Viscosity of stirred yoghurt pdf

The time dependent rheological behaviour of 4 commercial stirred yoghurts was evaluated at constant shear rate within the range 18 to 280 s. In recent years, however, demand has increased for lower viscosity yoghurt beverages that customers can drink using a straw. Yoghurt is a fermented dairy product, having several health benefits. Flow curves, covering the shear rate range 29920 s. Stirred yoghurt produced from uht milk enriched with skim milk powder and by using 11 commercial starter cultures was subjected to dynamic rheological measurements with a cone and plate device. Once the stirring has stopped the speed of the vortex is gradually reduced and. Viscosity measurements in food products and manufacturing. Effects of starter cultures on small deformation rheology of. Determination of yogurt quality by using rheological and. Rheological characteristics of 2 commercial brands of stirred yogurt were evaluated using a haake rotovisco model rv 20 with an m. Pdf the aim of this paper was to determine the changes in viscosity of stirred yoghurt from producer a n 20 and producer b n 20 throughout 21. The results represented that a significant decreased p viscosity of stirred yoghurt p viscosity of the stirred yoghurt from. Structure breakdown of stirred yoghurt in a circular pipe. Sensory evaluation revealed that there was a significant difference among sensory scores of yoghurt enriched with different levels of mung bean paste.

Post fermentation processing enzyme hydrolysis, vitamin fortification, vegetable oils, heat treatment set yoghurt is fermented in a retail container, filled after milk inoculation and is incubated in an incubation room at a. Rapid, noncontact viscosity measurements of stirred yoghurt. Pdf viscosity of stirred yoghurt during storage researchgate. Pdf rheological properties of stirred yoghurt as affected by gel ph. Pdf steadyshear viscosity of stirred yogurts with varying.

Stirred yoghurt samples were manufactured in pilot scale 2 kg at the facilities of the department of food science, university of copenhagen. Journal of the science of food and agriculture j sci food agric 85. Two independent sensory properties, nonoral viscosity and oral viscosity, were evaluated. The internal friction in a fluid can be easily demonstrated by observing a liquid that has been vigorously stirred to create a vortex. Spectroscopic prediction of rheological properties of stirred. Rheological and physical properties of yogurt enriched with. Yoghurt properties can be enhanced by the addition or treatment with various additives. It is defined as the internal friction of a liquid or its ability to resist flow. Data were recorded every 4 s for the first 400 s and every 26 s for the remaining 2600 s. Stirred yoghurt yoghurt is categorised as a cultured dairy product which is obtained from pasteurised milk or reconstituted milk that has been inoculated with yoghurt culture, and allowed to ferment under controlled conditions to develop a characteristic flavour and texture. Rapid, noncontact viscosity measurements of stirred. Physicochemical and sensory quality of mung bean vigna. The sensory and rheological characteristics of stirred yogurts varying in fermentation temperature, heat treatment of milk, dry matter content and composition of bacterial cultures were investigated. To determine the impact of production parameters and cooling speed on the rheological properties of stirred yogurt.

The viscosity and the gel structure is influenced by several factors in. In the early 1970s the work of steenbergen 1971a,b,c,d dealt with the reduced viscosity of stirred yoghurt, caused by the different process steps after incubation. Rheological and physical properties of yogurt enriched. Viscosity evaluation of yoghurt shimadzu corporation. The problem of dry matter standardization is present for long time. It was shown in this work that the simple rheological tests can be used to estimate the structure breakdown rate of stirred yoghurt in pipe flow. The steadyshear behavior of three types of stirred yogurt with varying ropiness was investigated experimentally. Nrs the missing link sensory and rheology study of low fat. Considerable change in viscosity of stirred yoghurt p 0,05 throughout the maintenance period was determined on the 0 and the 21st day for both yoghurts. Chemical, nutritional, rheological, and organoleptical. Rheological characteristics of stirred yoghurt, varying in dry matter content, fermentation temperature and composition of bacteria cultures, were evaluated using a bohlin vor rheometer. Drinkable yogurt, categorized as stirred yogurt with a low viscosity, is a growing area of interest based on its convenience, portability, and ability to deliver all of the health and nutritional benefits of stirred or set yogurt eder, 2003.

The viscosity of the stirred yoghurt from producer a was increased from 0,324 pa s on the 0 day to 1,912 pa s on the 21st day. A lowviscosity drinkable yoghurt, normally with a low fat content, is popular in many countries. Pdf steadyshear viscosity of stirred yogurts with varying ropiness. Structure breakdown of stirred yoghurt in a circular pipe as. Nrs the missing link sensory and rheology study of low. Show full abstract viscosity of stirred yoghurt p viscosity of the stirred yoghurt from. If youre manufacturing set or stirred yoghurts or labneh, youll know they differ in creaminess, firmness and viscosity. Most of the basic plain yogurts are set yogurts, which are fermented in the container that they are eventually sold in, while most fruitflavored yogurts are stirred yogurts, because flavors and fruit. Stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles. There is usually a slight reformation of the coagulm after the yoghurt has been packed drinking yoghurt.

Premixes for yoghurt and other cultured milk desserts. Yoghurt starter culture consists of a blend of streptococcus thermophilus and lactobacillus delbrueckii subsp bulgaricus. A certain yield stress must be applied in order to get the yoghurt to flow prentice, 1992. Yoghurt milk base was made by blending per batch 1. Composition determines the properties of stirred yogurt.

Pretreated milk inoculation starter culture stirred yoghurt cooling flavouring or essences e. Steadyshear viscosity of stirred yogurts with varying. The low viscosity is obtained through high agitation, which. Emulsifiers and stabilisers for yoghurt and yoghurt drinks. Yogurt b had higher viscosity than samples a between 1. Stirred yoghurt is a nonnewtonian fluid with a viscoelastic, thixotropic and shearthinning flow behavior. Pdf stirred yogurt was viewed as a concentrated dispersion of aggregates consisting of protein particles.

Rheology of stirred yogurts ramaswamy 1991 journal of. Oct 12, 2014 table 1 shows apparent viscosity of yogurt samples during 28 days storage at 4 c. Viscosity of different stirred yoghurt fortified with ppe was measured using brookfield viscometer brookfield engineering laboratories, usa, equipped with sc421 spindle running at 20, 30, 50, 60 and 100. Adding phytosterol emulsion may interrupt the gel structure of the enriched sample. And these differences place varying demands on the emulsifier and stabiliser system needed. Newtons law of viscosity, pressure and temperature. Yoghurt is typically eaten in a semisolid state using a spoon. Antioxidant activities and physical properties of stirred.

Fortification of banana stirred yogurt with calcium. Stirred yoghurt has a thick smooth consistency and is. Creamy stirred yogurt an indulgent treat for all the senses almost everyone enjoys a special treat after dinner. The aim of this paper was to determine the changes in viscosity of stirred yoghurt from producer a n 20 and producer b n 20 throughout 21 days of storage. This is because yogurt is a gelmatrix of casein micelles with entrapped water. C20 min had samples a, while samples c had the smallest viscosity. John montella and phillip s tong dairy product technology center, california polytechnic state university, san luis obispo, california 93407, usa.

Yoghurt was prepared with standardized cows milk and green gram paste was added to the stirred yogurt at the rates of 5, 10, 15, 20 and 25% ww. Viscosity of stirred natural yogurt at 5c as a function of time of exposure to constant shear. This might indicated that pumpkin positively affected the texture of the stirred yoghurt. Independent of the starter type used, yoghurt exhibited linear viscoelastic behaviour up to a shear strain amplitude. A low viscosity drinkable yoghurt, normally with a low fat content, is popular in many countries. Viscosity, hardness, adhesiveness, cohesiveness, and springiness are considered the most.

Steadyshear viscosity of stirred yogurts with varying ropiness article pdf available in journal of rheology 436. The viscosity and the gel structure is influenced by several factors including milk composition, casein concentration, incubation temperature, heat treatment of. The effect of mechanical shear in ambient yoghurt lund university. The rheological behavior of this product can be expressed in terms of the apparent viscosity, defined at a constant temperature and at a constant. Values of viscosity for control and calcium enriched banana yogurt ranged from 0. The physical attributes of yogurts, including the lack of visual whey separation and. Whether topped with chocolate, mixed with fruits or on its own, premium, indulgent yogurts have become the preferred choice of dessert for the health conscious consumer. The stirred yoghurt is fermented in a big container and after fermentation the coagulum is destroy gentle, cooled and pumping to the final package to the consumer. Kovac, effects of starter cultures on small deformation rheology of stirred yoghurt, lwt food science and technology, 28, 3, 319, 1995. As it is seen in this table, the apparent viscosity of enriched yogurts is lower than the control. The factors responsible for the increase in viscosity of stirred yoghurts are therefore in the manufacture of stirred yoghurts, a setstyle yoghurt gel is essentially. Food products viscosity data chart milk water worcestershire sauce ethyl alcohol soy soarce olive oil calpis cottonseed oil sake beerwhiskey 20%40 %50% sucrose aqueous solution canola oil castor oil gelatin egg yolk glucose syrup starch syrup whi te sauce 60.

Determination of yogurt quality by using rheological and textural parameters. As pressure increases the relative movement of molecules requires more energy hence viscosity increases. Flow properties of stirred yoghurt wiley online library. It covers both rheological and sensory evaluation of low fat stirred yoghurt prepared with different combinations of texturizers, like pectin, starches and gelatine. Stirred yoghurt with three different pumpkin varieties pulp american ap, domestic dp, and indian ip pumpkin at 15% was prepared and stored at 5. Torriano, rheological behaviour of lowfat and fullfat stirred yoghurt, international dairy journal, 5, 7, 661, 1995. Since texture and sensation when swallowing are extremely important characteristics of yoghurt, texture evaluations for viscosity and hardness are indispensable. The content of fat, dry matter, nonfat dry matter, lactic acid, ph and viscosity of stirred yoghurt were determined on the 0, 7th, 14th and the 21st day of storage of the product at. Most of the basic plain yogurts are set yogurts, which are fermented in the container that they are eventually sold in, while most fruitflavored. Figure 7 process of stirred ambient yoghurt, image from tetrapak dairy process hand book.

Creamy stirred yogurt an indulgent treat for all the senses. The physical attributes of yogurts, including the lack of visual whey separation and perceived viscosity, are crucial aspects of the quality and overall sensory consumer acceptance of yogurts. Sensory and microbiological quality of yogurt drinks with. Ambient yoghurt production is the same as stirred type whit the difference of the ambient yoghurt is heattreated after fermentation in order to inactivate the lab and so therefore. Show full abstract viscosity of stirred yoghurt p 500 cps stirred yoghurt.