Effect of reduced-calcium and high-calcium cheddar cheese consumption on the excretion of faecal fat: a 2-week cross-over dietary intervention study.

PURPOSE: Studies show that dairy fat consumed in the form of cheese reduce LDL-cholesterol concentration (LDL-c) compared to butter and mechanistic suggestions include the calcium content of cheese leading to enhanced faecal fat excretion. The aim of this study was to test the effect of varying the calcium content within a cheese, on faecal fat excretion as a primary outcome, and blood lipid markers, fasting glucose and calcium excretion as secondary outcomes. METHODS: 7 healthy males (BMI 18-25) participated in this randomized, cross-over control intervention, of 3 × 2 week periods. Diets contained 240 g/day cheese; a High Calcium Cheese (HCC) diet, a Reduced Calcium Cheese (RCC) diet, and a control arm: Reduced Calcium Cheese + CaCO3 Supplement (RCC + Supp) diet. Diets differed in calcium content and form but were otherwise controlled for energy and key macronutrients. Blood and 5-day faecal samples were collected. RESULTS: There was no significant difference in faecal fat excretion (g/day) between the diets (P = 0.066). Percent fat of faecel excretion was higher after RCC + Supp (P = 0.016). None of the individual fatty acids were different. Fasting LDL-c was significantly lower following the HCC diet vs. the other arms (P = 0.002). Faecal Ca was different across all diets (P = 0.001), lowest after RCC, and greatest after RCC + Supp. No differences were observed for fasting blood parameters or changes in anthropometry. CONCLUSION: Varying the calcium content within a cheese matrix significantly affected fasting LDL-c values. Results did not support higher faecal fat excretion as an underlying mechanism, but the high attrition rate was a limitation. Trial registerer Trial Registered at ISRCTN.org, registration number ISRCTN11663659 on 12.07.2022. Retrospectively registered.

Effect of pasture versus indoor feeding systems on quality characteristics, nutritional composition, and sensory and volatile properties of full-fat Cheddar cheese.

The purpose of this study was to investigate the effects of pasture-based versus indoor total mixed ration (TMR) feeding systems on the chemical composition, quality characteristics, and sensory properties of full-fat Cheddar cheeses. Fifty-four multiparous and primiparous Friesian cows were divided into 3 groups (n = 18) for an entire lactation. Group 1 was housed indoors and fed a TMR diet of grass silage, maize silage, and concentrates; group 2 was maintained outdoors on perennial ryegrass only pasture (GRS); and group 3 was maintained outdoors on perennial ryegrass/white clover pasture (CLV). Full-fat Cheddar cheeses were manufactured in triplicate at pilot scale from each feeding system in September 2015 and were examined over a 270-d ripening period at 8°C. Pasture-derived feeding systems were shown to produce Cheddar cheeses yellower in color than that of TMR, which was positively correlated with increased cheese ß-carotene content. Feeding system had a significant effect on the fatty acid composition of the cheeses. The nutritional composition of Cheddar cheese was improved through pasture-based feeding systems, with significantly lower thrombogenicity index scores and a greater than 2-fold increase in the concentration of vaccenic acid and the bioactive conjugated linoleic acid C18:2 cis-9,trans-11, whereas TMR-derived cheeses had significantly higher palmitic acid content. Fatty acid profiling of cheeses coupled with multivariate analysis showed clear separation of Cheddar cheeses derived from pasture-based diets (GRS or CLV) from that of a TMR system. Such alterations in the fatty acid profile resulted in pasture-derived cheeses having reduced hardness scores at room temperature. Feeding system and ripening time had a significant effect on the volatile profile of the Cheddar cheeses. Pasture-derived Cheddar cheeses had significantly higher concentrations of the hydrocarbon toluene, whereas TMR-derived cheese had significantly higher concentration of 2,3-butanediol. Ripening period resulted in significant alterations to cheese volatile profiles, with increases in acid-, alcohol-, aldehyde-, ester-, and terpene-based volatile compounds. This study has demonstrated the benefits of pasture-derived feeding systems for production of Cheddar cheeses with enhanced nutritional and rheological quality compared with a TMR feeding system.

Novel Fermentates Can Enhance Key Immune Responses Associated with Viral Immunity.

Fermented foods have long been known to have immunomodulatory capabilities, and fermentates derived from the lactic acid bacteria of dairy products can modulate the immune system. We have used skimmed milk powder to generate novel fermentates using Lb. helveticus strains SC234 and SC232 and we demonstrate here that these fermentates can enhance key immune mechanisms that are critical to the immune response to viruses. We show that our novel fermentates, SC234 and SC232, can positively impact on cytokine and chemokine secretion, nitric oxide (NO) production, cell surface marker expression, and phagocytosis in macrophage models. We demonstrate that the fermentates SC234 and SC232 increase the secretion of cytokines IL-1ß, IL-6, TNF-α, IL-27, and IL-10; promote an M1 pro-inflammatory phenotype for viral immunity via NO induction; decrease chemokine expression of Monocyte Chemoattractant Protein (MCP); increase cell surface marker expression; and enhance phagocytosis in comparison to their starting material. These data suggest that these novel fermentates have potential as novel functional food ingredients for the treatment, management, and control of viral infection.

The microbial content of raw and pasteurized cow milk as determined by molecular approaches.

The microbial composition of raw and pasteurized milk is assessed on a daily basis. However, many such tests are culture-dependent, and, thus, bacteria that are present at subdominant levels, or that cannot be easily grown in the laboratory, may be overlooked. To address this potential bias, we have used several culture-independent techniques, including flow cytometry, real-time quantitative PCR, and high-throughput DNA sequencing, to assess the microbial population of milk from a selection of commercial milk producers, pre- and postpasteurization. The combination of techniques employed reveals the presence of a previously unrecognized and diverse bacterial population in unpasteurized cow milk. Most notably, the use of high-throughput DNA sequencing resulted in several bacterial genera being identified in milk samples for the first time. These included Bacteroides, Faecalibacterium, Prevotella, and Catenibacterium. Our culture-independent analyses also indicate that the bacterial population of pasteurized milk is more diverse than previously appreciated, and that nonthermoduric bacteria within these populations are likely to be in a damaged, nonculturable form. It is thus apparent that the application of state-of-the-art approaches can provide a detailed insight into the bacterial composition of milk and could potentially be employed in the future to investigate the factors that influence the composition of these populations.

Chlorate Levels in Dairy Products Produced and Consumed in Ireland.

In recent years, chlorate has become a residue of concern internationally, due to the risk that it poses to thyroid gland function. However, little is known about its occurrence in dairy products of Irish origin. To address this, a study was conducted in which samples of milk (n = 317), cream (n = 199), butter (n = 178), cheese (n = 144) and yoghurt (n = 440) were collected from grocery stores in the Republic of Ireland. Sampling was conducted across spring, summer, autumn and winter of 2021. Samples from multiple manufacturers of each respective dairy product were procured and analysed for chlorate using UPLC-MS/MS. Chlorate was detected in milk, cream, natural, blueberry, strawberry and raspberry yoghurts. Mean chlorate levels detected in these products were 0.0088, 0.0057, 0.055, 0.067, 0.077 and 0.095 mg kg-1, respectively. Chlorate was undetected in butter and cheese (<0.01 mg kg-1). All products sampled, except yoghurt, were found to be compliant with the EU limit for chlorate in milk (0.10 mg kg-1). Some manufacturers produced product with greater incidence and levels of chlorate. Chlorate levels from samples tested at different times of the year did not differ significantly, with the exception of strawberry and raspberry yoghurts which had higher chlorate levels in the winter period.

Methods to mitigate Escherichia coli blooms in human ex vivo colon model experiments using the high throughput micro-Matrix bioreactor fermentation system.

Ex vivo colon model experiments are frequently employed as a means to assess the gut microbiome modulating potential of different foods, food ingredients and dietary supplements. A number of useful models already exist; however, they tend to be relatively low in terms of throughput (3-4 samples per experiment) with a long experiment duration of one to a number of weeks. Therefore, a need for a high-throughput system with a short duration time is required to enable screening of large numbers of samples. Therefore, we report here on the development of a system based on the Applikon micro-Matrix bioreactor which has the capacity to run 24 samples with an experiment duration of 48 h. However, Escherichia coli blooms are a common problem encountered in this model. Here, we describe the factors that contribute to such blooms and provide approaches to address them, providing:•Step by step optimisation of processes involved in conducting ex vivo distal colon experiments using the micro-Matrix bioreactor fermentation platform•Recommended steps for users on how to attenuate E. coli blooms in such ex vivo colon model experiments.

Diversity of the Microbiota of Traditional Izmir Tulum and Izmir Brined Tulum Cheeses and Selection of Potential Probiotics.

High-throughput DNA sequencing (HTS) was used to study the microbial diversity of commercial traditional Izmir Tulum (IT) and Izmir Brined Tulum (IBT) cheeses from Izmir, Türkiye. Simultaneously, cultivation-dependent methods were used to isolate, identify and characterize bacterial strains displaying probiotic potential. At the phylum level, Firmicutes dominated the microbiota of both cheese types comprising >98% of the population. Thirty genera were observed, with Streptococcus being the most abundant genus and with Streptococcus thermophilus and S. infantarius subsp. infantarius being the most abundant species. Genera, including Bifidobacterium and Chryseobacterium, not previously associated with IT and IBT, were detected. IT cheeses displayed higher operational taxonomic units (OTUs; Richness) and diversity index (Simpson) than IBT cheeses; however, the difference between the diversity of the microbiota of IT and IBT cheese samples was not significant. Three Lacticaseibacillus paracasei strains isolated from IBT cheeses exhibited probiotic characteristics, which included capacity to survive under in vitro simulated gastrointestinal conditions, resistance to bile salts and potential to adhere to HT-29 human intestinal cells. These findings demonstrate that Tulum cheeses harbor bacterial genera not previously reported in this cheese and that some strains display probiotic characteristics.

High-throughput sequencing for detection of subpopulations of bacteria not previously associated with artisanal cheeses.

Here, high-throughput sequencing was employed to reveal the highly diverse bacterial populations present in 62 Irish artisanal cheeses and, in some cases, associated cheese rinds. Using this approach, we revealed the presence of several genera not previously associated with cheese, including Faecalibacterium, Prevotella, and Helcococcus and, for the first time, detected the presence of Arthrobacter and Brachybacterium in goats' milk cheese. Our analysis confirmed many previously observed patterns, such as the dominance of typical cheese bacteria, the fact that the microbiota of raw and pasteurized milk cheeses differ, and that the level of cheese maturation has a significant influence on Lactobacillus populations. It was also noted that cheeses containing adjunct ingredients had lower proportions of Lactococcus species. It is thus apparent that high-throughput sequencing-based investigations can provide valuable insights into the microbial populations of artisanal foods.

Modification of fast-slow differential agar medium for selective isolation of potential starter lactic acid bacteria from cheese.

Starter Lactic Acid Bacteria (LAB) are responsible for converting lactose to lactic acid during cheese manufacturing and, as a result, play a critical role in defining the attributes of the final product. There is great interest in isolating novel starter LAB strains to provide alternatives to existing industry cultures or to help enhance the quality and safety of cheeses traditionally made without starter cultures addition [1]. The Fast-Slow Differential Agar (FSDA) medium was developed in 1984 and still remains the standard to rapidly differentiate fast and slow milk-coagulating lactic streptococci and thus avoid screening a large number of isolates for acid production capacity [2]. However, we found that FSDA was unable to selectively isolate fast acid-producing strains from young, traditional, starter-free Izmir Brined Tulum cheeses, due to the presence of a diverse microbiome including Non-Starter LAB and spoilage Gram-negative microbiota [1, 3]. Here, we describe a modified FSDA (mFSDA) with increased selectivity and recovery efficiency towards lactic streptococci, which was successfully used to rapidly isolate potential starters from Tulum cheeses [1] and could similarly outperform FSDA in raw milk cheeses and other varieties containing high levels of "background" microbiota. The main differences between FSDA and mFSDA media consist in the presence of nalidixic acid, ascorbic acid and yeast extract in mFSDA. These targeted additions provide mFSDA with a two-prong selectivity that (I) suppresses unwanted microbiota, and (II) increases the recovery efficiency of lactic streptocci adept to using milk nutrients. Specifically:•Nalidixic acid is an antibiotic that primarily inhibit Gram-negative bacteria [4].•Ascorbic acid and yeast extract stimulate the growth of lactic streptococci [5] and were added to complement skim milk in creating an environment favoring the growth of lactose-positive, casein peptides-utilizing LAB.•The pH indicator bromocresol purple enabled the chromogenic discrimination between LAB with different acid production capability.

Fermented Foods, Health and the Gut Microbiome.

Fermented foods have been a part of human diet for almost 10,000 years, and their level of diversity in the 21st century is substantial. The health benefits of fermented foods have been intensively investigated; identification of bioactive peptides and microbial metabolites in fermented foods that can positively affect human health has consolidated this interest. Each fermented food typically hosts a distinct population of microorganisms. Once ingested, nutrients and microorganisms from fermented foods may survive to interact with the gut microbiome, which can now be resolved at the species and strain level by metagenomics. Transient or long-term colonization of the gut by fermented food strains or impacts of fermented foods on indigenous gut microbes can therefore be determined. This review considers the primary food fermentation pathways and microorganisms involved, the potential health benefits, and the ability of these foodstuffs to impact the gut microbiome once ingested either through compounds produced during the fermentation process or through interactions with microorganisms from the fermented food that are capable of surviving in the gastro-intestinal transit. This review clearly shows that fermented foods can affect the gut microbiome in both the short and long term, and should be considered an important element of the human diet.

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.

Health Benefits of Lactic Acid Bacteria (LAB) Fermentates.

Consuming fermented foods has been reported to result in improvements in a range of health parameters. These positive effects can be exerted by a combination of the live microorganisms that the fermented foods contain, as well as the bioactive components released into the foods as by-products of the fermentation process. In many instances, and particularly in dairy fermented foods, the microorganisms involved in the fermentation process belong to the lactic acid group of bacteria (LAB). An alternative approach to making some of the health benefits that have been attributed to fermented foods available is through the production of 'fermentates'. The term 'fermentate' generally relates to a powdered preparation, derived from a fermented product and which can contain the fermenting microorganisms, components of these microorganisms, culture supernatants, fermented substrates, and a range of metabolites and bioactive components with potential health benefits. Here, we provide a brief overview of a selection of in vitro and in vivo studies and patents exclusively reporting the health benefits of LAB 'fermentates'. Typically, in such studies, the potential health benefits have been attributed to the bioactive metabolites present in the crude fermentates and/or culture supernatants rather than the direct effects of the LAB strain(s) involved.

Comparative genomics of lactic acid bacteria reveals a niche-specific gene set.

BACKGROUND: The recently sequenced genome of Lactobacillus helveticus DPC4571 revealed a dairy organism with significant homology (75% of genes are homologous) to a probiotic bacteria Lb. acidophilus NCFM. This led us to hypothesise that a group of genes could be determined which could define an organism's niche. RESULTS: Taking 11 fully sequenced lactic acid bacteria (LAB) as our target, (3 dairy LAB, 5 gut LAB and 3 multi-niche LAB), we demonstrated that the presence or absence of certain genes involved in sugar metabolism, the proteolytic system, and restriction modification enzymes were pivotal in suggesting the niche of a strain. We identified 9 niche specific genes, of which 6 are dairy specific and 3 are gut specific. The dairy specific genes identified in Lactobacillus helveticus DPC4571 were lhv_1161 and lhv_1171, encoding components of the proteolytic system, lhv_1031 lhv_1152, lhv_1978 and lhv_0028 encoding restriction endonuclease genes, while bile salt hydrolase genes lba_0892 and lba_1078, and the sugar metabolism gene lba_1689 from Lb. acidophilus NCFM were identified as gut specific genes. CONCLUSION: Comparative analysis revealed that if an organism had homologs to the dairy specific geneset, it probably came from a dairy environment, whilst if it had homologs to gut specific genes, it was highly likely to be of intestinal origin.We propose that this "barcode" of 9 genes will be a useful initial guide to researchers in the LAB field to indicate an organism's ability to occupy a specific niche.

Genome sequence of Lactobacillus helveticus, an organism distinguished by selective gene loss and insertion sequence element expansion.

Mobile genetic elements are major contributing factors to the generation of genetic diversity in prokaryotic organisms. For example, insertion sequence (IS) elements have been shown to specifically contribute to niche adaptation by promoting a variety of genetic rearrangements. The complete genome sequence of the cheese culture Lactobacillus helveticus DPC 4571 was determined and revealed significant conservation compared to three nondairy gut lactobacilli. Despite originating from significantly different environments, 65 to 75% of the genes were conserved between the commensal and dairy lactobacilli, which allowed key niche-specific gene sets to be described. However, the primary distinguishing feature was 213 IS elements in the DPC 4571 genome, 10 times more than for the other lactobacilli. Moreover, genome alignments revealed an unprecedented level of genome stability between these four Lactobacillus species, considering the number of IS elements in the L. helveticus genome. Comparative analysis also indicated that the IS elements were not the primary agents of niche adaptation for the L. helveticus genome. A clear bias toward the loss of genes reported to be important for gut colonization was observed for the cheese culture, but there was no clear evidence of IS-associated gene deletion and decay for the majority of genes lost. Furthermore, an extraordinary level of sequence diversity exists between copies of certain IS elements in the DPC 4571 genome, indicating they may represent an ancient component of the L. helveticus genome. These data suggest a special unobtrusive relationship between the DPC 4571 genome and its mobile DNA complement.

Irish Cheddar cheese increases glucagon-like peptide-1 secretion in vitro but bioactivity is lost during gut transit.

Appetite can be effectively reduced by targeting the production, secretion, circulation time or receptor of the enteric satiety hormone glucagon-like peptide-1 (GLP-1). The objective of this study was to investigate the potency of Irish Cheddar cheeses to modulate GLP-1 levels. Nine out of ten water-soluble extracts (WSEs) of representative Irish Cheddar cheeses, post 6 months ripening, significantly (p < 0.05) stimulated active GLP-1 secretion from the mouse enteroendocrine cell line STC-1. This secretion was associated with protein content and ripening time of cheese. C-57BL/6 mice (n = 9/10), who received the most potent sample, C2-WSE-8 M, had a significantly reduced cumulative food intake at 6 h compared to control (p < 0.05), but not overall treatment × time effect over a 7 h period. Simulated in vitro gastrointestinal digestion, that models the upper human gut, indicated loss of GLP-1 stimulating activity once C2-WSE-8M entered the intestinal phase, suggesting efficacy of C2-WSE-8M will depend on protection during gut transit.

Dairy matrix effects: response to consumption of dairy fat differs when eaten within the cheese matrix-a randomized controlled trial.

Background: Dairy fat consumed as cheese has different effects on blood lipids than that consumed as butter. It is unknown whether the effect is specific to fat interaction with other cheese nutrients (calcium, casein proteins), or to the cheese matrix itself. Objective: We aimed to test the effect of 6 wk daily consumption of ∼40 g dairy fat, eaten within macronutrient-matched food matrices, on markers of metabolic health, in overweight adults aged ≥50 y. Design: The study was a 6-wk randomized parallel intervention; 164 volunteers (75 men) received ∼40 g of dairy fat/d, in 1 of 4 treatments: (A) 120 g full-fat Irish cheddar cheese (FFCC) (n = 46); (B) 120 g reduced-fat Irish cheddar cheese + butter (21 g) (RFC + B) (n = 45); (C) butter (49 g), calcium caseinate powder (30 g), and Ca supplement (CaCO3) (500 mg) (BCC) (n = 42); or (D) 120 g FFCC, for 6 wk (as per A) (n = 31). Group D first completed a 6-wk "run-in" period, where they excluded all dietary cheese before commencing the intervention. Results: There was no difference in anthropometry, fasting glucose, or insulin between the groups at pre- or postintervention. However, a stepwise-matrix effect was observed between the groups for total cholesterol (TC) (P = 0.033) and LDL cholesterol (P = 0.026), with significantly lower postintervention TC (mean ± SD) (5.23 ± 0.88 mmol/L) and LDL cholesterol (2.97 ± 0.67 mmol/L) when all of the fat was contained within the cheese matrix (Group A), compared with Group C when it was not (TC: 5.57 ± 0.86 mmol/L; LDL cholesterol: 3.43 ± 0.78 mmol/L). Conclusion: Dairy fat, eaten in the form of cheese, appears to differently affect blood lipids compared with the same constituents eaten in different matrices, with significantly lower total cholesterol observed when all nutrients are consumed within a cheese matrix This trial was registered at ISRCTN as ISRCTN86731958.

Starter bacteria are the prime agents of lipolysis in cheddar cheese.

To assess the contribution of starter lactic acid bacteria (LAB) to lipolysis in Cheddar cheese, the evolution of free fatty acids (FFAs) was monitored in Cheddar cheeses manufactured from pasteurized milks with or without starter. Starter-free cheeses were acidified by a combination of lactic acid and glucono-delta-lactone. Starter cultures were found to actively produce FFAs in the cheese vat, and mean levels of FFAs were significantly higher in starter cheeses over ripening. The contribution of nonstarter LAB toward lipolysis appears minimal, especially in starter-acidified cheeses. It is postulated that the moderate increases in FFAs in Cheddar cheese are primarily due to lack of access of esterase of LAB to suitable lipid substrate. The results of this study indicate that starter esterases are the primary contributors to lipolysis in Cheddar cheese made from good quality pasteurized milk.

Thermus and the Pink Discoloration Defect in Cheese.

A DNA sequencing-based strategy was applied to study the microbiology of Continental-type cheeses with a pink discoloration defect. The basis for this phenomenon has remained elusive, despite decades of research. The bacterial composition of cheese containing the defect was compared to that of control cheese using 16S rRNA gene and shotgun metagenomic sequencing as well as quantitative PCR (qPCR). Throughout, it was apparent that Thermus, a carotenoid-producing genus, was present at higher levels in defect-associated cheeses than in control cheeses. Prompted by this finding and data confirming the pink discoloration to be associated with the presence of a carotenoid, a culture-based approach was employed, and Thermus thermophilus was successfully cultured from defect-containing cheeses. The link between Thermus and the pinking phenomenon was then established through the cheese defect equivalent of Koch's postulates when the defect was recreated by the reintroduction of a T. thermophilus isolate to a test cheese during the manufacturing process. IMPORTANCE Pink discoloration in cheese is a defect affecting many cheeses throughout the world, leading to significant financial loss for the dairy industry. Despite decades of research, the cause of this defect has remained elusive. The advent of high-throughput, next-generation sequencing has revolutionized the field of food microbiology and, with respect to this study, provided a means of testing a possible microbial basis for this defect. In this study, a combined 16S rRNA, whole-genome sequencing, and quantitative PCR approach was taken. This resulted in the identification of Thermus, a carotenoid-producing thermophile, in defect-associated cheeses and the recreation of the problem in cheeses to which Thermus was added. This finding has the potential to lead to new strategies to eliminate this defect, and our method represents an approach that can be employed to investigate the role of microbes in other food defects of unknown origin.

The Prevalence and Control of Bacillus and Related Spore-Forming Bacteria in the Dairy Industry.

Milk produced in udder cells is sterile but due to its high nutrient content, it can be a good growth substrate for contaminating bacteria. The quality of milk is monitored via somatic cell counts and total bacterial counts, with prescribed regulatory limits to ensure quality and safety. Bacterial contaminants can cause disease, or spoilage of milk and its secondary products. Aerobic spore-forming bacteria, such as those from the genera Sporosarcina, Paenisporosarcina, Brevibacillus, Paenibacillus, Geobacillus and Bacillus, are a particular concern in this regard as they are able to survive industrial pasteurization and form biofilms within pipes and stainless steel equipment. These single or multiple-species biofilms become a reservoir of spoilage microorganisms and a cycle of contamination can be initiated. Indeed, previous studies have highlighted that these microorganisms are highly prevalent in dead ends, corners, cracks, crevices, gaskets, valves and the joints of stainless steel equipment used in the dairy manufacturing plants. Hence, adequate monitoring and control measures are essential to prevent spoilage and ensure consumer safety. Common controlling approaches include specific cleaning-in-place processes, chemical and biological biocides and other novel methods. In this review, we highlight the problems caused by these microorganisms, and discuss issues relating to their prevalence, monitoring thereof and control with respect to the dairy industry.