Examination of growth of probiotic microbes by an isoperibolic calorimetry

Due to the increasing consumers’ interest in up-to-date nutrition nowadays the production of main part of fermented dairy products (e.g. yogurt, kefir) is made by using probiotic microbes. The majority of this product group are the flavoured variations, the sweetener of which is, first of all, still refined sugar (e.g. saccharose). Honey of natural origin, consequently preferred from the nutritional physiological point of view, is suitable to replace this refined carbohydrate. In our experiments we have sweetened the most frequently used milk containing of 1.6 and 3.6% fat with generally used saccharose of 10%, and the difference in the dry material content was equilibrated by drink water of 3% (control product). The experimental product was sweetened with robinia honey of 13% (dry material content was 77%). The fermentation was performed with a probiotic culture of 5%, which was clinically tested to be probiotic. The fermentation process was conducted in isotherm regime at 36 °C during 18 h in batch wessels using SETARAM Micro DSC II calorimeter. The calorimetric enthalpy was proportional to the probiotic microbe counts generated during the fermentation. Due to our experiments, we have come to the conclusion that honey instead of hindering much rather stimulates the growth of probiotic microbes. At sample pairs sweetened by saccharose and acacia honey, respectively, the higher enthalpy was measured at samples containing honey in all cases.     

Examination of proliferation of probiotic microbes by isoperibolic calorimetry

Due to the increasing consumers’ interest in up-to-date nutrition nowadays the production of main part of fermented dairy products (e.g. yogurt, kefir) is performed using probiotic microbes. The majority of this product group are the flavoured variations, the sweetener is, first of all, still refined sugar (e.g. saccharose). Honey of natural origin, consequently preferred from the nutrition-physiological point of view, could be proposed to replace this refined carbohydrate. To check its availability for this purpose the growth of microbes of the Hungarian culture of trade name Prebiolact-2 was examined. The probiotic properties of the culture are proved by clinical tests. At the determination of recipes of control and experimental samples we took into consideration that the milk composition and carbohydrate content of samples should have been the same, and they could differ only in carbohydrate-free component content of honey. During processing of the samples the minimum heat-treatment was applied to protect the biologically active components of honey to the greatest degree. Pasteurized-homogenized milk was used as raw material, in which granulated sugar and the honeys were solved, respectively, at 60 °C. The inoculation was made by Prebiolact-2 culture injected into the batch-wessel; the closed cells were agitated intensively for 10 s. General conclusion of thermal investigation is that the proliferation rate is longer lasting in case of honey treated milks. The acacia- honey resulted in the same probiotic proliferation as sugar did. In case of other herb-honeys the effect was smaller, very probably because of the strong bactericidal effect of herbs, which is very important from medical point of view. According to the results of the consumer survey over 85 % of them think that the consumption of herbs in the form of honey is especially beneficial from both dietary and market view.     

Evaluation of the Probiotic Characteristics of Newly Isolated Lactic Acid Bacteria

Lactic acid bacteria were isolated from fermented vegetables, sour dough, milk products, sheep and human excreta. The newly isolated cultures were evaluated for a number of probiotic characteristics like bile salt resistance, salt tolerance in general, survival in low pH, hydrophobicity of the cell surface, resistance to low phenol concentration, antimicrobial activity and susceptibility pattern against vancomycin and erythromycin. The selected cultures were further screened for their ability to produce the nutraceticals such as folic acid and exopolysaccharide (EPS). Two potent isolates, CB2 (from cabbage) and SD2 (from sour dough) were found to produce both extracellular and intracellular folate. One of the isolates from yogurt (MC-1) and the one from whey (W3) produced significant amount of EPS with a maximum production of 8.79 +/- 0.05 g/l by MC-1.     

Synthesis of citrate-stabilized hydrocolloids of hydroxyapatite through a novel two-stage method: a possible aggregates-breakdown mechanism of colloid formation

Long-term stable (>2 years) hydrocolloids of hydroxyapatite (HA) were synthesized via a low-temperature (18-50 °C) reaction of aqueous ammonium phosphate with calcium nitrate in the presence of citrate ions, followed by an aging process at high temperature (80-99 °C) for 4 h. Changing the reaction and/or aging temperature seldom yielded stable HA hydrocolloids. The as-prepared hydrocolloids were desalinated through ultrafiltration where their average particle size gradually decreased, bottomed out at 100-400 μS/cm, and sharply increased in parallel with a decrease in solution conductivity. The colloid formation is most likely through a temperature-sensitive aggregates-breakdown process. During low-temperature reaction, citrate-calcium chelation bridges the growing HA particles into loose aggregates. High-temperature aging disrupts these inter-particle links and thus breaks the aggregates, imparting negative charges to the HA, forming colloidal particles stabilized by surface charge. The decrease in mean particle size during early ultrafiltration suggested that the aggregate breakdown further proceeded through desalination. In conclusion, the temperature-dependent interactions between citrate ions and calcium sites on HA particles played key roles in the synthesis and stability of the HA colloids.     

Fire intumescent compositions based on the intercalated graphite

A possibility of creation of the swelling type fire-retardant compositions of paints and varnishes based on intercalated graphite dispersed in the polymer matrix in the amount of 5.0–15.0 mass percent was investigated and proved. The expediency of use of the rough aqueous dispersions of polymers obtained with the use of protective colloids as a binder was shown.     

A Comprehensive Study of the Impacts of Oat β-Glucan and Bacterial Curdlan on the Activity of Commercial Starter Culture in Yogurt

This study provides important information about the impacts of various levels of oat (OBG) and bacterial (curdlan) β-glucan and fat contents in milk on survivability and metabolism of yogurt starter cultures. The results show that addition of β-glucans in the concentration higher than 0.25% reduced starter bacterial counts during storage and prolonged the milk acidification process. A significant increase in lactose consumption by starter cultures was noted in the yogurt samples with OBG addition up to 0.75%. The highest (by 567% on average) increase in lactic acid content was noted in the control yogurts. Whereas the lowest (by 351%) increase in lactic acid content was noted in yogurts with OBG. After 28-day storage, the acetic aldehyde content was significantly influenced by fat content, type and addition level of polysaccharide. A higher increase in acetoin content was noted in samples with 0.25% than in samples with 1% of polysaccharides. In turn, significantly lower increases in diacetyl and 2,3-pentanedione contents were observed in the yogurt samples with OBG than in these with curdlan, with diacetyl production increase along with the higher concentration of the polysaccharide. The addition of OBG and curdlan to milk contributed to differences in the starter culture metabolism, consequently, in the milk acidification dynamics.     

Microencapsulation of Bioactive Ingredients for Their Delivery into Fermented Milk Products: A Review

The popularity and consumption of fermented milk products are growing. On the other hand, consumers are interested in health-promoting and functional foods. Fermented milk products are an excellent matrix for the incorporation of bioactive ingredients, making them functional foods. To overcome the instability or low solubility of many bioactive ingredients under various environmental conditions, the encapsulation approach was developed. This review analyzes the fortification of three fermented milk products, i.e., yogurt, cheese, and kefir with bioactive ingredients. The encapsulation methods and techniques alongside the encapsulant materials for carotenoids, phenolic compounds, omega-3, probiotics, and other micronutrients are discussed. The effect of encapsulation on the properties of bioactive ingredients themselves and on textural and sensory properties of fermented milk products is also presented.     

Use of Raman spectroscopy to determine the kinetics of chemical transformation in yogurt production

The kinetics of chemical transformation during the yogurt production was obtained using micro-Raman spectroscopy: Raman spectra were obtained as a function of the incubation time in the fermentation process from milk to yogurt. The milk fermentation by the lactic acid bacteria produces morphological, chemical and textural changes. The chemical transformations were followed using micro-Raman spectroscopy, while the aggregation process and some textural properties through the use of dynamic light scattering, viscosity and pH. Samples with three different starter culture concentrations and different incubation temperatures were prepared. The results indicate the presence of two regimes: the first one (primary metabolism) is characterized by an increment in the initial number of bacteria to reach a high concentration according to the conditions of food, temperature and space, together with some initial chemical transformations. The second regime corresponds properly to the fermentation process accelerated by the continuous reduction in pH due to the lactic acid production; this is accompanied by physical and chemical changes where new structures are created. Knowledge of the kinetics of chemical and physical transformations allows having a better control of the final product with an increase in the quality and shelf life of the final product; problems like phase separation, homogeneity, particle size, acidity, etc., can be controlled.     

利用高效液相色谱-串联质谱追踪酸奶发酵过程中的酪蛋白磷酸肽

酪蛋白磷酸肽(CPPs)是酪蛋白被磷酸化的片段,具有促进矿物元素吸收、抗氧化、预防龋齿等多种生物功能。该文利用高效液相色谱-串联质谱研究牛奶经嗜热链球菌(Streptococcus thermophilus)和保加利亚乳杆菌(Lactobacillus debrueckii subsp.bulgaricus)发酵后CPPs的释放规律。结果表明,在内源性蛋白酶的作用下牛奶含内源性CPPs,内源性CPPs主要来源于高丰度酪蛋白αs1-CN和β-CN。经乳酸菌发酵后,在乳酸菌蛋白酶的作用下更多酪蛋白的磷酸化位点暴露而产生大量CPPs,其中含SpSpSpEE特征结构的CPPs也在酸奶中检测到,CPPs的释放与酪蛋白结构密切相关。研究结果表明,牛奶经乳酸菌发酵后释放大量含特征结构SpSpSpEE的CPPs,可提高结合矿物元素的能力,从而增强其促进人体健康的生物功能。     

Determination of volatile and non-volatile products of milk fermentation processes using capillary zone electrophoresis and solid phase microextraction coupled to gas chromatography

The aim of the investigations was to develop analytical methods for the determination of selected volatile and non-volatile organic compounds numbering among the final products of milk fermentation. The analyzed compounds were as follows: biacetyl and carboxylic acids (formic, acetic, citric, and lactic). The model yogurt was prepared under controlled conditions in our laboratory by addition of the selected bacteria (Lactobacillus bulgaricus and Streptococcus thermophilus) to the milk sample. The temperature, time, and stirring were controlled during the fermentation process. Factors considered in SPMPE-GC-FID method development included fiber exposure time, salt addition, temperature of extraction, and temperature of desorption. Various SPME fibers, for example with PDMS, CAR/PDMS, PA, and PDMS/DVB coatings, were tested to obtain the highest recovery of the investigated compounds extracted from yogurt samples. Based on these preliminary experiments, qualitative and quantitative analyses for the determination of biacetyl were performed by SPME-GC-FID. Moreover, a capillary zone electrophoresis method was developed for the determination of carboxylic acids in the yogurt samples. The buffer composition as well as deproteinization by acetonitrile were found to have a crucial effect on the analysis.     

Evaluation of the combination of a dispersive liquid–liquid microextraction method with micellar electrokinetic chromatography coupled to mass spectrometry for the determination of estrogenic compounds in milk and yogurt

In this work, the suitability of a methodology based on dispersive liquid–liquid microextraction (DLLME) has been evaluated for the extraction of four endoestrogens (estriol, 17α‐estradiol, 17β‐estradiol, and estrone), an exoestrogen (17α‐etynylestradiol), and a mycotoxin (zearalenone), together with some of their major metabolites (2‐methoxyestradiol, α‐zearalanol, β‐zearalanol, α‐zearalenol, and β‐zearalenol) from different types of milk (whole and skimmed cow milk and semiskimmed goat milk) and whole natural yogurt. The methodology includes a previous protein precipitation with acidified ACN and a defatting step with n‐hexane. Separation of the analytes, determination, and quantification were developed by MEKC coupled to ESI‐MS using a BGE containing an aqueous solution of ammonium perfluorooctanoate as MS friendly surfactant. Calibration, precision, and accuracy studies of the described DLLME‐MEKC‐MS/MS method were evaluated obtaining a good linearity and LODs in the low micrograms per liter range.     

Concentration and temperature of eutectic points in glucose-water and saccharose-water systems, determined by the method of fractional melting of ice

Method based on fractional melting of ice was used to determine the concentration and temperature of eutectic points in aqueous systems with glucose and saccharose.     

Synthesis of Polyampholyte Janus-like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli-responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus-like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self-assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus-like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.     

Factors affecting the physical properties of edible composite film prepared from zein and wheat gluten

The effects of zein ratio, concentration of glycerol, liquid-solid ratio, ethanol concentration, pH and heat-treatment temperature on the properties of zein/wheat gluten composite films were researched. The results showed that elongation (E) increased with an increase in glycerol or ethanol concentrations, but it first increased and then decreased with increasing zein/wheat gluten ratio, heat-treatment temperature, pH and the ratio of liquid to solid; Tensile strength (TS) increased with the increase in heat-treatment temperature and pH, and decreased with the increase in glycerol or ethanol concentrations, and it reached a maximum value when the ratio of zein/wheat gluten was 20%, but had a minimum value when the ratio of liquid to solid was 8:1; Water Vapor Permeability (WVP) increased with an increase of glycerol concentration and the ratio of liquid to solid and ethanol concentration, but it decreased with increasing zein/wheat gluten ratio, heat treatment temperature, and pH of the film forming solution.     

Synthesis of Polyampholyte Janus‐like Microgels by Coacervation of Reactive Precursors in Precipitation Polymerization

Controlling the distribution of ionizable groups of opposite charge in microgels is an extremely challenging task, which could open new pathways to design a new generation of stimuli‐responsive colloids. Herein, we report a straightforward approach for the synthesis of polyampholyte Janus‐like microgels, where ionizable groups of opposite charge are located on different sides of the colloidal network. This synthesis approach is based on the controlled self‐assembly of growing polyelectrolyte microgel precursors during the precipitation polymerization process. We confirmed the morphology of polyampholyte Janus‐like microgels and demonstrate that they are capable of responding quickly to changes in both pH and temperature in aqueous solutions.     

Property changes of powdery polyacrylonitrile synthesized by aqueous suspension polymerization during heat-treatment process under air atmosphere

High molecular weight powdery polyacrylonitrile (PAN) polymers were prepared by aqueous suspension polymerization employing itaconic acid (IA) as comonomer and alpha,alpha(')-azobisisobutyronitrile (AIBN) as initiator at 60 degrees C. PAN polymers obtained with different monomer ratios were characterized by EA, DSC, FTIR and XRD. It is investigated that the oxygen element content in PAN polymers increased with the increase of required IA amounts in the feed and heat-treatment temperatures. DSC curves of PAN copolymers exhibited the triplet character, owing to the exothermic cyclization and oxidative reactions during heat-treatment process. Introduction of IA in the feed relaxed exothermic reactions of PAN polymers under air atmosphere. Structure and crystallinity changes were affected by required IA amounts in the feed and enhancement of heat-treatment temperatures. The characteristic functional groups (including C[triple bond]N, C=O, CH(2)) presented in FTIR spectra of PAN polymers indicated copolymerization reaction of AN and IA. Existence of some organic groups (C-O, C=C and/or C=N) indicated formation of ladderlike structure during heat-treatment process. PAN homopolymer had the better crystallinity (mainly peak intensity and peak area around 2theta = 17 degrees) than most RT-PAN copolymers. When heat-treatment temperature is around 210 degrees C, peak intensity, peak area, L(c) and CI of HT-PAN polymers corresponding to samples 1# and 2# got maxima, while crystallinity became weak at higher heat-treatment temperatures.     

Silver nanoparticles embedded temperature-sensitive nanofibrous membrane as a smart free-standing SERS substrate

Silver nanoparticles (AgNPs) embedded temperature-sensitive nanofibrous membrane as SERS substrate is capable of real-time monitoring the reduction of 4-nitrothiophenol into 4-aminothiophenol catalyzed by its embedded AgNPs, and the detected intermediate indicates that the reaction proceeds via a condensation route.     

Determination of Coccidiostats in Milk Products by LC–MS and Its Application to a Fermentation Experiment

A liquid chromatographic tandem mass spectrometric (LC–MS–MS) method for the determination of five chemical coccidiostats (decoquinate, diclazuril, halofuginone, nicarbazin, and robenidine) and five ionophore coccidiostats (maduramicin, monensin, narasin, salinomycin, and semduramicin) in yoghurt, kefir, and sour cream is presented. Lasalocid, the sixth ionophore listed in 124/2009/EC was not included because of its extremely dissimilar behavior during sample preparation. Main steps of the method include extraction with acetonitrile, centrifugation, clean-up on Oasis HLB solid phase extraction cartridge, evaporation under nitrogen stream, and LC–MS–MS determination. Selectivity, linearity, sensitivity, accuracy, repeatability, within-laboratory reproducibility, limit of determination, and limit of quantitation were determined during the validation procedure. The method proved to be applicable for both qualitative and quantitative determination of the ten above-mentioned target compounds. In our in-house fermentation experiments, milk fortified with coccidiostats was fermented to get yoghurt, kefir, and sour cream. Our results show that the coccidiostat content did not change significantly during fermentation for any of the target compounds.     

Effects of Fructose and Oligofructose Addition on Milk Fermentation Using Novel Lactobacillus Cultures to Obtain High-Quality Yogurt-like Products

The incorporation of prebiotics in fermented milk products is one of the best ways to promote health benefits while improving their sensory characteristics at the same time. The aim of this study was to evaluate the effects of the addition of fructose and oligofructose (1% and 2%) on the physicochemical, rheological, sensory, and microbiological quality attributes of fermented milk products inoculated with indigenous probiotic starter cultures of Lactobacillus isolated from Polish traditional fermented foods. The samples were evaluated during 35 days of refrigerated storage. The oligofructose and fructose caused increases in the populations of bacteria in comparison to the control fermented milk products without the addition of saccharides. The degrees of acidification in different fermented milk samples, as well as their viscosity, firmness, syneresis, and color attributes, changed during storage. The highest overall sensory quality levels were observed for the samples supplemented with L. brevis B1 and oligofructose. This study is the first attempt to compare the influences of different sugar sources on the physicochemical, rheological, sensory, and microbiological quality attributes of fermented milk products.     

Thermal stability of aDesulfovibrio gigas periplasmic hydrogenase in reverse micelles

The thermal and operational stabilities ofDesulfovibrio gigas periplasmic hydrogenase were studied at 30 and 50°C in aqueous and micellar media. At the lower temperature the hydrogenase was more stable in reverse micelles of a cationic surfactant. No inactivation was detected over almost 16 d of incubation of the hydrogenase in the reverse micellar solution, during which the enzyme lost around 50% of the initial enzymatic activity in the aqueous solution. At 50°C the hydrogenase was more stable in aqueous medium, because of the changes that occur with the temperature in the organic phase—precipitation of surfactant and solvent evaporation. It was found that only micellar solutions of this enzyme can be repeatedly used, since the hydrogenase is inactivated after the first cycle of oxireduction in aqueous medium. The effect of glycerol and the electron carrier methylviologen as stabilizers of hydrogenase activity was also investigated. The results are interpreted on the grounds of hydrogenase and surfactant electrostatic properties.