Semi-hard Cheese Research Articles

Prevention of Fungal Contamination in Semi-Hard Cheeses by Whey-Gelatin Film Incorporated with Levilactobacillus brevis SJC120.

Cheese whey fermented by lactic acid bacteria (LAB) was used to develop an edible film with antifungal properties. Five LAB strains isolated from artisanal cheeses were screened for antifungal activity and incorporated into a whey-gelatin film. Of the strains tested, Levilactobacillus brevis SJC120 showed the strongest activity against five filamentous fungi isolated from cheese and cheese-making environment, at both 10 °C and 20 °C. The cell-free supernatant from L. brevis inhibited fungal growth by more than 80%. Incorporation of bacterial cells into the film did not alter the moisture content, water vapor permeability, or mechanical and optical properties. The whey-gelatin film was also able to maintain the viability of L. brevis cells at 107 log CFU/g after 30 days at 10 °C. In cheeses wrapped with L. brevis film, the size of fungal colonies decreased by 55% to 76%. Furthermore, no significant differences (p > 0.05) were observed in cheese proteolysis or in the moisture, fat, and protein content of the cheese wrapped with films. The results showed that whey-gelatin film with L. brevis SJC120 can reduce the contamination of cheese with filamentous fungi and could be used as an alternative to conventional cheese preservation and packaging.

Optimization of Modified Atmosphere Packaging for Sheep’s Milk Semi-Hard Cheese Wedges during Refrigerated Storage: Physicochemical and Sensory Properties

Modified atmosphere packaging (MAP) has become a good potential strategy to retain quality throughout the shelf life of perishable foods. The aim of this work was to evaluate different packaging atmospheres on semi-hard protected designation of origin Idiazabal cheese wedges. Six different packaging treatments (air, vacuum, and CO2/N2 gas mixtures in the ratio of 20/80, 50/50, 80/20, and 100/0% v/v, respectively) were studied. Changes in gas headspace composition, cheese gross composition, weight loss, pH, acidity, colour, and textural and sensory properties were investigated during 56 days of refrigerated storage at 5 ± 1 °C. MAP was the most effective preserving technique compared to air- and vacuum-packaging treatments. The cheese characteristics with the greatest discriminating weight in the preservation techniques were paste appearance, holes, flavour, a* (redness) and b* (yellowness) colour parameters, and slope to hardness. Air-packaged cheeses, on 35 day, presented a mouldy flavour. Vacuum packaging affected paste appearance (greasy, plastic marks, and non-homogeneous colour) and holes (occluded and unnatural appearance) starting after 14 packaging days. MAP mixtures with CO2 concentration between 50/50 and 80/20% CO2/N2 (v/v) are recommended to ensure sensory quality and stability in the distribution of these raw sheep-milk cheese wedges.

Role of Feeding and Novel Ripening System to Enhance the Quality and Production Sustainability of Curd Buffalo Cheeses

The buffalo dairy sector is extending its boundaries to include new buffalo cheese productions beyond mozzarella, overcoming some barriers that make cheeses expensive and unsustainable. This study aimed to evaluate the effects of both the inclusion of green feed in the diet of Italian Mediterranean buffaloes and an innovative ripening system on buffalo cheese quality, providing solutions capable of guaranteeing the production of nutritionally competitive and sustainable products. For this purpose, chemical, rheological, and microbiological analyses were carried out on cheeses. Buffaloes were fed with or without the inclusion of green forage. Their milk was used to produce dry ricotta and semi-hard cheeses, ripened according to both respective traditional (MT) and innovative methods (MI); these are based on automatic adjustments of climatic recipe guided by the continuous control of pH. Green feed enhances the nutritional profile of the final products (high content of MUFAs and PUFAs). As far as the ripening method is concerned, to our knowledge, this is the first study that tests aging chambers, commonly used for meat, for the maturing of buffalo cheeses. Results pointed out the MI validity also in this field of application, as it shortens the ripening period without negatively compromising any of desirable physicochemical properties and the safety and hygiene of the final products. Conclusively, this research highlights the benefits of diets rich in green forage on productions and provides support for the ripening optimization of buffalo semi-hard cheeses.

Биотехнологические подходы улучшения органолептических характеристик полутвердых сыров с низкой температурой второго нагревания

Для традиционных сыров с низкой температурой второго нагревания, формуемых из пласта, необходимой микрофлорой являются мезофильные гомоферментативные лактококки Lc. lactis subsp. lactis, Lc. lactis ssp. cremoris и Lc. lactis ssp. diacetylactis. Соотношение между видами и подвидами заквасочных микроорганизмов отражается на качестве готовой продукции. Для исследуемой группы сыров соотношение между кислото- и газоароматообразующими лактококками является определяющим для формирования искомого сырного вкуса, сливочного аромата и характерного рисунка. В статье представлены результаты исследования динамики развития и метаболизма кислотообразующих лактококков Lc. lactis ssp. lactis и Lc. lactis ssp. cremoris и газо-ароматообразующих лактококков Lc. lactis ssp. diacetylactis в процессе созревания экспериментальных сыров и влияние их соотношения на формирование органолептических показателей. Сыры вырабатывались в экспериментальном цехе ВНИИМС по традиционной технологии для данной группы сыров. Установлено, что процессы роста и развития заквасочных микроорганизмов в сырах всех вариантов идентичны и максимум микрофлоры достигается к 15-м сут созревания, что обеспечивает нормальный уровень молочнокислого процесса. Результаты исследований показали, что при увеличении в составе закваски дозы Lactococcus lactis ssp. diacetylactis интенсифицируется процесс протеолиза и увеличивается количество летучих вкусо-ароматообразующих веществ сыра пропорционально дозе диацетильного лактококка, что коррелирует с усилением выраженности сырного вкуса. Установлено, что при использовании в составе бактериальных заквасок для выработки данной группы сыров комбинации мезофильных лактококков для получения искомых органолептических показателей необходимо учитывать соотношение кислото- и газо-ароматообразующих бактерий. Наилучшие результаты, обеспечивающие потребительские предпочтения, были получены при использовании производственной закваски на основе моновидовых БЗ отдельных подвидов лактококков, исходя из расчета количества жизнеспособных клеток и соотношения культур: 30 % Lc. lactis ssp. lactis, 30 % Lc. lactis ssp. cremoris и 40 % Lc. lactis ssp. diacetylactis. For traditional cheeses with a low temperature of the second heating formed from the formation, the necessary microflora are mesophilic homofermentative lactococci Lc. lactis subsp. lactis, Lc. lactis ssp. cremoris and Lc. lactis ssp. diacetylactis. The ratio between the types and subspecies of starter microorganisms affects the quality of the finished product. For the studied group of cheeses, the ratio between acid- and gas-aroma-forming lactococci is crucial for the formation of the desired cheese taste, creamy aroma and characteristic pattern. The article presents the results of a study of the dynamics of development and metabolism of acid-forming lactococci Lc. lactis ssp. lactis and Lc. lactis ssp. cremoris and gas-aroma-forming lactococci Lc. lactis ssp. diacetylactis during the maturation of experimental cheeses and the effect of their ratio on the formation of organoleptic indicators. The cheeses were produced in the experimental workshop of VNIIMS using traditional technology for this group of cheeses. It has been established that the processes of growth and development of starter microorganisms in cheeses of all variants are identical and the maximum microflora is reached by 15 days of maturation, which ensures a normal level of lactic acid process. The results of the studies showed that with an increase in the dose of Lactococcus lactis ssp diacetylactis in the starter culture intensifies the process of proteolysis and increases the amount of volatile flavor-forming substances of cheese in proportion to the dose of diacetyl lactococcus, which correlates with an increase in the severity of cheese taste. It has been established that when using a combination of mesophilic lactococci in bacterial starter cultures for the production of this group of cheeses to obtain the desired organoleptic parameters, it is necessary to take into account the ratio of acid- and gas-aroma-forming bacteria. The best results, ensuring consumer preferences, were obtained by using a production starter culture based on monospecies of individual lactococci subspecies, based on the calculation of the number of viable cells and the ratio of cultures: 30 % Lc. lactis ssp. lactis, 30 % Lc. lactis ssp. cremoris and 40 % Lc. lactis ssp. diacetylactis.

Impact of changes in the fat phase on the peculiarities of the formation of quality indicators of semi-hard and hard cheeses

Cheesemaking is a complex process that involves lactose metabolism, proteolysis and lipolysis. The flavor bouquet of ripening cheeses is formed as a result of changes in all the components of milk. The conditions of keeping and feeding a ruminant, its type, breed, as well as the technological features of cheese production influence this process. Milk fat contributes to the formation of the flavor bouquet of cheese, which undergoes separate changes in the stage of milk processing for cheese. We studied semi-hard cheeses — Dutch and Vityaz and hard cheese — Italiko, made from the same raw milk using the microflora characteristic of these cheeses. The temperature of the second heating ranged from 39°C to 54°C, depending on the type of cheese. To assess the quality of cheeses, their physical and chemical composition and degree of maturity, organoleptic indicators and the content of volatile flavoring compounds, acid number, Reichert-Meissl number and fatty acid composition of the fatty phase of cheeses were determined. In comparative studies of cheeses, the features of the formation of their quality indicators, due to the composition and manufacturing technology, were revealed. They manifested themselves in the flavor bouquet and texture of the product, as well as in the fatty acid composition of cheeses, confirming the importance of the fat phase in the quality formation of the studied cheeses during their production, ripening and storage. It has been proven that even a slight increase in the acid number of fat during the production of all cheeses contributes to the further transformation of the resulting free fatty acids into volatile flavoring compounds that take part in the formation of the taste and aroma of the finished product.

Полутвердый сыр, обогащенный растительной добавкой с антиоксидантными свойствами

Полутвердый сыр, обогащенный растительной добавкой с антиоксидантными свойствами

Isolation and characterization of new bacteriophages active against Clostridium tyrobutyricum and their role in preventing the late blowing defect of cheese

Lytic bacteriophages (phages) offer a great potential as biocontrol agents for spoilage Clostridium tyrobutyricum, responsible for butyric acid fermentation in semi-hard and hard ripened cheeses, resulting in late gas blowing defect. With this aim, we have isolated, identified and characterized new lytic phages of C. tyrobutyricum, and have evaluated their efficacy to control cheese late blowing by adding them to manufacture milk. Silage, soil, milk and cheese from dairy farms were screened for anti-clostridial phages, obtaining 96 isolates active against C. tyrobutyricum. According to host range, source and plaque morphology, we obtained 20 phage profiles, 8 of them (represented by phages FA3, FA21, FA29, FA52, FA58, FA67, FA70 and FA88) showing a wider host range and high quality lysis, which were further characterized. Selected isolates showed a non-contractile tail, belonging to the Siphoviridae family, and were grouped into 3 restriction profiles. Viable phages were detected after storage in sodium-magnesium buffer (SM buffer), skim milk and acidified skim milk (pH 5) for 7 d at 4 °C, 12 °C and 37 °C, although a decline in infectivity was observed in some cases. Good phage survival was also detected during semi-hard cheese manufacture and ripening (60 d), and cheese lactococci counts, pH, dry matter values, and volatile compounds were not affected by phage addition. In semi-hard cheese, phage FA67 impaired the early germination of C. tyrobutyricum spores and caused a significant decrease in clostridial vegetative cells counts at 14 d of ripening, delaying by 2 weeks the consumption of lactic acid, formation of butyric acid and appearance of late blowing symptoms, compared to the spoilt control cheese without the phage. This is the first report on the application of phage to control C. tyrobutyricum in cheese.

Effect of Lactobacteria on Bioactive Peptides and Their Sequence Identification in Mature Cheese.

An in silico study that featured the effect of starter cultures on the bioactivity and other health benefits of peptides in semi-hard cheese is presented in this contribution. Model Caciotta-type cheese samples were obtained in laboratory conditions in two variations. Sample A included starter cultures of Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris. Sample B included starter cultures of Lactococcus lactis subsp. lactis, Lactococcus lactis subsp. cremoris, and a culture of lactobacilli Lacticaseibacillus casei. The in silico method showed that the peptides inhibited angiotensin-converting enzymes (ACE) and ipeptidyl peptidase IV (DPP-4), as well as possessed antioxidant properties. Lactococcus lactis subsp. lactis and Lactococcus lactis subsp. cremoris had a greater effect on the formation of bioactive peptides.

Microbiological, morpho-textural, and volatile characterization of Portuguese Queijo de Nisa PDO cheese

Queijo de Nisa PDO (Protected Designation of Origin) is a semi-hard cheese obtained from raw ewe's milk clotted with cardoon (Cynara cardunculus, L.) rennet. The aim of the present study was to characterize the bacterial communities naturally occurring in Queijo de Nisa PDO cheese samples through viable counting and metataxonomic analysis. Moreover, physico-chemical and morpho-textural analyses were also performed, together with the analysis of volatile organic compounds (VOCs) through solid-phase microextraction (SPME) coupled with gas chromatography-mass spectrometry (GC–MS). In the analyzed samples, pH values were comprised between 4.84 and 5.74. As for lactic acid, the concentration varied between 0.83 and 2.10 g 100 g-1. Water activity varied between 0.942 and 0.960. Lightness of the samples ranged from 107.82 to 119.16, whereas hardness ranged between 34.45 N and 126.05 N. As for microbiological analyses, lactococci and lactobacilli counts were up to 9.01 Log CFU g-1. Coagulase-negative cocci and enterococci counts were up to 7 Log CFU g-1. Metataxonomic analysis revealed that Lactococcus lactis and Leuconostoc mesenteroides occurred at high frequency in all the analyzed samples. Moreover, Lactiplantibacillus plantarum, Lactococcus piscium, and Lacticaseibacillus zeae were also detected. The most represented VOCs were carboxylic acids, carbonyl compounds, alcohols, and esters. In the analyzed cheese samples, significant relationships between bacteria and VOCs were also evidenced. Of note, research on the microbiological and chemical features, as well as on morpho-textural characteristics, of Queijo de Nisa PDO cheese can increase the knowledge on the interactions between raw materials, environment, and autochthonous microorganisms, thus enabling protection of biodiversity and tradition.

Prospects for the Use of Non-Starter Strain Lactiplantibacillus Plantarum AG15 in Dairy Technology

The article presents the comprehensive study results of the technological and antioxidant potential of the Lactoplantibacillus plantarum AG15 strain recaptured from silage and demonstrating probiotic properties during dairy products fermentation. The work aims at determining influence of the L. plantarum AG 15 strain on the antioxidant characteristics of the creamy milk; and identifying the strain introduction potential in the hard cheese technology. The authors applied a step-by-step research scheme with the technological and antioxidant potential assessment of a non-starter strain of lactic acid bacteria L. plantarum AG15 under conditions of milk fermentation and cheese maturation. A man used strain L. plantarum AG15 for fatty milk fermentation and compared its effect with the starter strain Lactobacillus bulgaricus. Compared to L. bulgaricus, L. plantarum AG15 has lower acid-forming ability, forms a dense lactic acid gel with the high syneresis level. Milk fermented by the L. plantarum AG15 strain has greater antioxidant activity (tests for reducing and radical-binding ability), which reduces the accumulation level of malonic aldehyde in milk fat during storage. Considering the identified antioxidant and technological potential, at the next stage, the researchers used L. plantarum AG15 strain as a part of a cheese starter to produce semi-hard cheese. The additional introduction of the non-starter strain L. plantarum AG15 does not affect the chemical quality of cheese (moisture, protein and salt content), but improves its antioxidant properties, leading to a decrease in the milk fat oxidation. Changes in the microbial community structure of the starter culture through the introduction of a non-starter strain L. plantarum AG15 enables to produce cheese with improved antioxidant properties and a more pronounced acrid flavor, expanding the production possibilities of high-quality cheeses with the diverse taste.

Identification of Streptococcus infantarius subsp. infantarius as the species primarily responsible for acid production in Izmir Brined Tulum Cheese from the Aegean Region of Türkiye

Izmir Brined Tulum (IBT) Cheese is a traditional semi hard cheese produced in the Aegean region of Türkiye. Lactic acid bacteria (LAB) isolates from IBT cheese samples taken during manufacture and from mature IBT cheeses were investigated for their acid producing capability with the aim of detecting LAB strains responsible for acid production in IBT cheese. Forty two out of 216 isolates decreased the pH of milk to 5.0 or below in 18 h at 37 °C or 42 °C. 16S rRNA Sanger sequencing revealed the presence of LAB species that had not been detected in IBT cheese previously and, indeed, were identified for the first time as the primary acid producers. The majority of these acid producing isolates were identified as putative Streptococcus lutetiensis/Streptococcus infantarius subsp. infantarius (Sii). Further analysis by sequencing the groES/groEL genes of these isolates established that they were Sii. The remaining isolates from cheese samples taken during manufacture were identified as Streptococcus macedonicus, S. thermophilus, Lactococcus lactis subsp. lactis, Lactobacillus delbrueckii subsp. sunkii and L. delbrueckii subsp. indicus and, from mature cheeses, as Enterococcus faecalis and L. delbrueckii subsp. sunkii. Pulsed-field gel electrophoresis (PFGE) results revealed a large genetic diversity amongst the Sii isolates recovered from the IBT cheeses. It was also established that the Sii strains exhibited efficient and consistent acidification ability equivalent to S. thermophilus. Whole-genome sequencing (WGS) and comparative genome analysis of the representative Sii AYB210 strain provided further insights. More specifically, the genome of AYB210 differed from the previously sequenced African dairy isolate Sii CJ18 and the human isolate ATCC®BAA-102™. Modifications in the lactose operon, which may be an indicator of dairy adaptation, were identified and a high number of CRISPR spacers and putative bacteriocin, virulence factor and antibiotic resistance genes were also detected.

Quantitative assessment of furosine, furfurals, and advanced glycation end products in different types of commercially available cheeses

The aim of this study was to investigate the occurrence of Maillard reaction products of different types of commercially available cheeses. Cheeses are the commonly consumed dairy products characterized by their many different flavors, textures and aromas. Pasteurization, fermentation and ripening are the key steps of cheese manufacturing, which might lead to the formation of some harmful products. In this study, furosine, furfurals, two “representative” advanced glycation end products (AGEs) were analyzed by gas chromatography-triple quadrupole mass spectrometry (GC-MS/MS) and liquid chromatography-triple quadrupole mass spectrometry (LC-MS/MS). The content of furosine in cheeses were the highest, followed by AGEs, while levels of furfurals were relatively low. The contents of these Maillard reaction products in hard and semi-hard cheeses were significantly higher than those in soft and semi-soft cheeses. Finally, the correlation between proximate composition and Maillard reaction products was further analyzed. • The 32 cheeses are divided into two main categories based on their moisture content. • Furosine, furfurals, and advanced glycation end products in cheeses were quantitated. • Hard cheeses had higher contents of furfurals and advanced glycation end products. • Cheeses had the highest content of furosine and very low levels of furfurals. • Correlation analysis between proximate composition and furosine, furfurals, and AGEs.

Effect of chymosin‐induced hydrolysis of αS1‐casein on the tribological behaviour of brine‐salted semihard cheeses

This study investigated the effect of chymosin‐induced hydrolysis of αS1‐casein on the tribological behaviour of cheese. Residual chymosin activity was inhibited by adding a chymosin inhibitor (i.e. pepstatin A) to the curd–whey mixture during cheese manufacture. A significant difference was observed in the static and kinetic regimes of the extended Stribeck curves of cheese samples, suggesting that the chymosin‐induced hydrolysis of αS1‐casein affects the friction and lubrication properties of cheese, which may be relevant to the mouthfeel‐related sensory attributes of the cheese. Overall, the modulation of hydrolysis of αS1‐casein could be an approach to alter the friction‐related sensory attributes of cheese.

Production of Putrescine and Cadaverine by Paucilactobacillus wasatchensis.

Lactic acid bacteria (LAB) play a key role in many food fermentations. However, some LAB species can also cause food spoilage, e.g., through the formation of biogenic amines. Paucilactobacillus wasatchensis is a LAB that causes late gas production in Cheddar cheese, the molecular causes of which are not fully understood. This study reports on the ability of P. wasatchensis WDC04 to produce cadaverine and putrescine in broth supplemented with lysine and ornithine, as well as in a model cheese. The raclette-type semi-hard cheese produced with P. wasatchensis as an adjunct culture contained 1,085 mg kg−1 of cadaverine and 304 mg kg−1 of putrescine after 120 days of ripening. We identified two ornithine decarboxylase genes (odc) and a putrescine-ornithine antiporter gene (potE) in the genome sequence of P. wasatchensis. We could show that the two odc genes, which are located on two contigs, are contiguous and form the genetic cluster odc2-odc1-potE. Alignment searches showed that similar gene clusters exist in the genomes of Levilactobacillus paucivorans DSMZ22467, Lentilactobacillus kribbianus YH-lac9, Levilactobacillus hunanensis 151-2B, and Levilactobacillus lindianensis 220-4. More amino acid sequence comparisons showed that Odc1 and Odc2 shared 72 and 69% identity with a lysine and ornithine decarboxylase from Ligilactobacillus saerimneri 30a, respectively. To clarify the catalytic activities of both enzymes, the odc-coding genes were cloned and heterologously expressed as His-tagged fusion protein. The purified Odc1 protein decarboxylated lysine into cadaverine, while the recombinant Odc2 protein preferentially produced putrescine from ornithine but also exhibited low lysine decarboxylating activity. Both enzymes were active at pH of 5.5, a value often found in cheese. To our knowledge, this is only the second lysine decarboxylase in LAB whose function has been verified. The tandem arrangement of the genes in a single cluster suggests a gene duplication, evolving the ability to metabolize more amino. Divergent substrate preferences highlight the necessity of verifying the functions of genes, in addition to automatic annotation based on sequence similarity. Acquiring new biochemical data allows better predictive models and, in this case, more accurate biogenic amine production potential for LAB strains and microbiomes.

A study of lipolysis induced by adjuncts from edible Aspergillus sp. solid culture products on ripened semi-hard cheese.

Aspergillus sp. has been used in traditional Japanese fermented foods. Protease-containing culture products of A. oryzae have been applied as the adjunct enzyme source to enrich the flavor in ripened cheese. Although proteolysis was stimulated, the increase of free fatty acids (FFA) was recognized in some products. Since an excess amount of FFA accumulation can cause rancidity in cheese products, the assessment of lipase activity was considered to be essential for the cheese adjunct preparation. Although an equal lipase activity from the adjunct materials of A. kawachii NBRC 4308, A. luchuensis RIB 2604 and A. oryzae AHU 7139 was applied to semi-hard cheese, the FFA level was significantly higher in A. oryzae cheese than in the others. Furthermore, the profiles of volatile components were different in experimental cheeses. An in vitro study with experimental curds demonstrated that the high FFA might not depend on the lipase retainability on curds. On the contrary, the pronounced activation of the lipases occurred in A. oryzae after incubation with the curds. Moreover, incubation of the insoluble lipase that had been attached to the cells with skim milk curd extracts allowed the release of lipases from the cells into the medium with remarkable activation. A. oryzae AHU 7139 possessed a complex lipolytic system comprising extracellular and cell-binding lipases that were attributed to the increase in FFA in A. oryzae cheese. © 2022 Society of Chemical Industry.

Growth potential of three strains of Listeria monocytogenes and Salmonella enterica in Frescal and semi-hard artisanal Minas microcheeses: Impact of the addition of lactic acid bacteria with antimicrobial activity

This study aimed to determine the growth potential (δ) of L. monocytogenes (CLIST 3974, CLIST 3969, and CLIST 4162) and S. enterica [S. Typhimurium (ATCC SM 14028), S. Enteritidis (SM 64), and S. Montevideo (SM 129)] in the presence of a pool of lactic acid bacteria (LAB) with antimicrobial activity in Frescal and semi-hard Minas microcheeses. The δ was determined after storing Frescal cheese at 4 and 7 °C for 15 days and the and semi-hard Minas cheese during ripening (22 °C for 22 days). The δ of L. monocytogenes was significantly higher in Frescal Minas cheese with no added LAB (p > 0.05). On the other hand, in semi-hard cheese inoculated with LAB, inactivation of L. monocytogenes was observed. No significant differences were found in the δ of S. enterica in Frescal Minas cheese inoculated with LAB at 4 and 7 °C. S. enterica SM 14028 and SM 129 could grow in semi-hard cheeses non-inoculated with LAB, while when LAB was inoculated, S. enterica was inactivated. The findings of this study indicated that the δ of L. monocytogenes strains was more affected in cheeses inoculated with LAB than the δ of S. enterica.

An Overview of On-Farm Hygienic Milk Production

- The dairy sector has adopted hazard analysis of critical control points (HACCP) systems to ensure the food safety of dairy products. Through a chain management strategy, this allows for quality verification of final goods (European Commission, 2004b). Raw milk's quality and safety are critical for milk and the dairy products' safety and quality. Milk contamination with bacteria, chemical residues, and other pollutants affects the safety and quality of the products. Microbial contamination is the subject of this chapter. Salmonella spp, Listeria monocytogenes and Campylobacter jejuni are examples of human microbial pathogens discovered in raw milk. A very high microbiological quality of raw milk is essential for preventing process losses and achieving an optimum shelf life for dairy products, in addition to its importance for the public health. For example, faults in semi-hard cheeses are caused by the spore formers of butyric acid bacteria in the raw milk, and raw milk contamination with Bacillus cereus bacteria reduces the shelf life of pasteurized dairy products. Quality assurance methods for dairy farms are being created, and bacteriological structures are being used in farms bulk of raw milk payment systems, in order to guarantee that bulk tank milk has a high microbiological quality. Furthermore, dairy producers' sanitary milk production is critical for animal’s welfare and dairy industry's image. Infections of pathogenic microorganisms affect cows (e.g., udder tissue, gastrointestinal tract), resulting in lower milk production and even mortality. In conclusion, all components of the dairy production chain benefit from the management of the microbial ecology at the dairy farm, which leads to on-farm hygienic milk productions.

Prevalence of Clostridium spp., in Kashar cheese and efficiency of Lactiplantibacillus plantarum and Lactococcus lactis subsp. lactis mix as a biocontrol agents for Clostridium spp.

Clostridium sporogenes and Clostridium tepidium strains were detected in traditional Kashar cheese samples with late blowing characteristics. To control Clostridium spp., in Kashar cheese, dairy originated Lactic Acid Bacteria (LAB) strains were tested under in vitro conditions and during Kashar production. Two strains, Lactiplantibacillus plantarum and Lactococcus lactis subsp. lactis demonstrated anticlostridial activity in vitro and the co-inoculum of these two strains (107 cfu g−1) were tested during the challenge test on Kashar cheese production in which a contamination ratio of 104 cfu g−1 with spores of Cl. sporogenes were applied. Kashar samples were stored at 4 °C and 25 °C during 40 days of storage period and microbiological and physicochemical properties of Kashar samples were determined during this period. A decrement of nearly 1 log cfu g−1 in Cl. sporogenes numbers was observed in Kashar samples produced with co-inoculum of Lb. plantarum and L. lactis subsp. lactis stored at 4 °C but this was not the case for the Kashar samples stored at 25 °C. This study revealed the potential of distinct LAB strains to control Cl. sporogenes spores in semi-hard cheese samples as biocontrol agents at 4 °C storage.

Possible inhibitory effect of microbial transglutaminase on the formation of biogenic amines during Trappist cheese ripening

ABSTRACT Trappist cheese (semi-hard, rennet-coagulated cheese with round eyes) was manufactured and matured for 4 weeks at 12 ± 1°C, 85% relative humidity (RH). The effect of microbial transglutaminase (MTGase) was followed by measuring the levels of free amino acids (FAAs) and biogenic amines (BAs) every 2 weeks during 4 weeks of cheese ripening. Results show that MTGase can decrease the cadaverine production by 30%, but only at the initial stage of ripening. Application of MTGase results in 49% less putrescine, 12% less tyramine production at the end of 4 weeks ripening time, and can decrease histamine levels by 8% after 2 weeks of ripening time in the examined semi-hard cheese type.

Development of a risk assessment model to predict the occurrence of late blowing defect in Gouda cheese and evaluate potential intervention strategies

Late blowing defect (LBD) is an important spoilage issue in semi-hard cheese, with the outgrowth of Clostridium tyrobutyricum spores during cheese aging considered to be the primary cause. Although previous studies have explored the microbial and physicochemical factors influencing the defect, a risk assessment tool that allows for improved and rational management of LBD is lacking. The purpose of this study was to develop a predictive model to estimate the probability of LBD in Gouda cheese and evaluate different intervention strategies. The spore concentration distribution of butyric acid bacteria (BAB) in bulk tank milk was obtained from 8 dairy farms over 12 mo. The concentration of C. tyrobutyricum from raw milk to the end of aging was simulated based on Gouda brined for 2 d in saturated brine at 8°C and aged at 13°C. Predicted C. tyrobutyricum concentrations during aging and estimated concentration thresholds in cheese at onset of LBD were used to predict product loss due to LBD during a simulated 1-yr production. With the estimated concentration thresholds in cheese ranging from 4.36 to 4.46 log most probable number (MPN)/kg of cheese, the model predicted that 9.2% (±1.7%) of Gouda cheese showed LBD by d 60; cheeses predicted to show LBD at d 60 showed a mean pH of 5.39 and were produced with raw milk with a mean BAB spore count of 143 MPN/L. By d 90, 36.1% (±3.4%) of cheeses were predicted to show LBD, indicating that LBD typically manifests between d 60 and 90, which is consistent with observations from the literature and the cheese industry. Sensitivity analysis indicated that C. tyrobutyricum maximum growth rate as well as concentration threshold in cheese at onset of LBD are the most important variables, identifying key data needs for development of more accurate models. The implementation of microfiltration or bactofugation of raw milk (assumed to show 98% efficiency of spore removal) in our model prevented occurrence of LBD during the first 60 d of aging. Overall, our findings provide a framework for predicting the occurrence of LBD in Gouda as well as other cheeses and illustrate the value of developing digital tools for managing dairy product quality.