Quality Evaluation of Kithul (Caryota urens) Treacle Available in the Market with Respect to Chemical and Sensory Parameters and Identification of Volatile Flavor Compounds

Abstract

Caryota urens is a native tree in tropical Asian continent and it is grown in wet and intermediate wet zone of Sri Lanka. This palm is capable of storing large volumes of Carbohydrates, which is converted to sugars. Tapping the inflorescence enables the collection of the exudate sap from which the main product treacle is manufactured. According to the Sri Lanka standard specifications for treacle the total sugar content should be more than 65%. The kithul sap has about 8-9% sugar. During the process of preparation of kithul treacle there is a tendency for the manufactures to add cane sugar to obtain higher yield. Due to this quality of product is affected and the original kithul flavor is reduced. The objective of the study was to evaluate some market samples of treacle to identify the amount of adulteration. According to the work done by Industrial Technology Institute, the ratio of reducing sugars to total sugars was found to be a useful parameter to detect whether kithul treacle samples are adulterated with cane sugar. In addition an attempt was made to identify the flavor profile of some kithul treacle samples to see weather there are definite volatile flavor compounds responsible for the kithul flavor. Five market samples of kithul treacle were randomly collected and they were tested for chemical parameters such as brix value, pH value, acidity, amount of reducing sugar, total sugars and the sensory parameters such as color, consistency, taste & flavor and overall acceptability. These parameters were compared with those of pure kithul treacle. According to the results brix value of samples varied between 64.4 - 72.0 and pH value varied between 4.09 to 4.95, acidity was between 0.17 %- 0.21% and amount of reducing sugars varied between 5.93% - 24.03%. Amount of total sugars varied between 64.02%-71.15 %. There was a relationship between chemical and sensory parameters, and according to the results 50% of samples were not within the required ratio (0.1 - 0.2) of reducing sugars to total sugars. Those samples may have been adulterated with cane sugar. According to the results of sensory evaluation there was no difference in color at 5% significance level. However taste & flavor, overall acceptability and consistency were different in samples. During preliminary studies of volatile flavor components in kithul treacle using Gas Chromatography-Mass Spectrometiy, it was observed that Benzene acetaldehyde and 2-Furancarboxaldehyde were common in all Gas Chromatography-Mass Spectrometry chromatograms. Further studies are necessary to conclude volatile flavor profile of kithul treacle.