No abstract

Honey adulteration is a topical issue because increasingly sophisticated adulteration methods are constantly being developed and the official (legislative) determination of the quality indicators of honey is unable to detect most methods of honey adulteration. In addition, while the popularity among consumers is constantly growing, the worldwide production of honey is unstable. The aim of this review was to provide a current overview of methods suitable for the detection of individual methods of adulteration. Bee product, NIR, HPLC, isotope analysis

In this study, the origin and pathways of detoxication of ammonia in the body of fish are analysed. Ammonia is toxic for an organism even in trace amount. The role of direct deamination of amino acids such as histidine, serine, asparagine and glutamine is emphasized with regard to ammonia production, the functional association of transamination and deamination is reflected in a transdeamination reaction, where the central role is played by the enzyme glutamate dehydrogenase. Furthermore, less known sources of ammonia occurring during natural restoration of body cells and tissues are discussed. Particularities of biochemical processes in fish, such as the non-existence of ureosynthetic cycle along with a sudden change of environmental conditions can easily disturb the balance between production and excretion. If the detoxication abilities of fish are exceeded, ammonia acts as a toxicant, thus leading to accidental mortalities of fish.

The aim of the study was to obtain the physicochemical characteristics and the content of Cd, Pb, Hg, Cu and Zn in three groups of honey (blossom, blends and honeydew). Physicochemical constituents were examined according the European Honey Commission recommended methods and heavy metals were determined by atomic absorption spectrometry. Among the groups of honey significant differences in the amount of mineral substances, pH, electrical conductivity (P < 0.01) and free acidity (P < 0.05) were found. Differences were not found in water content and insoluble matter. The average concentration of hydroxymethylfufural (HMF) and sucrose varied in individual groups of honey, however, these differences were not statistically conclusive. Concentrations of risk elements (Cd 0.5-77.4 µg/kg, Pb 0.02-1.0 mg/kg, Hg 0.67-2.93 µg/kg, Cu 0.06-1.55 mg/kg and Zn 0.2-22.9 mg/kg) were far below the allowable limits and showed statistically significant differences (P< 0.01) for Cd, Hg Cu in the individual groups of honey. The content of Pb and Zn did not differ significantly in individual groups, however, significant correlations between HMF and Pb (r = 0.63, P < 0.05) and HMF and Zn (r = 0.5, P < 0.05) were found.

Cholesterol concentrations in goat milk, goat milk cheeses, ewe’s milk, ewes milk cheeses, dairy bioproducts, and concentrations of cholesterol, stigmasterol and sitosterol in butter, butter with added vegetable fats and margarines were evaluated by RP HPLC method. Parallel analyses by capillary GC were performed. Prior to the final chromatographic analyses the saponification step was used, followed by the extraction of the unsaponificable residue into <I>n</I>-hexane. Parameters of RP HPLC method were compared with parameters of GC determination. The detection limits (LOD) determinated on the bases of blank samples analysis were 5.2 mg/kg for cholesterol, 4.8 mg/kg for stigmasterol and 14.7 mg/kg for sitosterol. Recovery ranged between 80–92%, repeatibility expressed as RSD of 12 parallel samples measurements was 4.2–6.8%. Accuracy tested on the SRM 1845 Whole Egg Powder (NIST) was 95.7%.

The aim of this study was to evaluate the effects of temperature and storage time on the formation of biogenic amines (BAs) in the traditional Czech curd cheese (Olomoucké tvarůžky). Samples were stored for 7 weeks at 5 °C and 20 °C. BAs were studied as dansyl derivatives by the RP-HPLC method with fluorescence detection, histamine was determined using a photodiode array detector. Physical and chemical properties were analyzed as specified by the Czech National Standard, as were the sensory characteristics (colour, odour, texture and flavour). The major amines found were cadaverine (124-2 413 mg·kg -1 ) and tyramine (117-1 058 mg·kg -1), followed by putrescine (75-767 mg·kg -1) and histamine (74-411 mg·kg -1 ). Low concentrations of tryptamine, spermine and spermidine were present. Total concentrations of BAs significantly increased with storage time (P  0.01), depending significantly on temperature (P  0.01). Total BAs in cheese stored at 20 °C compared to 5 °C were more than three times higher, reaching 4 600 mg·kg −1 at the end of storage. The toxicologically critical value of 900 mg·kg −1 for the sum of histamine + tyramine + putrescine + cadaverine was reached 17 days later in the cheese stored at 5 °C compared to 20 °C. When stored at 5 °C, the samples retained adequate sensory characteristics for the entire safe storage time. The effects of storage conditions on BAs formation are relevant to reducing the risk associated with consumption of cheese high in BAs.

ABSTRACT:The freezing point (FP) was established in 48 bulk tank samples of raw and 48 samples of pasteurized goat milk that were collected in the course of lactation. Alongside, non-fat solids (NFS) content was monitored. Milk freezing point measurements were carried out using the thermistor cryoscope method in compliance with the standard CTS 570538 (1998). The mean freezing point of raw milk was found to be in an interval of -0.5513 ± 0.0046°C, variation ranged from -0.5466°C to -0.5567°C, with higher values in the spring months and a drop at the end of lactation. FP corresponded to the NFS content. The average freezing point of goat milk heat-treated on the farm to the temperature of 72°C over a period of 20 s was -0.5488 ± 0.0046°C, pasteurisation brought an average increase in FP by 0.0025°C.

The aim of this study was to assess the quality of raw cow's milk from an automatic milking system. Samples of milk (48) were analyzed chemically and microbiologically and the somatic cell count, freezing point and inhibitor residues were determined. For comparison purposes, milk analysis data from two farms using conventional machine milking and 2008 milk analysis report data for the Czech Republic were used. All physical and chemical characteristics of the study samples were within the established limits