The partition coefficients (K ow) of benzoic acid and sorbic acid in systems of fish oil (sand eel)-water, fish oil-buffer solution, rape oil-water and olive oil-water were experimentally determined in a temperature range from 5 to 43°C and pH from 4.5 to 6.5°C. The dimerization of benzoic acid in fish oil-water system was observed at 25°C. Two modifications have been made to the Nordic Food Analysis Standard for the determination of sorbic acid by HPLC. The experimental results show that the K ow of benzoic acid and sorbic acid in fish oil-buffer system is ca. 100 times lower than that in fish oil-water system. The K ow values of benzoic acid and sorbic acid in fish oil and water system decrease with increasing system pH values. The partition coefficients of plant origin and fish origin oils are in the same order of magnitude even though their molecular structures are very different.

A method for estimation of the upper temperature limit of water loss by food systems during preservation (drying, baking, extrusion, smoking, etc.) is proposed. These temperatures are related to the lower and higher critical solution temperatures, which were shown to depend on the chemical structure of system components. A determination method for the lower and higher critical solution temperatures in the plasticization curves obtained by calorimetry was developed.

Glyphosate is used widely to control weeds. Glyphosate is a broad spectrum, non-selective, systemic and post-emergent herbicide. Glyphosate excessive use and impact on the environment is promoting the analysis of glyphosate in water, soil and food materials. Methods to analyse glyphosate at low levels are needed because glyphosate has a short half-life due to easy microbial degradation. Glyphosate has a high polarity and solubility in water, has high binding affinity with soil and is non-volatile. The absence of chromophoric groups in the molecular structure makes the detection difficult. Therefore, detection can be achieved by derivatisation, which makes glyphosate more volatile and stable for spectroscopic analysis. Derivatisation is commonly done by alkyl chloroformates, acylating agents, 9-fluoroenylmethylchloroformate, 4-methoxybenzenesulfonylfluoride and o-phthalaldehyde. Immunosensors allow detection at microlevels. Nanocrystals and nanotechnology allow detection at nanolevels. Here, we review methods to derivatise and analyse glyphosate.

In this paper we are concerned with adsorption, structure, topography, and dynamic properties (relaxation phenomena and surface dilatational rheology) of food dairy proteins (beta-casein, caseinate, and whey protein isolate, WPI), water-insoluble lipids (monopalmitin, monoolein, and monolaurin) and phospholipids (dipalmitoyl-phosphatidyl-choline, DPPC, and dioleoyl-phosphatidyl-choline, DOPC) at the air-water interface. Combined surface chemistry (surface film balance and static and dynamic tensiometry) and microscopy (Brewster angle microscopy, BAM) techniques have been used to determine the static and dynamic characteristics of these emulsifiers and their mixtures at the air-water interface. The derived information shows that biopolymer (proteins) and low-molecular-weight-emulsifier (LMWE, monoglycerides and phospholipids) type and their mixtures affect the interfacial characteristics of adsorbed and spread films. Important functional differences have been established between proteins, lipids and phospholipids. The static and dynamic characteristics of mixed films depend on the interfacial composition and the surface pressure (pi). At higher surface pressures, collapsed protein residues may be displaced from the interface by LMWE molecules with important repercussions on the interfacial characteristics of the mixed films.

A turn-on fluorescent chemosensor (H-1) for cyanide anions based on dihydroxy phenazine was designed and synthesised. The sensor H-1 exhibits high sensitivity and good selectivity for cyanide in pure water. The CN− response mechanism involves a hydrogen bonding and deprotonation process in the sensor, which induced prominent fluorescence enhancement. The detection limit of the sensor toward CN− is 5.65×10−7M, and other anions had nearly no influence on the probing behavior. In addition, test strips based on the sensor were fabricated, which also exhibit a good selectivity to CN− in water. Notably, this sensor was successfully applied to detect CN− in food samples, which proves a very simple and selective platform for on-site monitoring of CN− in agriculture samples.

The aim of this study was to determine thermal properties of pseudoplastic polysaccharides (guar gum, κ-carrageenan and xanthan gum) which find many applications as food hydrocolloids in food industry. There was an obvious relationship between thermal dependency of heats of fusion of hydrocolloids in powder form and activation parameters of hydrodynamic flow in solutions, respectively. Results of thermal analysis confirmed, that powder samples of hydrocolloids as typical foodstuffs of low moisture content less than 15 w% after room conditioning, exhibited varying ability to bind water as depending on their molecular structure. The peak temperature of the endothermic polysaccharide order-disorder phase transition process was found in the temperature range of 50–85 °C. It was influenced simultaneously by the applied heating rate and the samples moisture content. Studied samples moisture content was ranging between 9–40 w.% as was obtained after different conditioning. Observed reaction enthalpy (ΔH) associated with phase transition and water evaporation (proved by appropriate weight loss of the samples Δmw) was ranging from 140 to 670 J/g. Activation energy (Eₐ) of this process in powder samples was calculated from the kinetic parameters using three kinetic models developed by Friedman, Kissinger and model-free kinetics. The latter kinetic models were compared with the Arrhenius model, which was used to determine Eₐ of polysaccharide solutions on reflecting sensitivity of their molecular structure to the temperature and the solvent. According to the Arrhenius model, there were obtained the highest values of Eₐ for κ-carrageenan solutions, indicating the highest resistance of their molecular structure to temperature. This fact can be related to the observed the lowest value of the reaction enthalpy in the case of powder samples, suggesting that energy obtained during the order-disorder transition to change the carrageenan powder structure is limited. On the other hand, xanthan gum was the least temperature dependent sample; activation energy of xanthan solutions was only in the range of 2–6 kJ/mol. Concurrently, ΔH of xanthan powder was determined as the largest of all samples under study. In general, there was found an indirect relationship between activation energy of the solutions determined by viscometry and reaction enthalpy of the powders determined by thermal analysis. Results of the Arrhenius model also indicate that the energy necessary to promote viscous flow of solutions is higher for hydrocolloids in distilled water rather than in 0.07 M KCl aqueous solutions, suggesting the suppression of the polyelectrolyte effect. In both cases, Eₐ was substantially reduced by application of higher shear rate.