Determination of the fruit content of apricot and strawberry jams and spreads and apricot and peach fruit preparations by gravimetric quantification of hemicellulose.

An innovative method developed for fruit content determination based on the quantification of hemicellulose was applied to apricot and peach fruit preparations, apricot and strawberry jams and spreads. For this purpose, the hemicellulose fraction was isolated from the alcohol-insoluble residue from peaches, apricots, and strawberries, yielding the amount of the respective fresh fruit per gram hemicellulose. Fruit preparations from peaches with 34.4%, 47.2% and 66.4% fruit content were produced using pectin and carrageenan, xanthan or starch, respectively, as hydrocolloids. Jams from apricots and strawberries were prepared with pectin. Fruit contents of apricot jams were 34.1% and 48.2%, and 36.6% and 46.4% in strawberry jams, respectively. Furthermore, a range of commercial apricot spreads and jams and one strawberry spread as well as apricot and peach fruit preparations were examined. The fruit content was calculated based on the amount of hemicellulose. Calculated fruit contents were in good agreement with the respective product specifications (e.g. 62.6% vs. 66.4%, 35.2% vs. 34.1%, 67.5% vs. 70.0% and 54.0% vs. 53.7%, respectively) with deviations ranging between 0.3% and 4.2%. Maximal deviation was found only in the case of a self-made peach fruit preparation (40.9% vs. 34.4%), where interference of added hydrocolloids and fruit ingredients probably resulted in significant overestimation of the fruit content. Although sample preparation needed to be adapted to different fruit matrices, this novel method proved to be suitable for the determination of fruit contents of fruit preparations, spreads and jams. For the first time, this method was successfully applied to industrially manufactured fruit products without knowledge of fruit specification and the complex recipes of jams, spreads, and fruit preparations, respectively.