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Undesirable thermal processes or storage conditions lead to physical and chemical quality loss of every food. The objective of this study was to determine the total solid content, starch, reducing sugars, nitrates and nitrites in raw and thermal processed red and white potato samples purchased from different geographic origin in Croatia. The potatoes were processed with and without the skin, and cooking processes were carried out in classic way, in the pressure cooker and in the microwave oven. Standard methods of analysis for above-mentioned parameters were used. The results showed no significant influence (P < 0.05) of the geographic origin on investigated parameters in raw samples (except for nitrates), but there were significant differences (P < 0.05) in composition between the kinds of samples (red and white). Thus, samples of white potato had higher total solids, starch and reducing sugars content than red potato samples, while red potatoes had higher nitrites and nitrates content. Thermal treatment showed that the total solid content is higher in potatoes processed with skin then those processed without the skin. The starch content in both kinds of potatoes increased after thermal processes if potato was processed without skin. The content of reducing sugars was the highest in samples of raw potato. The nitrites and nitrates content were decreasing during thermal treatments. Thermal processing (classic way, under pressure or with microwaves) and the manner on which the potatoes were cooked (with or without skin) significantly influenced on all investigated parameters especially in red potatoes samples.

The purpose of this study was to investigate the possibility of monopotassium salt of 2,5-dimercapto-1,3,4-thiadiazole (DMTD) as potential inhibitor of enzymatic browning of fresh-cut fruits and vegetables. The synthesis of monopotassium salt of 2,5-dimercapto-1,3,4-thiadiazole is presented. The oxidation of phenolic compounds, chlorogenic acid (CA) and 3,4-dihydroxy phenilalanine (L-DOPA), catalized by mushroom polyphenol oxidase (PPO), was investigated in the presence of DMTD. Also DMTD was evaluated on the cut surface of apples (Jonagold variety), as browning inhibitor. Inhibition of PPO activity in model solutions of phenolic compounds was measured by spectrophotometer, and the enzymatic discoloration on the cut surface of apples was measured by the tristimulus colorimeter. DMTD was effective as an inhibitor of oxidation of phenolic compounds used in assay as well as inhibitor of browning on cut surfaces of apples. For the comparison, as inhibitors of enzymatic browning, ascorbic acid (AA), and benzoic acid (BA) were used too.

Acetaldehyde, diacetyl and ethanol are compounds that are critical to the aroma and flavour of fermented milk products. In this work twelve commercial brands of plain yogurt were stored within 10 days on two different temperature levels and every two or three days changes in acetaldehyde, diacetyl and ethanol were established. At the same time sensory evaluation was carried out too. The aim of the study was to investigate the relationship between sensory evaluation and acetaldehyde, diacetyl and ethanol, in the term of linear regression. Expert panel ˘s ratings were regressed against concentrations of aroma compounds for both temperature levels and linear relationship among them were determined. Consequently very accurately predicting equations were obtained using regression analysis. Coefficients of correlation were generally high (from -0,8164 to -0,9990). The most pronounced relationship expressed as correlation coefficients between expert panel ˘s ratings and contentrations of each individual compounds was observed with ethanol (r = -0,9990 ) in yogurt sample stored at +4 0C. The least linear correlation coefficient have been obtained between expert panel ˘s ratings and diacetyl (r = -0,8164) in sample stored at +20 0C.

Wheat quality is a complex trait. The value of each parameter can be expressed mathematicaly as an index. By using indexes, all quality parameters show certain interrelationships. Forty various flours of winter wheat were tested. The results of the investigation have shown that yiled of bread can be evaluated by parameters of chemical and physical characteristic of protein and starch. Volume of bread and quality of crumb of bread can be evaluated by rheological properties of dough.