Predrag Pudja

Effect of milk protein standardization, by ultrafiltration, on the manufacture, composition and maturation of Cheddar cheese

Skim milks were pre-acidified to pH 6·4 and concentrated by ultra-filtration to give retentates with protein levels of 210 g/1. Retentates were blended with skim milk and cream to give standardized milks with protein levels ranging from 30 to 82 g/1. These were used for the manufacture of Cheddar cheese in conventional equipment. Increasing milk protein level resulted in reduced gelation times, increased curd firming rates and a decrease in the set-to-cut time when cutting at equal firmness values (i.e. elastic modulus, G′, ∼ 16 Pa). As the curd firming rates increased with milk protein level, it became increasingly difficult to cut the curd cleanly, without tearing, before the end of the cutting cycle. Reflecting the tearing of curd, and consequent curd particle shattering, fat losses in the running wheys were greater than those predicted on the basis of volume reduction (due to ultrafiltration) for milks with protein levels > 50 g/1. Reduction of setting temperatures, in the range 31–27 °C, and the level of added rennet brought the set-to-cut times and curd firming rates of concentrated milks closer to those of the control milk. While increasing milk protein level in the range 30–70 g/1 had little effect on cheese composition, it resulted in slower proteolysis and maturation.

Rennet coagulation properties of retentates obtained by ultrafiltration of skim milks heated to different temperatures

Skim milks were heated at temperatures ranging from 72 °C × 15 s to 100 °C × 120 s to give levels of whey protein denaturation (WPD) varying from ∼1 to 70%. The different milks were then ultrafiltered to yield retentates with protein levels ranging from ∼3 to 19%. Rennet was added on a volume basis and the coagulation properties of renneted retentates measured by low amplitude oscillation rheometry. n nFor all heat treatments, the shear storage modulus, G′, increased more than proportionally with protein concentration (P), i.e. G′ ∞ Pn, where n ∼ 2, at times ⪢3600 s. A similar trend was noted for curd firming rates, with the power law index being ∼2.4. On heating under normal pasteurization conditions, i.e. 72 °C × 15 s, gelation time increased slightly with protein concentration. At the higher heat treatments, gelation time decreased markedly with protein concentration (especially at levels of WPD ∼70%), and approached those of the normal pasteurized milk at protein levels of 12–18%, depending upon the heat treatment and gel time definition.

Composition, microstructure and maturation of semi-hard cheeses from high protein ultrafiltered milk retentates with different levels of denatured whey protein

Abstract Standardized milks, heated at 72–100 °C to denature ~5–63% of the whey protein, were ultrafiltered to yield retentates with protein and fat levels of ~18.5 and 14%, respectively. Retentates were converted into semi-hard cheeses using specialized coagulation and gel-cutting equipment, with scalding and further syneresis being carried out in conventional cheese vats. High heat treatment of milk necessitated an increase in set temperature, a reduction in set pH and higher scalding temperatures in the cheese vat. Cheese from milk heated at 72 °C for 15 s had a mean composition of ~39.8% moisture, 28% protein, 45.1% fat-in-dry matter, 3.5% salt-in-moisture ( S M ) and an ex-brine (1 day) pH of 5.27. Increasing levels of whey protein denaturation (WPD) resulted in cheeses having higher moisture, S M , and whey protein levels, lower ex-brine pH values and lower rates of pH increase during a 182-day ripening period. Cheeses with high levels of WPD also showed poorer curd fusion and lower yield (fracture) values during ripening. Higher levels of denatured whey protein in cheese were associated with a higher degree of primary proteolysis. However, the levels of small peptides (

Textural and cooking properties and viscoelastic changes on heating and cooling of Balkan cheeses

The growth in food service and prepared consumer foods has led to increasing demand for cheese with customized textural and cooking characteristics. The current study evaluated Kačkavalj, Kačkavalj Krstaš, and Trappist cheeses procured from manufacturing plants in Serbia for texture profile characteristics, flow and extensibility of the heated cheese, and changes in viscoelasticity characteristics during heating and cooling. Measured viscoelastic parameters included elastic modulus, G, loss modulus, G″, and loss tangent, LT (G″/G). The melting temperature and congealing temperature were defined as the temperature at which LT=1 during heating from 25 to 90°C and on cooling from 90 to 25°C. The maximum LT during heating was as an index of the maximum fluidity of the molten cheese. Significant variation was noted for the extent of flow and extensibility of the heated cheeses, with no trend of cheese type. As a group, the Kačkavalj cheeses had relatively high levels of salt-in-moisture and pH 4.6-soluble N and low protein-to-fat ratio and levels of αs1-CN (f24-199). They fractured during compression to 75%; had relatively low values of cohesiveness, chewiness, and springiness; melted at ~70 to 90°C; reached maximum LT at 90°C; and congealed at 58 to 63°C. Conversely, the Kačkavalj Krstaš and Trappist cheeses had low levels of primary proteolysis and salt-in-moisture content and a high protein-to-fat ratio. They did not fracture during compression, had high values for cohesiveness and chewiness, melted at lower temperatures (56-62°C), attained maximum fluidity at a lower temperature (72-78°C), and congealed at 54 to 69°C. There was a hysteretic dependence of G and LT on temperature for all cheeses, with the LT during cooling being higher than that during heating, and G during cooling being lower or higher than the equivalent values during heating depending on the cheese type. Monitoring the dynamic changes in viscoelasticity during heating and cooling of the cheese in the temperature range 25 to 90°C provides a potentially useful means of designing ingredient cheeses, with the desired attributes when heated and cooled under customized specification.

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.

Raman Spectroscopy as a Rapid Tool for Quantitative Analysis of Butter Adulterated with Margarine

Butter adulteration with margarine continues to be a threat for consumers; therefore, new rapid analytical tools are needed for quality control/quality assurance purposes. In this study, we used Raman spectroscopy coupled with partial least squares regression to quantify butter adulteration with margarine. The main difference between Raman spectra of butter and margarine comes from two bands associated to C=C double bond (1656 and 1268xa0cm−1) and the band associated to phospholipids’ choline group (973xa0cm−1). The intensity of these peaks decreases with a decreasing margarine content. The coefficient of determination (R2u2009=u20090.994) and root-mean-square error of prediction (RMSEPu2009=u20092.754) display very good overall model performance. The sample preparation procedure that we employed was notably simplified compared to previous studies. This confirms that Raman spectroscopy can be effectively applied to quantify butter adulteration with margarine and further indicates that simplification of the analysis procedure is possible. These results could aid the efforts for implementation of this technique in routine rapid quality analysis of butter.

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.

Total quality index of Agaricus bisporus mushrooms packed in modified atmosphere

BACKGROUNDnThe aim of this study was to develop a total quality index and examine the effects of modified atmosphere packaging (MAP) on the quality of Agaricus bisporus mushrooms stored for 22 days at 4 °C. Mushrooms were packaged under three MAPs: high nitrogen packaging (HNP), low carbon dioxide packaging (LCP) and low oxygen packaging (LOP). Passive MAP with air inside initially was used as the atmosphere treatment (AIR).nnnRESULTSnThis research revealed two phases in quality deterioration of A. bisporus mushrooms. During the first week, most of the quality parameters were not statistically different. Thereafter, odor intensities were stronger for all four types of packaging. Color difference and browning index values showed significantly lower color changes for AIR and LOP compared with HNP and LCP mushrooms.nnnCONCLUSIONnThe best total quality index was calculated for LOP, followed by LCP and AIR. The findings of this study are useful with respect to examining two-component MAPs, separating the limiting factors (O2 and CO2 ) and evaluating quality deterioration effects and the total quality index of A. bisporus mushrooms.