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Gdańsk, Poland

Zareba D.,Katedra Biotechnologii
Zywnosc. Nauka. Technologia. Jakosc/Food. Science Technology. Quality | Year: 2010

Typical aroma compounds of fermented milk drinks are: acetaldehyde, diacetyl, lactic acid, acetic acid, acetoin, and others. The content of the above mentioned compounds determines the required and acceptable flavour and taste qualities of fermented milk drinks. The composition of soymilk is different from the composition of cow's milk; therefore, the soymilk is characterized by different taste and flavour characteristics than the cow's milk. The objective of this paper was to assess the aroma stability of soy yoghurts during the 4 weeks of cold storage. In order to enhance the detailed interpretation of the research results on the aroma stabilization, the viability of yoghurt bacteria was determined, as were changes in pH of soy yoghurts during their storage. A chromatographic analysis GC-MS using a SPME technique performed showed that there were no significant changes in the profile of volatile compounds contained in soy yoghurts during the 4 weeks of cold storage. The glucose added had no significant effect on the intensification of changes in the aroma profile of yoghurts during their storage. In the composition of volatile compounds, the following compounds were identified: ethanol, 1-heksanol, acetoin, 2,3-butanedione (diacetyl), 2,3-pentanedione, hex-anal, nonanal, butanoic acid, and acetic acid. Source


Wroniak M.,Katedra Technologii Zywnosci | Chlebowska-Smigiel A.,Katedra Biotechnologii
Zywnosc. Nauka. Technologia. Jakosc/Food. Science Technology. Quality | Year: 2013

The objective of the research study was to assess the impact of purity of rapeseed and oil purification method on chemical characteristics and microbiological quality of cold pressed oils. The research scope comprised: analysis of basic quality characteristics of 11 industrial batches of "00" rapeseed varieties, pressing in an expeller, oil purification using a natural settling and decanting or centrifuging methods, and quality analysis of fresh pressed and stored oils. In the seed samples studied, contents of water, fat, and contaminations were determined, and in the oil samples: degree of hydrolysis, primary and secondary degree of lipid oxidation, Totox ratio, and oxidative stability in a Rancimat test. The total number of microorganisms and the amount of fungi were determined in the seeds and oils. In addition, isolated types of mold were identified. The individual batches of rapeseed were characterized by a varying quality as regards their contents of fat, water, and useful and useless contaminations. The microbial contamination of seeds was at a level of 103-104 cfu/g. A positive linear correlation was found between the content of contaminants and the microbiological quality of seeds. The cold-pressed rapeseed oils were characterized by a medium degree of hydrolysis and oxidation of lipids. The quality of oils depended on the seed contamination. The quality of the centrifuged oils was higher than that of the decanted oils. The treatment method affected the chemical and microbiological quality of the oils during storage. A 6 month storage of oils purified by decantation caused a higher reduction in their quality compared to the centrifuged oils. The degree of hydrolysis and oxidation of lipids increased and the total count of microorganisms increased. However, the microbiological contamination of cold-pressed oils was very low (at a level of 101 to 102 cfu/cm3), i.e. from 10 to 1000 times lower than the contamination of rapeseed. Spore-forming bacteria, yeast, and mold were found on the seeds and in the oils studied. Among the fungi, a prevailing microflora were molds of the genus Penicillium, Fusarium, Alternaria, Rhizopus, Aspergillus, and Cladosporium. Source


The objective of this study was to determine the effect of calcium chloride on textural properties and meltability of processed cheese analogues produced on the basis of acid casein, whey protein preparations (50 % demineralised whey powder - DWP 50; whey protein concentrate - WPC 35; whey protein isolate - WPI), and milk fat. The texture of cheese analogues produced was analysed using a TA-XT2i Texture Analyser, by a 15 mm dia cylindrical sampler. A Textural Profile Analysis (TPA) was carried out to determine the following properties: adhesiveness, springiness, and cohesiveness of processed cheese analogues. A puncture test of processed cheese analogues was performed with the use of a TA-XT2i Texture Analyser, by a 10 mm dia cylindrical sampler. The viscosity of the processed cheese analogues was measured using a Brookfield DV II+ rotational viscometer with a Helipath Stand (F). The meltability of the processed cheese analogues was measured using a modified Schreiber test. The application of calcium chloride affected the rheological properties and meltability of the processed cheese analogues. The processed cheese analogues with WPI added were characterized by the highest hardness and adhesiveness, whereas the processed cheese analogues with the addition of WPC 35 showed the lowest hardness and adhesiveness. All the samples analyzed were characterized by high springiness. A higher amount of calcium chloride caused the springiness of analogues to increase, but it did not cause any significant changes in the springiness between successive concentrations except for the samples with WPC 35 added. With the increase in the calcium chloride concentration, the cohesiveness of the analogues with DWP 50 and WPC 35 added increased, whereas in the samples with the addition of WPI, the increase in the calcium chloride concentration did not significantly impact their cohesiveness. With the increasing calcium chloride concentration, the viscosity of the processed cheese analogues with WPI added increased, too, whereas in the case of the samples with WPC 35 and DWP 50 added, an inverse relationship was reported. All the samples analyzed were characterized by good meltability. However, with the increasing CaCl2 concentration, the meltability of the analogues with WPC 35 and DWP 50 added decreased, whereas in the case of the analogues with WPI added, it was found that their meltability improved (0.5 - 1.5 %). The understanding of the impact of individual components of the processed cheese analogues on their physicochemical properties allows for the monitoring of the texture of the final product by using an appropriate set of formulas as well as by selecting technological parameters of the process. Source


Solowiej B.,Katedra Biotechnologii
Zywnosc. Nauka. Technologia. Jakosc/Food. Science Technology. Quality | Year: 2012

The objective of this study was to manufacture processed cheese analogues with added κ-carrageenan and to evaluate their textural properties and meltability. The hardness of processed cheese analogues manufactured was measured using a TA-XT2i Texture Analyser and a 10 mm diameter cylindrical sampler (penetration rate: 1 mm/s; constant temperature: 21°C). Using a puncture test, the force was determined that allowed the sampler to sink 20 mm deep in the cheese. The texture of the processed cheese analogues was examined using a TA-XT2i Texture Analyser and a 15 mm diameter cylindrical sampler (penetration rate: 1 mm/s; constant temperature: 21°C). Using a texture profile analysis (TPA) determined were the parameters: adhesiveness, springiness, and chewiness of processed cheese analogues. The viscosity of processed cheese analogues was measured using a Brookfield DV II+ rotational viscometer with a Helipath Stand (F). The meltability of processed cheese analogues was analysed using a modified Schreiber test. An increase in the κ-carrageenan content ranging from 0.05 to 0.3 % caused the hardness and chewiness of the processed cheese analogues to increase, and their adhesiveness and meltability to decrease. The addition of κ-carrageenan in the amount from 0.05 to 0.3 % did not cause the springiness of processed cheese analogues to decrease. Along with the increasing content of κ-carrageenan in the range between 0.05 and 0.3 %, the viscosity of 11 % and 12 % acid casein-based samples increased, whereas the viscosity of 13 % acid casein-based samples decreased as compared to the model analogues. Source


Koziol J.,Katedra Biotechnologii | Skrzypczak K.,Katedra Biotechnologii | Gustaw W.,University Przyrodniczy w Lublinie | Wasko A.,Katedra Biotechnologii
Zywnosc. Nauka. Technologia. Jakosc/Food. Science Technology. Quality | Year: 2013

Probiotic strains of the Bifidobacterium genus multiply poorly in milk. The objective of this study was to modify the Garches medium through replacing a nitrogen source by some selected milk protein preparations and to verify their ability to stimulate the growth of probiotic strains of the Bifidobacterium genus. The Bi30 and KD14 strains were characterized by the highest proteolytic activity; slightly lower values were determined for other strains of the Bifidobacterium genus. For the growth of Bb-12 (1.2×108cfu/ml), the most favourable medium was that containing a whey protein isolate (WPI). Based on the results obtained after the incubation of KN29, it was found that the WPI and a- lactalbumin (a-la), the compounds of the culture medium that was designed using a Plackett-Burman model, were those to stimulate the growth of that strain to the highest degree. The highest density of cells of Bb-12 and KN29 bacteria was reported during the incubation of those strains on the media supplemented with a sodium caseinate (KNa) and calcium caseinate (KCa), and in the case of the whey protein preparations, this effect was reported for the media with WPI and α-la. Source

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