Biopreservative and Anti-Mycotoxigenic Potentials of Lactobacillus paracasei MG847589 and Its Bacteriocin in Soft White Cheese

Probiotics and their bacteriocins have increasingly attracted interest for their use as safe food preservatives. This study aimed to produce soft white cheese fortified with Lacticaseibacillus MG847589 (Lb. paracasei MG847589) and/or its bacteriocin; cheese with Lacticaseibacillus (CP), cheese with bacteriocin (CB), and cheese with both Lacticaseibacillus and bacteriocin (CPB) were compared to control cheese (CS) to evaluate their biopreservative and anti-mycotoxigenic potentials for prolonged shelf life and safe food applications. The effects of these fortifications on physiochemical, microbial, texture, microstructure, and sensory properties were studied. Fortification with Lacticaseibacillus (CP) increased acidity (0.61%) and microbial counts, which may make the microstructure porous, while CPB showed intact microstructure. The CPB showed the highest hardness value (3988.03 g), while the lowest was observed with CB (2525.73 g). Consequently, the sensory assessment reflected the panelists' preference for CPB, which gained higher scores than the control (CS). Fortification with Lb. paracasei MG847589 and bacteriocin (CPB) showed inhibition effects against S. aureus from 6.52 log10 CFU/g at time zero to 2.10 log10 CFU/g at the end of storage, A. parasiticus (from 5.06 to 3.03 log10 CFU/g), and P. chrysogenum counts (from 5.11 to 2.86 log10 CFU/g). Additionally, CPB showed an anti-mycotoxigenic effect against aflatoxins AFB1 and AFM1, causing them to be decreased (69.63 ± 0.44% and 71.38 ± 0.75%, respectively). These potentials can extend shelf life and pave the way for more suggested food applications of safe food production by fortification with both Lb. paracasei MG847589 and its bacteriocin as biopreservatives and anti-mycotoxigenic.

The influence of yak casein micelle size on rennet-induced coagulation properties

BACKGROUND

Yak milk formed stronger rennet-induced gels if the milk contained smalled casein micelles and a higher concentration of calcium. Also casein gels could formed after a shorter incubation time if the milk contained smalled casein micelles. The objective of this study was to estimate the importance of yak casein micelle size on rennet-induced coagulation properties.

RESULTS

Three fractions of different-sized, undamaged casein micelles (Ф112.17 ± 0.83 nm, Ф207.13 ± 0.59 nm and Ф269.37 ± 2.89 nm) were obtained by ultracentrifugation. The smallest casein micelles had the highest concentrations of calcium (803.21 ± 8.49 mM), phosphate (445.52 ± 10.66 mM), and κ-casein/total casein (19.45%). Rheological analyses determined the optimal gelation times of small, medium, and large casein micelles to be 9.5 ± 0.5, 10.8 ± 0.5, and 13.3 ± 0.2 min, respectively. Higher κ-casein concentration in the small casein micelles appeared to facilitate their shorter incubation time. Both the faster caseinomacropeptide (CMP) release rate and rennet-induced aggregation rate of small casein micelles contributed to a faster change in turbidity. Furthermore, small casein micelles had the highest elastic modulus (G', 73.21 ± 4.5 Pa) 60 min after the addition of rennet. This was consistent with micro-photographs, which showed that small casein micelles could form a more homogeneous gel, which had smaller pore sizes. Trial cheese manufacture verified that yak cheese containing small casein micelles, formed curd faster and the cheese had higher texture profile analysis (TPA) values for hardness, cohesiveness, and springiness.

CONCLUSION

This is important information for the optimization of yak cheese industrial production. © 2020 Society of Chemical Industry.

Effect of Exopolysaccharides-producing Starter Culture on the Flavor Profile and Characteristics of Low Fat Ras Cheese

BACKGROUND AND OBJECTIVE

The application of the exopolysaccharide-producing starter culture for improving the texture and technical properties and evaluating flavor profile of low-fat Ras cheese was studied. The experimental design was performed to compare flavour compounds of traditional and exopolysaccharide producing starters (EPS) for different levels of fat milk cheese.

MATERIALS AND METHODS

Control (4% fat) with traditional starter, T1 (0% fat) with EPS, T2 (1% fat) with EPS), T3 (2% fat) with EPS and T4 (3% fat) with EPS were used. The physicochemical, textural profile analysis and organoleptic properties of fresh and stored cheeses (4 months) were determined. Also, the microscopic structural changes in fresh low-fat Ras cheese with EPS were evaluated.

RESULTS

The results indicated that addition of EPS producing cultures with decreasing fat of cheese milk lead to an increase in the moisture of treatments as well as hardness, cohesiveness, springiness, chewiness and gumminess of the resultant cheese. The data indicated that control cheese (full-fat and without EPS-producing cultures) had the lowest values of acidity. The changes in pH values among all cheese treatments and during storage period followed opposite trend to that of titratable acidity. There were negative correlation between the rate of fat reduction and the values of SN (soluble nitrogen).

CONCLUSION

Addition of EPS-producing cultures in Ras cheese milk improved sensory evaluation of resultant cheese, whereas cheese with 3% fat and EPS-producing culture (T4) selected as best Ras cheese sample.