Dr Saumya BhaduriDr Saumya Bhaduri received his Master of Science in Biochemistry and PhD in Biochemistry from the University of Calcutta, India. He immigrated to the United States as an NIH Fellow at the University of Nebraska in Lincoln, NE. Dr. Bhaduri worked as a faculty member for 6 years at the Institute of Molecular Virology in St. Louis, MO. He later served as a faculty member at Washington University Medical School in St. Louis, MO. After 5 years in the Pathology Department, Dr. Bhaduri joined the USDA/ARS as a Senior Scientist in the Eastern Regional Research Centre (ERRC) in Philadelphia, PA.

During his time at the USDA/ARS, Dr. Bhaduri created and established the first molecular biology laboratory at ERRC. He received a year-long sabbatical fellowship in order to further his exploration of DNA sequencing of food borne pathogens at the University of Reading, England. Over the course of his extensive experience at various institutions, Dr. Bhaduri’s major research areas focused on initiation of protein synthesis and genetic code, molecular virology, mapping of the histidine operon, and detection and isolation of foodborne pathogens.

Starter bacteria in yoghurt

This article discusses the origins and role of starters in dairy fermentations, the ecology of starter bacteria, the classification of starter bacteria,  the types of starter culture used and concludes with some observations on artisanal cultures. The author has  provided a broader perspective on the use of starter cultures in food fermentations in the Encyclopedia of Food Microbiology. The chapter can be downloaded from Elsevier Ltd. This article should be read in conjunction with the article  discussing the major functions of starters in dairy fermentations and the relative importance and effectiveness of the antimicrobial agents produced by starters

This section gives an overview of developments in this area including opportunities for novel functional foods. The rare involvement of lactobacilli and starter bacteria in human infections is mentioned and a summary of traditional microbiological approaches to the enumeration of probiotic bacteria is included.

The last major update to this article was published in February 2008, since then there have been a number of significant developments. These include the failure of major European dairy companies to obtain ratification by the EFSA of health claims for probiotic products, the deaths of patients on a probiotic trial in the Netherlands, evidence that perhaps some bacteria designated as probiotics may have the potential to aggravate allergies in neonates. Additionally one major researcher has questioned where any strain of Lb. acidophilus has been shown to meet the criteria for a probiotic! However, there has been other more positive research indicating that particular strains of bacteria, in particular lactic acid bacteria, do have the potential to enhance immunity, reduce allergy, and to alleviate distant site infection. This work has very clearly shown that dairy companies and others have a responsibility to use only well characterised strains that have been shown to have probiotic effects in medical trials. Interesting Reid (2007) has stated "a potential major problem for probiotics is the misuse of the term. This can arise from products being poorly manufactured, or being referred to as probiotic without any relevant documentation. The net effect, deleterious to the overall field of probiotics, might be that such products are found to be ineffective, when in fact they were not even probiotic in the first place." Interestingly there is now a growing consensus that there is a world-wide, critical shortage of well qualified food scientists and technologists in commercial food manufacturing. These developments will be taken into consideration in the next major update to this article.

The next major update will summarise recent work on the gut flora and how this complex flora is thought to influence health. Recent research suggests that the gut flora can influence mood e.g. depression and its modification may have the potential to influence body mass and obesity. The main evidence for the latter has come from animal studies and anecdotal accounts of the consequences of faecal microbiota transplants also known as a stool transplants. This work suggests very significant potential for new generation probiotic products.

Gut problems e.g. dyspepsia (indigestion) are common and the Internet has many sites advocating probiotics for treating a range of symptoms. This article, while it may be of interest to the general public, does not promote the medical use of commercial yoghurt products, none of which currently have EFSA endorsements as probiotics in Europe, to treat gastrointestinal problems. I am aware of people experiencing dyspepsia who treated their symptoms with commercial yoghurt products and subsequently found that they had a range of physical medical conditions ranging from ulcers, hiatus hernia to more malign conditions that required surgical intervention. I am positive about the potential health benefits of probiotics but urge readers with health issues to discuss their problems with physicians, who certainly in Europe, take care not to do harm before self-treating with yoghurt type products.

Growth and acid production by starter cultures may be inhibited by bacterial viruses, bacteriophages, or added substances including antibiotics, sterilant and detergent residues, or free fatty acids produced by or as a result of the growth of microorganisms, and natural often called indigenous antimicrobial proteins.

Milk should not contain antibiotic residues.  Milk production in the UK is regulated by the Dairy Products (Hygiene) Regulations 1995.  These regulations include the standards for raw milk.  Prior to 1990 milk was deemed to be contaminated if an antibiotic concentration of > 0.01 international units (iu) /ml was present, the standard has now been increased to 0.006 iu/ml.  Manufacturers buying milk from producers impose stringent financial penalties on farmers producing contaminated milk and have procedures to exclude this from the food chain.  Despite legislation and financial penalties, there is evidence to suggest that residues occasionally still cause problems.  In a survey of the causes of slow acid production by cheese starters in the UK (Boyle and Mullan, 2000, unpublished results) found that, some 28 % of respondents attributed slow acid problems to antibiotics. 

Milk provides the newborn (neonate) with nutrients and an array of antimicrobial factors.  These are believed to help protect neonates from infection until their own immune system has developed.This section of the dairy science website reviews the properties and potential nutritional and industrial significance of the major antimicrobial systems of milk, with particular reference to the lactoperoxidase system.

Blown cheeseThis article is based on a paper, summarising many years of research, published in the International Journal of Dairy Technology. The paper “Mullan, W.M.A. (2000). Causes and control of early gas production in Cheddar cheese. International Journal of Dairy Technology. 53, 63-68. Since then the author has continued to work in this area and in particular with major Cheddar cheese manufacturers in the US. This newer work is not discussed in this article.

Currently many cheesemaking plants are experiencing open texture problems including unwanted slits/cracks in cheese due to unwanted gas production. Some of these problems are caused by the growth of thermophilic / thermoduric lactic acid bacteria in biofilms in pasteurizers. Normal caustic cleaning will not eliminate these and enhanced cleaning and sanitation procedures are required.  While this contribution may not specifically deal with these problems this area can be discussed further in the forums.

Characteristics - Saras del Fèn is a ripened ricotta cheese produced from a mixture of goats’, ewes’ and cows’ milk. The cheese is egg-shaped with a weight of 500-1500 g. Ripening lasts at least 20 days but can be longer than 1 year. It is wrapped during ripening, following local tradition, in hay characteristic of local alpine high pastures. There is no  crust in the fresh product but ripened products have an elastic crust that is wrinkled, soft, grey with yellow and white highlights. The dough is ivory or yellowish without holes. The texture is soft, elastic and sticky. The odour is fine and delicate in fresh products but strong and persistent in aged products. The taste is mainly sweet and fine but savoury, salty and hot in aged products

Subcategories

We use cookies to improve our website and your experience when using it. Cookies used for the essential operation of the site have already been set. To find out more about the cookies we use and how to delete them, see our Privacy Policy.

I accept cookies from this site