The effect of the addition of selected phenolic acids on the rheological properties of heated solutions of whey proteins

This study measured the flow behaviour of whey protein isolate mixtures with cinnamic or ferulic acids. Samples were heated in a vacuum (80 °C, –0.9 atm, 280 r.p.m., 0.5 h). The flow curves of all samples showed a non- Newtonian shear thinning flow and the viscoelastic properties were typical for weak gel systems. At pH 6.0, 6.7, and 8.0, the highest shear stress values were obtained with 20, 40, and 40 mg of cinnamic acid g–1 protein, respectively. At pH 6.0, the use of ferulic acid (20 mg g–1 protein) resulted in the elevation of shear stress values, but at pH 8.0, ferulic acid caused a decrease in shear stress values in comparison to cinnamic acid. The thixotropic area (AT) was increased in mixtures containing 20–40 mg cinnamic acid g–1 protein (at pH 6.7) and 20 mg of cinnamic acid g–1 protein (at pH 6.0). Similarly, the addition of ferulic acid (40 and 20 mg g–1 protein at pH 6.7 and 6.0, respectively) caused a significant increase in AT. At pH 8.0, no significant differences in AT values were observed between samples. Such systems can be applied with reference to health promoting foods such as WPI-based desserts

Whey protein aerated gels as a new product obtained using ambient temperature magnesium and iron(II) induced gelation

The objective of the research was to obtain aerated gels by magnesium and iron(II) ion induced gelation of preheated whey protein isolate dispersions. Preliminary research allowed finding conditions of the pH, protein, and ion concentrations to produce aerated gels capable of holding air bubbles. A novel method applying gelation and aeration process simultaneously was used. Aeration using a laboratory mixer at 2000 r.p.m. produced stronger aerated gels than using a homogenizer at 8000 r.p.m. The gelation process was monitored using an ultrasound viscometer and a constant increase of dynamic viscosity was noted. A different aerated gel microstructure was observed for magnesium and iron(II) induced gels, which probably resulted in differences in the texture and viscosity, as well. The aeration process decreased hardness. In some cases texture parameters correlated with the viscosity measured using an ultrasound viscometer. Aerated whey protein gels could be applied as matrices for food applications or to controlled release of active ingredients

Distribution of Cell Envelope Proteinases Genes among Polish Strains of Lactobacillus helveticus

Most of the lactic acid bacteria (LAB) are able to grow in milk mainly due to the activity of a complex and well-developed proteolytic system. Cell envelope-associated proteinases (CEPs) begin casein hydrolysis and allow for releasing the peptides, enclosed in the structure of native milk proteins that are essential for growth of Lactobacillus helveticus. The biodiversity of genes encoding CEPs among L. helveticus strains can have an effect on some technological parameters such as acid production, bacterial growth rate in milk as well as liberation of biologically active peptides. The study reveals significant differences in the presence of various variants of CEPs encoding genes among ten novel Polish strains and indicates the intraspecific diversity exhibited by L. helveticus. In terms of distribution of CEPs genes, four different genetic profiles were found among the microorganisms analyzed. Furthermore, the strains exhibited also various levels of proteolytic activity. Molecular analysis revealed that prtH3 is the most abundant CEPs-encoding gene among the strains investigated. The results indicate also that ecological niche and environmental conditions might affect proteolytic properties of L. helveticus strains. The greatest variety in terms of quantity of the detected CEP encoding genes was noticed in L. helveticus 141, T105 and T104 strains. In these strains, the combination of three nucleotide gene sequences (prtH/prtH2/prtH3) was identified. Interestingly, T104 and T105 exhibited the highest proteolytic activity and also the fastest dynamic of milk acidification among the tested strains of L. helveticus

Effect of some selected prebiotics on rheological properties of set yoghurt

Celem pracy było określenie wpływu dodatku oligofruktozy P95 oraz inuliny GR i HPX na właściwości reologiczne oraz wielkość synerezy jogurtu otrzymanego metodą termostatową. Oznaczano twardość, lepkość pozorną i wielkość synerezy jogurtów stałych. W celu określenia wpływu fruktooligosacharydów na przebieg fermentacji monitorowano ten proces przy użyciu reometru oscylacyjnego. W przypadku jogurtu kontrolnego tworzenie skrzepu rozpoczęło się po ok. 90 min, natomiast tworzenie się skrzepu w przypadku pozostałych jogurtów zaczęło się po ok. 105 min. Najmniejszą twardość miał jogurt kontrolny – 0,23 N. Natomiast największą uzyskał jogurt z dodatkiem inuliny HPX w ilości 3 % – 0,28 N. W przypadku jogurtów z dodatkiem P95 zaobserwowano nieco wyższą twardość w porównaniu z próbą kontrolną. Najmniejszą ilością wydzielanej serwatki charakteryzował się jogurt z dodatkiem 3 % P95. Generalnie wraz ze wzrostem dodatku fruktooligosacharydów malała wielkość synerezy w badanych jogurtach. Zastosowanie fruktooligosacharydów pozwala na otrzymania jogurtów o odpowiednich właściwościach reologicznych i prozdrowotnych.The objective of this paper was to determine the effect of the additions of P95 fructooligosaccharide and GR and HPX inulins on the rheological properties and the syneresis extent of yoghurt produced using a thermostat method. The hardness, apparent viscosity, and syneresis extent of set yoghurts were determined. In order to determine the effect of fructooligosaccharides on the course of fermentation process, this process was monitored using an oscillatory rheometer. In the case of control sample of yoghurt, the curd began to form ca. 90 minutes after the process started whereas, in the case of all other yoghurts, the curd started to form after about 105 min. The control sample of yoghurt had the lowest hardness value of 0.23 N. The yoghurt with the HPX inulin added in the amount of 3 % had the highest hardness: 0.28 N. As for the yoghurts with P95 inulin added, a slightly higher value of hardness was reported compared to the control sample. The lowest amount of whey excreted was found in the case of yoghurt with the added 3 % amount of P95. Generally, for all of the yoghurts examined, the syneresis extent decreased with the increasing amounts of fructooligosaccharides added. The application of fructooligosaccharides allows for manufacturing yoghurts characterized by proper rheological and pro-health properties

Effect of addition of different of whey protein concentrates [WPC] on rheological properties of set-type yogurt

Celem pracy było określenie wpływu koncentratów białek serwatkowych różniących się składem chemicznym na właściwości reologiczne jogurtów otrzymanych metodą termostatową. Zwiększenie suchej masy mleka przeznaczonego do produkcji jogurtów osiągnięto poprzez dodatek 1, 2 lub 4% WPC 35, WPC 65, WPC 85 i WPC odtłuszczonego (WPCO). Przebieg fermentacji jogurtu monitorowano przy wykorzystaniu reometrii oscylacyjnej oraz oznaczano lepkość, twardość i gumowatość gotowego produktu. W przypadku jogurtu kontrolnego skrzep powstawał po 126 min fermentacji. Dodatek odtłuszczonego mleka w proszku (OMP) spowodował skrócenie czasu do 119 min, natomiast po dodaniu WPC 85 i WPCO zaobserwowano wydłużenie okresu niezbędnego do powstania skrzepu jogurtowego odpowiednio do 148 i 165 min. Największą twardością charakteryzowały się jogurty z 4% dodatkiem WPC 85 i WPCO, jednak miały one zbyt gumowatą teksturę.The aim of this paper was to examine the effect of different types of protein concentrates on rheological properties of set type yogurts. Yogurts were supplemented by addition of 1,2 or 4% of WPC35, 65WPC, WPC 85 and defatted WPC(WPCO). The process of yogurt fermentation was monitored with using of dynamic oscillation rheometry and following parameters such as: viscosity, hardness and gumminess were determined. In case of yogurt where no milk protein powder was added, the curd started to form after 126 minutes of fermentation. The addition of skimmed milk powder (SMP) decreased the curding time and it was 119 minutes. For WPC 85 and WPCO, the increase of curding time was observed and it was 148 and 165 minutes respectively. The hardest yogurts were obtained with 4% of WPC 85 and WPCO addition, but these yogurts characterized with too gummy structure