Utilization of orange-fleshed sweet potato in the formulation of dry soup recipes

Present study was carried out to evaluate the suitability of an orange- fleshed sweet potato variety Salih and chickpea for formulating a dry soup mix. In the first stage of the experiment comparisons were performed between two varieties of sweet potato, Salih and local variety (white) in their physio-chemical properties and their influence on the dry soup mix. The obtained results indicated that Salih contained 19.3% peel and 80.7% flesh while the Local contained 16.3% peel and 83.7% flesh. On the other hand the local was found better in overall drying ratio and drying ratio. The results indicated that the drying method used in this study was found to decrease the moisture content from 77.9 to 2.1and 72.3 to 2.0% in Salih and local varieties, respectively. Salih variety was found to be higher in the protein content, fat, fiber, ash, total and reducing sugars, ascorbic acid and titerable acidity before and after processing; beside that it recorded a higher value in optical density after processing. The results of the reconstitution characteristics of the local variety were found to be better in solubility, wettability and sinkability of the produced flour. Sensory evaluation results reflected that the soup prepared from Salih variety had higher scores of appearance, taste, flavor, consistency and overall acceptability so it was used to make the soup. The physio-chemical characteristics of chickpea seeds and flour revealed that the preparation method of chickpea flour has hardly affected the produced flour. In the second stage of the experiment, three different dry soup mixes were formulated by mixing of Salih variety and chickpea flours in different proportions namely, 0: 100, 40: 60 and 50: 50 respectively. Physiochemical, microbiological and oraganoleptic tests were conducted for the different three recipes during storage at intervals of 0, 1.5, 3, 4.5, 6, 7.5 and 9 months. The results of the physical tests indicated that the soup made from 50% Salih variety flour recorded the highest mean values in moisture content (2.89%), optical density at 330 nm was (1.61), solubility index (42 ml.sediment) while the soup made from whole chickpea recorded the highest mean values in bulk density (0.719gm/ml) and wettability and sinkability (220, 223 seconds). Hygroscopicity test at the relative humidity (R. H.) 52% and 26 deg C of the dry soup mix revealed that the product is hygroscopic. The sorption isotherm at 30 deg C and different equilibrium relative humidities (ERHs) have shown that fungal growth accrued at the high ERR (86%) and caking was observed even at very low ERH (23%). The results of the chemical tests revealed that the highest values of the protein (19.5%), (fat 5.4%), (ash 8.6%), reducing sugars (16.3%) and fat acidity contents (48 ml KOH/100gm) in the soup made from whole chickpea flour, whereas the soup made from 50% Salih variety flour recorded highest value in fiber (2.03%), total sugar (10.77%) and ascorbic acid (l0.78mg/l00g). The highest value (0.2467%) of Phosphor (P) was found in the soup mix containing 500/0 Salih variety flour and all the other minerals (Ca, Na, K, Mg and Fe) were higher in the control soup mix. All minerals content decreased gradually during storage. Total bacterial count (cfu/g) of all dry soup mixes decreased gradually during storage, no bacterial growth was recorded in soup mixes made from 40 and 50% Salih variety flour by the end of the storage period, also there was no growth of E. coli, Salmonella ssp, Mould and yeast in all the soups during storage. Sensory evaluation reflected that the soup made from 40% Salih variety flour was found to be best in appearance, taste, flavour, consistency and overall acceptability during the storage period