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BIODETERIORATION OF FOOD

BIODETERIORATION OF FOOD

ALL food undergoes deterioration to some degree once harvested or slaughtered. The deterioration includes loss of nutritional value, organoleptic changes, and most importantly safety may become compromised. It is the challenge of the food industry to control this deterioration and maintain the safety of the food, while making sure that the food is as convenient, nutritious and available as it can possibly be.

FOOD BIODETERIORATION

Any undesirable change in the property offood caused by the vital activities of organisms.It is a result of the metabolic processes of microorganisms acting singly or in groups to break down complex organic substances or of the damage caused by insects, rodents or birds.

In laymans term, SPOILAGE.

BIODETERIORATION

Biodeterioration is DIFFERENT from biodegradation, in that the former isUndesirable Uncontrollable Caused by organisms.It is NOT the natural degradation that occurs in some organic materials or food caused by intrinsic enzymes.

DIFFERENT

TYPES OF BIODETERIORATION

1. Chemical Biodeterioration 2. Physical Biodeterioration

CHEMICAL BIODETERIORATION

1. Biochemical assimilatory biodeteriorationThe organism uses the food components for nourishment, i.e., as an energy source.2. Biochemical dissimilatory biodeterioration The chemical change in the food is a result of waste products from the organism in question.

NOTE: Both have the same result, i.e., the material becomes spoilt, damaged or unsafe.

PHYSICAL BIODETERIORATION

1. Mechanical biodeteriorationThis occurs when the food is physically disrupted/damaged by the growth or activities of the organism.2. Soiling/foulingThis occurs when the appearance of a product is compromised, BUT it does NOT necessarily makes the product unsafe; it only renders the product unacceptable to consumers.

Living organisms can be divided on the basis of their nutritional requirements into two: Autotrophic organisms see all inorganic materials as a potential source of nutrients, while heterotrophic organisms can only use organic matter.

Food biodeterioration is generally caused by heterotrophs, specifically chemoheterotrophs.

autotrophs and heterotrophs. Autotrophsare organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis).Heterotrophscannot synthesize their own food and rely on other organisms -- both plants andanimals-- fornutrition. Technically, the definition is that autotrophs obtain carbon from inorganic sources like carbon dioxide (CO2) while heterotrophs get their reduced carbon from other organisms. Autotrophs are usually plants; they are also called "self feeders" or "primary producers". Photoheterotroph These heterotrophs use light for energy but cannot use carbon dioxide as their carbon source. They get their carbon from compounds such as carbohydrates, fatty acids and alcohol. E.g. purple non-sulfur bacteria, green-non sulfur bacteria and heliobacteria.Chemoheterotroph Heterotrophs that get their energy by oxidation of preformed organic compounds, i.e. by eating other organisms either dead or alive. E.g.animals, fungi, bacteria and almost all pathogens.

8 Chemoheterotophs that can cause food biodeterioration are referred to as biodeteriogens. They include the following:1. Bacteria2. Fungi3. Insects4. Higher animals

Autotrophsare organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis).Heterotrophscannot synthesize their own food and rely on other organisms -- both plants andanimals-- fornutrition. Technically, the definition is that autotrophs obtain carbon from inorganic sources like carbon dioxide (CO2) while heterotrophs get their reduced carbon from other organisms. Autotrophs are usually plants; they are also called "self feeders" or "primary producers". Photoheterotroph These heterotrophs use light for energy but cannot use carbon dioxide as their carbon source. They get their carbon from compounds such as carbohydrates, fatty acids and alcohol. E.g. purple non-sulfur bacteria, green-non sulfur bacteria and heliobacteria.Chemoheterotroph Heterotrophs that get their energy by oxidation of preformed organic compounds, i.e. by eating other organisms either dead or alive. E.g.animals, fungi, bacteria and almost all pathogens.

9From Mans earliest history, control of food biodeterioration has long been a concern. Thus, the basic principles for such control that were applied thousands of years ago have remained unchanged.If possible, eat food immediately after harvest. Physically protect food from pests by storing in sealed containers.Preserve by drying, salting or adding spices.

Autotrophsare organisms that can produce their own food from the substances available in their surroundings using light (photosynthesis) or chemical energy (chemosynthesis).Heterotrophscannot synthesize their own food and rely on other organisms -- both plants andanimals-- fornutrition. Technically, the definition is that autotrophs obtain carbon from inorganic sources like carbon dioxide (CO2) while heterotrophs get their reduced carbon from other organisms. Autotrophs are usually plants; they are also called "self feeders" or "primary producers". Photoheterotroph These heterotrophs use light for energy but cannot use carbon dioxide as their carbon source. They get their carbon from compounds such as carbohydrates, fatty acids and alcohol. E.g. purple non-sulfur bacteria, green-non sulfur bacteria and heliobacteria.Chemoheterotroph Heterotrophs that get their energy by oxidation of preformed organic compounds, i.e. by eating other organisms either dead or alive. E.g.animals, fungi, bacteria and almost all pathogens.

10 Why do food spoil?Food is made up of water, proteins, fats, carbohydrates and a host of vitamins and minerals. These components are hydrolyzed by microorganisms.Hydrolysis products impart undesirable odors and flavorsBacteria produce toxins, thereby compromising food safety.unnecessary spoilage owing to poor procedures and hygiene in farming, harvesting, storage and distribution.11Factors affecting food spoilageChemical composition of foodType of organisms involvedEnvironmental conditions of food and microorganismsChanges occurring in food12Mechanisms of food spoilageFermentationThe conversion of carbohydrates into organic acids, alcohol and CO2 by microorganisms under anaerobic conditionPutrefactionThe breakdown of proteins by microbial enzymes, usually produced by anaerobic spoilage microorganismsLypolysisThe breakdown of fats into glycerol and free fatty acids13

Microbial deterioration of carbohydrates

Microbial deterioration of proteins and protein foods

Microbial deterioration of edible oils and fats

CARBOHYDRATES are the most abundant class of organic compounds on Earth, being the primary constituents of plants and exoskeletons of crustaceans and insects. Therefore, they are virtually an unavoidable element of our daily life, especially considering that it is an ever-present component of our food.15

CARBOHYDRATESCarbohydrates are organic compounds that contain carbon, oxygen and hydrogen.Basic chemical formula Cn(H2O)n], and thus designated as hydrates of carbonThey can be simple sugars or complex molecules. Food carbohydrates include monosaccharides (e.g., glucose), disaccharides (e.g., lactose and sucrose) and polysaccharides (e.g., dextrins, starches, celluloses, pectins).16

Types of Carbohydrate Deterioration1. Preliminary breakdown of polysaccharides by enzymes2. Fermentation of monosaccharides and disaccharides to pyruvic acid via the EMP pathway3. Production of microbial polysaccharides or dextrans from disaccharides4. Production of pectin esterases and polygalacturonidases that degrade pectin17Preliminary breakdown of high-molecular-weight polysaccharides by enzymesYields a mixture of low-molecular-weight sugars, such as oligosaccharides, disaccharides, and monosaccharidesExample: Degradation of starch by bacterial or fungal amylases(C6H10O5)n + nH20 nC6H12O6 (glucose)(C6H10O5)n + n/2 H20 n/2 C12H22O11 (maltose)

NOTE: Many bacilli, streptomyces, and aspergilli have extracellular enzymes such as cellulose, amylases and other glucanohydrolases.Fermentation of monosaccharides and disaccharides to pyruvic acid by microorganisms via the Embden-Meyerhof-Parnas PathwayC6H12O6 + 2 NAD+ + 2 ADP + Pi 2 CH3COCOOH + 2 NADH + 2 ATP + H+

Metabolic fate of pyruvateConversion of pyruvic acid to lactic acid by lactobacilliReductive decarboxylation of pyruvic acid to ethanol by yeasts

LactobacilliCH3COCOOH + NADH + 2 ATP + H+ NAD+ + CH3CHOHCOOH YeastCH3COCOOH + NADH2 CH3CH2OH + CO2 + NAD+

NOTE: Generally, microbial metabolites produced by spoilage organisms (e.g., lactobacilli, acetobacters and yeast) are directly derived from pyruvate.Pyruvic acidEthanolLactic acidPyruvic acidMicrobial dextrans are polysaccharides in which the a-D-glucopyranose units are linked by a-1-6 glycosidic bondsThey form unpleasant slimes in and on food, making food unpalatable and unacceptable to consumers.Example: Slimy and ropy texture of fruit concentrates infected by L. mesenteroides or B. mesentericusProduction of microbial polysaccharides or dextrans from disaccharidesPectin is a structural heteropolysaccharide in the primary cell walls of terrestrial plantsPectin-degrading enzymes cause soft rot.Bacillus polymyxa, Erwinia carotovora and Sclerotinia sclerotiorum are associated with soft rot in vegetables, whereas Peni

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