Blackberry, sugar contents

Table II shows that sucrose levels are highest in peach fruit and very low in blackberry, cherry, and grape. The % C.V. for sucrose content for many of the fruit samples is extremely high, most likely because of enzymic or chemical hydrolysis. The average sucrose content of plum fruit is 38 of total sugars, while processed plums contain only 1. Presence of large quantities of sucrose in prune juice has, in fact, been used as an indication of adulteration ( ). Cherries and grapes contain invertase Cllj 12) which may account for sucrose not being detected in some samples and may also explain the high % C.V. for those fruits. In examining apple Juice concentrates, we did not detect sucrose in seven-fold concentrates whereas we did in fo ar-fold apple concentrates (7.) > the time-temperature conditions allowing for complete hydrolysis in the more concentrated product.

An isomer of citric acid is (1J ,2S)-1-hydroxypropan-1,2,3-tricarboxylic acid (8-67), also known as D-isocitric acid u-threo isomer), which is another intermediate of the citric acid cycle. This acid is the dominant acid in blackberries (Table 8.17) and occurs in other fruits in small or insignificant amounts (e.g. in apples). The isocitric acid content is one of the most important markers in the estimation of the proportion of fruit in coloured fruit mixtures, for example in mixtures of blackcurrants, strawberries and raspberries with apples. The concentration ratio of citric acid to isocitric acid is also employed for the detection of adulteration, and can reveal the addition of synthetic citric acid to optimise the taste of fruit drinks, especially in the case of added sugar. 

---