| Abstract: |
SUMMARYCitrus fruits are the main fruits produced in Egypt. Since different citrus fruits and vegetables under investigation vary in their chemical constituents, manufacturing of different blends of such fruits and vegetables juices and nectars are one of the main objectives of this currant study. Manufacturing different blends would possess balanced nutrition of value and palatable taste, preferable to consumers. The present research was carried out to study the effect of processing procedures such as pasteurization and cold storage on the qualities of manufactured fruits vegetable blends. -It is very important to make balance in nutritional value of different produced blends. Therefore, blends prepared from orange Balady orange, soukkary, mandarin, grapefruit, prickly pear and carrot were formulated as follows:1- Soukkary and Balady orange juices in a ratio of 1:3 (w/w), 2- Soukkary and mandarin juices in a ratio of 1:3 (w/w),3- Grapefruit and balady orange juices in a ratio of 1:2 (w/w), 4- Grapefruit and mandarin juices in a ratio of 1:4 (w/w),5- Prickly pear and Balady juices in a ratio of 1:3 (w/w),6- Carrot and Balady juices in a ratio of 1:3 (w/w). - Utilization of sugar substitutes which are safe to human health in preparing some low calory foods was is the scope of this investigation. The obtained results could be summarized in the main following points : 1- The chemical composition of the juices blends mostly contained an average of the chemical composition of their original juices.2- While the pasteurization process had no obvious effect on total titrable acidity, there was a slight increase in total soluble solids and pH value in all juices blends. 3- Ascorbic acid was found to decrease by extending the storage period up to (6) six months at 4ºC.4- There was a marked decrement in pectic substances content, of the blends after pasteurization, while there were a slightly decreased during cold storage (at 4oC).5- Non-reducing sugars in blends juice were found to invert gradually during storage into the reducing form which increased corresponding by (the inversion process due to inversion processed). 6- Total count of viable microorganisms (baceria & yeast) decreased greatly after storage of all samples. 7- Organoleptic evaluation test reveals that the juice blend was more palatable compared to the citrus juice individually repesented among all samples. 8- Volatile compounds (limonene content, oxygenated terpin and ester content) decreased after storage of the tested blends, but there was an increase existed in alcoholic compounds in the tested blends.Low calory blends : A- Preparation of low calory blends : The low calory blends were prepared by substituting the traditional sweeteners (sucrose) by different amounts of stevioside compounds (from 0.25 up to 0.125 mg/100ml.) in both the selected blends (S+B) and (G+B).B- Sensory evaluation of the low calory blends : The current study shows a significant difference between the taste of the traditional blend (Sweetened by sucrose) and the low calory one (which was completely substituted by stevioside compounds). On the other hand, the partially stevioside substituted samples 0.025 and 0.125 substitution percent) was close to the traditional blend. On contrary there was no significant difference in the color of all the (S+B) or (B+G) blend groups, while the taste of the G+B blend group varied an unpattern made for the traditional and the low calory blend. C- sugar fractionation of the low calory blends ; The sugar fractionation of the stored blends showed that at the zero time of storage, the highest sugar amount which could be detected was fructose in both blend groups. The storage of both group blends led to completely disappearance of the sucrose and a decrease of the glucose and fructose. D- Chemical consitutents of the low calory blends: The present study showed that total soluble solids (T.S.S.) , pH value, pectin methyl esterase and ascorbic acid of both low calory blends contents (S+B and G+B) were slightly increased after 6 weeks of storage at 4ºC. while total and reducing sugars content of the same blends decreased. The stored produced blends were palatable with respect to the microbiological assays. E- Stevioside compounds stability: Rebaudioside A, stevioside, rebaudioside C, dulcoside A, rebaudioside E and rebaudioside D. are six predomin compounds that could be detected in the stevioside of blends samples. All the identified stevioside compounds in both low calory blends decreased as a result of storage at 4ºC for 6 weeks. All the stevioside compounds (except in 3 compound No. 6 of G+B blend) highly correlated with the storage period for 6 weeks at 4ºC. The slope (the change of each compound/wk) of dulcoside A and rebaudioside D compound in S+B blend was higher than that found in G+B . Consequently, such compounds were more stable in S+B blend than in G+B when stored at 4ºC for 6 weeks.
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