Specificity of the AMP-6000 Method for Enumerating Clostridium Endospores in Milk

Enumeration of endospores of butyric acid-forming clostridia in cheese milk is an essential part of milk quality monitoring for cheese producers to avoid late blowing, severe spoilage caused by clostridia during ripening. However, due to the lack of an internationally standardized method, different methods are used and it is important to consider how the choice of method affects the results. This is particularly relevant when clostridial spore counts in milk are considered for quality payments. The aim of this study was to evaluate the specificity of the AMP-6000 method for the enumeration of endospores of cheese spoiling clostridia in milk. First, to assess the prevalence of Clostridium diversity and to determine potential non-target species, we identified isolates from positive reactions of the AMP-6000 method used to quantify clostridial endospores in raw milk and teat skin samples by MALDI-TOF MS. Based on these results, a strain library was designed to evaluate method inclusivity and exclusivity using pure cultures of target and non-target strains according to ISO 16140-2:2016. Most target Clostridium tyrobutyricum strains, as well as all tested C. butyricum and C. sporogenes strains were inclusive. However, C. beijerinckii may be underestimated as only some strains gave positive results. All non-target strains of bacilli and lysinibacilli, but not all paenibacilli, were confirmed to be exclusive. This study provides performance data to better understand the results of microbiological enumeration of butyric acid-forming clostridia in milk and serves as a basis for future methodological considerations and improvements.

The ailments that stem from cheese and relevant precautions taken in the Ottoman Empire from the 19th century to the 20th century

The increase in cheese production, sale, and consumption due to the settled lives of societies has led to an increase in cheese-related diseases. It has become essential to better understand cheese-borne diseases and to develop control measures. In this study, cheese-related diseases and precautions taken in the Ottoman Empire from the 19th to the 20th centuries were investigated in Ottoman archival sources. Of these documents, cheese spoilage was detected in 12 and cheese-related disease in 9. Cheeses that caused diseases or disorders in the relevant period were called spoiled cheese. One document states that a person died of a cheese-borne illness. Cheese poisoning occurs mainly from unsalted, fresh cheeses. It has been determined that tin-free copper pots were used in cheese production and sales and covered with herbs such as hemlock during maturation. In the relevant period, microbiological and chemical analyses of cheeses in terms of health were carried out in food control laboratories. Since the mercury chloride solution is used to disinfect animal udders, it has been stated that it contaminates the milk used in cheese production. Authorities have requested a boric acid solution (5% boric acid in hot water) instead of this solution for udder disinfection. In the Ottoman Empire, it was requested to take necessary sanitation and hygiene measures to prevent spoilage and cheese-related diseases in the production areas or sales places of cheese. Clean and tinned containers should be used in cheese production, storage, and sale, and poisonous herbs should not be used during cheese ripening. It was also essential to analyze them in laboratories at internal and external customs. Knowing the precautions taken in the past to prevent the deterioration of food or the occurrence of diseases has led to modern food safety practices being applied today.

Low-Level Clostridial Spores' Milk to Limit the Onset of Late Blowing Defect in Lysozyme-Free, Grana-Type Cheese

The growth of clostridial spores during ripening leads to late blowing (LB), which is the main cause of spoilage in Grana Padano Protected Designation of Origin (PDO) cheese and other hard, long-ripened cheeses such as Provolone, Comté, and similar cheeses. This study aimed to verify the cause-effect relationship between the level of clostridial butyric spores (BCS) in milk and the onset of the LB defect. To this end, experimental Grana-type cheeses were produced without lysozyme, using bulk milk with different average BCS content. The vat milk from the so-called "virtuous" farms (L1) contained average levels of BCS of 1.93 ± 0.61 log most probable number (MPN) L^-1, while the vat milk from farms with the highest load of spores (L2), were in the order of 2.99 ± 0.69 log MPN L^-1. Cheeses after seven months of ripening evidenced a strong connection between BCS level in vat milk and the occurrence of LB defect. In L2 cheeses, which showed an average BCS content of 3.53 ± 1.44 log MPN g^-1 (range 1.36-5.04 log MPN g^-1), significantly higher than that found in L1 cheeses (p < 0.01), the defect of LB was always present, with Clostridium tyrobutyricum as the only clostridial species identified by species-specific PCR from MPN-positive samples. The L1 cheeses produced in the cold season (C-L1) were free of defects whereas those produced in the warm season (W-L1) showed textural defects, such as slits and cracks, rather than irregular eyes. A further analysis of the data, considering the subset of the cheesemaking trials (W-L1 and W-L2), carried out in the warm season, confirmed the presence of a climate effect that, often in addition to the BCS load in the respective bulk milks (L1 vs. L2), may contribute to explain the significant differences in the chemical composition and some technological parameters between the two series of cheeses. Metagenomic analysis showed that it is not the overall structure of the microbial community that differentiates L1 from L2 cheeses but rather the relative distribution of the species between them. The results of our trials on experimental cheeses suggest that a low-level BCS in vat milk (<200 L^-1) could prevent, or limit, the onset of LB in Grana-type and similar cheeses produced without lysozyme.