Both the rowanberries (Sorbus) and the chokeberries (Aronia) belong to the family Rosaceae. The berries of these cultivars are suitable for production of health-food products. The main components in the dry matter of fruits are carbohydrates, primarily sugars. The aim of this experiment was to determine the content of simple sugars and sorbitol in different fresh rowanberry cultivars and chokeberries and to compare the composition of these compounds after freezing and thawing of berries. The experiments were done in the Customs laboratory of the National Customs Board, State Revenue Service (Latvia). The rowanberries were picked in the Pure Horticultural Research centre, and black chokeberries were obtained from farm 'Ceplīši' (rural municipality of Pure). The contents of dry matter and soluble solids were analyzed in fresh berries, and the contents of sugars and sorbitol were analyzed both in fresh berries and in berries after freezing and thawing of 13 different cultivars of rowanberries and one black chokeberry. For determination of the soluble solids content, the refractometric method was used, and for determination of the glucose, fructose, sucrose and sorbitol content, high performance liquid chromatography was used. The results showed that rowanberries and chokeberries contained 3.24-7.24 g 100 gE-1 of sorbitol which was the dominant compound in all investigated berries. The highest content of sorbitol was found in the wild rowanberries and rowanberries Sorbus aucuparia var. sibirica, but fruits of rowanberry×pear 'Alaya Krupnaya' contained the least content of sorbitol. After freezing and thawing of berries, the content of sugars and sorbitol were decreased by 5-23% with some exclusion.

The major sugars in six cultivars grown in Latvia are analysed. The content of glucose, fructose and sucrose in strawberry, blackcurrant and redcurrant berries was determined by applying the method of high performance liquid chromatography (HPLC). By using the obtained calibration curves, concentrations of diverse sugars were found in the analyzed samples. Fructose or fruit-sugar, the same as glucose, is mainly the source of energy in the human body though it is decomposed faster and easier than glucose. In all the researched berry cultivars, the amount of fructose was the largest, particularly in blackcurrants. Six strawberry, black- and redcurrant cultivars were evaluated as raw materials for industrial production. The investigation involved chemical and sensory analyses of fresh berries. The results indicate that pH and sugars of fresh berries influence their quality. Furthermore, high level of sugar adversely affects taste stability. Taste degradation in berries is parallel to flavour deterioration. It is concluded that the main emphasis should be given to the properties of fresh berries.