This document summarizes various biochemical changes that occur in meat during storage and how they can be used as determinants of meat quality. It discusses changes in pH, carbohydrates, nitrogenous compounds, lipids, and nucleotides during storage. Specific compounds and processes discussed include lactic acid formation, lipid oxidation, protein degradation products like TVBN and biogenic amines, and nucleotide degradation. Measurement of these compounds at different storage times can provide information about microbial quality, freshness, and spoilage of meat. Identifying patterns in biochemical changes during storage helps understand the chemical changes affecting food quality over time.

1. Major credit seminar on
Biochemical changes as
determinants for evaluating meat
quality during storage
By: Rohit Kumar Jaiswal

2. CONTENT
• Introduction
• Changes occurs during storage:
– pH
– Carbohydrates
– Nitrogenous compounds
– Lipids
– Nucleotides
• Identification of meat
spoilage
• Conclusion

3. Biochemical changes and food quality
• Biochemical change: Phenomenon occurs in living tissues
• It informs the biochemical consequences of transformation of
various substrates
• Relation to food quality:
 Provides a deep understanding of those chemical changes occurring in
foods
 Changes in concentration of various substrates /metabolites can be
linked to different quality parameters
 Helpful in preventing spoilage and enhancing consumers satisfaction

4. Meat and its nutritive composition
• Animal tissues: suitable for use as food
• More precisely edible postmortem component originating from
live animals
By: Forrest JC et al.,2012

5. Biochemical changes in meat components
• Meat is a perishable entity
• Undergoes various physico-chemical changes during storage
which occurs in aqueous phase of meat.

6. pH values of dairy, meat, poultry, and fish products
1.Change in pH
By: Jay JM et al., 2005

7. Mechanism of pH change in meat
pH at slaughter :
7.0
Ultimate pH : 5.5
Increase in pH
Endogenous
enzymes/
Growth of microbes
Favours bacterial
growth
Glycogen
Lactic acid
WHC
Colour
Texture

8. Trends in pH change during storage
(Dragoev,2015)

9. Estimation of pH and its relation to
microbial quality
• pH can be measured by following methods –
– Digital pH meter
– Chemical indicator method (Nitrazine yellow)
• Interpretation of Nitrazine yellow: (FSSAI, 2015)
• pH measurement of meat gives clue regarding microbiological quality
of meat
– Normal pH(Ultimate pH) : good microbiological quality
– More than ultimate pH : Bacterial
pH Colour Inference
6.0 Yellow Good keeping quality
6.4 Olive Green Not having same good keeping
quality
6.8 Bluish violet suspect on signs of incipient spoilage

10. Fermentation type Products
Alcoholic Fermentation Ethanol, CO2
Homofermentative lactic acid Fermentation Lactic acid
Heterofermentative lactic acid Fermentation Lactic acid, Acetic acid, Ethanol, CO2
Propionic acid Fermentation Propionic acid, Acetic acid, CO2
Butyric acid Fermentation Butyric acid, Acetic acid, CO2, H2
Mixed acid Fermentation Lactic acid, Acetic acid, CO2, H2, Ethanol
2,3-butanediol Fermentation CO2, Ethanol, 2,3-butanediol, Formic acid
2. Changes in carbohydrates2. Changes in carbohydrates

11. Changes(mg/100g) in glucose content in beef, pork and chicken
during storage
(Nychas et al.,1994)

12. Cabohydrates degradation metabolites as quality
determinants
• Ethanol concentration increase as a function of time
(Rehbein,1993)
• Changes in the concentration of organic acids
– N-butyrate
– L-lactic acid
– D-lactate
– Acetic acid
• D-Lactic acid in pork as a freshness indicator monitoring by using D-
lactate dehydrogenase co-immobilized with l-alanine aminotransferase
(Shu et al.,
1993)
POTENTIAL INDICATOR
METABOLITES

13. Proteins Polypeptides Amino Acids
PeptidasesProteinases
Anaerobic
decomposition
Anaerobic
decomposition
Proteins
Peptides
Amino Acids
Proteins
Peptides
Amino Acids
Volatile products
ProteolysisProteolysis
PutrefactionPutrefaction
3. Changes in nitrogenous organic components3. Changes in nitrogenous organic components
H2S
Methyl mercaptans
Indole
Skatole
Cadaverine
Putrescine
Histamine
H2S
Methyl mercaptans
Indole
Skatole
Cadaverine
Putrescine
Histamine

14. Products from microbial decomposition of amino
acids
Chemical process Products
Oxidative deamination Keto acid + NH3
Hydrolytic deamination Hydroxy acid + NH3
Reductive deamination Saturated fatty acid + NH3
Desaturation deamination Unsaturated fatty acid +
NH3
Mutual O-R between pairs of amino
acids
Keto acid + fatty acid +
NH3
Decarboxylation Amine + CO2
Hydrolytic deamination +
decarboxylation
Primary alcohol + CO2 +
NH3
Reductive deamination +
decarboxylation
Hydrocarbon + CO2 + NH3
Oxidative deamination +
decarboxylation
Fatty acid + CO2 + NH3

15. 3.1. Volatile bases
.
• TVBN/TVN
. • Ammonia +DMA+TMA
.
• Production by deamination of specific amino acids
.
• Indication of protein degradation and its value increases
with storage period of meat (Hassan and Omama,2011)

16. Production and estimation of TVBN
• Ammonia (deamination of amino-acids;nucleotide catabolites)
• Dimethylamine ( autolytic enzymes during frozen storage)
• Trimethylamine ( spoilage bacteria)
Different methods for estimation of TVBN:
 MgO with direct distillation
 MgO with steam distillation
 TCA extraction/steam distillation
 MgSO4 extraction/steam distillation
 TCA extraction /micro diffusion
 Ethanol extraction/direct distillation

17. TVBN as quality determinants
• TVBN as a quality indicating metabolites in stored meat and is
correlated well with microbiological and sensory attributes.
(Balamatsia et al.,2007)
• Concentration increased with storage time.

18.  TVBN increased with storage time at a faster rate at 7 ± 1 0
C
compared to 0 ± 10
C.
TVBN (mg/100 g) Inference
35-40 Good quality fish
50-70 Upper limit
100-200 Salted and dried fish
By : K Gopakumar , 2002

19. TVBN used in indicator sensor
(Shukla et al .,2014)

20. 3.2. Biogenic amines production
.
• Biogenic amines are produced by decarboxylation of free amino acids
mediated by amino-acid decarboxylase enzymes.
(Silla Santos, 1996)
.
• Decarboxylation by two biochemical pathways :
• Endogenous decarboxylase
• Exogenous enzymes
.
• Small concentration of BAs are found in fresh food, while the
concentration of most BAs usually increases during storage
(Rokka et al., 2004)

21. Formation of biogenic amines
(Ruiz-Capillas and Jiménez-Colmenero ,2004)

22. Importance of Putrescine and Cadaverine
• Lysine −−−−−−−−−→ H2N(CH2)5NH2
Cadaverine
• Ornithine or
arginine −−−−−−−−−→ H2N(CH2)5NH2
Putrescine
Biogenic
amines
Species Common
Bacterial species
Storage
condition
Putrescine Beef Pseudomonads Vacuum-
packaged
Cadaverine Pork Enterobacteriace
ae
Aerobically
stored
Decarboxylase
Decarboxylase

23. Biogenic amines index
• The amount of putrescine, histamine, and cadaverine shows the freshness
of meat and is defined as biogenic amines index (BAI) (Karmas
1981)
(Hernandez-Jover,1996)
BAI Freshness quality
<5 High quality fresh meat
5-20 Indicates meat of acceptable quality
with initial signs of spoilage
20-50 Meat of low quality
>50 Spoiled meat

24. 3.3. Protein oxidation
• Meat contain high amounts of proteins, susceptible to oxidative reactions.
• These processes are commonly linked to a decrease in muscle protein
functionality, leading to increasing water losses, weaker protein gels or less
stable emulsions (Xiong, 2000)
Mechanism and consequences of protein oxidation

25. Protein degradation products as quality determinants
• TVBN
• BAI
• Protein oxidation can be monitored by measuring the formation of carbonyl
groups (DNPH method) and the decrease in sulfhydryl groups.
(Stadtman,1990)
Free amino acids
• Sum of free amino-acids along with water soluble protein content increase during
storage.
Tyrosine value
• It is an indicator of proteolysis as it measures tyrosine and tryptophan in non-
protein extract of meat.
ERV (FSSAI ,2015)

26. 4.Change in lipids4.Change in lipids
Enzymatic
(Lipase)
Oxidative
(Autooxidation)
4.1 Lipolysis /Hydrolytic Rancidity
Triacylglycerol Glycerol Free fatty acids
(Volatile bad odour)(Volatile bad odour)
26

27. 4.2 Oxidative changes/Auto-oxidation
Mechanism of oxidation

28. Estimation of lipid oxidation and its use as
quality determinants
• Free fatty acid measures degree of hydrolytic rancidity
• TBA test (2-thiobarbituric acid test) is the most widely used (Melton,
1983)
• Thiobarbituric acid value measures the carbonyl residues resulting from
lipid peroxidation
• TBARS did not seem to have relationship with the storage time
• Peroxide value measures concentration of peroxides and hydroperoxides
at initial stage of oxidation
Effect of lipid oxidation on quality :
Causes rancidity, flavour deterioration, loss of nutritional value and safety,
biological damage, ageing, functional property changes

29. Changes in peroxide content, TBARS and phospholipid content in chicken breast meat as
affected by freezing temperature and 6 months of storage (freezing temperature 7 0
C, 12 0
C
and 18 0
C)

30. 5. Changes in nucleotides and its use
• Immediately after death, adenosine triphosphate (ATP) begins to degrade
to uric acid through the pathway:

31. Nucleotide degradation products used as quality
determinants

32. Identification of meat spoilage
• Physical observations
• Off flavour
• ERV
• Dye
• pH
• TBA and peroxide values

33. Conclusion
• Biochemical changes in meat had a major role in maintaining
quality of meat
• Deviation in range of any components of meat affects its
acceptability
• Changes can be utilised as quality indicators by meat
industries as intelligent packaging
• Rapid platform tests can be evolved by utilising these changes
in future which is challenging
• More number of research required in this field for quality
control

34. Thank you