International Dairy Journal最新文献

This study aimed to assess the effects of ripening at refrigeration and ambient temperatures on physic-chemical and microbiological parameters of artisanal Minas cheeses (made from raw milk) and to model the kinetics of lactic acid bacteria – $LAB$, Escherichia coli – $Ec$, and coagulase-positive staphylococci – $Sa$ along the ripening. Cheese pH, acidity, and moisture, fat, and protein contents were quantified, as well as $LAB$, $Ec$, and $Sa$ concentrations. Richards and simplified Lotka-Volterra models were used to describe the microbial kinetic data. The fits were assessed by statistical indices, and the Monte-Carlo method was applied to identifiability analysis. Cheese moisture was reduced along the ripening, increasing protein concentration and acidity values. Cheese pH showed a reduction followed by an increase. $LAB$ concentration increased to the stationary phase after a few days; $Ec$ and $Sa$ concentrations increased and then decreased due to interactions with $LAB$ and low moisture content. Mathematical models successfully described the kinetics of $LAB$, $Ec$, and $Sa$ in cheese throughout ripening. Most parameters were not correlated to each other and were estimated with narrow confidence intervals.

Our previous study suggested that bound phenolic acids of rice bran were converted into free phenolic acids during fermentation and these free phenolic acids improved the yogurt stability. Thus, this work investigated the effect of adding ferulic acid, the major phenolic acid of rice bran, on the yogurt stability. It was observed that the syneresis of yogurt was reduced by adding 100 μg/mL ferulic acid before fermentation, which suggested that ferulic acid increased the yogurt stability. Accordingly, adding ferulic acid made the yogurt gel more compact. However, 100 μg/mL ferulic acid had no significant impact on the pH, viscosity, and viscoelasticity of yogurt. Thus, the interaction between ferulic acid and milk protein was investigated. It was observed that ferulic acid interacted with milk protein through the hydrogen bond and van der Waals force. Therefore, it was speculated that ferulic acid interacted with milk protein molecules and induced the more compact structure of yogurt, thus improving the yogurt stability. However, adding ferulic acid after fermentation had no significant impact on the yogurt stability, because the gelation of milk protein caused by fermentation hindered the interaction between ferulic acid and milk protein.

Listeria monocytogenes is a serious pathogen with several serogroups that differ in virulence and distribution among countries. This study determined the serogroups and virulence of 116 L. monocytogenes from sheep milk (n = 52) and goat milk (n = 64) in Jordan by several multiplex PCR. The results showed that the L. monocytogenes isolates belong to five serogroups. Most isolates (37.9%) belonged to serogroup 4b (d, e), followed by serogroup 1/2a (3a) (31.9%), serogroup 1/2b (26.7%), and serogroup 4a/c (2.6%) and serogroup IV (serotypes 1/2c and 3c) (0.9%). All isolates carried the internalin (inlA, inlC, inlJ) and lmo 2672 genes. Additionally, 36.4% and 29.0 % of 4b and 1/2b isolates carried the Listeriolysin S gene (llsX). Therefore, L. monocytogenes in sheep and goat milk are potential public health hazards because they belong to the major listeriosis-causing serogroups (4b, 1/2a, and 1/2b), and carry major virulence genes. Small ruminants’ milk and cheeses should be considered high-risk foods for L. monocytogenes infection. Thus, safe production practices should be monitored and enforced in small dairy shops.

Enzymatic dephosphorylation of casein removes phosphate groups from serine residues and reduces the negative charge. In contrast, succinylation caps the ε-amino group of lysine residues and increases the negative charge on the caseins. The effect of these modifications on the self-association of α_s1-casein was studied using analytical ultracentrifugation. Dephosphorylation and succinylation have contrasting effects on α_s1-casein self-assembly. Native α_s1-casein was a mixture of dimers, trimers and higher order oligomers under these experimental conditions. Increasing the level of succinylation dissociated oligomeric α_s1-casein resulting in an increase in the monomeric protein. In contrast, dephosphorylated samples formed larger assemblies compared to the native α_s1-casein. Experiments performed at protein concentrations of 1, 2 or 3 mg mL⁻¹ provided consistent results indicating that across this concentration range there is no major difference in the assembly formation. This study demonstrated the utility of analytical ultracentrifugation to understand casein assembly, which will underpin the understanding of proteins structures in dairy foods.

Colostrum, the first food given to mammals after birth, plays a critical role in newborn nutrition. It is characterized by its high nutrient content, presence of immunoglobulins, and functional compounds. This study collected and freeze-dried colostrum from four different animals (Karayaka sheep, Saanen goats, Danish red cows and buffalo). Chemical and functional properties (total phenolic content and antioxidant capacity), mineral, as well as mineral content, amino acid composition, and fatty acid profile of the dried samples, were determined. Nutritional properties (protein efficiency ratio (PER), biological value (BV) and net protein utilization (NPU)) of powdered colostrum were also determined. It was found that buffalo colostrum had higher fat and protein content, while goat colostrum had high antioxidant activity. Buffalo and goat colostrums had a biological value (BV) of 94.96–97.78. Major minerals were more abundant in cow colostrum and minor minerals were more abundant in sheep colostrum. In terms of essential fatty acids, sheep and goat colostrums stood out. In conclusion, this comprehensive analysis of the composition of colostrum from different species sheds light on the different nutrient profiles and potential health benefits and provides a theoretical basis for the development of commercial products from goat, sheep, cow and buffalo colostrum.

This study is the first to screen of lactic acid bacteria strains with antimicrobial effect against spore outgrowth of Bacillus sporothermodurans and characterize their technological properties. Eighty strains were isolated from Tunisia raw milk but only 8 isolates were selected based on their antagonistic activity against germinated spores of B. sporothermodurans and nine pathogenic bacteria. Phenotypic and genotypic characterization allowed us to distinguish three different species, namely Lactiplantibacillus plantarum, Levilactobacillus brevis and Lactococcus lactis. The lactic acid strains able to produce protease and lipase enzymes. The important antagonistic activity was observed in presence of L. lactis TLAB6 strain which produced a bacteriocin and lactic acid. The bacteriocin produced by the L. lactis TLAB6 is heat stable and resistant to trypsin. The results suggest that the selected LAB with antibacterial activity against germinated spore and technological properties may be used to preserve the food and formulate of bioactive functional foods.

The functional properties of foods are closely related with its matrix. This study examined the impact of curcumin-fortified Lactobacillus helveticus MB2-1 fermented milk gel on the intestinal lipid digestion and bioaccessibility of curcumin through dynamic digestion method. The gel properties, microstructure, oil droplets stability, free fatty acid (FFA) release and curcumin bioaccessibility during digestion of the curcumin-fortified milk gels fermented by L. helveticus MB2-1 or tradition commercial starters (Streptococcus thermophilus and Lactobacillus bulgaricus) were investigated and compared. The curcumin-fortified L. helveticus MB2-1 fermented milk gel was found to present higher apparent viscosity, more thicker properties, and firmer texture, which affect the gastrointestinal digesta status together with the release of oil droplets and solubilized curcumin, promote lipid digestion as well as enhance the bioaccessibility of curcumin during digestion. These results may provide valuable references for the design of therapeutic dairy products beneficial to health in terms of food matrix.

The study aims to produce yoghurt from kefir beverage and evaluate its fermentation kinetics, volatile organic compounds, texture, and microbial characteristics. Kefir, a fermented milk product, is known for its health benefits due to probiotic microorganisms. To improve its sensory properties, kefir was combined with yoghurt starter cultures (Lactobacillus delbrueckii and Streptococcus thermophilus), sodium caseinate, and lactose, and incubated for 12 and 24 h. Comprehensive analyses were conducted on the obtained yoghurts, encompassing fermentation parameters (pH and acidity), volatile organic compounds, and textural properties. The levels and viability of specific microorganisms within the samples were examined through propidium monoazide quantitative PCR (PMA-qPCR). The results showed that samples with Na-caseinate had higher firmness, consistency, and cohesiveness. Viscosity increased with the addition of Na-caseinate and lactose after 24 h. PMA-qPCR analysis revealed higher microorganism levels in samples with Na-caseinate and lactose. Solid-phase microextraction (SPME) and gas chromatography–mass spectrometry (GC-MS) analysis showed that diacetyl was the most common compound, and acetaldehyde and diacetyl levels decreased in yoghurts compared to kefir beverages. PMA-qPCR revealed that Streptococcus thermophilus had higher viability in samples with both Na-caseinate and lactose, while Lactobacillus delbrueckii had the highest viability in samples that contained only Na-caseinate incubated for 12 h. The study suggests that kefir-based yoghurt can be developed into a product with better sensory qualities and increased consumer appeal due to improved texture and aroma.

This work proposes the use of Near Infrared Spectroscopy (NIR) and multivariate analysis to identify and quantify potential adulterants in grated hard cheeses. The study includes permitted additives (microcellulose and silicon dioxide) at levels higher than those regulated, as well as non-permitted substances like wheat flour, wheat semolina, and sawdust. An authentication approach was developed using One-Class Partial Least Squares (OC-PLS) and Data-Driven Soft Independent Modeling of Class Analogy (DD-SIMCA). Excellent results were obtained by DD-SIMCA using multiplicative scattering correction (MSC), projecting all unadulterated grated hard cheese samples within the acceptance area (i.e., 100% of sensitivity in both the training and test sets) and 77 out 80 adulterated samples outside the acceptance area (i.e., 96% of specificity in the test set). Additionally, satisfactory quantification results were obtained by Partial Least Squares (PLS) for the study of microcellulose, wheat flour, and sawdust, with root mean square error of prediction (RMSEP) values of 1.217, 1.317, and 0.562% w/w, R²_pred values of 0.945, 0.945, and 0.957, and relative error of prediction (REP) values of 4.285, 4.271, and 4.836%, respectively. The proposed methodology provides a simple, rapid, and low-cost analytical tool to identify and quantify adulterations in grated hard cheeses, with the aim to protect consumers from deceptive practices that compromise the nutritional quality of this widely consumed food.

This study utilized whey protein concentrate (WPC) as the primary protein source, employing the Maillard reaction to link it with three distinct carbohydrates: lactose, maltodextrin, and gum Arabic. Mixtures were prepared with a 1:4 protein-to-carbohydrate ratio, and conjugation was performed using dry heating at a temperature of 60 °C, 50% relative humidity for 8 h processing time. Under the same conditions, native WPC was heated as a control group. The formation of conjugates was tracked by monitoring absorbance changes, browning index (BI), and reduction in free amino groups (FAG). All conjugates exhibited significant loss of FAG, correlating with an increase in BI. Shifts in protein fingerprint bands observed via Fourier Transform Infrared Spectroscopy suggested potential protein-carbohydrate interactions, while X-ray diffraction showed increased sample crystallinity post-conjugation. Solubility assessments across pH levels (3.0–8.0) indicated a 10–13% rise in solubility for conjugated samples compared to mixtures, broadening their potential applications. Moreover, the emulsion stability index demonstrated improved stability after conjugation. Overall, the Maillard reaction-mediated conjugation enhanced the solubility and stability of emulsions.