Microbial rancidity

Rancidity is the result of unsaturated fats or oils in food undergoing oxidation, leading to an unpleasant smell and taste. Microbial rancidity, on the other hand, occurs when microorganisms such as bacteria or molds utilize enzymes like lipases to break down fat and modify the chemical composition of food.

The oxidation of lipids and the proliferation of unwanted microorganisms in food products contribute to spoilage, off-flavors, rancidity, and deterioration. As a result, these products become unsuitable for consumption and may even contribute to the development of cancer, atherosclerosis, heart disease, and allergies.

Microbial-based rancidity is a prevalent issue that can trigger recalls of affected products.

Managing this process involves careful selection of appropriate preservatives. Spices and herbs have been used since ancient times as folk medicine and natural preservatives in food. They prolong the shelf life of food by preventing rancidity through their antioxidant properties and by exhibiting bacteriostatic or bactericidal effects against harmful bacteria that can cause foodborne illnesses.

Reducing microbial rancidity requires inhibiting or eliminating the microorganisms responsible. Additionally, techniques such as pasteurization and the addition of antioxidant ingredients like vitamin E can be employed to alleviate this problem.
Microbial rancidity

Black mold

Black mold otherwise known as “Aspergillus niger” often occurs on fruits that have become moist on the surface or broken; or it may occur on other products occasionally. Aspergillus niger is the thermophilic organism; hence it occurs most frequently in hot regions.

It does not produce a moldy taste or odor; it is much less prevalent and is easier to control than is the blue mold. This disease is most prevalent in subtropical and tropical production areas where high temperatures favor its development. While black mold can cause some problem in the field most losses occur in storage.

The spore of the organism seem to be present everywhere, but they are able to infect fruit such as grapes only when there are skin breaks or punctures, or when the ripening grapes are wet – as, by rain or sprinkler irrigation during maturing. 

 

This disease causes unsightly, black, dusty fungal growth on and between the bulb scales. The entire surface of the bulb may be turned black in several cases, and a bulb rot may follow.
Black mold

Preservation to maintain food quality

The deterioration of food quality occurs due to various physical, chemical, enzymic or microbiological factors.

Food preservation is the process of treating and handling food to stop or greatly slow down food spoilage. A number of preservation techniques are available for maintaining food quality, which act by slowing or reducing microbial growth.

Among food preservation methods are include: canning, pickling, drying and freeze-drying, irradiation, pasteurization, smoking, and the addition of chemical additives.

Thermal processes with high heat transfer rates from heating source to the food result in better quality. The traditional method of sterilization and the aseptic method are commonly and predominant thermal processing techniques for commercial sterilization of canned foods.

The packaging of food is typically designed to maintain the quality of food products during storage, transportation and end use. It prevents quality deterioration, and facilitates distribution and marketing efficiencies.

Through the correct selection of both materials and packaging technology, food freshness can be maintained to obtain the required shelf life.
Preservation to maintain food quality

Toxin spoilage

It was not until 1960, when the famous ‘Turkey X’ disease killed 100,000 turkey poults in Great Britain and various other disasters followed in rapid succession, that the Western world became aware that common spoilage moulds could produce significant toxins.

Food poisoning micro-organisms are called pathogens or pathogenic organisms. These produce toxins which are released into the food the organisms grow on.

The toxin can be either exotoxins, which are toxins, released into food by microorganisms during growth and before the food is eaten or endotoxins which are released by microorganisms eaten with contaminated food.’

In processing of food, there is possibility that the food may carry low numbers of pathogens, which could be insufficient to cause clinical symptoms but which could multiply at some later stage in the product life-cycle, especially under uncontrolled conditions in the home and cause food poising.

Ingestion of contaminated food due to the presence of poisons or toxicants causes food poisoning. Food poisonings may be classified onto four types depending on the type of poison contaminating the food:
 *Bacterial
*Fungal
*Biological
*Chemical

Botulism, the most serious form of bacterial food poisoning, is caused by neurotoxins produced by Clostridium botulinum. The toxins are absorbed from intestinal tract and transported via the circulatory system to motor nerve synapses, where their action blocks normal neural transmissions.
Toxin spoilage

The appearance of food spoilage

During storage and distribution, foods are exposed to a wide range of environmental conditions. Food spoilage occurs when products develop undesirable odors, flavors and appearances due to microbial growth.

Quite often, the evidence of microbial growth is easily visible as in the case of slime formation, cotton-like network of mold growth, iridescence greening in cold cuts and in cooked sausage, and even discrete large colonies of bacteria. Food spoilage also produces undesirable aromas and color defects.  

In liquid such as juice, microbial spoilage is often manifest by the development a cloudy appearance or curd formation.

Spoiled food, such as moldy bread, soured milk or bad fish may not cause any harm or illness if consumed.

On the other hand, if food is contaminated with pathogenic bacteria then a potentially dangerous food poisoning may occur.
The appearance of food spoilage 

Irradiation sterilization

Irradiation or ionizing radiation is a type of ‘cold’ sterilization, where the piece being sterilized is not exposed to heat. However, due to the poor heat transfer properties of many types of products, small increases in temperature above ambient can occur in the irradiated product.

Similar to sterilization by heat that requires high temperatures for specified times, sterilization of foods by irradiation requires high enough radiation doses to inactivate bacterial spores.

Radiation sterilization can be accomplished using one of three forms of radiation: gamma sterilization using radioisotopes, electron beam using electron accelerators, or beta radiation using an electron accelerator.

The irradiation sterilization process extends beyond treatment of health care products to commodities and irradiation of food to destroy pathogens such as salmonella and E. coli to make our food safer to eat.

Irradiation sterilization of foods, including meats and poultry, was extensively studied in the 1950s and 1960s, mostly by the US government. Irradiation sterilization effectively kills microorganisms because of its ability to break the chemical bonds of organic compounds, producing highly reactively species known as free radicals.
Irradiation sterilization

Sanitation and microorganisms

Sanitation is applied science.  Sanitation relates physical, chemical, biological and microbial principles of food, the environment and health.

Knowledge of microorganisms is important to the sanitation specialist because their control in part of a sanitation program. These organisms metabolize in a manner similar to microorganisms. They intake nourishment, then discharge waste products.

Some microorganism cause food spoilage and foodborne illness, but others are beneficial in food processing and preparation. To reduce food spoilage and to eliminate foodborne illness, this microbial proliferation must be controlled. Food deterioration should be minimized to prolong the time during which acceptable level of flavor and wholesomeness can be maintained.

Most foods spoil easily because they have the nutrients that microbes need to grow.  Foods that are packages for foodservice in stores especially fresh meats have a large surface area exposed. Bacteria can grow rapidly in these foods.

Food is acceptable for a longer time, and foodborne illness is less likely if the growth of microbes is controlled. Proper sanitation during food processing, preparation, and serving can controls food spoilage and pathogenic bacteria.
Sanitation and microorganisms 

Preserving foods

Food preservation is an action or a method of maintaining foods at a desired level of properties or nature for their maximum benefits.

Microbial growth in foods is one of the leading causes of food spoilage. To preserve foods it is necessary either to destroy of all microorganisms that contaminate it or to bring about conditions that prevent the microbes from carrying out their ordinary life processes.

Although preservation is aimed mainly at microbial spoilage, it must be remembered that there are other types of spoilage factors such as oxidation.

Over the years, many food preservation technologies have been developed and these include:
*Chilling
*Freezing
*Reduction in water activity
*Acidification
*Fermentation
*Chemical preservative
*Compartmentalization
*Heating
*Vacuum and modified-atmosphere packaging
*Physical technologies
Preserving foods

Polymerase chain reaction

The polymerase chain reaction forts appeared in 1985 as a method for the prenatal diagnosis of sickle cell anemia. It was based on the remarkable insight of Kary Mullis, who realized that repetition of a DNA extension reaction bounded by two synthetic oligonucleotide primers would generate a large quantity of any specified DAN sequence. Since then, PCR has been used in more than 275,000 scientific publications.

This technique has been applied in different areas due to its versatility, specificity and sensitivity. Methods based on the polymerase chain reaction (PCR) have been proved to be very efficient and applicable in foods.

Accordingly, PCR has been successfully used for microorganism identification , for the detection of ingredients of food products, e.g cereal, vegetables, animal and fish species. Detection and identification of pathogens like Shigella sonnei, S. Flexneri, S. boydii, S. dysenteriae, Salmonella paratyphi A & B, Aeromonas hydrophila, Staphylococcus aureus, Clostridium perferinges, type A Clostridium botulinum in canned peas, corn and lima beans, Vibrio cholera in seafood, enteric virus on oysters, toxigenic S. aureus in beef, pork, cheese and milk, enteroinvasive E. coli in raw milk and Listeria monocytogenes in poultry have been successful using PCR.

The minimum detectable level of organisms, type of interferences associated with each food sample, precautions to be taken in sample preparation, need for pre-enrichment and correlation of the results with the conventional methods are all important considerations in standardization of the methods.

PCR is a simple, versatile, sensitive specific and reproducible assay. It consists of an exponential amplification of an DNA fragment, and its principle is based on the mechanism of DNA, replication in vivo: dsDNA is denatured to ssDNA, duplicated and this process is repeated along the reaction according to the formula.
Polymerase chain reaction

Salmonella in chocolate

Chocolate and cocoa-derived products are considered sensitive ingredients, primarily due to historical associations with food industry Salmonella outbreaks.

Salmonella in cocoa make it a sensitive ingredient. When contaminated, the numbers of salmonellae are usually low, less than 1/g.

Organisms capable of surviving the processes used in chocolate manufacture belong primarily to the genus Bacillus. It is known that Salmonella may survive for many months in chocolate.

Additionally salmonella is protected by the fat in chocolate against the acidity of gastric juice and consequently relatively lower levels of Salmonella may cause salmonellosis.

The key to low spore counts in chocolate appears to be the quality of the cocoa bean.

Sources of Salmonella in chocolate have been tracked back to cocoa and milk powder.

Salmonella contamination potential also may be linked to various components of processing from cross-contamination between raw and roasted beans, environmental cross –contamination from inadequate segregation between clean and unclean process zones.

Another important factor that increase the risk of salmonellosis associated with chocolate products is the apparent low infectious dose.

It is evident from a number of outbreaks that very low levels of Salmonella present in chocolate are capable of causing illness.
Salmonella in chocolate

Pest Control of Fruits and Vegetables

Pest Control of Fruits and Vegetables
Insects, rodents, plant disease, and weeds can devastate food crops, and human history is filled with famines attributable to these scourges. Large scale agricultural production tends to increase the susceptibility of crops to these hazards. Pesticides are currently an integral component of an agricultural system that produces increased yields of fresh fruits and vegetables with good visual quality. Pesticides have become a major cost of production of fruit and vegetable farmers. The use of pesticides is associated with risks of increase pest resistance, environmental contamination, exposure to farm workers, and escalating costs. With mounting regulatory pressure on pesticides it is likely that fewer compounds will be available to the farmer and that these compounds will be available for only a few crops of high economic value.

Damage to fruits and vegetables by pests is not limited to loss of visual quality. Insects and rodents can inoculate plants in the field with microorganisms that can present a health hazard, particularly if the product is not properly washed and is eaten raw. These dangers are compounded if untreated animal wastes such as manure, a potent source of human pathogens, are used for fertilization, particularly with vegetables grown close to the ground. Mold, which can be held in check by fungicide, can infect fruits and vegetables products. Mycotoxins produced by molds, such as patulin in apple products and ochratoxin in citrus fruits, present additional concern. The potential danger of these naturally occurring mycotoxins has been documented but the practical implications of decreased fungicide use are not clear.
Pest Control of Fruits and Vegetables