Introduction To Food Microbiology PDF

SBP3093 INTRODUCTION TO FOOD Dr. Hanis Nadia Yahya MICROBIOLOGY [email protected]  COURSE CONTENT Weeks Topics Notes 1 Introducti...

SBP3093 INTRODUCTION TO FOOD Dr. Hanis Nadia Yahya MICROBIOLOGY [email protected]  COURSE CONTENT Weeks Topics Notes 1 Introduction to food microbiology Face to Face Intrinsic factors affecting growth and survival of microorganisms Online 2 in food Practical starts at week 2 Extrinsic factors affecting growth and survival of microorganisms Online 3 in food Microbial spoilage of different foods Online 4-5 Coliforms and indicator organisms Online 6 Practical ends at week 6 (6 topics) Food-borne diseases (food infection, causative agents, symptoms, Test 1 at week 7 (depends on students' 7-8 prevention) preference) Food-borne diseases (food intoxication, causative agents, Online 9-10 symptoms, prevention) Methods used control of microorganism in food and food Face to Face 11-12 processing. Group Presentation Pre-recorded presentation 13 All topics FINAL EXAM 14  ASSESMENT Online Test - 20% Final Exam - 50% Presentation- 10% Laboratory Assessment- 20% TOTAL= 100% OUTCOMES Explain the factors that affect microbial growth in food and types of microorganisms that influence food quality, food spoilage and food poisoning. Justify the appropriate microbial quality in food safety for microorganisms in food. Explain the techniques of laboratory microbial analysis on microbial quality and safety of food THE SCOPE OF FOOD MICROBIOLOGY Microbiology is the science which includes the study of the occurrence and significance of bacteria, fungi, protozoa and algae from the beginning until the end of the food chain. Food Chain The series of processes by which food is grown or produced, sold, and eventually consumed. MICRO-ORGANISMS AND FOOD All food that we consumes carry microorganism The micro-organisms present will originate from the natural micro-flora of the raw material and those organisms introduced in the course of harvesting/slaughter, processing, storage and distribution. Generally, these microflora has no effect on the food and to us, in some instances though (i) they can cause spoilage; (ii) they can cause foodborne illness; (iii) they can transform a food’s properties in a beneficial way – food fermentation. FOOD SPOILAGE ▪Food spoilage is the process where a food product becomes unsuitable to ingest by the consumer. ▪These microorganisms use food supply as a source of nutrients for their own growth ▪Also important for deterioration/decomposition ▪In food industry, we want to keep our food’s shelf life longer- economic point of view HOW MICROORGANISMS CAN CAUSE DETERIORATION OF THE FOOD? When they utilize the nutrients of the food, it involved changes in the food compound like: Synthesis a new compound that cause spoiling of the food or (grape-alcohol production) Produced enzymatic changes and contributing off- flavours by mean of breakdown of product.  FOOD SAFETY ▪ Food has been associated with transmission of diseases. ▪ Diseases related with food are called foodborne /diseases or illness. Eg 1: Salmonellosis- is an infection with a bacteria called Salmonella, Salmonella live in the intestinal tracts of animals, including birds. Salmonella are usually transmitted to humans by eating foods contaminated with animal feces. Eg 2: Campylobacteriosis -is an infection caused by bacteria of the genus Campylobacter. These bacteria live in the intestines of healthy birds, and most raw poultry meat commonly has Campylobacter on it. Campylobacter is one of the most common bacterial causes of diarrheal illness Eg 3: Escherichia coli (E. coli) is a bacteria species that normally lives in the intestines of healthy people and animals. More than 700 serotypes of E. coli have been identified. Most varieties of E. coli are harmless or cause relatively brief diarrhea, but a few strains can cause severe abdominal cramps, bloody diarrhea and vomiting.  FERMENTATION Microbes can however play a positive role in food. Interactions between microorganisms and food give beneficial to human. Examples Penicillium fungus are named after cheeses. One of them is P. roqueforti, gives blue cheeses Cheesemakers add P. roqueforti to the milk, so it's present throughout the cheese. The blue mold grows and produce the beautiful blue veins that characterize these cheeses. WHAT ARE THE IMPORTANCE OF MICROORGANISMS IN FOOD? Food bioprocessing Good (desirable) Food biopreservation Probiotics Foodborne disease Bad(undesirable) Food spoilage GOOD (DESIRABLE)- FOOD BIOPROCESSING ▪ Food bioprocessing means foods produce by using biological process. ▪ In this process, food-grade microorganisms are used to produce different types of fermented food using raw materials from animal and plant sources (this process known as “starter culture”). ▪Starter culture- A concentrated preparation of live cells that is added to raw material to initiate fermentation rapidly. FOOD BIOPRESERVATION ▪Is a food biological preservative by using antimicrobial metabolites (taken from certain microorganisms in order to control pathogenic and spoilage microorganisms in foods) ▪In biopreservation, beneficial bacteria are used to prevent food spoilage and get rid of harmful pathogens. Eg: Lactic acid bacteria (LAB) are the most commonly used due to their unique properties and because they are harmless to humans. LABs release antimicrobials ( such as lactic and acetic acid, hydrogen peroxide, and peptide bacteriocins) that stop spoilage and inhibit the growth of potentially harmful pathogens. PROBIOTICS Probiotics refers to a concentrated supplement of beneficial live cells of bacteria (friendly bacteria) culture taken orally intended to improve our health by promoting our body’s natural immunity and improving digestion system. The example of probiotics in food Milk- baby nowadays is added with Lactobacillus acidophilus and Bifidus bacteria. Yogurt- rich with live bacteria culture such as Lactobacillus bulgaricus and Streptococcus thermophillus. Cheese- friendly bacteria that is added in cheese is Lactobacillus. SOURCES OF MICROORGANISM Foods, by their very nature are nutritious and it should be expected that they will offer suitable substrates for the growth and metabolism of micro-organisms Diversity of Microorganism Viable micro-organisms may be found in a very wide range of habitats, from the coldest of brine (cold and salty) ponds in the frozen wastes of polar regions, to the almost boiling water of hot springs. Can be divided into 1) atmosphere [airborne bacteria, airborne fungus], 2) soil [bacteria, fungi, protozoa and algae], 3) water, 4) plants [bacteria, yeast, mould], 5) animal origin. ATMOSPHERE Microorganism could presence in the air but not in abundance quantity unless the environment have been exposed or contaminated aerosol generated from an animal or human source, or from water. Airborne bacteria The bacterial flora can be shown to be dominated by Gram-positive rods and cocci such as bacillus, streptomyces or a related genus of actinomycetes. Hard to predict the microflora in the open air → could have so many possible contamination from the environment Airborne fungus Fungi such as Penicillium and Aspergillus are normally responsible for food spoilage. Other fungi found are Fusarium and Cladosporium. They produces large number of small spores which are resistant to desiccation and light damage (more resistant) SOIL The soil environment is extremely complex and different soils have their own diverse flora of bacteria, fungi, protozoa and algae. Microorganism from soil are associated with food spoilage – ability to degrade complex organic materials Soil bacteria and fungi produce resistant structures since physico-chemical (acidity, pH, moisture, temperature) of soil parameters can change very rapidly. Eg : Bacillus and Clostridium, WATER ❑ The bacteria isolated from the waters of the open oceans often have a requirement for salt, grow best at the relatively low temperatures of the oceans and are nutritionally adapted to the relatively low concentrations of available organic and nitrogenous compounds. ❑If these waters have been contaminated with sewage/other human activities, there is always the risk that enteric organisms may be present and will be concentrated in the sea life like fishes and shellfish. Eg: members of the Enterobacteriaceae, Staphylococcus, Vibrio parahaemolyticus ❑ The fresh waters of rivers and lakes also have a complex flora of microorganisms which will include aquatic species as well as components introduced from terrestrial, animal and plant sources ❑Fungus also presence in water- responsible for spoilage of food commodity associated with water such as crops cultivated with overhead irrigation from a river or lake PLANTS ❑Phylloplane flora- microorganism on leaf surfaces, Rhizoplane flora- microorganism surface of the roots. ❑Eg: Moulds- Cladosporium (black yeast), Aureobasidium pullulans. Bacteria-Gram-negative rods, such as Pectobacterium, Erwinia, Pseudomonas and Xanthomonas. ❑ The numbers of organisms on the surfaces of healthy, young plant leaves may be quite low but the species which do occur are well adapted for this highly specialized environment. ❑Lactobacillus and Leuconostoc which may become important in the production of such fermented vegetable products as sauerkraut. ❑Aspergillus flavus is a fungus which has the ability to produce the carcinogenic metabolite known as aflatoxin which may infect the growing plant in the field and produce its toxic metabolites before harvesting and storage. ANIMAL ORIGIN ❑All healthy animals carry a complex microbial flora, part of which may be very specialized and adapted to growth and survival on its host, and part of which may be transient, reflecting the immediate interactions of the animal with its environment. The gut is also part of the external surface of an animal. Skin ❑The surface of the skin is not a favourable place for most micro-organisms since it is usually dry and has a low pH due to the presence of organic acids secreted from some of the pores of the skin. However, it could be a medium for bacteria transmission from one place to another. ❑ The normal skin flora is dominated by Gram-positive bacteria from the genera Staphylococcus, Corynebacterium and Propionibacterium. ANIMAL ORIGIN The Nose and Throat The nose and throat with the mucous membranes are colonized by a different group of micro-organisms. They are usually harmless but may have the potential to cause disease, especially following extremes of temperature, starvation, overcrowding or other stresses which lower the resistance of the host and make the spread of disease more likely in both humans and other animals. Staphylococcus aureus is carried on the mucous membranes of the nose by a significant percentage of the human population and some strains of this species can produce a powerful toxin capable of eliciting a vomiting response. CONCLUSION It can be seen that most foods cannot be sterile but have a natural flora and acquire a transient flora derived from their environment. To ensure that food is safe and can be stored in a satisfactory state, it is necessary to either destroy the micro-organisms present, or manipulate the food so that growth is prevented or hindered. The manner in which environmental and nutritional factors influence the growth and survival of micro-organisms will be considered in the next chapter.