No abstract

Abstract. Every kind of honey is a very precious natural product which is made by Mellifera bees species. The chemical composition of honey depends on its origin or mode of production. Honey consists essentially of different sugars, predominantly fructose and glucose. There are also nonsugar ingredients like proteins and amino acids, as well as some kind of enzymes, such as: invertase, amylase, glucose oxidase, catalase and phosphatase. The fact that honey is one of the oldest medicine known worldwide is remarkable. Scientists all over the world have been trying to improve analytical methods as well as to implement new ones in order to reaffirm the high quality of honey the benefits of which may be distracted or disturbed. There are many methods and popular analytical techniques, including as follows: mass spectroscopy and molecular spectroscopy (especially FTIR spectroscopy). The infrared spectroscopy technique is one of the most common analytical methods which are used to analyse honey nowadays. The main aim of the task was to use ATR-FTIR infrared spectroscopy to compare selected honey samples as well as typical sequences coming out from certain functional groups in the analysed samples.

The effect of heating at various temperatures (30, 40, 50, 60, 70 and 80 °C) on dynamic viscosity, colour, 5-hydroxymethylfurfural (5-HMF) concentration and diastase activity of raw rape honey were assessed. In fresh honey, moisture, ash, free acidity, pH and electrical conductivity averaged 185.3 g kg(-1), 1.2 g kg(-1), 18.71 mEq kg(-1), 4.2 and 0.25 mS cm(-1), respectively. Heating significantly (p ≤ 0.05) increased lightness (L*), yellowness (b*), chroma (C*), hue (h°) values, but decreased redness (a*). The viscosity at 20 °C (33.6 Pa s) differed significantly (p ≤ 0.01) with those at 30, 40 and 50 °C (8.2, 2.5, and 1.6 Pa s, respectively). Diastase activity decreased concomitant with heating at higher temperatures. Honey heated at 80 °C for 15 min showed the maximum increase of 5-HMF content, with an average of 1.9 mg kg(-1) (62 %), compared to unheated samples. Heating for 15 min between 50 °C and 80 °C did not significantly degrade the quality of the honey, but, slightly enhanced formation of 5-HMF and reduced the diastase activity.

The physicochemical properties, colour characteristics and dynamic viscosity of fresh rapeseed honey (control, CON) and those stored for 18 months at room temperature (RT) or in freezer (FRO) were compared. The significant decrease of pH after storage was found. Honey stored at RT showed an increase of 5-hydroxymethylfurfural (HMF) (?543.0 %) and decrease of diastase activity (-24.4 %), while in FRO samples the decreasing course (-50.5 and -7.3 %, p [ 0.05) were found in comparison with CON samples (3.07 and 28.37 mg kg -1 ). The negative correlation between HMF content and diastase activity was found. The temperature of storage significantly influenced colour parameters, however, RT differentiated colour of honey to a greater extent (DE = 20.37) than FRO (DE = 8.07). The lightness (L*), hue (h°), whiteness index (WI) and colour intensity (ABS 450 ) of CON honey samples were similar to honey from FRO. The dynamic viscosity was significantly higher in honey stored in FRO in comparison to CON honey and honey stored at RT. However, in comparison with CON honey, higher (almost twice) viscosity for honey stored at RT was observed.

The milk obtained from six cow breeds (Polish Holstein‐Friesian Black‐White and Red‐White, Simmental, Jersey, Polish Red and Polish Black‐White) managed in the Lubelskie region and the Bieszczady Mountains was analysed. A total of 3618 milk samples collected between 2005 and 2008 were evaluated for the total solids content, percentage concentrations of fat, protein and lactose, and the freezing point: the mean milk freezing point was −0.538°C. The freezing point of milk was influenced by breed, successive lactations, lactation stage and the geographic region. In milk with a high urea concentration (over 300 mg/L), the increased apparent protein level caused a decrease in the milk freezing point values. The combined influence of geographic region and production season showed significant interactions for daily milk yield and total solids content (P < 0.01) and the milk freezing point (P < 0.05).