Effects of freezing on nutritional properties and microbiological quality of meat
-
Upload
barana-rangana -
Category
Health & Medicine
-
view
920 -
download
2
description
Transcript of Effects of freezing on nutritional properties and microbiological quality of meat
![Page 1: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/1.jpg)
Effects Of Freezing On Nutritional Properties And Microbiological Quality Of Meat
NUVINI SAMARATHUNGADepartment Of Food Science & Technology
University Of PreadeniyaSri Lanka.
![Page 2: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/2.jpg)
WHAT IS FREEZING
• Freezing is the unit operation in which the temperature of a food is reduced below its freezing point and a proportion of the water undergoes a change in state to form ice crystals.
![Page 3: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/3.jpg)
FREEZING• It is a food preservation method• Potentially deliver a high degree of safety, nutritional value and sensory quality • Preventing, or at least minimizing, microbial and chemical changes
![Page 4: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/4.jpg)
AT THE FREEZING TEMPERATURE
• Form ice crystals
• Death and injury occur
• Mechanically damage cells
• Some water will remain unfrozen
• At these temperatures no microbial growth is possible
![Page 5: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/5.jpg)
MAIN EFFECT OF FREEZING
• Nutritional Effects• Microbiological Effect
![Page 6: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/6.jpg)
NUTRITIONAL EFFECTS• Carbohydrates and
protein may undergo limited oxidation
• Fats are susceptible to rancidity
• Vitamins are particularly susceptible to oxidative damage
![Page 7: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/7.jpg)
EFFECTS OF FAT• Polyunsaturated fatty acids are particularly prone to oxidation• Formation of volatile products•Give rise to the aroma and taste characterized as ‘rancid’
![Page 8: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/8.jpg)
EFFECTS OF VITAMINS
• The vitamin E is damaged losses during freezing and storage • A survey of frozen meals analyzed after freezing, storage reported losses of up to 85% of thiamin, 55% of vitamin A, 33% vitamin E, 25% niacin and pyridoxine.
![Page 9: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/9.jpg)
EFFECT OF FREEZING ON THE MICROBES IN MEAT
• It is generally the case that total numbers of micro-organisms decrease slightly during freezing• The micro-organisms associated with raw meat, poultry and fish are varied. They include bacteria, protozoa, viruses and for meats
![Page 10: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/10.jpg)
During freezing
• The freezing point being lower than that of pure water
• unfrozen water increases
• microbial growth is possible
• Further more freezing reduced water activity.
• No microbial growth is possible
Temperature (°C)
aw
0 1
-5-10-15-20-40
0.9530.9070.8640.8230.68
![Page 11: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/11.jpg)
MICROBIOLOGICAL EFFECT• Bacterial spores are virtually unaffected by freezing• Most vegetative gram-positive bacteria are relatively resistant • Gram-negatives bacteria show the greatest sensitivity
![Page 12: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/12.jpg)
CONCLUSION
• There is little loss of nutrients during the freezing
• Proteins and carbohydrate are unchanged
• Fats are susceptible to rancidity
• The vitamin E is damaged
• There are little loss of other vitamins
• It is generally the case that total numbers of micro-organisms decrease
• Cannot be completely destroy all micro-organisms in foods
![Page 13: Effects of freezing on nutritional properties and microbiological quality of meat](https://reader036.fdocuments.in/reader036/viewer/2022081413/549a721ab47959696c8b490f/html5/thumbnails/13.jpg)
THANK YOU