EVALUATION OF QUALITY AND SAFETY FOR SOME PROCESSED FOODS IN RELATION TO ENZYME ACTIVITY
EMAN KAMAL NABIH HANAFI;
Abstract
The objective of the present study was to shed light on the assessment of quality and safety of frozen green beans, pasteurized orange juice and refrigerated bolti fish by evaluating:
1. The effect of blanching on green beans with different methods i.e. (microwave, steam and boiling water) and freezing followed by frozen storage at -18±2°C for 6 months on physicochemical properties, stability of chlorophylls, color characteristics, microbiological assessment as well as the activity of peroxidase, catalase and ascorbic acid oxidase enzymes. Also, the sensory evaluation of fresh and frozen green beans was investigated.
2. The effect of pasteurization on orange juice by different methods i.e. (heat and microwave) for various times followed by refrigeration storage at 4±1°C for 60 days on physicochemical properties, browning index, microbiological quality as well as the activity of pectin methyl-esterase and ascorbic acid oxidase enzymes. The sensory evaluation of tested orange juice was also undertaken.
3. The effect of refrigeration at 4±1°C on bolti fish either fresh or treated with 1% acetic acid, 3% citric acid and mixture of the two on physicochemical properties, chemical indices (TBA and TVN), microbiological attributes and the activity of catalase and protease enzymes. The sensory evaluation of bolti fish was also studied.
The obtained results could be summarized as follows:
Part 1. Quality and safety attributes for green beans:
Green beans was blanched with different methods and freezing followed by frozen storage at -18±2°C for 6 months. Blanching methods before freezing included, boiling water blanching for 2 and 4 min. in boiling water with and without a mixture of chemicals containing (0.5% potassium metabisulphite, 0.1% magnesium oxide and 0.1% sodium bicarbonate), steam blanching for 3 and 5 min. with and without pretreatment with the mixture of chemicals and; microwave blanching for 30 and 60 sec. with and without pretreatment with the mixed chemicals. The obtained results showed that:
1.1. Physicochemical analysis:
1.1.1. Moisture content:
Blanching in boiling water caused to increase the moisture content of green beans at initial time of blanching, especially for samples treated with the mixture of chemicals through blanching which recorded 0.90 to 1.11% increasing after 2 and 4 min., respectively. However, by extending the time of microwave and steam blanching, the moisture content was reduced. On the other hand, with the progressive time of storage at -18±2˚C, the moisture contents of green beans were significantly (p≤0.05) decreased for all frozen blanched samples particularly for samples untreated with the mixture of chemicals.
1.1.2. Ash content:
There was a decremental pattern in ash contents after blanching especially for green beans blanched in boiling water. Consequently, by increasing the time of blanching, the loss (%) of ash contents were decreased for microwave and steam blanched green beans, while, boiling water blanched samples recorded a decremental trend in ash contents by increasing the time of blanching. Also, there was an increase of ash contents by using the mixture of chemicals. On the other hand, by increasing the storage time at -18±2˚C, ash contents were significantly (p≤0.05) decreased in all blanching methods used, particularly for samples that had not been treated with the mixture of chemicals.
1.1.3. Retention of ascorbic acid:
The ascorbic acid contents were reduced for all tested green beans samples after blanching. Ascorbic acid was comparatively higher in microwave blanched samples (95.2-92.1%), moderate in steam blanched samples (92.1-84.1%) and lower in the boiling water blanched samples
1. The effect of blanching on green beans with different methods i.e. (microwave, steam and boiling water) and freezing followed by frozen storage at -18±2°C for 6 months on physicochemical properties, stability of chlorophylls, color characteristics, microbiological assessment as well as the activity of peroxidase, catalase and ascorbic acid oxidase enzymes. Also, the sensory evaluation of fresh and frozen green beans was investigated.
2. The effect of pasteurization on orange juice by different methods i.e. (heat and microwave) for various times followed by refrigeration storage at 4±1°C for 60 days on physicochemical properties, browning index, microbiological quality as well as the activity of pectin methyl-esterase and ascorbic acid oxidase enzymes. The sensory evaluation of tested orange juice was also undertaken.
3. The effect of refrigeration at 4±1°C on bolti fish either fresh or treated with 1% acetic acid, 3% citric acid and mixture of the two on physicochemical properties, chemical indices (TBA and TVN), microbiological attributes and the activity of catalase and protease enzymes. The sensory evaluation of bolti fish was also studied.
The obtained results could be summarized as follows:
Part 1. Quality and safety attributes for green beans:
Green beans was blanched with different methods and freezing followed by frozen storage at -18±2°C for 6 months. Blanching methods before freezing included, boiling water blanching for 2 and 4 min. in boiling water with and without a mixture of chemicals containing (0.5% potassium metabisulphite, 0.1% magnesium oxide and 0.1% sodium bicarbonate), steam blanching for 3 and 5 min. with and without pretreatment with the mixture of chemicals and; microwave blanching for 30 and 60 sec. with and without pretreatment with the mixed chemicals. The obtained results showed that:
1.1. Physicochemical analysis:
1.1.1. Moisture content:
Blanching in boiling water caused to increase the moisture content of green beans at initial time of blanching, especially for samples treated with the mixture of chemicals through blanching which recorded 0.90 to 1.11% increasing after 2 and 4 min., respectively. However, by extending the time of microwave and steam blanching, the moisture content was reduced. On the other hand, with the progressive time of storage at -18±2˚C, the moisture contents of green beans were significantly (p≤0.05) decreased for all frozen blanched samples particularly for samples untreated with the mixture of chemicals.
1.1.2. Ash content:
There was a decremental pattern in ash contents after blanching especially for green beans blanched in boiling water. Consequently, by increasing the time of blanching, the loss (%) of ash contents were decreased for microwave and steam blanched green beans, while, boiling water blanched samples recorded a decremental trend in ash contents by increasing the time of blanching. Also, there was an increase of ash contents by using the mixture of chemicals. On the other hand, by increasing the storage time at -18±2˚C, ash contents were significantly (p≤0.05) decreased in all blanching methods used, particularly for samples that had not been treated with the mixture of chemicals.
1.1.3. Retention of ascorbic acid:
The ascorbic acid contents were reduced for all tested green beans samples after blanching. Ascorbic acid was comparatively higher in microwave blanched samples (95.2-92.1%), moderate in steam blanched samples (92.1-84.1%) and lower in the boiling water blanched samples
Other data
| Title | EVALUATION OF QUALITY AND SAFETY FOR SOME PROCESSED FOODS IN RELATION TO ENZYME ACTIVITY | Other Titles | تقييم جودة وسلامة بعض الأغذية المصنعة وعلاقتها بالنشاط الإنزيمى | Authors | EMAN KAMAL NABIH HANAFI | Issue Date | 2014 |
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