultures in sauerkraut fermentation and thereby reducing the quantity of salt used in the process. This, in turn, would reduce the amount of waste salt that would enter in our water resources. Phage, naturally present in sauerkraut fermentation, could potentially affect the starter cultures introduced. Thus, a mechanistic mathematical model was developed to quantify the growth kinetics of the phage and starter cultures. The model was validated by independent experiments with two Leuconostoc mesenteroides strains isolated from sauerkraut and their corresponding phage. Model simulations and experimental evidence showed the presence of phage-resistant cell populations in starter cultures which replaced phage-sensitive cells, even when the initial phage density (P 0 ) and multiplicity of infection (MOI) were low (P 0 < 1 ؋ 10 3 PFU/ml; MOI < 10 ؊4 ) in the MRS media. Based on the results of model simulation and parameter optimization, it was suggested that the kinetic parameters of phage-host interaction, especially the adsorption rate, vary with the initial phage and host densities and with time. The model was validated in MRS broth. Therefore, the effects of heterogeneity and other environmental factors, such as temperature and pH, should be considered to make the model applicable to commercial fermentations.Traditionally, sauerkraut fermentation is carried out by a small population of lactic acid bacteria (LAB) indigenous to cabbage in the presence of 2 to 3% salt (24). Sauerkraut fermentation is carried out in two stages, a heterofermentative stage followed by a homofermentative stage. Leuconostoc mesenteroides initiates the early heterofermentative stage and is primarily responsible for the quality characteristics, such as flavor and aroma, of sauerkraut (22). Salt serves as a selecting agent for LAB and thus is an important factor in deciding the microbial succession during sauerkraut fermentation. During the fermentation process, excess brine is discharged in effluents from processing plants. Due to the environmental concerns about waste salt disposal and the associated economic issues, it may be desirable to reduce the salt concentration by 50% or more. To ensure quality with low-salt fermentations, starter cultures may be needed to maintain the desired flavor and texture of the finished product.In previous studies, Leuconostoc species have been used as starter cultures for sauerkraut fermentations. The starter cultures were found to prolong the heterolactic fermentation, which is responsible for the characteristic flavor and aroma of sauerkraut (4, 13). Recent studies have investigated the genetics and ecology of bacteriophage from fermentating sauerkraut (20,30). Phage active against several LAB have been isolated from commercial fermentations, including L. mesenteroides, which is a potential starter culture for sauerkraut fermentation (20,30). These studies raised the possibility that phage may interfere with the use of starter cultures in low-salt vegetabl...

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