Antimicrobial Compounds Applied to Dairy Food

Luisa Angiolillo, Annalisa Lucera, Matteo A. Del Nobile and Amalia Conte

Department of Agricultural Sciences, Food and Environment, University of Foggia, Italy

Dairy products are susceptible to physical, chemical and microbiological deterioration throughout storage and distribution (Cha and Chinnan, 2004). In these products, contamination can occur in the liquid milk, resulting in the inoculation of the whole product, or after milk gelation, in this case, contaminating cells remain near the contact area. The probability of consuming a contaminated cheese has even been estimated at 65.3% for soft cheese made with raw milk (Cao-Hoang et al., 2010). Depending on the type of cheese, the physicochemical properties of the matrix, the origin of the contamination (from raw materials, during the cheese making or ripening), and the contaminant species, pathogenic bacteria can develop more or less toward the interior of the product.

During processing, the pathogenic bacteria risk is diminished by the pasteurization of raw milk, the control of the length of maturation, and of the storage temperature of cheese. This temperature—together with some intrinsic properties such as pH, water activity, and the presence of antimicrobial compounds produced by starter culture— constitute a hurdle system. However, colonization of cheese surface by microorganisms constitutes a significant risk due to its high water content and favorable pH for microbial growth (Conte et al., 2013). In the dairy industry, quality is traditionally measured on the entire process of milk handling involving raw materials, product manufacturing, packaging, storage, and distribution. Farmed animals represent a major reservoir of pathogens that can be transferred to milk. The predominant human bacterial pathogens that can potentially be transferred to milk include mainly Listeria monocytogenes, Salmonella spp., Staphylococcus aureus, and pathogenic Escherichia coli. Raw milk provides a potential growth medium for the development of these bacteria (Farrokh et al., 2013).

Although pasteurization destroys potential pathogenic microorganisms, post-pasteurization processing can lead to the recontamination of dairy products. L. monocytogenes can cause illnesses, extending from those with mild flu-like symptoms to more serious. Between 1998 and 2008, at least 25% of reported outbreaks of listeriosis in the United States were of dairy origin (Cartwright et al., 2013). Listeria can contaminate the dairy environment from

Advances in Dairy Products, First Edition.

Edited by Francesco Conto, Matteo A. Del Nobile, Michele Faccia, Angelo V. Zambrini, and Amalia Conte. © 2018 John Wiley & Sons Ltd. Published 2018 by John Wiley & Sons Ltd.

manure or improperly fermented silage and can be introduced in the human food supply chain. S. aureus is a causative agent of bovine mastitis capable of producing thermostable enterotoxins. Dairy products contain low levels of enterotoxigenic staphylococci; however, temperature abuse above 10 C and poor starter culture activity during fermentation are factors involved in dairy-related outbreaks of staphylococcal intoxication (Cretenet et al., 2011). E. coli O157:H7 is a Shiga toxin-producing Escherichia coli (STEC) serotype of high virulence. The number of cases of severe disease caused by STEC in dairy products has remained quite low, probably thanks to compliance with good hygienic practices at the farm level.

Salmonella is found in the environment and in the gastrointestinal tract of farmed and wild animals. A total of 108,614 confirmed cases of salmonellosis were reported in the European Union in 2009 (EFSA, 2012). Dairy products along with meat and eggs are the most common causes of foodborne Salmonella infection. Salmonellosis from contaminated milk and dairy products has been associated with inadequate pasteurization and post process contamination. Control measures in the food dairy industry are designed to prevent or minimize bacterial contamination, including the appearance or growth of foodborne pathogens.

Good manufacturing practices, sanitation, and hygiene measurements for raw material and food industry environment do not completely eliminate the occurrence of food- borne outbreaks, however. Thus, research into increasing the role of controlling pathogenic and spoilage microorganisms in food is essential. Strategies such as thermal treatment (high or low), water activity (aw) reduction, nutrient restriction, acidifica- tion/fermentation (low pH), altering redox potential (Eh), modified atmosphere packaging, nonthermal physical treatments, or the use of antimicrobials have been traditionally applied to enhance the shelf life of dairy products. Antimicrobial agents also include chemical compounds added to control spoilage microorganisms.

The classification of antimicrobials is extremely difficult. However, depending on origin, they can be divided into traditional (chemical substances) and novel substances, called “naturals” (from animal, plant, and microbial sources). Details on each group are reported below.

 
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