Birch and maple saps contain carbohydrates and organic acids, B complex vitamins and vitamin C, tannins, flavonoids, glycosides and mineral substances. The aim of the study was to quantitatively determine the concentrations of bioactive compounds and mineral substances in Latvian birch (Betula pendula Roth.) and maple (Acer platanoides L.) saps. Electrical conductivity was determined (629 and 967 S/cm in birch and maple saps, respectively) to characterise the total amount of mineral substances. In birch and maple saps the titratable acidity (0.50 and 0.70 mmol of NaOH per litre of sap, respectively) and formol number (0.25 and 0.20 mmol NaOH per litre of sap, respectively) were determined. The protein concentration was found to be higher in maple sap (171 and 127 mg/l, respectively). The antioxidant concentration, determined using quercetin as a standard, was 0.35 mg of quercetin equivalents (QE)/l in birch sap and 0.77 mg QE/l in maple sap. In conclusion, Latvian maple sap contains more bioactive and mineral compounds than birch sap. Latvian birch sap contains up to 20% more glucose and fructose than birch sap produced in Finland, but Latvian maple sap contains 10 to 40% less sucrose than sap produced in North America.

-Fructose is the dominant monosaccharide in bilberry juice and red bilberry juice, but glucose is dominant in the cranberry juice. Dominant polyphenols are catechine and chlorogenic acid. In the bilberry and red bilberry juices, the most common acids are citric, quinic and tartaric acids, in the cranberry juice -citric, quinic and malic acids. When bilberry juice is heat-treated for 30 min at 98 C  1 C, HMF content is 2-fold higher than in samples treated at 60 C  1 C. In solutions from lyophilisates of wild berry juice, turbidity and translucent coloration have been determined.

Ceramics are widely used as kitchen ware. Pottery in contact with food can be a source of various compounds from clay and glazing. The potential migration of toxic lead and cadmium from ceramic is well-known and is evaluated by the specific maximum migration levels (acceptable limits being set by the Food Contact Materials Regulation (EC) 1935/2004). Besides lead and cadmium other elements have been detected in glazed ceramic ware that could migrate during food processing. Migration experiments were performed on 10 commercially available glazed and unglazed stewing potteries (produced in Latvia and China). The migration of iron, aluminium, calcium, magnesium and silicon from the ceramics was carried out in 4% (v/v) acetic acid water solution (24, 48 and 72 h at 20 C; 30, 60 and 90 min at 180 C). The concentrations of elements which had migrated into the test solutions were measured by absorption spectrometry (Fe, Al and Si) and titration (summary Ca and Mg). The migration of iron, aluminium, calcium, magnesium and silicon was observed in all tested ceramics samples. Overall, the migration of studied elements was higher in unglazed stewing potteries and increased with temperature. Migration was decreased in repeatedly used ware.

Oxidation of fats and oils reduces the nutritional value of food and causes various health problems. The addition of antioxidants prevents the oxidation of fats in the food. The antioxidant activity of antioxidants represents the ability to inhibit the process of oxidation. The antioxidant activity of herbal extracts has usually been assessed in a linoleic acid emulsion system. The aim of the present study was to evaluate inhibition of conjugated diene formation in Latvian linseed oil. Ethanol extract of the calyx of Hibiscus sabdariffa L., vanillin, α-tocopherol and 2,6-di-tert-butyl-4-methylphenol as additives were compared for their antioxidative activity. The samples of linseed oil with additives were incubated for 24 h at 60 °C and then analysed using UV spectrophotometry (λ = 234 nm). The antioxidant activity of additives was characterised by the percentage of formation of conjugated dienes. The ability of additives to inhibit oxidation in linseed oil decreases as follows: vanillin, 2,6-di-tert-butyl-4-methylphenol and α-tocopherol. Our results indicate that linseed oil can be used to test antioxidative activity of substances.