PRICKLY PEAR PEELS AS A NEW SOURCE OF NATURAL LIQUID SWEETENER AND ITS APPLICATION IN TOFFEE MANUFACTURE

Abstract

Prickly pear peels liquid sweetener (PPPLS) was prepared from prickly pear peels (PPP) and used as substitute sweetening agent for glucose syrup or sucrose at levels of 25, 50, 75 or 100% in toffee manufacture. The physico-chemical and sensory properties were determined just after preparation and intervals every one month during storage at room temperature for six months. Prickly pear peels (PPP) considered as by product that characterized by their higher content of sugars reached to 11.43 %. The chemical and physical properties, sensory evaluation as well as utilization of natural liquid sweetener produced from prickly pear peels were studied. The data revealed that reducing sugars comprised about 86.06 %of total sugars, while, non reducing sugars comprised about 6.04 % of PPPLS. Results indicated that PPPLS is a good source of many important elements such as K, Ca, Mg, Na and Fe. Vitamin C was considered as the predominant vitamin (2.74 mg/100g) followed by B1 (0.471mg/100g). Sensory evaluation of PPPLS indicated the possibility of using such PPPLS as a sugar substitute in toffee. Toffee was prepared using PPPLS as substitutes of glucose syrup or sucrose in the percent 25, 50, 75 and 100 %. Relation between time and temperature during cooking of experimental samples were studied. No remarkable differences were obtained in the behavior of heating curve due to addition of PPPLS at the studied levels. Effect of cooking temperature on moisture content and hardness of toffee processed using PPPLS were also studied. Hardness value of control sample increased from 343 to 605 N when the cooking temperature was increased from 114 to 118 ºC. Same behavior was noticed by PPPLS-supplemented samples. Changes that occur in sugars composition of toffee with processing using PPPLS were studied. The reducing sugars were gradually increased with the increasing sucrose substitution of PPPLS to reach its maximum 94.61 % of the total sugars, adversely, non reducing sugars that reach its minimum 5.39 % of the total sugars. Chemical composition of toffee tested samples was determined in the start of storage time while, acid value, peroxide value, fatty acid pattern and sensory attributes were determined during storage period at room temperature for six months. Generally, the difference in chemical composition between the formulas is slight. While, acid and peroxide values of all experimental manufactured samples were gradually increased versus storage period with significant difference. Total saturated fatty acids content of oil extracted from all samples increased, adversely, total unsaturated fatty acids content which decreased at the long storage period. In addition, all toffee manufactured samples showed acceptability in sensory evaluation after processing and at intervals during storage. Use of PPPLS up to 50% in toffee manufacture led to enhance all sensory attributes. The obtained information is useful for the further chemical and nutritional investigations of prickly pear peel, and also for industrial utilization of the major by-product of the prickly pear fruit.