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No abstract

This study was carried out to compare physical, chemical, thermal and technological properties of four rice varieties (Hybrid1, Jasmine, Waxy and Black) grown in Egypt as well as to investigate the possibility of using their rice flour as substitution of wheat flour in preparation of some bakery products namely biscuits. Physical properties such as milling output, head rice percentage and kernel physical attributes of rice varieties were measured. Chemical composition, gelatinization temperature (GT), gel consistency (GC), in vitro starch digestibility and cooking properties of rice were also determined. In addition, biscuit using milled rice flours as substitution of wheat flour at levels of 25 and 50% was prepared, and its sensory analysis as well as its functional properties were evaluated. The results revealed that Hybrid1 rice had the highest milled percentage but Jasmine variety had the highest head rice percentage. Waxy rice had the highest contents of total carbohydrates and starch. Black rice contains high content of ether extract, ash and crude fibers, but it contain lower content of total carbohydrates and starch compared with another varieties. In addition, brown rice in all varieties had higher contents of crude protein, ether extract, ash and crude fibers but it contain lower contents of total carbohydrates and starch compared with those of milled rice. Waxy rice had the highest gel consistency (GC) and gelatinization temperature (GT) among the other varieties; but it had the lowest content of amylose. Black rice had the lowest GT and the highest amylose content. Also, the results cleared that no significant differences were found among all rice varieties in starch digestibility using αamylase. Cooking qualities revealed that Hybrid1 rice had the longest cooking time (22 min) compared to the others, while the other varieties had somewhat similar cooking time. Generally, brown rice had significantly cooking time higher than that of milled rice. Water uptake of milled rice was significantly higher than that of brown. In milled rice, water uptake were in order; Hybrid1 > Jasmine > Black > Waxy. Organoleptic evaluation indicated that, biscuit samples prepared using rice flour of studied varieties as substitutions of wheat flour until 50% were very acceptable, where most samples have sensory characteristics scores higher than those of control (wheat flour biscuit). Water loss during baking of biscuit was higher in formulas contained rice flour than that of control and it increased with increasing of rice replacement ratios. Water uptake of samples prepared with rice flours as substitution of wheat flour was significantly higher than that of control sample (free from rice flour). Water uptake values of biscuits contained higher substitution ratio (50%) were significantly higher than those of samples contained lower ones. Specific lightness of biscuit made using rice flour as substitution of wheat flour was somewhat lower than that of wheat flour biscuit with the exception of black rice was the highest.

This study was performed to investigate the possibility of using the brown or germinated brown rice flour at different substitution levels of wheat flour for soft bread (Toast) making, evaluate the quality of produced bread and know the optimal substitution levels for producing high quality bread. Chemical composition, some nutrients and amino acids of wheat flour 72%, ungerminated and germinated brown rice flours were determined. Pasting characteristics of starch and farinograph of dough were measured. In addition, sensory characteristics of prepared bread were evaluated. The obtained results indicated that ungerminated and germinated brown rice contain lipids, crude fiber, ash and reducing sugars higher than those of wheat flour. They contain higher contents of potassium and iron but lower contents of sodium and magnesium than those of wheat flour. In addition, they contain all essential and non-essential amino acids. Total essential amino acids of ungerminated brown rice (39.81%) and germinated brown rice (40.99%) were very higher than that of wheat flour 72% (25.03%). Pasting characteristics measurements showed that wheat flour starch has gelatinization temperature and viscosity at 95 o C lower b bu ut t i it t h ha as s s se et tb ba ac ck k h hi ig gh he er r t th ha an n u un ng ge er rm mi in na at te ed d a an nd d g ge er rm mi in na at te ed d b br ro ow wn n r ri ic ce e s st ta ar rc ch he es s.. Germinated brown rice starch has low breakdown and high setback compared with ungerminated brown rice.. The results of farinograph indicated that using ungerminated or germinated brown rice caused decreasing the development and stability time but increasing the weakness of the dough, especially for ungerminated brown rice. Sensory characteristics of produced bread revealed that the effect of ungerminated or germinated brown rice on the flavor and texture (crump and crust) was very little, while its effect on the color (crump and crust) and mouth satisfaction was somewhat remarkable but all changes were in the acceptable limits. Germination process of brown rice improved its nutritional value and quality attributes of bread therefore, the using of germinated brown rice is more suitable for making of bread (Toast) than ungerminated brown rice.

The changes in citrus peels (CP) moisture content, drying rate, moisture ratio, drying time and energy consumption at various drying air temperatures was studied. The effect of drying temperatures and residual moisture contents on the quality of CP after drying was also evaluated. The test samples were dried in a laboratory scale hot air dryer at air temperature in the range of 40-70 o C and a constant air velocity of 1m/s to desired moisture for save storage and final moisture level of drying conditions. Cakes prepared from blendes containing different proportion (0, 10, 15 and 20%) of dried orange and mandarin peels were also evaluated for chemical composition and sensory attributes. The results indicated that, the drying temperature was very effective in removing moisture from citrus peels. The drying time was decreased by 50% and specific energy consumption decreased by about 28.5% with increasing drying temperature from 40 to70 o C for drying citrus peels. The simple exponential equation satisfactorily described the drying behavior of CP as indicated by the higher coefficient of determination. The optimal drying temperature was 60°C to reach 10±0.2%, w.b, moisture level, which reduced drying time and saved energy consumption and product quality. Meanwhile, overdrying to reach final moisture levels of citrus peels (5.4±0.2%)with higher drying air temperature sharply increased the losses of vitamin C, carotenoids and essential oils. Incorporation 15% of dried orange and mandarin peels in cakes formula increased dietary fiber by 33.5 and 29.6%, ether extract by 2.9 and 4.6% and ash by 30.6 and 29.0%, respectively, while protein and total carbohydrates contents were slightly decreased. Highly acceptable cakes could be obtained by incorporating 15% of orange and mandarin peels dried to 10%, w.b., moisture content in the cakes formulation and it can be used as value-added food ingredients.