BACILLUS CEREUS SPORES IN BIOFILMS
The resistance of endospores against heat and disinfectants as well as their hydrophobic properties enable them to attach to processing equipment easily, and subsequently survive cleaning processes (Andersson et al., 1995). Typically, pasteurisation does not effectively inactivate endospores due to their heat resistance. This limits the possibilities of extending the shelf life of pasteurised products or manufacturing minimally processed food (Lücking et al., 2013). Important to consider is the structure of EPS that acts as a diffusional barrier to antimicrobial penetration. The composition and structure of EPS are said to influence both diffusional resistance and an oxidising chemical demand. The resistance of spores is likely due to several interrelated factors, including diffusion barriers, differential metabolic activity, and the cellwall ultrastructure (Mittelman, 1998). Concerns are apparent over emerging heat-resistant spores that can withstand ultrahigh temperature processing during the production of products that are commercially sterile. Further concerns have been whether contaminated ingredients in combination with harsh food processing conditions increase the adaptation of highly resistant spore producers (Postollec et al., 2012). The occurrence of spore-forming bacteria in dairy products can deleteriously affect the quality and safety of the product. Some spore-formers produce toxins and may cause food poisoning. B. cereus – an aerobic spore-former – has the potential to cause emetic and diarrhoeal type food poisoning by the production of the heat-stable cereulide and heat-labile enterotoxins (Lücking et al., 2013).
CLEANING IN PLACE (CIP)
CIP is the cleaning of the inner surfaces of pipelines, filters, vessels, and processing equipment without dismantling the equipment. Cleaning solutions and chemicals involved in the CIP process include different kinds of detergents, sanitisers and disinfectants (Thomas and Sathian, 2014).
The efficiency of the CIP process is determined by factors such as chemicals used, the mechanical power involved, temperatures employed as well as the contact time of the treatment (Wirtanen and Salo, 2003; Thomas and Sathian, 2014). Any remaining organic contamination, milk and water plaque have to be removed. Therefore, the CIP sanitation program is set to assure the removal of organic and inorganic contamination, as well as the disinfection of 99% of surface microorganisms (Vlková et al., 2008; Thomas and Sathian, 2014). Usually, CIP comprises either the spraying of surfaces or the circulation of the chemical cleaning solutions through the plant at a certain temperature accompanied by specific flow rates. CIP systems aid in shortening the required time for cleaning, while recovering cleaning solutions in the CIP system. Due to the CIP system being automated, it supposedly allows for safe and reproducible results as well as an economically optimal process (Thomas and Sathian, 2014).
1. INTRODUCTION AND PROBLEM STATEMENT
2. LITERATURE REVIEW
2.1 EXTENDED SHELF LIFE (ESL) MILK
2.2 ESL MILK PROCESSING
2.3 BACTERIA IN ESL MILK
2.5 PROBLEMS CAUSED BY BIOFILMS
2.6 METHODS TO DETECT BIOFILMS
2.7 BIOFILM PREVENTION AND CONTROL
2.8 CLEANING AND DISINFECTION
2.9 CLEANING IN PLACE (CIP)
3. HYPOTHESIS AND OBJECTIVES
4.2 EFFECT OF CIP ON THE STRUCTURE OF SPORES FROM BACILLUS CEREUS STRAINS ISOLATED FROM FILLER NOZZLES FROM ESL MILK PROCESSING LINES AND RAW MILK
4.3 EFFECT OF CIP ON THE ATTACHMENT, VIABILITY AND GROWTH OF SPORES FROM BACILLUS CEREUS STRAINS ISOLATED FROM RAW MILK AND FILLER NOZZLES FROM AN ESL MILK PROCESSING PLANT
5. GENERAL DISCUSSION
5.1 CRITICAL REVIEW OF METHODOLOGY
5.2 RESEARCH FINDINGS
6. CONCLUSIONS AND RECOMMENDATIONS
8 RESEARCH OUTPUT FROM THIS WORK