Thesis (Ph.D.) - Cairo University - Faculty of African Postgraduate Studies - Department of Natural Resources

This study was carried out to investigate the effect of pre-treatments and drying temperature on the physical, chemical and organoleptic properties of three different date varieties (Sakkoti , Siwi and Barhi) at the khalal stage. Each variety was sorted to three groups to use as whole,halves and pieces and pretreated with ascorbic acid, sodium meta bisulphite,sulfur dioxide and control.Then, these date products were dried at 50, 55, 60 and 65{u02DA}C, respectively till ~20% moisture content in oven at constant velocity and the data fitted in five mathematical models. Drying data was fitted into the models equation using SPSS- Statistical Package Software and the three varieties were evaluated at khalal stage and after pre-reatments and drying of physical, chemical, microbiological and sensory evaluations.The dried date fruits utillized in cup cakes and whole date fruits coated with chocolate then the products evaluated organolibiticaly.The results showed that dipping dates in sodium meta-bisulphite solution or sulfur dioxide then, dried at 60{u02DA}C produce high quality parameters of semi-dry dates comparing with other treatments.The Midilli model was selected as the best fit empirical model that describes the behavior of date whole, halves and pieces during drying at 55, 60 and 65{u00B0}C.Drying of dates at the Khalal stage can produce valuable products such as whole dried dates, date halves, date pieces and date powder.Incorporation of date pieces or date powder when used to enhance the nutritional value of baked products so that the date powder used instead of sugar in cup cakes and pieces dates used as fortified tell the level of 20% was acceptable by the panelists for all sensory attributes and date fruits coated with chocolate. So, Sodium meta-bisulphite pre-treatment at 60{u02DA}C and the Midilli model was selected as the best fitted empirical model that describes the behavior of date whole, halves and pieces during drying at 55, 60 and 65{u00B0}C.Drying of dates at the Khalal stage can produce valuable products may be used to preserve date quality during drying. Incorporation of date pieces or powder can be used to enhance the nutritional value of baked products tell the level of 20% without impairing the product quality

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