Vol.4, No.9B, 29-32 (2013) Agricultural Sciences http://dx.doi.org/10.4236/as.2013.49B005 Copyright © 2013 SciRes. OPEN ACCESS Rheological properties of low fat yogurt containing cress seed gum Armita Behnia 1* , Hojjat Karazhiyan 2 , Razieh Niazmand 3 , Abdol Reza Mohammadi Nafchi 4 1 Department of Chemical Engineering, Islamic Azad University, Shahrood Branch, Shahrood, Iran; * Corresponding Author: armita.behnia@gmail.com 2 Department of Food Science and Technology, Islamic Azad University, Torbat-Heydarieh Branch, Mashhad, Iran 3 Department of Food Chemistry, Research Institute for Food Science and Technology (RIFST), Mashhad, Iran 4 Department of Food Science and Technology, Islamic Azad University, Damghan Branch, Damghan, Iran Received July 2013 ABSTRACT Yogurt—a milk based mix fermented by lactic acid bacteria is a valuable health food for both young and old. Milk is the main ingredient of yogurt. However, most yogurts contain addi- tional solids such as milk solids nonfat to boost the nonfat milk solids. Stabilizers such as natu- ral gums are added to improve and maintain gel firmness and consistency, while also for many people to improve appearance and mouth feel. Hydrocolloids specifically stabilize gel structure, increase viscosity and either from networks with milk constituents and establish a separate gel structure. In current research, a natural local plant Iranian hydrocolloid, cress seed gum, is added to yogurt formulation and its rheological properties are evaluated using a rotational vis- cometer. Different famous rheological models have been used to fit shear stress-shear rate data’s. The results demonstrated that cress seed gum has a good potential to be used as a stabi- lizer in yogurt formula. Keywords: Yogurt; Hydrocolloids; Cress Seed Gum; Rheological Properties; Viscosity 1. INTRODUCTION The growing awareness of the relationship between diet and health has led to an increased demand for food products that support health above and beyond providing basic nutrition. One of these products is yogurt that is made from milk. Yogurt essentially has all the nutritive components of milk [1]. Yogurts are prepared by fermen- tation of milk with bacterial cultures consisting of a mix- ture of Streptococcus subsp. Thermophiles and Lactoba- cillus delbrueckii subsp. Bulgaricus [2]. Recently, con- sumption of whole dairy products (e.g. full fat yogurt) has declined due to the awareness of the probable harm- ful effect of fat on consumer’s health, thus dietary habits of consumers have been changed and market interest has tended to change in favor of low or nonfat dairy products [3]. According to the Code of Federal Regulations of FDA, low fat yogurt and nonfat yogurt are similar in description to yogurt but contain 0.5% to 2% and less than 0.5% milk fat, respectively [4,5]. Milk fat has an important role in the texture, flavor and color develop- ment of dairy products [6]. Because of reduction of fat and subsequently reduction of total solids content in low fat and nonfat yogurts, they exhibit weak body, poor tex- ture, and whey separation unless various stabilizer blends or ropy strains of yogurt bacteria are used [7]. It is a big challenge for many food scientists to produce a suitable fat substitute to provide the functionality of the missing fat [8]. Therefore, manufacturers have followed different strategies including the milk solid nonfat in yogurt milk, in addition of nondairy based stabilizers, and usage of milk proteins as fat substitutes [9]. Although, enhancing the total solid content of skim yogurt similar to full fat products is a traditional and common method which leads to improvement in viscosity and water binding in yogurt [10]. Hydrocolloids are used in food products as thickeners, stabilizer, gelling agents and emulsifiers. They improve the texture of the products, increase water reten- tion while enhancing lower energy value; they are often employed in low-calorie foods [11]. Stabilizers are used to produce a thick, cohesive body, smooth texture and to prevent wheying off [12] and to improve consistency (increase viscosity) and reduce syneresis [13]. Stabilizers such as pectin or gelatin are often added to the milk base to enhance or maintain the appropriate yogurt properties including texture, mouth feel, and appearance viscosity/ consistency and to prevent whey separation [2]. The ef- fects of some stabilizers such as waxy maize starch, ge- latin, xanthan gum, low methoxy pectin, guar gum, lo- cust bean gum, and λ-carrageenan on the microstructure