Jelena Miocinovic

Improved solvent extraction procedure and high-performance liquid chromatography-evaporative light-scattering detector method for analysis of polar lipids from dairy materials

A normal-phase high-performance liquid chromatography-evaporative light-scattering detector method employing dichloromethane, methanol, and acetic acid/triethylamine buffer as the mobile phase was developed for analysis of polar lipids (PLs). This method was applicable for analysis of PLs from both dairy materials and soy lecithin. All of the PLs of interest such as glycolipids, phospholipids, and sphingomyelin were well separated with a total run time of 22.5 min and without necessitating the removal of neutral lipids beforehand. Peak retention times were stable, and the method was reproducible. In this study, a modified method of using solvents for extraction of PLs from dairy matrices was also investigated. The modified method offered higher extraction efficiency, consumed less time, and in some cases saved solvent use.

Feasibility of discrimination of dairy creams and cream-like analogues using Raman spectroscopy and chemometric analysis

Dairy cream and its analogues with sunflower oil, coconut oil and palm oil in different milk fat/vegetable fat ratios were prepared and analysed using Raman spectroscopy. The linear discriminant analysis was conducted in order to classify the samples. Samples were well separated and displayed distinguishing linear arrangement along the principal component that expressed the variation in lipid unsaturation. Good separation of sunflower oil and milk fat samples was obtained in contrast to the samples with coconut and palm oil, where the substantial overlapping occurred. The method permitted classifying of the samples in terms of the type of fat used. Calibrated model was extremely sensitive (100%) for dairy cream. The results indicated that it is possible to consider the Raman spectroscopy coupled with chemometric analysis as a rapid way for the detection of dairy cream adulteration with sunflower, coconut and palm oils.

The aflatoxin M1 crisis in the Serbian dairy sector: the year after

ABSTRACT During the last 3 years, high aflatoxin M1 (AFM1) concentrations in milk and dairy products occurred in Serbia. It resulted in periodical change of the official regulations regarding maximum levels (MLs) of AFM1 as set by the Serbian Government. The aim of this study was to compare the occurrence of AFM1 in raw milk and dairy products during 2015 and also to determine whether there were some differences in AFM1 level among seasons. The AFM1 level exceeded the European Union ML in 29.3% of raw milk and 4.2% of milk product samples. The highest level of AFM1 in raw milk was found during the autumn season, while during the rest of the 2015, it was significantly lower. Although the improvement of dairy products safety was evident in 2015 when compared to 2013 and 2014, the cause of high concentrations in raw milk remained unresolved yet. This study indicates that dairy plants introduced control measures and refused reception of too high contaminated raw milk.

A comparison of composition and emulsifying properties of MFGM materials prepared from different dairy sources by microfiltration

Milk fat globule membrane (MFGM), due to its specific nature and composition, is known as material possessing advantageous nutritional as well as technological properties. In this study MFGM materials were produced from several dairy sources such as buttermilk (BM), butter serum (BS) and buttermilk whey (BMW) by microfiltration (MF). The obtained materials, depending on the sources, were called BM-MFGM, BS-MFGM and BMW-MFGM, respectively. The compositions of starting materials and the isolated MFGM materials as well as their emulsifying properties were analyzed and compared. As expected, the MF resulted in enrichment of polar lipids (PLs), major components of MFGM. On dry matter basis, BM-MFGM and BS-MFGM were about 2.5 times higher in PLs compared to their beginning materials while BMW-MFGM was about 8.3 times compared to buttermilk powder (BMP). Sodium dodecyl sulfate polyacrylamide gel electrophoresis showed that the microfiltered products still contained a high amount of non-MFGM proteins such as caseins, β-lactoglobulin, and α-lactalbumin. Emulsions of 35% soya oil in water were prepared with the mentioned materials using a homogenizer at various pressures. Generally, emulsions prepared with BMP and butter serum powder had significantly higher particle sizes than those prepared with the MFGM materials. This result along with microscopy observation and viscosity measurement indicated the presence of aggregated particles in the former emulsions, probably as a result of lack of surface-active components. The differences in composition, especially in content of PLs and proteins of the materials were the main reasons for the differences in their emulsifying behaviors.

Organic and conventional milk – insight on potential differences

Purpose The purpose of this paper is to investigate if there is a difference in hygiene parameters of raw milk produced in organic and conventional farm of similar size. In parallel, the aim was to determine if there are differences in pasteurized organic and conventional milk samples delivered on the market. Design/methodology/approach Raw milk samples were analyzed for aerobic colony count (ACC), somatic cell count (SCC), acidity, temperature, fat and protein content. On the other side, final products of organic and conventional pasteurized milk with 2.8 percent declared milk fat were analyzed for Raman spectroscopy, color change and sensorial difference. Findings Results of raw milk analysis showed statistically significant differences in fat content, SCC, acidity, temperature and ACC (p<0.05). It is of note that ACC for organic milk were lower for approx. 1 log CFU/ml compared to conventional milk samples. Pasteurized organic milk samples had a significantly higher L* value than those samples originating from conventional farms, indicating that organic is “more white” compared to conventional milk. According to the results of triangle test, with 95 percent confidence no more than 10 percent of the population is able to detect a difference. Research limitations/implications A limitation of this research is the fact that good veterinary practices at farms, namely, animal health and adequate usage of medicine for treating the animals, animal welfare and animal feeding were not analyzed. Originality/value This study analyzed potential differences in organic and conventional milk at two important production stages of the milk chain – at receipt at dairy plant (raw milk) and perceived by consumers (final product).

Traditional and Emerging Technologies for Autochthonous Lactic Acid Bacteria Application

Autochthonous strains of lactic acid bacteria, isolated from traditional cheeses, may be used as starter cultures in order to standardize the quality of traditional cheeses and/or as potentially beneficial bacteria, allowing the creation of new functional products. In addition to their good technological and biochemical properties, probiotic strains have to meet the criteria that include the Generally Recognized as Safe status, stability and activity/survival in the gastrointestinal tract (GIT) conditions as well as the health effects tested in in vitro and in vivo conditions. Some lactobacilli isolated from traditional Serbian cheeses have shown great tolerance to low pH and high bile salts concentration indicating their potential probiotic ability. In order to preserve the desirable properties of probiotic bacteria, it is necessary to apply the appropriate techniques for their preparation and storage. Different encapsulation techniques such as extrusion, emulsion, drying and spray-coating technique are available in order to achieve better viability and target delivery to GIT. Autochthonous potential probiotic strains (Lactobacillus paracasei 08, Lactobacillus plantarum 564) survived well the spray-drying process indicating that this microencapsulation technique could be a cost-effective way in protection of these strains. Screening and incorporation of new autochthonous potentially probiotic strains in different cheeses provides an opportunity to improve the healthy status and quality of the final products with desirable properties, considering their positive influence on the flavor of cheeses, in particular, low-fat and low-salt cheeses, goat cheeses, etc.