Residues and Quality Factors in Meat and Fish

Residues in Meat and Fish

Residues in the flesh can be categorized as follows:

Naturally occurring residues: Heavy metals like copper, cobalt, nickel, manganese, and zinc are present in low levels in meat. However, they tend to accumulate at higher concentrations in the viscera.
Residues caused by human waste:
- Antibiotics: Used to treat and prevent diseases and increase growth in animals. This can lead to the development of resistant pathogenic bacteria such as Salmonella, Campylobacter, and Escherichia coli.
- Pesticides: Organophosphates can enter the animal’s body through the skin, ingestion, and respiration. In cows, they are excreted through milk.
- Dioxins: These compounds can disrupt the endocrine system. The tolerable weekly intake may be up to 7 picograms per kilogram of body weight. Dioxins dissolve in fat and have high stability, with a half-life of 7 years.
Residues of secondary origin: These can be avoided by phasing out PVC, eliminating all chlorinated pesticides, removing paper laundering, and avoiding incomplete incineration of waste.

Let’s examine some statements about the composition and quality of fish and meat:

The glandular cells of fish skin mainly contain galactosamine and glucosamine sulfate. TRUE
Red muscle contains a higher amount of myoglobin but less fat. FALSE
The difference in the connective tissue of warm-blooded animals and fish is that the latter (elastoramas) is less structured and has amorphous regions. TRUE
The structure of fish muscle consists of transverse wraps (myocommata) and horizontal wraps (myosepta). TRUE

The change of Trimethylamine oxide (TMAO) to Trimethylamine (TMA) is carried out by a reduction reaction. FALSE
Polyunsaturated fatty acids, such as long-chain eicosapentaenoic acid (EPA) and docosahexaenoic acid (DHA), are more stable in fatty fish. FALSE
Rigor mortis in cold-blooded animals has the same duration as in warm-blooded animals. FALSE
Cold-water species can be kept reasonably well for up to 3 weeks on ice, unlike tropical fish. FALSE
The oxidation products of lipids react with proteins, which are added during drying. TRUE
“Pink” or creamy decomposition in the middle of fish with over 10% salt is due to Pseudomonas. FALSE
Tropical fish have a shorter shelf life, as bacterial and chemical changes are faster. TRUE

In modified atmosphere storage, the presence of oxygen decreases the growth of Clostridium botulinum types B and E and inhibits the growth of bacteria and fungi. FALSE
In lean fish, the optimum atmosphere composition is 30% O₂, 40% CO₂, and 30% N₂, while in oily fish, it is 0% O₂, 60% CO₂, and 30% N₂. This difference is due to the varying lipid content, not different rates of microbial growth. FALSE

The assessment of fish quality through the presence of degradation products includes the analysis of free amino acids, mainly methionine. FALSE
Denaturation of fish protein during freezing occurs because solutes are concentrated, reducing the water-holding capacity and increasing muscle drip. TRUE
The discoloration of crustaceans is due to astaxanthin being oxidized to astacene. TRUE
Tissue softening and loss of volatile compounds associated with warming do not occur during fish canning while cooking. TRUE
The color change in seafood is related to metal ions. FALSE
The processing of surimi is based on the solubilization characteristics of myofibrillar proteins, not connective tissue proteins. FALSE
Fish meal is valuable as animal feed because of its vitamin B₁₂, choline, pantothenic acid, riboflavin, calcium, copper, iron, and phosphorus content. TRUE