Microbiology

• Microorganisms like all living things metabolize nutrients in food in order to grow.
• Metabolism carried out in the absence of oxygen is called fermentation.
• Some products of fermentation impart desirable characteristics in food.
• All common sugars, except lactose, are fermented by yeast.
• Sucrose, fructose, and glucose are fermented quickly and maltose more slowly.
• Bacteria are used to make a wide range of food products.
• Outbreaks of food illnesses can be contributed to factors such as mishandling in food service establishments, improper holding temperatures, inadequate cooking, contaminated equipment, food from unsafe source, cross contamination from raw to cooked, poor personal hygiene, presence of pathogen in the raw material, and the ability of the pathogen to grow advantageously in a particular type of food.
• The highest incidence of foodborne illnesses occurs from May to September.
• Diarrhetic shellfish poisoning is a type of foodborne algal toxin that affects shellfish, causing gastrointestinal disorders.
• Paralytic shellfish poisoning is a type of foodborne algal toxin that affects shellfish, causing neurological symptoms.
• Foodborne algal toxins can accumulate in finfish and shellfish feeding on several species of toxic microscopic algae, causing disease symptoms.
• Pathogenic viruses need viable host cells for growth and thus cannot grow in prepared food.
• Neurotoxic shellfish poisoning is a type of foodborne algal toxin that affects shellfish, causing neurological symptoms that are less severe than paralytic shellfish poisoning.
• Botulism is a foodborne intoxication caused by a neurotoxin with some gastric symptoms, which is fatal if not immediately treated.
• Ciguatera poisoning is a type of foodborne algal toxin that affects fin fish such as sea bass, grouper, and snapper, causing gastrointestinal and neurological symptoms.
• The primary route of infection for foodborne viruses and enteropathogenic protozoa and bacteria is through ingestion.
• Pathogenic bacteria can grow in many foods and increase in number with a few viable cells to millions.
• The most important bacteria in food manufacturing are Lactobacillus species, also referred to as lactic bacteria.
• Dairy industry uses lactic acid producing bacteria, along with the addition of rennet, to assist in the coagulation of casein proteins in milk.
• As the culture grows in the milk, it converts the sugar lactose into lactic acid, which ensures the correct level of acidity and gives the cheese its moisture.
• As the cheese ripens, the culture gives it a balanced aroma, taste, texture.
• Lactic bacteria are also responsible for the ‘holes’ in cheeses such as Emmenthal.
• Choosing the right mixture of culture is essential for a high-quality cheese.
• In yoghurt and other fermented milk products, the culture is responsible for the taste and texture of the final product.
• Depending on the acidity, the product will have either a mild or strong taste, and the viscosity depends on the quantity of polysaccharides – chains of sugar molecules – that are produced.
• Yogurt starter cultures of several types of bacteria including lactobacillus bulgaricus and streptococcus thermophilus produce lactic acid and other flavour compounds.
• In recent years, probiotic cultures have become popular in dairy products because of their health benefits.
• These cultures are all very carefully selected strains, and there is good evidence that they help improve digestion, safeguard the immune system, and keep the body’s intestinal flora in balance.
• Meat industry uses meat starter cultures to make dried, fermented products such as salami, pepperoni, chorizo and dried ham.
• The emergence of a pathogenic vancomycin resistant enterococcus, causing severe infections in patients who have catheters, intravenous devices, or are undergoing dialysis, is an example of such antibiotic resistant genes spreading throughout the gut microbiota to susceptible recipient commensal bacteria.
• Findings confirmed that intestinal strains Lactobacillus rhamnosus, Lactobacillus reuterii, Lactobacillus GG, and Enterococcus spp. persisted in the intestinal tract in higher numbers than the dairy strains Lactobacillus casei subsp. alactus and Lactobacillus delbrueckii subsp. lactis.
• Survival of live bacteria in foods is an issue, as probiotics are usually anaerobic bacteria and do not survive well during temperature changes.
• An in vitro study compared the survival of 47 strains of Lactobacillus ssp.
• Those isolated from the human gut showed better survivability than probiotic strains isolated from food or dairy products.
• It may be prudent for strains used as probiotics to be susceptible to at least 2 of the common molecules used in human antibiotherapies due to the potential risks of developing less well known probiotic microbiota.
• One theoretical risk is bacteremia developing from the overgrowth of probiotic organisms or indigenous colonic microbiota.
• Escherichia coli and yeasts such as Saccharomyces boulardii and Saccharomyces cerevisiae have all reported probiotic effects, but their positive effects are strongly counterbalanced by safety risks.
• 5 strains from this study were selected for a feeding experiment.
• However, some strains have been associated with nosocomial and antibiotic infections.
• Lactobacillus casei subsp. alactus and Lactobacillus delbrueckii subsp. lactis could be used as a probiotic.