A Lactic Acid Bacteria Consortium Impacted the Content of Casein-Derived Biopeptides in Dried Fresh Cheese

This study aimed to define a consortium of lactic acid bacteria (LAB) that will bring added value to dried fresh cheese through specific probiotic properties and the synthesis of bioactive peptides (biopeptides). The designed LAB consortium consisted of three Lactobacillus strains: S-layer carrying Levilactobacillus brevis D6, exopolysaccharides producing Limosilactobacillus fermentum D12 and plantaricin expressing Lactiplantibacillus plantarum D13, and one Enterococcus strain, Enterococcus faecium ZGZA7-10. Chosen autochthonous LAB strains exhibited efficient adherence to the Caco-2 cell line and impacted faecal microbiota biodiversity. The cheese produced by the LAB consortium showed better physicochemical, textural and sensory properties than the cheese produced by a commercial starter culture. Liquid chromatography coupled with matrix-assisted laser desorption/ionization-time of flight tandem mass spectrometry (LC-MALDI-TOF/TOF) showed the presence of 18 specific biopeptides in dried fresh cheeses. Their identification and relative quantification was confirmed by liquid chromatography-tandem mass spectrometry (LC-MS/MS) using multiple reaction monitoring (MRM). The results also showed that their synthesis resulted mainly from β-casein and also α-S1 casein degradation by proteolytic activities of the LAB consortium. The designed LAB consortium enhanced the functional value of the final product through impact on biopeptide concentrations and specific probiotic properties.

Effect of transglutaminase on fresh cheese quality propertises using citric acid as a coagulant

The purpose of this study was to evaluate the effect of microbial transglutaminase (MTGase) on cheese quality properties using citric acid as a coagulant agent. The experimental results showed that citric acid has a temperature-dependent ability to agglomerate milk proteins. The process of protein coagulation at 50°C by citric acid (2.0%) gave fresh cheese with yield production (% H), dry matter content (% TS) and cheese solids yield (CSY) of 12.81%, 41.17%, 38.73%, respectively. The reconstituted milk was incubated with MTGase under different conditions of enzyme concentration (0-6.0 IU / g protein), processing temperature (30-50 °C) and time (60-180 min.). Enzyme treatment at 37 °C with enzyme concentration of 2 IU/g protein for 2 hrs showed the highest values of yield (15.03%), dry matter content (46.96%) and cheese solids yield (46.83%). Analytical results of the sensory score, acidity, whey separation and color difference of fresh cheese samples during storage (28 days) showed that using MTGase better maintained the quality of the product. Furthermore, MTGase also improved water holding capacity (reduced whey separation) during storage and did not affect the color of fresh cheese products. Moreover, the physicochemical and microbiological parameters of the product were also determined. The results showed that the quality of fresh cheese coagulated by citric acid met CODEX STAN 221-2001 for unripened cheese including fresh cheese.

Influence of Food Matrices and the Population of Interfering Microorganisms on the Determination of Listeria monocytogenes by Conventional Methods and VIDAS

In this study, the possible influence of the food matrix and the interfering population of microorganisms on the detection and count of Listeria monocytogenes in three common foods of the Spanish diet (Spanish omelette, fresh cheese and vegetable salad) was determined. Four groups were assayed: one control, two groups with interfering microorganisms (Salmonella Enteritidis, Staphylococcus aureus and Proteus mirabilis) with different levels of L. monocytogenes and a final group only contaminated with L. monocytogenes. The samples were analyzed with the normalized method (UNE-EN ISO 11290:2018) and with an alternative technique (VIDAS). The results show that the presence of interfering microorganisms did not seem to interfere with the determination of L. monocytogenes. Furthermore, the type of food did not seem to influence the determination of L. monocytogenes, but the culture media used showed differences. In fact, regardless of the type of food, the ALOA medium showed higher sensitivity than the other media, with higher recovery in 100% of samples (only for the Spanish omelette in Group B was the result the same as that for PALCAM, −8.11 log cfu/g). The results obtained using the VIDAS were not influenced by any of the factors or conditions used and show 100% efficiency.

Surveillance of Fresh Artisanal Cheeses Revealed High Levels of Listeria monocytogenes Contamination in the Department of Quindío, Colombia

Listeriosis is a foodborne disease caused by Listeria monocytogenes. Because outbreaks of listeriosis are associated with the ingestion of contaminated dairy products, surveillance of artisanal cheeses to detect the presence of this microorganism is necessary. We collected three types of artisanal non-acid fresh cheese (Campesino, Costeño, and Cuajada) from 12 municipalities of the Department of Quindío, Colombia. L. monocytogenes was identified using VIDAS® and confirmed with API® Listeria Rapid Kit. L. monocytogenes was detected in 104 (53.6%) of the 194 artisanal fresh-cheese samples analyzed. The highest percentages of contamination were detected in Salento (90.9%), Calracá (65.5%), Armenia (64.9%), and Filandia (50%). A significant association between municipality and contamination with L. monocytogenes was identified. However, no association could be established between the type of cheese and the occurrence of the bacterium. This is the first study on the presence of L. monocytogenes in artisanal fresh cheeses sold in the municipalities of the Department of Quindío, and the findings revealed very high percentages of contaminated samples. The presence of L. monocytogenes in artisanal cheeses remains a public health threat in developing countries, especially Colombia, where existing legislation does not require the surveillance of L. monocytogenes in food.

Protein characterisation and antioxidant potential of fresh cheese obtained by kombucha inoculum

Protein profile, in vitro gastrointestinal digestion and antioxidant potential of two fresh cheese samples obtained by kombucha inoculum and traditional starter culture have been investigated in this study. There is a significant difference in protein profile and bioactive potential between fresh cheese samples. Kombucha fresh cheese contains higher proportion of protein, predominantly the casein fractions (α-casein and β-casein) compared to fresh cheese obtained by traditional culture. After gastrointestinal digestion (with pepsin and pancreatin), significantly higher amount of soluble protein and higher degree of hydrolyses were measured in kombucha fresh cheese sample than sample obtained by traditional culture. During gastrointestinal digestion, for fresh cheese with traditional starter both fractions of casein are degraded more rapidly by pepsin than in kombucha fresh cheese. The hydrolysates of cheese obtained by kombucha inoculum showed higher phenolic content and higher antiradical scavenging abilities than hydrolysates of fresh cheese produced with traditional starter. These results suggest that kombucha inoculum contributes to improvement of product’s bioactive potential.

Goat Paratuberculosis: Experimental Model for the Evaluation of Mycobacterium Persistence in Raw Milk Cheese

Mycobacterium avium subsp. paratuberculosis (MAP) is the causative agent of chronic proliferative enteritis found in ruminants, known as paratuberculosis (PTB). The spread of PTB is increasing in countries with advanced animal husbandry practices, leading to significant economic losses. Moreover, a supposed zoonotic role of MAP in Crohn’s disease (CD) in humans has been discussed by the scientific community; however, although the association between MAP and CD has generally been accepted, it is still up for debate if MAP is the main cause of CD, a contributing factor, or merely a commensal organism for the development of CD. The aim of this study was to assess the survival of MAP during the entire production process of a traditional Italian goat’s raw milk fresh cheese, the “Robiola di Roccaverano”, assessing the survival rate and persistence of MAP in the final product. A mix of MAP field isolates from goats of the Roccaverano area and a reference ATCC strain were used to carry out milk in experimental inoculation. Samples of milk, curd and cheese were taken in two consecutive batches of production. Microbiological challenge tests, evaluated by f57-qPCR, showed a significant decrease in MAP charge during the cheesemaking process for both batches, suggesting the productive process has an impact on MAP survival.

Proteolytic potential of psychrotrophic microorganisms isolated from fresh cheese

Devido a importância econômica da indústria de laticínios, a qualidade dos derivados lácteos deve ser uma preocupação constante. Algumas propriedades sensoriais e tecnológicas do leite e derivados estão relacionadas à microbiota deterioradora contaminante, representada, principalmente, por bactérias psicrotróficas proteolíticas que produzem enzimas termoresistentes. Os queijos frescos produzidos artesanalmente são geralmente fabricados com leite cru, por isso, é de grande importância conhecer a microbiota desses produtos. Portanto, o objetivo deste trabalho foi enumerar e isolar as bactérias psicrotróficas proteolíticas além de avaliar o potencial deteriorador desses microrganismos isolados de queijos frescos artesanais comercializados em Salinas, MG, Brasil. Após o isolamento das bactérias psicrotróficas proteolíticas presentes no queijo fresco, os isolados foram caracterizados em termos de coloração de Gram, forma e atividade de oxidase. A atividade proteolítica dos isolados foi confirmada pela formação de halo de hidrólise em meio de cultura específico. Os resultados destacaram a predominância de bactérias proteolíticas psicrotróficas Gram-positivas quando foi avaliada a microbiota deterioradora das amostras de queijo fresco. Considerando o potencial proteolítico, 34% dos isolados foram classificados como altamente proteolíticos. Os resultados mostraram que a contaminação inicial de queijos frescos pode interferir na qualidade microbiológica destes produtos.