BY DAKSHITA NAITHANI

INTRODUCTION

Food spoiling is described as any alteration that the customer finds objectionable. Spoilage happens at any given point of time in the food chain. Insect damage, physical damage, indigenous enzyme activity in animal or plant tissue, and microbial infections can all contribute to spoilage. The majority of natural products have a definite shelf life. 

Meat and its derivatives are nutrient-dense foods that are devoured by people all over the world.

Meat deteriorates biologically and chemically from the time it is slaughtered until it is consumed. Microbial spoilage may occur in meat and its products such as ham, sausages, cooked meat, dried meats, minced meat, and so on.

Contamination source and causes

Natural processes such as oxidation or autolytic activity in the muscle following slaughtering can cause meat decomposition. Microbial contamination of meat is caused by a number of variables, including the animal’s microflora, the type of container used, and how the meat is handled and stored. Knives, utensils, hands, and workers’ clothes, among other things

Numbers of microbes of microbes resides on the meat and their products. Some of important are listed below:

 Brochothrix thermosphacta

It can grow in both aerobic and anaerobic environments, and meat is a niche for it. This microorganism is frequently found in irradiated meat and poultry and is responsible for the bad odour of meat.

Carnobacterium

Carnobacterium is a gram-positive bacterium with nine different species. C. divergens has been demonstrated to show green discoloration of ham as a result of H₂O₂ generation.

Clostridium tetani

Clostridium creates a huge quantity of gas in packed meat, which, when combined with bad smells, causes the container to blow open.

Enterobacteriaceae

These bacteria can act as facultative anaerobes, oxidase-negative glucose fermenters, and nitrate suppressants, and they can influence to the rotting of meat.

Leuconostoc

D-lactate and ethanol are produced by Leuconostoc, a lactic acid generating bacterium. The discolouration, gas generation, and buttery odour of rotting meat are aided by these bacteria.

Pseudomonas

Pseudomonas has been identified as the most common bacterium found in rotting meat. Pseudomonas is widely recognised for successfully exploiting meat as a niche due to its capacity to break down glucose and amino acids under aerobic and cold conditions.

The spoilage of different types of meat are :

Spoilage of fresh meat

The enzymes and microbial activity in fresh meat causes it to decay. Proteolytic effects on muscle and connective tissue, as well as fat hydrolysis, are caused by autolysis alterations. Salmonella, E.coli, Listeria and other microbial diseases have been identified in fresh meat.

Spoilage of meat

Rotting of meat is caused by three fundamental mechanisms: microbial growth, oxidation, and enzymatic autolysis. Meat is a great substrate for microbial development due to its nutritional makeup, high water content, and mild pH. Staphylococcus, Streptococcus, Clostridium, and Salmonella are among the bacteria found in an animal’s lymph nodes, which might influence meat.

Spoilage of refrigerated meat

Fresh meat may be present in good condition for 5-7 days when refrigerated at 4°C. The development of psychrophilic microbes is favoured by a cool environment over time. Contamination of meat by rotting and dangerous bacteria can occur due to poor hygiene. B. thermosphacta and lactic acid bacteria are the microbes that cause refrigerated meat deterioration in general.

Factors spoilage of meat and meat products

Buffer capacity and pH

Muscle pH drops to 5.4-5.8 after slaughtering, however meat from stressed animals and cooked products, such as sliced ham, have pH levels greater than 6. The presence of tissue and a high pH in meat results in a faster deterioration process owing to microbial growth and nutritional absorption.

Water activity

The quantity of water in a meal that is available for the growth of microorganisms, including diseases, is measured by water activity (aw). Raw meat has a value of 0.98-0.99, while cooked meat has a value of 0.94; these values enable most bacteria to thrive. Pathogens cannot develop or produce toxins if the water activity is less than 0.85.

Packaging and gaseous atmosphere

The constitution of rotting flora is heavily influenced by packaging circumstances and the gaseous content of the environment surrounding the meat. Aerobic conditions favour the development of Pseudomonads over everything else. Lactic acid bacteria are the most prevalent microbes in vacuum or CO₂-modified environment packed goods, and they are the bacteria that cause the most deterioration.

Storage temperature

The duration of the lag phase, the maximum specific growth rate, and the ultimate cell number are all affected by temperature. Lower temperatures inhibit microbial contamination and alter the microbiota makeup of meat. The dominance of lactic acid bacteria in sealed beef products is likewise maintained in cold circumstances. In sealed refrigerated beef, psychrophilic Clostridium spp. were found. The growth of Enterobacteriaceae, Pseudomonas spp., and Acinetobacter spp. is influenced by abuse of temperature.

General types of Spoilage of meats and meat Products.

Spoilage under Aerobic condition

The spoilage of meats and meat products due bacterial in aerobic conditions are:

 Surface slime: Surface slime generated by Pseudomonas, Acinetobacter, Micrococcus, Streptococcus, Leuconostoc, and Bacillus results in spoilage. Lactobacillus species have also been shown to generate slime. Microbes are benefited from the thin layer development on meat because it delivers nutrients from the substrate.

Changes in colour of meat pigments: As a result of bacteria producing oxidising chemicals such as Peroxides or Hydrogen Sulphide, the red colour of meat, known as its “bloom,” might change to green, brown, or grey. Greening of sausage has been linked to Lactobacillus which is mainly hetero fermentative and Leuconostoc species.

Changes in fats: The oxidation of lipids in meat occurs chemically in the presence of oxygen and can be accelerated by light and copper. Lipolytic bacteria can induce some lipolysis as well as speed up the oxidation of lipids. Fat rancidity can be induced by lipolytic Pseudomonas and Achromobacter species.

Phosphorescence: Luminous bacteria, such as Photobacterium spp., develop on the surface of the flesh and create this rare abnormality. Other bacteria that generate red pigments might be responsible for the red spot.

Off odours and off tastes: Unpleasant odours and taste develop in meat as a result of bacteria growing on the surface. They emerge before other symptoms of deterioration. Meat sourness can be induced by volatile acids such as formic, acetic, butyric, and propionic acids, as well as yeast proliferation.

Spoilage due to moulds in aerobic condition

Moulds are actively involved the spoilage meat in aerobic conditions. Common types of spoilage are listed below.

Stickiness: Stickiness is caused by fungus bud development, which makes the surface of the flesh sticky to the touch. As a result of this form of deterioration, flesh takes on an odd look.

Whiskers: In the absence of sporulation, a little amount of mycelial development can occur resulting in whisker growth. Moulds such as Thamnidium elegans, Mucor mucedo, M. lusitanicus, or M. racemosus, Rhizopus, and others can create this sort of fuzzy growth.

Black spot and White spot: Cladosporium herbarum is the most prevalent source of this sort of spot, although other moulds with dark colours might also be to fault. White spot is most frequently reported by Sporotrichum carnis, although it can also be caused by any mould with moist, yeast-like colonies, such as Geotrichum.

Green patches:  Species of Penicillium such as P. expansum, P. asperulum, and P. oxalicum are responsible for the green patches on meat.

Decomposition of fats:  The oxidation of fats is caused by the hydrolysis of fats caused by lipase produced by moulds.

Spots on surface: Yeast and mould spoilage is generally confined to a large extent and may be cut away without harming the remainder of the meat.

Spoilage under Anaerobic Conditions

Facultative and anaerobic bacteria are able to grow within the meat under anaerobic conditions and cause spoilage. Few are listed below:

Souring: It can be generated by the meat’s natural enzymes during age or ripening, bacterial synthesis of fatty acids or lactic acid, or proteolysis without putrefaction induced by facultative or anaerobic bacteria and frequently referred to as “stinking sour fermentation.” Clostridium species and fecal coliform feed on carbohydrates and produce acid and gas. The development of lactic acid bacteria is prevalent in vacuum sealed meats, especially in gastight wrappers.

 Putrefaction: Putrefaction is the disintegration of protein caused by anaerobic bacteria producing foul-smelling chemicals including hydrogen sulphide, indole, skatole, ammonia, and amines. In most cases, Clostridium spp. are to blame, however facultative bacteria can also cause or contribute to putrefaction. Clostridia-induced putrefaction is frequently accompanied by gas production.

Taint:  Having a foul odour and a poor taste. Temperature, in addition to air, has a significant impact on meat decomposition. Many microbes, including Pseudomonas, Lactobacillus, Leuconostoc, Streptococcus, and Flavobacterium species, generate slimes, discoloration, and growth patches on the surface and can induce sourness.