الفهرس 
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Abstract
A grand total of two hundreds and forty samples (drawn from 20 original samples) of fresh local beef liver were purchased randomly from different butcher’s shops at Kalyobia Governorate and subjected to physical, bacteriological and chemical examination at 0 time, chilling and freezing temperature (-18°C).
This work was done to achieve the incipient spoilage, and how long the fresh liver could be consumable during chilling and frozen storage.
from the obtained results one can conclude that the organoleptic study is less important because the liver may be acceptable organoleptically but the incipient spoilage happened.
The present study can be reviewed the bacteriological status of
fresh, chilled and frozen liver as well as the role of bacteria on their spoilage at different stages of storage.
The most important quick, simple and reliable chemical tests for measuring the incipient and complete spoilage in frozen liver were :
pH, ERV, TVN, urea, creatinine, uric acid, TBA.
The current study considered the presence of correlations between organoleptic tests, microbiological examination and chemical examination as well as investigating the validity of some common methods used to detect the onset and complete spoilage of frozen liver stored at refrigeration (2-5°C) and freezing temperature (-18°C) for 7 months.
Lower pH during the first weeks of frozen storage may be due to lactic acid increase, while the rise in pH values at the end of the frozen storage period is due to breakdown of protein and consequently the increase of ammonia and free amino group.
The increase in T.V.N. may be due to denaturation and aggregation of protein due to frozen storage which leads to marked increase in total nitrogen content in the form of a volatile substance.
The decrease in protein concentration of frozen liver may be due to drip loss during thawing which contains nitrogenous compound, or due to break down of nitrogenous substance to form volatile nitrogen, or due to denaturation with loss solubility of protein. Hence, the concentration of protein decreased with long period of frozen storage.
The measurement of TBA was very important in the current study because the liver undergoes oxidative rancidity during frozen storage.
In the first weeks of frozen storage the TBA decreased. This may be due to the formation of volatile compounds reactive with TBA. Then, TBA increased during frozen storage due to the oxidative deterioration of the lipids. The measuring of liver enzymes as AST, ALT and AP did not seem to be effective because there was no specific limits can be taken as guides to evaluate the degree of spoilage.
It is clear from the obtained results that the onset of spoilage happened at the 3rd day of chilling, and complete spoilage happened at the 7th day of chilling at (2-5°C). however, during the frozen storage, the incipient spoilage occurred at the 4th month of storage and the complete spoilage happened at the ’7th month from the frozen storage at (-18°C).