Bacteriocins are bacterially produced antimicrobial peptides with narrow or broad host ranges. Many bacteriocins are produced by food-grade lactic acid bacteria, a phenomenon which offers food scientists the possibility of directing or preventing the development of specific bacterial species in food. This can be particularly useful in preservation or food safety applications, but also has implications for the development of desirable flora in fermented food. In this sense, bacteriocins can be used to confer a rudimentary form of innate immunity to foodstuffs, helping processors extend their control over the food flora long after manufacture.

Bacteriocins: developing innate immunity for food

The microbial profile of cheese is a primary determinant of cheese quality. Microorganisms can contribute to aroma and taste defects, form biogenic amines, cause gas and secondary fermentation defects, and can contribute to cheese pinking and mineral deposition issues. These defects may be as a result of seasonality and the variability in the composition of the milk supplied, variations in cheese processing parameters, as well as the nature and number of the non-starter microorganisms which come from the milk or other environmental sources. Such defects can be responsible for production and product recall costs and thus represent a significant economic burden for the dairy industry worldwide. Traditional non-molecular approaches are often considered biased and have inherently slow turnaround times. Molecular techniques can provide early and rapid detection of defects that result from the presence of specific spoilage microbes and, ultimately, assist in enhancing cheese quality and reducing costs. Here we review the DNA-based methods that are available to detect/quantify spoilage bacteria, and relevant metabolic pathways in cheeses and, in the process, highlight how these strategies can be employed to improve cheese quality and reduce the associated economic burden on cheese processors.

/pdf/nucleic-acid-based-approaches-to-investigate-microbial-45pzu5iuuh.pdf

Nucleic acid-based approaches to investigate microbial-related cheese quality defects

The principal pathways for the formation of flavour compounds in cheese (glycolysis, lipolysis and proteolysis) are reviewed. Depending on variety, microflora and ripening conditions, lac- tate may be metabolized by a number of pathways to various compounds which contribute to cheese flavour or off-flavours. Citrate metabolism by citrate-positive lactococci or Leuconostoc spp. is important in certain varieties (e.g., Dutch cheeses). Lipolysis results directly in the formation of flavour compounds by liberating free fatty acids (FFA). FFA may also be metabolized to alkan-2-ones and fatty acid lactones. Proteolysis of the caseins to a range of small- and intermediate-sized peptides and free amino acids (FAA) probably only contributes to the background flavour of most cheese varieties, but FAA are important precursors for a range of poorly-understood catabolic reactions which produce volatile compounds essential for flavour.

/pdf/biochemical-pathways-for-the-production-of-flavour-compounds-13h2yk3u72.pdf

Biochemical pathways for the production of flavour compounds in cheeses during ripening: A review

Rennet-coagulated cheeses are ripened for periods ranging from about two weeks to two or more years depending on variety. During ripening, microbiological and biochemical changes occur that result in the development of the flavour and texture characteristic of the variety. Biochemical changes in cheese during ripening may be grouped into primary (lipolysis, proteolysis and metabolism of residual lactose and of lactate and citrate) or secondary (metabolism of fatty acids and of amino acids) events. Residual lactose is metabolized rapidly to lactate during the early stages of ripening. Lactate is an important precursor for a series of reactions including racemization, oxidation or microbial metabolism. Citrate metabolism is of great importance in certain varieties. Lipolysis in cheese is catalysed by lipases from various source, particularly the milk and cheese microflora, and, in varieties where this coagulant is used, by enzymes from rennet paste. Proteolysis is the most complex biochemical event that occurs during ripening and is catalysed by enzymes from residual coagulant, the milk (particularly plasmin) and proteinases and peptidases from lactic acid bacteria and, in certain varieties, other microorganisms that are encouraged to grow in or on the cheese. Secondary reactions lead to the production of volatile flavour compounds and pathways for the production of flavour compounds from fatty acids and amino acids are also reviewed.

/pdf/biochemistry-of-cheese-ripening-ukq5dvnz64.pdf

Biochemistry of Cheese Ripening

http://sgpwe.izt.uam.mx/files/users/uami/acym/Enterococos_en_alimentos_y_salud-2006.pdf

The role and application of enterococci in food and health.

This book is the most comprehensive introductory text on the chemistry and biochemistry of milk. It provides a comprehensive description of the principal constituents of milk (water, lipids, proteins, lactose, salts, vitamins, indigenous enzymes) and of the chemical aspects of cheese and fermented milks and of various dairy processing operations. It also covers heat-induced changes in milk, the use of exogenous enzymes in dairy processing, principal physical properties of milk, bioactive compounds in milk and comparison of milk of different species. This book is designed to meet the needs of senior students and dairy scientists in general

Dairy chemistry and biochemistry

Cheese: Historical Aspects Overview of Cheese Manufacture Chemistry of Milk Constituents Bacteriology of Cheese Milk Starter Cultures Enzymatic Coagulation of Milk Post-Coagulation of Renneted Milk Gel Salting of Cheese Curd Cheese Yield Microbiology of Cheese Ripening Biochemistry of Cheese Ripening Cheese Flavor Cheese Rheology and Texture Factors that Affect Cheese Quality Acceleration of Cheese Ripening Fresh Acid-Curd Cheese Varieties Principal Families of Cheese Processed Cheese and Substitute or Imitation Cheese Products Cheese as a Food Ingredient Pathogens and Food-Poisoning Bacteria in Cheese Nutritional Aspects of Cheese Whey and Whey Products Analytical Methods for Cheese Table of Sources Index

Paul L.H. McSweeney

Papers

Nucleic acid-based approaches to investigate microbial-related cheese quality defects

Biochemical pathways for the production of flavour compounds in cheeses during ripening: A review

Biochemistry of Cheese Ripening

Dairy chemistry and biochemistry

Fundamentals of Cheese Science