Investigating the effect of some hydrocolloids on the stability and rheological and sensory properties of buttermilk using the response surface method (RSM).

Master's Thesis in Food Science and Industry (M.Sc)

Treatment: Food Industry Engineering

Abstract

In this research, the effect of Zedo and CHO gums at 5 levels 0, 0.1, 0.2, 0.28 and 0.4% and gum arabic and xanthan gum at the levels of 0, 0.5, 0.9, 1.4, 1.8 and 0.08, 0.1, 0.15 and 0.2% respectively on the stability, rheological and sensory properties of buttermilk during 59 days of storage using the central rotatable composite design (CCRD) method. The response level (RSM) was checked. The results showed that the viscosity of buttermilk increased and the moisture percentage and syneresis decreased (p<0.05). With the passage of storage time, acidity and L* index increased and pH decreased (p<0.05). Low concentrations of xanthan gum and xanthan gum led to a decrease in the a* index, and high concentrations led to an increase in the a* index. However, both gum arabic and gum arabic led to an increase in the b* index. According to the results of fluctuating rheology tests, pseudoplastic and shear-thinning behavior was observed in samples containing gum, and with increasing concentrations of all 4 types of gum, the viscoelastic moduli (G' and G'') increased. The storage modulus (G'') was also larger than the loss modulus (G''). According to the results of the sensory evaluation, with the increase in the concentration of xanthan and CHO gums, the score of taste and color decreased, and with the increase of xanthan, arabic and CHO gums, the texture score decreased. According to the experimental model obtained by the response level method, the relationship between the studied variables was found to be appropriate. The concentrations of 0.2%, 0.2%, 1% and 0.4% were determined as the optimal conditions for xanthan, zodo, arabic and CHO gums, respectively, and 56 days of storage. In optimal conditions, viscosity, humidity and syneresis were 13.2 pascal/second, 86.6% and 1.15% respectively, L*, a* and b* indexes were 61.8, 10.7 and 7.4 respectively and the color, taste and consistency scores were 3.2, 4.5 and 4.5 out of 5 respectively.

Key words: buttermilk, stabilization, CHO commercial stabilizer, rheology, xanthan, degumming, gum arabic

Chapter 1

General

1-1- Introduction

Current consumption of fermented products Milk and lactic drinks, such as buttermilk, have become very popular. Lactic drinks[1] are products whose production process includes milk fermentation by lactic acid bacteria and then diluting the resulting curd with water, whey, or travide[2], which according to market demand, using additives such as sugar, pulp, or fruit juice, reach the optimal formulation (Laurent and Boulengor, 2003). Whey drinks, drinking yogurt[3], ayran and buttermilk are examples of these products. According to the national standard of Iran, simple buttermilk is a drink obtained from the fermentation of milk, the dry matter of which is standardized by diluting yogurt (after fermentation) or milk (before fermentation) (Codex, 2009). and among the beverages available in the market in terms of health characteristics, it has taken a special place (Kyani et al., 2008). Buttermilk has a high value in terms of nutritional value, usefulness for the consumer, helping to digest food and so on, but due to the presence of compounds such as proteins in this product, after production and during storage, it becomes biphasic (about 50-55% phase separation within a month) and takes on an undesirable and non-uniform appearance in terms of appearance and vision (Azerikia and Abbasi, 2009). As a result, despite its potential advantages, consumers do not show much desire to buy and consume it. Therefore, producers are facing sales problem and unwillingness in the market. According to the statistics of the Ministry of Agricultural Jihad, the amount of buttermilk production in the country in 1381, 1382 and 1385 was 12, 48 and 120 thousand tons respectively (Agricultural Statistics, 1382). style="direction: rtl;">One ??of the major problems in the production of acidic milk drinks is their biphasing during production and storage, which is caused by low viscosity..

Statement of the problem

One ??of the major problems in the production of acidic milk drinks is their biphasing during production and storage, which is caused by low viscosity, low pH and their effect on protein sedimentation. (Koksoy and Kilik, 2004).

Basically, the stability of casein micelles in the natural pH of milk is due to the presence of capacaseins on the surface of casein micelles, which prevent the micelles from approaching each other by forming a hairy layer [4] on their surface and spatial and electrostatic repulsion mechanisms. If, for any reason, hair layers are separated (broken by milk curdling enzymes) or disintegrated (loss of effective net charge by decreasing pH, increasing ionic strength, and decreasing solubility), instability occurs in casein micelles. Because as a result of the acidification of the environment, calcium phosphate is gradually removed from the micelle, the negative electric charge of the micelle decreases and the casein micelle disintegrates (Laurent and Boulangor, 2003). A practical solution to solve this problem is to add stabilizers or gums to dairy drinks (Tollstrap et al., 2007). The term hydrocolloids is used for all polysaccharides obtained from plants, seeds and microbial sources (Dickinson, 2002). Hydrocolloids are divided into two types of absorbent hydrocolloids [5] and non-absorbent hydrocolloids [6]. Both types of hydrocolloids can cause stability in the system. Absorbent hydrocolloids refer to charged polysaccharides that can interact with proteins through electrostatic forces, which strongly depends on the pH and ionic strength of the solution (Sierb et al., 1998).

If absorbent hydrocolloids are used, the stability of the system is possible through steric hindrance and electrostatic repulsion or through both. On the other hand, non-absorbent hydrocolloids prevent biphasing by increasing the viscosity of the continuous phase and trapping water in the three-dimensional network and immobilizing the particles (Oward and Meleud, 2005). The effect of the mixture of hydrocolloids on viscosity is different according to the performance of the hydrocolloids used, some of which have strong interaction with each other and some show weak interaction with each other. Determining the viscosity of a mixture of hydrocolloids is difficult due to their complex rheological properties (Azrikiya and Abbasi, 2010). Many reports have been presented regarding the stability of acidic drinks using different hydrocolloids.

1-3- Necessity of conducting research

Hydrocolloids, as thickening materials (creating viscosity), forming gels and stabilizers. In addition to these properties, hydrocolloids are used to stabilize emulsions and create desirable sensory properties in food products (Dickinson, 2002). The rheological properties of hydrocolloids are important especially when they are used to improve texture in food formulations (Kayasir and Dugan, 2006).

Because the unpleasant taste resulting from the addition of hydrocolloids is always a limiting factor, therefore determining the appropriate level of hydrocolloids is considered one of the important factors in the production of fermented milk products (Gallardo et al., 2007).

The synergistic phenomenon of hydrocolloids can be the result of joining together different hydrocolloid molecules (Williams and Phillips, 2000). Among the very common examples of the synergistic combination of hydrocolloids, we can mention the addition of locust bean gum to capcarrageenan in order to produce softer and more transparent bridges, as well as the addition of locust bean gum to xanthan to intensify bridge formation. Therefore, due to the fact that the mixture of hydrocolloids is usually used in order to create new rheological properties or to improve these properties in food products and to reduce production costs, it is necessary to investigate the mixture of hydrocolloids in the stability of buttermilk. Its soluble part is absorbed on the surface of caseins and prevents particles from approaching through steric hindrance and electrostatic repulsion. On the other hand, the insoluble part stabilizes the system by increasing the viscosity of the continuous phase and creating a three-dimensional network (Mohammadi et al., 2009).