Volume 30 (2013): Edition 1 (December 2013)

Highbush blueberries are a relatively new crop in Latvia raising interest in farmers who wish to diversify their commercial horticultural activities. It is considered that soil properties are one of the possible shortcomings limiting establishment of high-productive plantations in areas where soil reaction is close to neutral. The research objective was to test the main soil characteristics in a commercial highbush blueberry plantation where initial soil properties were changed as a result of soil modification (deep tillage, peat additions) before planting of bushes and afterwards maintained (mulching with acid peat and sawdust) periodically. The research was carried out in 2011 - in a farm where the blueberry plantation had been established seven years ago. The experimental plots were arranged on a complex slope, by choosing different parts of terrain. Soil - Haplic Cambisol, sandy loam, formed on a low calcareous moraine. Original topsoil’s reaction was pH KCl 5.37. Five experimental plots, each consisting of seven bushes, were set up. Research showed that modification of topsoil significantly changed the physical and agrochemical properties of soil. Soil bulk density reduced, porosity and soil aeration increased. Sphagnum peat (pH KCl 3.0) as a soil modifier allowed efficiently reducing the soil reaction at the soil root zone and provided an optimal environment for blueberries. Soil properties were not the determinant factor that limited establishment of a productive blueberry plantation. Soil properties adjusted accordingly to the requirements of highbush blueberry gave the possibility of establishing plantations also in typical mineral soils that develop on a low calcareous moraine.

The main purpose of the present research was to investigate the changes in physical-chemical parameters of fresh Latvian cranberries during storage. Cranberry (′Steven′, ′Bergman′, ′Pilgrim′, ′Early Black′, and ′Ben Lear′) fruit were collected at a processing plant in Kurzeme region, Latvia, in the first part of October 2010. For the experiments, also wild cranberries were collected in the bogs of the same region and at the same time. The berries were rinsed with tap water for 3±1 min, then strained for 10±1 min (mainly for visual cleanness), and afterwards stored in closed non-perforated polypropylene (PP) boxes in air ambiance and in glass jars in a cold boiled-water ambiance at 3±1 °C. Quality parameters of the berries were tested each three months using standard methods: vitamin C content - by high-performance liquid chromatography (HPLC); organic acids - by HPLC; moisture - by oven-dry method; colour parameters - by device COLOR TEC PMC; pH - by potentiometric method; anthocyanin - by spectrophotometrical method; and phenolic compounds - by HPLC. The shelf life of cranberries packaged in closed PP boxes in air ambiance was six months, but of cranberries packaged in glass jars in water ambiance - 12 months. The research showed that differences in moisture content, pH value, colour intensity, and anthocyanin content among the cranberry cultivars under different ambient conditions during storage were not significant. During 12 months of cranberry storage in glass jars in water ambiance, the content of vitamin C decreased on average by 90%, organic acids - by 54%, and phenolic compounds - by 60%. During six-month storage in closed PP boxes in air ambiance, the content of vitamin C decreased on average by 99%, organic acids - by 30%, and phenolic compounds - by 34%.

The aim of the present research was to summarize the results of investigations carried out on the influence of different biodegradable polymer packaging materials on the shelf life and quality of several food products during storage. In Latvia, most of consumers consider that polymers as a material for food packaging are overly used, and they support the idea of introducing new eco-friendly food packaging. Biodegradable films were investigated for their ability to extend the shelf life of apple salad and minimally processed shredded carrots stored at 4 °C. It was found that they can guaranty the same as or even a longer shelf life than that provided by conventional polymer films. Bio PLA transparent films, thermoformed PLA containers, and cellulose-based films were tested for fresh produce packaging. Ceramis®-PLA-SiOx barrier coated films were tested for their influence on the quality of food products - rye bread, apple-black currant marmalade candies, and soft cheese Kleo - during storage. PLA and PHB films showed satisfactory results for packaging of perishable foods - salad with meat in mayonnaise. Ceramis®-PLA-SiOx films were used for vacuum packaging and also for mild thermal treatment (Sous vide) of soft cheese, providing its prolonged shelf life. Some BoPLA films specially envisaged for packaging of confectionery were tested for milk pomade sweet - sherbet - packaging. Its quality was evaluated mainly by moisture content and by changes in hardness during storage. The results suggest that biodegradable packaging materials can be a successful alternative to the conventional polymers for packaging of several food products, which could provide an essential contribution in reducing the environmental pollution.

Beer is a complex mixture - over 400 different compounds have been characterized in beer. Significant health and product quality promoting benefits have been attributed to its bioactive secondary metabolites such as phenolics. Polyphenols and phenolic acids present in beer are natural antioxidants. The aim of the research was to characterize the bioactive compounds in Latvian barley beer, such as phenolic acids and flavanols. In an experiment, different lager-type beers produced in Latvia were analysed. The total phenolic content was determined spectrophotometrically according to the Folin-Ciocalteu colorimetric method and expressed as gallic acid equivalents. Individual phenolic compounds were determined using high performance liquid chromatography (HPLC). The antioxidant potential of beer was analyzed by the 2,2-diphenyl-1-picrylhydraziyl (DPPH) radical assays and expressed as micromoles of Trolox equivalents. The research showed that the total phenolic content of dark beer samples (320.8-863.6 mg GE L-1) was mostly higher than that of the light beers (300.9-475.2 mg GE L-1). In total, eleven phenols were determined in the analysed samples. Also the sum of individual phenolics in dark beer samples was higher than in the light beer brands. All beer samples exhibited a strong DPPH radical scavenging activity: from 441.3 to 1064.2 μmol TE L-1 for the light beer samples, and from 726.2 to 1748.7 μmol TE L-1 for the dark beer. The research suggests that composition of beer phenolic compounds was not dependent on the type of beer - light or dark.