The aim of this research was to compare the commercially available kvass concentrate to the kvass extract which was experimentally produced from the naturally fermented kvass. Dry matter was determined according to the standard ISO 2173:2003, active acidity-ISO 10523:2012, and apparent viscosity was measured with a DV-III Ultra Brookfield rheometer, using a spindle SC4-18 with the speed 50 rpm at 26.9 °C. Sugars were determined using high-performance liquid chromatography. The sensory evaluation of kvass drinks (recombined kvass concentrate and extract) was performed according to the ISO 4121:2003. The dry matter content in the kvass concentrate (Ltd. Ilgzeem) was 69 %; it was diluted with distilled water to the dry matter content 32.4 ± 0.2 % of kvass extract (made from Ltd. Liepzeme kvass). Active acidity in the kvass concentrate was significantly (p = 0.012) lower (pH 2.86) than in the kvass extract (pH 4.18). Apparent viscosity in the kvass extract was 13.68 mPas and in the kvass concentrate 5.22 mPas. Major sugars in the kvass extract were fructose and glucose and in the commercial kvass concentratefructose. Hedonic evaluation showed that there were no significant differences (p > 0.05) in the preference of kvass drinks. The intensity of aroma, flavour and acidity was significantly more pronounced in the kvass drink made from the commercial kvass concentrate.

Naturally fermented rye bread kvass is a seasonal product with a pronounced rye bread flavour having the highest demand during hot summer days. However, non-pasteurised and non-filtered kvass has a very short shelf-life. There are numerous benefits of drying to extend kvass shelf-life, however it can have a significant influence on the product composition and quality. The aim of this research was to assess and compare nutritional value, vitamins, sugars and aroma volatiles in naturally fermented and spray dried kvass. Naturally fermented non-pasteurised, non-filtered bread kvass was used to produce dry kvass at the University of Warmia and Mazury in Olsztyn, Poland. Maltodextrin was used in 25% quantity to kvass dry matter in order to aid the spray drying process. Nutritional value of liquid kvass (7% solids) and dry kvass (powder, 93% solids) was determined according to EU Regulation 1169/2011, B vitamins -according to AOAC 986.27 (B1), AOAC 970.65 (B2) and AOAC 961.14 (B3). Content of sugars was determined using high performance liquid chromatography, whereas aroma volatiles were assessed using solid phase microextraction in combination with gas chromatography/mass spectrometry. Drying process had a significant influence on the content of B vitamins in kvass; the highest decrease was observed for niacin (vitamin B3). The content of major sugars was lower in dry kvass based on the dilution by the addition of maltodextrin. Totally 26 different volatile compounds were detected in liquid and dry kvass, total values of peak areas were significantly lower in dry kvass (p<0.05).

Fermented products have gained worldwide popularity for their nutritional and health aspects. Many studies have been done on this topic, including fermented cabbage (sauerkraut). Yet little or no studies are done on evaluation of fermented cabbage juice which is considered as by-product of sauerkraut production, still rich in bioactive compounds. In order to reduce food waste, sustainable solutions are being searched for to preserve valuable fermented cabbage juice. The aim of this study was to evaluate chemical and physical composition of concentrated fermented cabbage juice and their changes after storage. The fermented cabbage juice was concentrated on falling film evaporator from 9.2 till 34.3 °Brix. Physio-chemical (moisture, pH, total soluble solids, total phenol content, antiradical activity by DPPH and ABTS+, ascorbic acid, total sugar profile, nitrates and minerals) and microbiological (lactic acid bacteria, total plate count) analyses were carried out. Concentrated fermented cabbage juice is a source of minerals and phenol compounds as well as salt substitute in food applications. After 6 months of storage there is significant degradation of ascorbic acid but total phenol content is not affected. The evaporation process did not inhibit microbiological activity; as a result, there is a decrease in lactic acid bacteria but increase in total plate count.

Promocijas darba KOPSAVILKUMS Dr. sc. ing. zinātniskā grāda iegūšanai SUMMARY of the Doctoral Dissertation for the scientific degree of Dr. sc. ing.