الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
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Abstract
Freezing of vegetables is a world wide method ~or its preservation in order to be consumed at different seasons with moderate price. Retention of fresh quality is a principle objective of freezing. So for assessment of quality o~ frozen products, the ~resh vegetable is tM standard for comparison. Under the usual conditions o~ storage of frozen foods, mcrobial growth is prevented entirely and the aotion of food enzYmes is greately retarded. One of the most damaging effects of enzyme activity is the organoleptic changes including physical changes, that may occur in cOlor, oder, skin texture and that may give an indica tion of spoilage during freezing and storage. storage , by freezing is not destructive 1;0 nutrients, mainly I ascorbio acid (vitamin c). Thus the estimation of ascorbio acid contents of frozen vegetables as a func ’tion of storage time is worthwhile. This study was conducted on the effect of storage condi tions on the degree of keeping quality and vitamin c oontents of frozen beans and peas with the following objectives . Study the effect of storage by freezing on,its quality by organoleptic evaluation ”color, odor, skin texture”, enzymes aotivity specially catalase and peroxidase, the standard plate count and the asoorbio aoid oontent. 2. Study the quality retention of the frozen vegetables stored over a’range of low temperature and time stor age, finding a borderline for the deterioration of frozen vegetables. 3. study the effeot of the added water and ioe during prooessing on the quality assessment of the frozen vegetables. A total of 1000 samples of beans and peas were ohosen at randam during every stage of processing operation inoluding fresh, washed, blanohed and frozen packaged from Edfina Plant and laboratory prooessed according to the same stages of prooessing used in Edfina. Samples were tested as follows: 1. Bean, peas samples were tested organoleptioally, chemioally for enzymes aotivity and asoorbio aoid contents, baoteriologioally for baoterial load. The samples were examined at different stages of prooessing and storage at -18°0, -12°0 for 6 mon ths, refrigeration temperature (+4°0) for 10 days and at room temperature (20-25°0) for 5 days. 2. Also)O samples of water and ioe were oolleoted from Edfina Plant, laboratory tap water and sub jeoted for testing its baoterial load by the estimation of the standard plate count. The results of this study revealed the followings: 1. Laboratory examination of beans and peas during - - different stages of prooessing showed that the organo leptio evaluation was as~essed as grade 11 A”. Enzymes catalase, peroxidase were po,sitive in the fresh, washed beans and peas, changed to negative after blanching. The mean values of standard plate count were 8.2 X 105/gm, 4.8 X 105 in fresh Edfina, laboratory prooessed beans respeotively, 1.4 X 106/gm, 1.1 X 106 in fresh Edfina and laboratory prooessed peas. Washing of vegetables with tap water showed small reduotion in the bacterial count. Blanching caused apperciable reduction, it was 79.27, 92.92 in Edfina, laboratory prooessed beans respeotively, 97.29 in Edfina, laboratory prooessed beans respeotively, 97.29 in Edfina and laboratory prooessed peas. Freezing has small reduotion effeot on the total bacterial oount. Asoorbio aoid oontent was 18.6 mg/100 gm, 19.4 mg in fresh Edfina and laboratory prooessed beans res pectively, 23.2 mg, 24.1 DIg in fresh Edfina and labor atory prooe ssed peas. Washing of vegetables.with tap water showed small red uction in the asoorbio aoid oontent. Blanohing oaused appreoiable reduotion in the asoorbio acid oontent, it was 84.95, 50.52 in Edfina and laboratory prooessed beans respeotively, 18.97, 17.01, in Edfina and laboratory prooessed peas. Freezing has a small reduotion effeot on the asoorbio acid. oontent. . 2. Storage at -18°e The results showed that the organoleptio evaluation of beans and peas was assessed as grade ”A” during the storage period for both Edfina and laboratory prooessed frozen vegetables. The soores were 15 during storage for 6 months in Edfina peas, laboratory prooessed peas and beans, but decreased to 14 in Edfina beans after the 5~ and 6th months with sligth ohange in color, but with no indioations of spoilage. Enzymes oatalase and peroxidase were negative during the storage - period for all sample s. The standard plate count of Edfina and laboratory ~ocessed beans was decreased gradually within 1.34, 1.46 duriDg 6 months storage, with final reduotion of 93.9, 94.79 oaloulated from the fresh state. Meanwhile the standard plate count of Edfina and labor ~or.1 processed peas was deoreased within 0.28, 0.24 during 6 months storage, with final reduotion of 97.71, 97.70 caloulated from the fresh state. The asoorbic acid contents .of Edfina and laboratory processed frozen beans was decreased within 0.53, 0.52 during 6 months storage, with final reduction of 85.48, 52.58 oalculated from the fresh state. Meanwhile the ascorbic acid oontents of Edfina wm laboratory prooessed peas was deoreased within 1.59, 0.81 dUring 6 months storage, with final reduction of 22.85, 19.09 calculated from the fresh state. These results showed that the reduotion in the standard plate count and ascorbio acid content of Edfina and laboratory processed beans and peas were statistically signifioant at 0.01 level of significance during the 6 months storage. The findings emphasised that the bacterial content for both Edfina and laboratory processed frozen products were according to the Egyptian regulations and world standards, and fit for human consumption. J. Storage at -12°0 The results showed that the organoleptic evaluation of beans and peas was asse ssed as grade” A” dur ing the storage period for both Edfina and laboratory processed frozen vegetables. The scores were 15 during storage for 6 months in Edfina , and laboratory processed peas, decreased to 14 at the 6!!! month in laboratory processed beans, more decrease was obvious in Edfina beans reaching 13 at the 5!a month, 12 at the 6!a month with slight ohange in color but with no indications of spoilage. Enzymes catalase and perexidase were negative during 6 months storage for the frozen vegetables. The standard plate count of Edfina and laboratory .processed beans was decreased gradually within 0.98, 0.42 during 6 months storage, with final reduction of 91.72, 93.54 calculated from the fresh state. ~anwhi1e the standard plate count of Edfina and laboratory processed peas was deoreased within 0.22, 0,17 during 6 months storage, with final reduction of 97.~ , 97.5 calculated from the fresh state. The asoorbic acid contents of Edfina and laboratory processed frozen beans was decreased within 3.58, 4.62 during 6 months storage, with final reduction of 86.66, 56.19 ca1cu1ated from the fresh state. Meanwhile the ascorbic acid oontents of Edfina and lab oratory processed peas was deoreased within 4.87, 4.27 during 6 months storage, with final deorease of 27.87, 21.36 ca1ou1ated from the fresh state. Thus, frozen vegetables stored at -12°0 for 6 months, were oonsidered fit for human oonsumption during this period with slight change in oolor in oase of fro. zen lj)eans. These results showed that the peroentage reduotion of standard plate count of frozen beans and peas at -18°0:> t.be percentage reduction at -12°0 during the 6 months storage period. ilso it is obvious that the percentage decrease in asorbie acid contents of frozen beans and peas at -12°0) the percentage deorease in asoorbio acid oontents at -18°0 during the 6 months storage period. 4. Storage at refrigeration temperature ”4°0” The results showed that frozen .beans began to deteriorate organoleptically at the 6jh day of storage and frozen peas at the 3rd day. The quality decreased from grade ”A” to grade ”B” in both beans and peas, PH decreased to 5.7, 6.4 in beans and peas respectively. At this stage there was clear ohange in the enzymatic reactions, ohanging from negative to po.sitive in both catalase and peroxidase. Meanwhile the standard plate count increased oorrelated with the ohanges appeared organoleptioally and also with the po.sitivity of the enzymes to reach . 8.9 X 104 t 105/gm in beans and peas with inorease of 20.27, 170.27, 170.27, 15.59 caloulated from the frozen state. The results showed that the borderline for spoilage of frozen beans and peas when stored at + 4°0 . ft began to deteriorate at the 6th day in beans and at the 3~ day in peas, then its signs were sharpely and ob viously after that until it became unfit for human oonsumption. 5. Keeping frozen beans and peas at room temperature ”20-25°0”. The results showed that frozen beans and peas began to deteriorate organo1eptioally at the 2nd day. The qua lity decreased from grade ”A” to grade ”0”, PH decreased to 5.5, 4.5 in beans and peas. At this stage there was olear change in the enzymatic reaotions ohanging from negative to po,sitive in both oata1ase and peroxidase. Meanwhile the standard plate count increased corr I elated with the ohanges appeared organoleptically and also with the po,sitivity of the enzymes to reach 105, 9.8 X 104 per gram in beans and - peas with increase of 38.88, 164.86caloulated from the frozen state. ~corbio acid oontent was decreased to reaoh 2.3 mg, 12.-9 mg/100 gm in beans and peas respeotively with deorease of 30.3, 26.7 caloulated from the frozen state. The results showed that the borderline for spoilage of frozen beans and peas, when kept at room temperature H n began to deteriorate at the 2Ba day for beans and peas, then its signs were sharpely and obviously after that until it beoame unfit for human oonsumption. 6. Examinatio~ of water and ioe: The results showed that the standard plate oount was highest in oase of Edfina oooling water being 3.8 X l04/ml, while it was 3.7 X l04/ml in case of ioe water and lowest in oase of laboratory tap water being 2.5 X l03/ml. These values affeoted the standard plate oount of vegetables during the- oooling prooess used after blanohing, and also the final frozen produot. The plate oount of Edfinavegetables after blanohing was higher than the plate oount of laboratory prooessed vegetables, it was 1.7 X lOS/gm in Edfina beans, 3.4 X 104 in laboratory . processed beans. In Edfina peas it was 3.8 X 104/gm, while in laboratory processed peas it was 3.1 X 104/gm. Aooording to these results the following was recommended: 1. Frozen vegetables should be stored and transported at -18°0. A temperature of -12°0 or above is not ~eoommended. 2. Frozen vegetables delivered to the retail store should not be allowed at room temperature. 3. Water and ice used for cooling after blanching should meet the bacteriological and chemical standards tor drinking water, recirculated supply of water is an unsound practice. 4. The process plant must regulate the frequency of cleaning even when the plant is not in operation. 5. Public health education for food handlers to insure good sanitation.