Food Microbiology and Parasitology(3)

UNIT 1: INTRODUCTION TO FOOD MICROBIOLOGY AND PARASITOLOGY Unit Objectives By the end of this unit the learner should be able to: 1. Introduction and definition of terms 2. Describe the background of food microbiology and parasitology 3. State the importance of food microbiology and parasitology 1.1 Definitions of terms Microbiology- It is the study of microorganisms Microorganisms- They is living entities of microscopic size and include bacteria, viruses, yeast, algae & protozoa, mound (fungi) Parasitology- It is the study of parasites, their host and relationship between them Prokaryote- they are unicellular organisms that lack a membrane bound nucleus mitochondria or any other membrane bound organelle. Food microbiology is the study of the microorganisms that inhabit, create, or contaminate food, including the study of microorganisms causing food spoilage. "Good" bacteria, however, such as probiotics, are becoming increasingly important in food science. In addition, microorganisms are essential for the production of foods such as cheese, yogurt, bread, beer, wine and, other fermented foods. Food Contact Surface: Surfaces such as countertops, utensils or equipment which come into direct contact with food. These areas offer opportunities for cross-contamination if not properly cleaned and sanitized. Food Handler: Any person who handles opened or unopened food, equipment, utensils or surfaces used for food preparation and serving. Food Hygiene: All measures necessary to guarantee the safety of food at all stages of the food chain. Food Suitability: Guarantee that food is acceptable for human intake according to its intended use. Parasite: An organism that grows, feeds, and is sheltered on or in a different organism and contributes to its host. Pathogen: A microorganism (bacteria, parasites, viruses, or fungi) that is infectious and causes disease. biol 2 Prepared by B. Koech Food Microbiology and Parasitology CNO 44 & 47 2019 Personal hygiene: Individual cleanliness and habits. Arthropod: A phylum of organisms characterized by exoskeletons and segmented bodies. Definitive host: The organism in which a parasite reaches reproductive maturity. Helminths: A variety of wormlike animals. Intermediate host: An organism infected by a parasite while the parasite is in a developmental form, not sexually mature. Nematodes: A type of helminth characterized by long, cylindrical bodies; commonly known as roundworms. Protozoa: Single-celled animal-like microscopic organisms that must live in the presence of water. Trematodes: A class of worms characterized by flat, oval-shaped bodies; commonly known as flukes. Vector: Any agent, living or otherwise, that carries and transmits parasites and diseases. Physical Hazard: Any object that can get into food during the production process and contaminate the food product. Potentially hazardous food: A food that is natural or synthetic and that requires temperature control because it is capable of supporting growth of pathogens. Sampling: Procurement of test samples under defined conditions. Acid-fast staining: Staining procedure that differentiates between bacteria based on their ability to retain a dye when washed with an acid alcohol solution. 3 Prepared by B. Koech Food Microbiology and Parasitology CNO 44 & 47 2019 1.2 Introduction of food microbiology and parasitology  Food microbiology encompasses the study of microorganisms, which have both beneficial and deleterious effects on the quality, and safety of raw and processed food products. Food microbiology focuses on the general biology of the microorganisms that are found in foods including: their growth characteristics, identification, and pathogenesis.  Humans obtain food from animals and plants, and these must be healthy. Foods of animal origin are made up of water, carbohydrate, proteins and various minerals and vitamins. Foods of animal and plant origin are highly perishable.  Food production occurs in specific areas and at certain periods of the year due to variation in weather conditions. Food has therefore to be collected and stored for use during periods of low or no food production or has to be stored /packed and transported over long distances to reach available markets  Generally, foods when fresh are free of microorganisms (bacteria, fungi, viruses etc), while food surfaces may have a low load of microorganisms. Food spoilage is complicated by the fact that food begins to deteriorate shortly after harvesting, gathering on slaughtering Gram-positive bacteria (those that retain the purple crystal violet dye when subjected to the Gram-staining procedure) - the cell wall adjoining the inner or cytoplasmic membrane is thick (15- 80 nanometers), consisting of several layers of peptidoglycan, also known as murein. Intertwine within the cell wall are polymers composed of glycerol, phosphates, and ribitol, which are known as teichoic acids. In general, Gram-positive bacteria produce extra cellular substances that typically account for most of the virulence factors and this is illustrated by Staphylococcus aureus. Gram-negative bacteria (which do not retain the crystal violet) - the cell wall adjoining the inner membrane is relatively thin (10 nanometers) and is composed of a single layer of peptidoglycan surrounded by a membranous structure called the outer membrane. The outer membrane of Gramnegative bacteria invariably contains a unique component, lipopolysaccharide (LPS or endotoxin), which is toxic to animals. Food safety is a major focus of food microbiology. Pathogenic bacteria, viruses and toxins produced by microorganisms are all possible contaminants of food. However, microorganisms and their products can also be used to combat these pathogenic microbes. Probiotic bacteria, including those that produce bacteriocins, can kill and inhibit pathogens. Alternatively, purified bacteriocins such as nisin can be added directly to food products. Finally, 4 Prepared by B. Koech Food Microbiology and Parasitology CNO 44 & 47 2019 bacteriophages, viruses that only infect bacteria, can be used to kill bacterial pathogens. Thorough preparation of food, including proper cooking, eliminates most bacteria and viruses. However, toxins produced by contaminants may not be liable to change to non-toxic forms by heating or cooking the contaminated food due to other safety conditions. 1.3 Background of food microbiology and parasitology  Microbiology is defined as the science that deals with the study of microorganisms, including algae, bacteria, fungi, protozoa, and viruses. Specifically, bacteria are the most abundant of all organisms, they are unicellular, are relatively small ranging in size from 0.5- to 5.0 µm, and for the most part they reproduce asexually.  Although there are bacterial species capable of causing human illness (pathogens) and food spoilage, there are also beneficial species that are essential to good health and the environment (examples: synthesize vitamins, digest plant cellulose, fixing nitrogen in plant roots, etc.). A microorganism or microbe is a microscopic organism, which may be single-celled or multicellular. The study of microorganisms is called microbiology, a subject that began with the discovery of microorganisms in 1674 by Antonie van Leeuwenhoek, using a microscope of his own design.  Microorganisms are very diverse and include all bacteria, archaea and most protozoa. This group also contains some fungi, algae, and some micro-animals such as rotifers.  Many macroscopic animals and plants have microscopic juvenile stages.  Some microbiologists classify viruses and viroids as microorganisms, but others consider these as nonliving.  What was the roles of Robert Koch, Louis Pasteur, Lazarro Spallanzani? 1.4 Prokaryotes and Eukaryotes Microorganisms and all other living organisms are classified as either prokaryotes or eukaryotes. Prokaryotes and eukaryotes are distinguished on the basis of their cellular characteristics. For example, prokaryotic cells lack a nucleus and other membrane‐bound structures known as organelles, while eukaryotic cells have both a nucleus and organelles 5 Prepared by B. Koech Food Microbiology and Parasitology CNO 44 & 47 2019 1.5 Importance of Food Microbiology & Parasitology  Determining the microbiological quality of food and food ingredient by using appropriate techniques.  Determining the microbial types involved in spoilage and health hazards and identifies the source.  Understanding factors contributing to the emergence of new pathogens or the re-emergence of old pathogens  Understanding the basic mechanism of pathogenesis of food borne microbes.  Designing corrective procedures to control the spoilage and pathogenic micro-organisms in food.  Learning rapid methods of isolating and identifying pathogens and spoilage bacteria from the food and the environment. 6 Prepared by B. Koech Food Microbiology and Parasitology CNO 44 & 47 2019  Identifying how new technologies adapted for food processing can have specific microbiological and designing methods to overcome the problem.  Designing effective sanitation procedures to control spoilage and pathogen problems in food processing facilities.  Effectively using desirable micro-organisms to produce fermented foods.  Knowing about food regulations i.e. of the state, federal land or international.  Understanding the microbial/microbiological problems of imported food.