2024-2025 Food Technology (BBT10002) Module 1 (Part II) PDF

BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Module 1 Introduction to food science and technology (Food Technology BBT10002) ____________________________________________________________...

BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Module 1 Introduction to food science and technology (Food Technology BBT10002) ________________________________________________________________________________________ Table of Contents S. No. Topic Page No. Food Microbiology Development of early food microbiology (before 1900 A.D.) Food microbiology and its scope 2-13 Importance of micro-organisms in foods 1 Classification and nomenclature of micro-organisms Micro-organisms in food Important micro-organisms in food Normal micro flora of some common foods Food Biochemistry 2 Key Components of Food Biochemistry 13-14 Applications of Food Biochemistry 3 Food Additives 15 4 Model questions 16-20 5 References 20 Department of Biotechnology Brainware University, Kolkata 1 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 1. FOOD MICROBIOLOGY Food microbiology is the study of microorganisms that interact with food and their impact on food safety, quality, and shelf life. Microorganisms such as bacteria, yeasts, molds, and viruses are naturally present in the environment and can contaminate food at various stages, from production to consumption. Understanding food microbiology is essential for ensuring food safety, preventing foodborne illnesses, and maintaining the overall quality of food products. Why it is necessary to understand food microbiology? It is essential for ensuring food safety, preventing foodborne illnesses, and maintaining the overall quality of food products. By understanding the fundamental principles of food microbiology and how these translate into both positive and negative effects for consumers, we can make our food establishments safer. We can focus on prevention and on promotion of a culture of food safety, to ensure the opening scenario in the lesson would never really happen. 1.1 DEVELOPMENT OF EARLY FOOD MICROBIOLOGY (BEFORE 1900 A.D.) Early Homo ancestors, recognizing the need to prevent food spoilage and illness, used ice and fire for food preservation despite lacking knowledge of the underlying causes. By 8000 B.C., with the advent of agriculture and animal husbandry, early civilizations developed various preservation techniques such as drying, smoking, salting, and fermentation to ensure a steady food supply throughout the year. Although early societies likely did not fully understand the link between food and disease, religious guidelines later emerged to protect health, addressing issues like consuming meat from diseased animals or improperly handled foods. The discovery of microorganisms by Leeuwenhoek in the 1670s and Pasteur’s subsequent research in the 1870s laid the groundwork for modern food microbiology, linking microorganisms to food spoilage and safety. Table below mention few of the key observations: Year Food Fermentation 1822 C.J. Person named the microscopic organism found on the surface of wine during vinegar production as Mycoderma mesentericum. Pasteur in 1868 proved that this organism was associated with the conversion of alcohol to acetic acid and named it Mycoderma aceti. In 1898, Martinus Beijerinck renamed it Acetobacter aceti 1837 Theodor Schwann named the organism involved in sugar fermentation as Saccharomyces (sugar fungus). 1838 Charles Cogniard-Latour suggested that growth of yeasts was associated with alcohol fermentation 1860 Louis Pasteur showed that fermentation of lactic acid and alcohol from sugar was the result of growth of specific bacteria and yeasts, respectively 1883 Emil Christian Hansen used pure cultures of yeasts to ferment beer. Food Spoilage 1804 Francois Nicolas Appert developed methods to preserve foods in sealed glass bottles by heat in boiling water. He credited this process to Lazzaro Spallanzani (1765), who first used the method to disprove the spontaneous generation theory 1819 Peter Durand developed canning preservation of foods in steel cans. Charles Mitchell introduced tin lining of metal cans in 1839 1870 L. Pasteur recommended heating of wine at 145 °F (62.7°C) for 30 min to destroy souring bacteria. F. Soxhlet advanced boiling of milk for 35 min to kill contaminated bacteria. Later, this method was modified and named pasteurization, and used to kill mainly vegetative pathogens and many spoilage bacteria Department of Biotechnology Brainware University, Kolkata 2 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 1895 Harry Russell showed that gaseous swelling with bad odors in canned peas was due to growth of heat-resistant bacteria (spores). Foodborne Diseases 1820 Justin Kerner described food poisoning from eating blood sausage (due to botulism). Fatal disease from eating blood sausage was recognized as early as A.D. 900. 1849 John Snow suggested the spread of cholera through drinking water contaminated with sewage. In 1854, Filippo Facini named the cholera bacilli as Vibrio cholera, which was isolated in pure form by Robert Koch in 1884. 1885 Theodor Escherich isolated Bacterium coli (later named Escherichia coli) from the feces and suggested that some strains were associated with infant diarrhea 1895 Marie von Ermengem isolated Bacillus botulinus (Clostridium botulinum) from contaminated meat and proved that it caused botulism Microbiology Techniques 1854 Heinrich Schröder and Theodore von Dusch used cotton to close tubes and flasks to prevent microbial contamination in heated culture broths. 1878 Joseph Lister isolated Streptococcus (now Lactococcus) lactis in pure culture by serial dilution from sour milk. 1880s Robert Koch and his associates introduced many important methods that are used in all branches of microbiology, such as solid media (first gelatin, then agar) to purify and enumerate bacteria, Petri dish, flagellar staining, steam sterilization of media above 100rC, and photography of cells and spores 1884 Hans Christian Gram developed Gram staining of bacterial cells. 1.2 FOOD MICROBIOLOGY AND ITS SCOPE Although processes of food spoilage and methods of food preservation and food fermentation have been recognized since ancient times, it was not until the 1800s that the relationship between foods and micro-organisms was established. In 1837 Schwann proposed that the yeast which appeared during alcoholic fermentation was a microscopic plant, and between 1857 and 1876 Pasteur showed that micro- organisms were responsible for the chemical changes that take place in foods and beverages. Their observations laid the foundation for the development of food microbiology as we know it today. Soon after these early discoveries were made, knowledge about the role that micro- organisms play in food preservation, food spoilage and food preservation, food spoilage and food poisoning accelerated rapidly until food microbiology gradually emerged as a discipline in its own right. Food microbiology is now a highly developed area of knowledge with the main areas of interest highlighted in the figure. Department of Biotechnology Brainware University, Kolkata 3 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Not all groups of micro-organisms are of equal interest to the food microbiologist. Bacteria come very much on top of the list with molds and yeasts also of considerable importance and viruses less so. The associations that these organisms have with the manufacture and consumption of foods are summarized in figure below Fig: Various groups of micro-organisms and their associations with food Protozoa and algae have minimum direct impact on the production, processing and consumption of food. Food-borne disease can be caused by some protozoa and others belonging to this group are important in the treatment of wastes. Algae are used to produce alginates; some have the potential for use in the production of single-cell protein and some marine species produce toxins that might enter our food along with sea foods. 1.3 IMPORTANCE OF MICRO-ORGANISMS IN FOODS Food-borne Diseases: Many pathogenic micro-organisms (bacteria, molds and viruses) can contaminate foods during various stages of their handling, between production and consumption. Consumption of these foods can cause food borne diseases. Food borne diseases can be fatal and may also cause large economic losses. Foods of animal origin are associated, more with food borne diseases than foods of plant origin. Mass production of food, introduction of new technologies in the processing and storage of food, changes in food consumption patterns, and increased import of food from other countries have increased the chances of large outbreaks as well as the introduction of new pathogens. Effective intervention technologies are being developed and implemented to ensure the safety of consumers against food borne diseases. New methods are also being developed to effectively and rapidly identify the pathogens in contaminated foods. Food Spoilage: Except for sterile foods, all foods harbor micro-organisms. Food spoilage stems from the growth of these micro-organisms in food or is due to the action of microbial enzymes. New marketing trends, consumers’ desire for foods that are not overly processed and preserved, extended shelf life, and chances of temperature abuse between production and consumption of foods have greatly increased the chances of food spoilage and, in some instances, with new types of micro-organisms. The major concerns are the economic loss and wastage of food. New concepts are being studied to reduce contamination as well as control the growth of spoilage microbes in foods. Department of Biotechnology Brainware University, Kolkata 4 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Food Bioprocessing: Many food-grade micro-organisms are used to produce different types of fermented foods using raw materials from animal and plant sources. Consumption of these foods has increased greatly over the last 15 to 20 years and is expected to increase further in the future. There have been great changes in the production and availability of these micro-organisms (starter cultures) to meet the large demand. In addition, novel and better strains are being developed by using genetic engineering techniques. Food Additives: Microbial enzymes are also being used to produce food and food additives. By employing genetic recombination techniques, and using diverse microbial sources enzymes of higher purity & activity are obtained. Many types of additives from microbial sources are being developed and used in food. Some of these include single-cell proteins, essential amino acids, colour compounds, flavour compounds, stabilizers and organic acids. Food Biopreservation: Antimicrobial metabolites (e.g. bacteriocins and organic acids like acetic, propionic and lactic acids) of desirable Micro-organisms are being developed and used in foods in place of preservatives of non-food (chemical) origin to control pathogenic and spoilage micro-organisms in food. Economic production of these antimicrobial compounds and their effectiveness in food systems have generated wide interest. Probiotics: Consumption of foods containing live cells of bacteria and that have apparent health benefits has generated interest among consumers. The role of these bacteria for health and bacterial efficacy benefits is being critically investigated. 1.4 CLASSIFICATION AND NOMENCLATURE OF MICRO-ORGANISMS Living cellular organisms, on the basis of phylogenetic and evolutionary relationships, are grouped into five kingdoms in which bacteria belong to prokaryote (before nucleus), while the eukaryotic (with nucleus) molds and yeasts are grouped under fungi. Viruses are not considered as living cells and are not included in this classification system. For the classification of yeasts, molds, and bacteria, several ranks are used after the kingdom. These are divisions, classes, orders, families, genera (singular, genus), and species. The basic taxonomic group is the species. Several species with similar characteristics form a genus. A family is made up of several genera, and the same procedure is followed in the hierarchy. Ranks above species, genus, and family are seldom used in food microbiology. Among bacteria, a species is regarded as a collection of strains having many common features. A strain is the descendent of a single colony (single cell). Among the strains in a species, one is assigned as the type strain; it is used as a reference strain while comparing the characteristics of an unknown isolate. The basic taxonomic group in bacteria, yeasts, and molds is the species, and each species is given a name. The name has two parts (binomial name); the first part is the genus name and the second part is the specific epithet (adjective). Both parts are Latinized; when written, they are italicised (or underlined) with the first letter of the genus written in a capital letter and species name in small letters. For e.g. Bacillus subtilis (genus is Bacillus and species is subtilis). 1.5 MICRO-ORGANISMS IN FOOD The Micro-organisms most common to food are bacteria and fungi. The fungi, which are less common than bacteria, consist of two major types of Microorganisms, viz. molds and yeasts. Apart from these, food may contain viruses and other parasites such as protozoans, worms etc. Department of Biotechnology Brainware University, Kolkata 5 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Bacteria: Bacteria are unicellular Micro-organisms that are approximately one micro meter (10-3 mm) in diameter with variations in morphology from short and elongated rods (bacilli), spherical or ovoid forms(cocci), vibrio (comma shaped) and even spiral in shape (Refer Fig. 1.3). Cocci (meaning “berry”) are sphere shaped bacteria. Individual bacteria closely combine in various forms according to genera. Some sphere-shaped bacteria occur in clusters similar to a bunch of grapes (i.e. staphylococci). Other bacteria (rod shaped or sphere shaped) are linked together to form chains (i.e. streptococci in case of cocci chain). Certain genera of sphere-shaped bacteria are found together in pairs (diplococci i.e. Pneumococci) or as a group of four (Square or cubical packets formation; i.e. Sarcinia), while other genera appear as an individual bacterium. Other bacteria (in majority) are rod shaped and possess flagella and are motile. Fig.: Types of bacterial cells and their groupings Department of Biotechnology Brainware University, Kolkata 6 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Bacteria produce various pigments which range from shades of yellow to dark pigments such as brown or black. Certain bacteria have pigmentation of intermediate colors such as red, pink, orange, blue, green, or purple. These bacteria cause food discoloration, especially, among foods with unstable color pigments such as meat. Some bacteria also cause discoloration by slime formation. Molds: Molds are multicellular micro-organisms with mycelial (filamentous) morphology. These microbes are also characterized by their display of a variety of colors and are generally recognized by their mildewy or fuzzy, cotton like appearance. Molds can develop numerous tiny spores that are found in the air and can be spread by air currents. These spores can produce new mold growth if they are transferred to a location that has conditions conducive to germination. Molds generally withstand greater fluctuation in pH than bacteria and yeasts and can frequently tolerate more temperature fluctuation. Although molds thrive best at or near a pH of 7.0, a pH range of 2.0 to 8.0 can be tolerated, even though an acid to neutral pH is preferred. Molds thrive better at ambient temperature than in a colder environment, even though growth can occur below 0°C. Although mold growth is optimal at a water activity (Aw) of approximately 0.85, growth can and does occur below 0.80. At an Aw of 0.90 or higher, bacteria and yeasts grow more effectively and normally utilize available nutrients for growth at the expense of molds. When the Aw goes below 0.90, molds grow more effectively. That is why foodstuffs, such as pastries, cheeses, and nuts, that are low in moisture content are more likely to spoil from mold growth. Yeasts: Yeasts are generally unicellular and differ from bacteria in their large cell size and morphology, and because they produce buds during the process of reproduction by division. Like molds, yeasts can be spread through the air, or other means, and alight on the surface of foodstuffs. Yeast colonies are generally moist or slimy in appearance and creamy white colored. Yeasts prefer an Aw of 0.90 - 0.94, but can grow below 0.90. These micro-organisms grow best in the intermediate acid range, pH from 4.0 to 4.5. Food that is highly contaminated with yeasts will frequently have a slightly fruity odor. Viruses: Viruses are 10- 450 nm in size; cannot reproduce without a living host; attack only susceptible host cell lines; infect plants, animals, and bacteria; and have the capacity to produce specific diseases in specific hosts. Transmission occurs in foods, water and air. Viruses that infect bacteria are called bacteriophages. Viruses are included in the order Virales. Viruses are too small to be visualized with an ordinary compound microscope. Only after the electron microscope was developed, the direct observation of viruses was possible. Viruses consist of a DNA or RNA core surrounded by a protein coat. Because they lack all the apparatus for normal cellular metabolism, they must utilize the cellular machinery of the host cell to grow and divide. However, viruses can multiply rapidly once they invade a host cell. Parasitic Organisms: A number of parasitic worms can also be transmitted by food to cause diseases in humans.  Cestodes are flatworms that inhabit the intestinal tract, heart, and lungs of animals. Beef, swine, dogs and other canine species, bears, and fish can all harbour tapeworms and flatworms, which can be transmitted to and can infect humans.  Trematodes are non-segmented flatworms that possess a mouth and oral sucker and depend on a snail as an intermediate host before infecting humans by being ingested in drinking water or aquatic plants. Intestinal flukes, pyriform worms from fish, sheep and Chinese liver flukes, and oriental lung flukes are all examples of food-transmitted parasites.  Nematodes or true roundworms also can be transmitted from animals to humans. Eggs carried in excrement from roaches and dung beetles ingested by cattle, sheep and hogs contaminate Department of Biotechnology Brainware University, Kolkata 7 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 humans. Trichinosis is an inflammation of the muscle tissue caused by ingesting the worm Trichinella spiralis. Pork is the most common vector. Capillary worms, whipworms, and pinworms are other examples of nematode parasites.  Protozoa are microscopic single-celled animals, which can be taken in with food or water to cause human illness. Entamoeba histolytica, Toxoplasma gondii, Balantidium coli, and Giardia lamblia are the most common food borne protozoan parasites. 1.6 IMPORTANT MICRO-ORGANISMS IN FOOD Important Mold Genera: Molds are important in food because they can grow in conditions in which many bacteria cannot, such as low pH, low water activity (a w), and high osmotic pressure. They are important spoilage micro-organisms. Many strains also produce mycotoxins and have been implicated in food borne intoxication. Many are used in food bioprocessing. Finally, many are used to produce food additives and enzymes. Some of the most common genera of molds found in food are listed here: Fig.: Common mold species found in foods  Aspergillus: They are widely distributed and contain many species that are important in food. They have septate hyphae and produce a sexual spores (black color) or conidia. Many are xerophilic (able to grow in low Aw) and can grow in grains, causing spoilage. They are also involved in spoilage of foods such as jams, cured ham, nuts, and fruits and vegetables (rot). Some species/strains produce mycotoxin (e.g., Aspergillus flavus produces aflatoxin). Many species/strains are also used in food and food additive processing. Aspergillus oryzae is used to hydrolyze starch by alpha- amylase in the production of sake. Aspergillus niger is used to process citric acid from sucrose and to produce enzymes like-galactosidase.  Alternaria: They are also septate and form dark-brown colored many celled conidia on the conidiophere. They cause rot in tomatoes and rancid flavor in dairy products. Species: Alternaria tenuis. Department of Biotechnology Brainware University, Kolkata 8 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25  Penicillium: They are widely distributed and contain many species. They have septate hyphae and form conidiophore on a blue-green, brushlike conidia head. Some species are used in food production, such as Penicillium roquefortii and Penicillium camembertii in cheese. Many species cause fungal rot in fruits and vegetables.  Mucor: They are widely distributed. They have nonseptate hyphae and produce sporangiophores. They produce cottony colonies. Some species are used in food fermentation and production of enzymes. They cause spoilage of vegetables. Species: Mucor rouxii  Rhizopus: The hyphae are aseptate and form sporangiophores in sporangium. They are involved in the spoilage of many fruits and vegetables. Rhizopus stolonifer is the common black bread mold. Important Yeast Genera: Yeasts are important in food due to their ability to cause spoilage. Many are also used in food bioprocessing. Some are used to produce food additives. Several important genera are briefly described below  Saccharomyces: Cells are round, oval, or elongated. It is the most important genus and contains heterogeneous groups. Saccharomyces cerevisiae variants are used in baking for leavening of bread and in alcoholic fermentation. They are also involved in spoilage of food with the production of alcohol and CO2.  Pichia: They are oval to cylindrical cells and form pellicle in beer, wine, and brine to cause spoilage. Some are also used in oriental food fermentation. Species: Pichia membranaefaciens.  Rhodotorula: They are pigment (red, pink or yellow) forming yeasts and can cause discoloration of foods, such as in meat, fish, and sauerkraut. Species Rhodotorula glutinis.  Candida: Many spoil foods with high acid, salt, and sugar and form pellicle on the surface of liquids. Some can cause rancidity in butter and dairy products (Candida lipolytica).  Zygosaccharomyces: Involved in spoilage of foods, containing high sugar/ salt levels ex. honey, sirups, molasses, soy sauce. (Zygosaccharomyces nussbaumeri). These yeasts are termed osmophilic, because they can grow in high concentrations of solutes. Important Viruses: Viruses are important in food for three reasons. Some are able to cause enteric disease and thus, if present in a food, can cause food borne diseases. Hepatitis A and Norwalk viruses have been implicated in food borne outbreaks. Several other enteric viruses, such as Poliovirus, Echovirus, and Coxsackievirus, have the potential of causing food borne diseases. In some countries where the level of sanitation is not very high, they can contaminate foods and cause disease. Some bacterial viruses (bacteriophages) are used in the identification of species/ strains by a process called tranduction (e.g., in Escherichia, coli, Lactococcus lactis). Finally, some bacteriophages can be very important due to their ability to cause fermentation failure. Many lactic acid bacteria, used as starter cultures in food fermentation, are sensitive to different bacteriophages. These phages can infect and destroy starter culture bacteria, causing product failure. Among the lactic acid bacteria, bacteriophages have been isolated for many species in genera Lactococcus, Streptococcus, Leuconostoc, and Lactobacills. Methods are being studied to genetically engineer lactic acid start cultures so that they become resistant to multiple bacteriophages. Table: Human Intestinal Viruses with High Potential as Food Contaminants Types of Viruses Example Picornaviruses Polioviruses, Coxsackievirus A, Coxsackievirus B, Echovirus, Enteroviru Department of Biotechnology Brainware University, Kolkata 9 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Reoviruses Reovirus, Rotavirus Parvoviruses Human gastrointestional viruses Papovaviruses Human BK and JC viruses Adenoviruses Human adenoviruses Important Bacterial Genera: Bacterial classification is rapidly changing. In the following Table below, only those species and genera currently approved and listed in Bergey’s Manual have been used Table: Genera of Bacteria Important in Food Group Family Genera Spiral and curved bacteria Spirallaceae Campylobacter Pseudomonas, Altermonas, Pseudomonadaceae Gram-negative aerobic rods Gluconobacter, Xanthomonas and cocci Halobacteriaceae Halobacterium, Halococcus Genera of uncertain affinity Alcaligenes, Acetobacter, Brucella Escherichia, Citrobacter, Salmonella, Enterobacteriaceae Shigella, Klebsiella, Enterobacter, Gram-negative facultative Serratia, Proteus, Yersinia, Erwinia anaerobic rods Vibrionaceae Vibrio, Aeromonas Genera of uncertain affinity Flavobacterium, Chromobacterium Gram-negative diplococci and Moraxella, Acinetobacter diplococcobacilli Neisseriaceae Micrococcus, Staphylococcus Gram-positive cocci Micrococcaceae Streptococcus, Leuconostoc, Streptococcaceae Pediococcus, Lactococcus, Enterococcus Peptococcaceae Sarcina Endospore forming rods and Clostridium, Bacillus Bacillaceae cocci Gram-positive asporogenous Lactobacillaceae Lactobacillus rod of regular shape Genera of uncertain affinity Listeria Non spore-forming rods of Arthrobacter, Brevibacterium, Coryneform bacteria irregular shape Propionibacterium Rickettsia Rickettsiaceae Coxiella Common Bacterial Groups in Foods Among the Micro-organisms found in foods, bacteria constitute a major important group. This is not only because many different species can be present in foods, but is also due to their rapid growth rate, ability to utilize food nutrients, and their ability to grow under a wide range of temperatures, aerobiosis, pH, and water activity, as well as to survive under adverse situations, such as survival of spores at high temperature. For convenience, bacteria important in foods have been arbitrarily divided into several groups on the basis of similarities in certain characteristics. This grouping does not have any taxonomic significance. Some of these groups and their importance in foods are listed here. Lactic Acid Bacteria: Those bacteria that produce relatively large quantities of lactic acid from carbohydrates. Include species mainly from genera Lactococcus, Leuconostoc, Pediococcus, Lactobacillus and Streptococcus thermophilus. Acetic Acid Bacteria: Those bacteria that produce acetic acid, such as Acetobacter aceti. Department of Biotechnology Brainware University, Kolkata 10 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Propionic Acid Bacteria: Those bacteria that produce propionic acid and are used in dairy fermentation. Include species such as Propionibacterium freudenreichii. Butyric Acid Bacteria: Those bacteria that produce butyric acid in relatively large amounts. Some Clostridium spp., such as Clostridium butyricum. Proteolytic Bacteria: Those bacteria that are capable of hydrolyzing proteins due to production of extracellular proteinases. Species in genera Micrococcus, Staphylocccus, Bacillus, Clostridium, Pseudomonas, Alteromonas, Flavobacerium, and Alcaligenes; some in Enterobacteriaceae and Brevibacterium are also included in this group. Lipolytic Bacteria: Able to hydrolyze triglycerides due to production of extracellular lipases. Species in genera Micrococcus, Staphylococcus, Serratia, Pseudomonas, Alteromonas, Alcaligenes and Flavobacterium are included in this group. Saccharolytic Bacteria: Able to hydrolyze complex carbohydrates. Include some species in genera Bacillus, Clostridium, Aeromonas, Pseudomonas, and Enterobacter. Thermophillic Bacteria: Able to grow at 50°C and above. Include some species from genera Bacillus, Clostridium, Pediococcus, Streptococcus, and Lactobacillus. Psychrotrophic Bacteria: Able to grow at refrigerated temperature (10%). Include some species of Bacillus, Micrococcus, Staphylococcus, Pediococcus, Vibrio Streptococcus, Clostridium and Corynebacterium. Aciduric Bacteria: Able to survive at low pH (below 4.0). Include some species of Lactobacillus, Pediococcus, Lactococcus, Enterococcus and Streptococcus. Osmophilic Bacteria: Can grow at a relatively higher osmotic pressure (environment) than other bacteria. Some species from genera Staphylococcus, Leuconostoc, and Lactobacillus are included in this group. They are much less osmophilic than yeasts and molds. Gas-producing Bacteria: Produce gas (CO2, H2, H2S) during metabolism of nutrients. Include spices from genera Leuconostoc, Lactobacillus, Brevibacterium and Escherichia. Slime Producers: Produce slime due to synthesis of polysaccharides. Include some species or strains of Xanthomonas, Leuconostoc, Alcaligenes, Enterobacter, Lactococcus, and Lactobacillus. Spore formers: Ability to produce spore. Include Bacillus, Clostridium and Desulfotomaculum spp. They are again divided into aerobic, anaerobic, flat sour thermophilic and sulfide-producing spore formers. Department of Biotechnology Brainware University, Kolkata 11 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 Aerobes: Require oxygen for growth and multiplication. Species of Pseudomonas, Bacillus, and Flavobacterium are included in this group. Anaerobes: Cannot grow in the presence of oxygen. Include species of Clostridium. Facultative Anaerobes: Able to grow both in the presence and absence of oxygen. Lactobacillus, Pediococcus, Leuconostoc, enteric pathogens, some species of Bacillus, Serratia, and coliforms are included in this group. Coliforms: Include mainly species from Escherichia, Enterobacter, Citrobacter, and Klebsiella, and used as index of sanitation. Fecal Coliforms: Include mainly Escherichia coli. Also used as index of sanitation. Enteric Pathogens: Include pathogenic Salmonella, Shigella, Campylobacter, Yersinia, Escherichia, Vibrio, Listeria, Hepatitis A, and others that can cause gastrointestinal infection 1.7 NORMAL MICRO FLORA OF SOME COMMON FOODS Under normal conditions a food generally harbours only a few types of Microorganisms. They constitute those that are naturally present in raw foods (which provide the ecological niche) and those that get in from outside sources to which the foods are exposed from the time of production until consumption. The predominant type(s) will be the ones for which the optimum growth condition is present. The normal microflora of different food groups are listed below Meat: The carcass of a healthy animal slaughtered for meat and held in a refrigerated room is likely to have only nominal surface contamination while the inner tissues are sterile. Fresh meat cut from the chilled carcass has its surface contaminated with micro-organisms characteristic of the environment and the implements (saws or knives) used to cut the meat. Each new surface of meat, resulting from a new cut, adds more micro-organisms to the exposed tissue. Among the most common species of bacteria occurring on fresh meats are Pseudomonads, Staphylococci, Micrococci, Enterococci and Coliforms. The low temperature at which fresh meats are held favors the growth of psychrophilic Micro-organisms. Poultry: Freshly dressed eviscerated poultry have a bacterial flora on their surface (skin) that originates from the bacteria normally present on the live birds and from the manipulations during killing, defeathering, and evisceration. Under good sanitary conditions the bacterial count has been reported to be from 100 to 1000 bacteria per square centimeter of skin surface, whereas under less sanitary conditions the count may increase 100-fold or more. Pseudomonads constitute the major contaminants on the skin of freshly dressed poultry. Eggs: The interior of a freshly laid egg is usually free of micro-organisms; its subsequent microbial content is determined by the sanitary conditions under which it is held, as well as the conditions of storage, i.e. temperature and humidity. Micro-organisms particularly bacteria and molds, may enter the egg through cracks in the shells or penetrate the shells when the “bloom” (thin protein coat) covering the shell deteriorates. The type of micro-organisms involved reflect those present in the environment. Fruits and Vegetables: They are normally susceptible to infection by bacteria, fungi, and viruses. Microbial invasion of plant tissue can occur during various stages of fruit and vegetable development, and the Department of Biotechnology Brainware University, Kolkata 12 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 likelihood of spoilage increases. A second factor contributing to the microbial contamination of fruits and vegetables pertains to their post-harvest handling. Mechanical handling is likely to produce breaks in the tissue which facilitates invasion by micro-organisms. The pH of fruits is relatively acid i.e. ranging from 2.3 (for lemons) to 5.2 (for bananas). This restricts bacterial growth but does not retard fungal growth. The pH range for vegetables is slightly higher pH 5.0 to 7.0 and hence they are more susceptible than fruits to bacterial attack. Shellfish and Finfish: The microbial flora of freshly caught oysters, clams, fish, and other aquatic specimens is very largely a reflection of the microbial quality of the water from where they are harvested. Of particular significance is whether the water is sewage-polluted, in which case the aquatic food is potentially capable of transmitting various pathogenic Micro-organisms. Shellfish that grow in contaminated water can concentrate viruses and may be the source of Hepatitis infection. For example, raw oysters and clams from polluted waters have caused numerous epidemics in various parts of the world. Milk: Milk is an excellent growth medium for all of the common spoilage organisms, including molds and yeasts. Fresh, non-pasteurized milk generally contains varying numbers of Micro-organisms, depending on the care employed in milking, cleaning, and handling of milk utensils. Raw milk held at refrigerator temperatures for several days invariably shows the presence of several or all bacteria of the following genera: Enterococcus, Lactococcus, Streptococcus, Leuconostoc, Lactobacillus, Microbacterium, Propionibacterium, Micrococcus, Coliforms, Proteus, Pseudomonas, Bacillus, and others. Those unable to grow at the usual low temperature of storage tend to be present in very low numbers. The pasteurization process eliminates all but thermoduric strains, primarily, Streptococci and Lactobacilli, and spore formers of the genus Bacillus (and clostridia if present in raw milk). The spoilage of pasteurized milk is caused by the growth of heat-resistant Streptococci utilizing lactose to produce lactic acid, which depresses the pH to a point (about pH 4.5) where curdling takes place. 2 FOOD BIOCHEMISTRY Food biochemistry is the study of the chemical processes and compounds that occur in food, and how these processes impact its composition, quality, nutritional value, and safety. It bridges the gap between food science and biochemistry, offering insights into the molecular-level changes that food undergoes during its production, storage, and consumption. Key Components of Food Biochemistry Macronutrients: o Proteins: These are essential for growth and repair in the body. In food biochemistry, the focus is on the structure, function, and changes that proteins undergo during cooking and digestion. o Carbohydrates: These are the primary source of energy. Understanding their structure, types (simple vs. complex), and how they break down during digestion is crucial. o Fats: These are important for energy storage, insulation, and cell structure. The study involves understanding different types of fats, their nutritional value, and their behavior during cooking. Micronutrients: Department of Biotechnology Brainware University, Kolkata 13 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 o Vitamins: These are organic compounds required in small amounts for normal growth and metabolism. Each vitamin has specific roles and functions in the body. o Minerals: These are inorganic elements that play various roles, including structural functions (like calcium in bones) and regulatory functions (like iron in blood). Enzymes: o These are biological catalysts that speed up biochemical reactions in food. Enzymes play critical roles in processes like ripening, fermentation, and digestion. Food Additives: o These include preservatives, colorants, flavor enhancers, and emulsifiers. Understanding their chemical nature and how they affect food safety and quality is a key part of food biochemistry. Natural Toxins and Anti-nutrients: o Some foods contain naturally occurring substances that can be toxic or interfere with nutrient absorption. Understanding these components helps in ensuring food safety. Flavor and Aroma Compounds: o These compounds are crucial for the sensory attributes of food. Biochemistry helps in understanding how these compounds are formed, how they change during cooking, and how they interact with other food components. Food Safety and Spoilage: o The biochemical processes leading to food spoilage involve microbial growth and enzymatic activity. Understanding these processes helps in developing methods to preserve food and ensure its safety. Applications of Food Biochemistry  Food Processing and Preservation: Techniques such as pasteurization, fermentation, and freezing are developed based on the principles of food biochemistry to extend shelf life and ensure safety.  Nutritional Analysis: Food biochemistry helps in analyzing the nutritional content of foods, understanding the bioavailability of nutrients, and developing fortified foods.  Quality Control: Biochemical tests are used to monitor food quality and detect contaminants or adulterants.  Product Development: Knowledge of food biochemistry is essential for developing new food products with desired nutritional and sensory properties. Understanding food biochemistry is fundamental to improving food quality, enhancing nutritional value, ensuring food safety, and developing innovative food products. This interdisciplinary field combines chemistry, biology, and nutrition to address the challenges and opportunities in the food industry. Department of Biotechnology Brainware University, Kolkata 14 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25 3 FOOD ADDITIVES Food additives are substances added to food to enhance its flavor, appearance, texture, shelf life, or nutritional value. They play a crucial role in modern food production and processing, ensuring that foods remain safe, nutritious, and appealing from the point of manufacture until consumption. Here is a detailed introduction to the topic of food additives: Types of Food Additives Preservatives:  Purpose: Extend shelf life by preventing spoilage caused by microorganisms such as bacteria, yeast, and molds.  Examples: Sodium benzoate, potassium sorbate, and calcium propionate. Antioxidants:  Purpose: Prevent oxidation, which can cause rancidity in fats and oils, and loss of color and flavor in foods.  Examples: Ascorbic acid (vitamin C), tocopherols (vitamin E), and butylated hydroxyanisole (BHA). Colorants:  Purpose: Enhance or restore the color of food to make it more appealing. They can be natural or synthetic.  Examples: Caramel color, annatto extract, and tartrazine (a synthetic yellow dye). Flavor Enhancers:  Purpose: Enhance the existing flavor of food without imparting a distinct flavor of their own.  Examples: Monosodium glutamate (MSG) and inosinate. Sweeteners:  Purpose: Provide sweetness with or without additional calories. They can be natural or artificial.  Examples: Sugar (sucrose), high fructose corn syrup, aspartame, and stevia. Emulsifiers:  Purpose: Help mix ingredients that usually do not blend well, such as oil and water.  Examples: Lecithin, mono- and diglycerides, and polysorbates. Thickeners and Stabilizers:  Purpose: Improve the texture and consistency of food, preventing separation of ingredients.  Examples: Xanthan gum, guar gum, and gelatin. Nutritional Additives:  Purpose: Enhance the nutritional value of food by adding vitamins, minerals, and other nutrients.  Examples: Vitamin D in milk, iodine in salt, and folic acid in flour. Despite their benefits, some food additives have been subject to controversy and public concern over potential health risks. These concerns often arise from:  Allergic Reactions: Certain additives can cause allergic reactions or sensitivities in some individuals. Department of Biotechnology Brainware University, Kolkata 15 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25  Long-term Health Effects: Questions about the long-term safety of some synthetic additives persist, even if they are deemed safe at current usage levels.  Misleading Information: Misinformation and lack of understanding about food additives can lead to unwarranted fear and avoidance. 4. MODEL QUESTIONS Multiple Choice Question Who proposed that yeast in alcoholic fermentation was a microscopic plant?  A. Pasteur  B. Schwann  C. Koch  D. Lister  Answer: B Which scientist showed that micro-organisms were responsible for chemical changes in foods and beverages?  A. Schwann  B. Koch  C. Pasteur  D. Lister  Answer: C What type of micro-organisms are most important in food microbiology?  A. Viruses  B. Bacteria  C. Protozoa  D. Algae  Answer: B Which of the following micro-organisms has the least direct impact on food production and processing?  A. Bacteria  B. Molds  C. Yeasts  D. Algae  Answer: D What is the main cause of food spoilage?  A. High temperature  B. Growth of micro-organisms  C. Lack of oxygen  D. Low pH  Answer: B Which micro-organisms are used in the production of single-cell protein?  A. Bacteria  B. Molds  C. Yeasts  D. Algae  Answer: D What type of micro-organism is Saccharomyces cerevisiae?  A. Bacterium  B. Mold  C. Yeast Department of Biotechnology Brainware University, Kolkata 16 BSCBT and 1st Semester Food Technology (BBT10002) Section B 2024-25  D. Virus  Answer: C Which micro-organisms can grow at refrigerated temperatures (