عنوان مقاله [English]
Introduction: Cheese is one of the most consumed dairy products and it has a special flavor depending on its type. Cheese contains protein, fat, water, minerals, and vitamins, which are used daily for breakfast. In the last two decades, there has been a considerable increase in tendency to consume low fat or fat free dairy products due to the adverse effects of the excess fat on human health. Nowadays, the study of alternative methods to achieve the desired texture and the use of antimicrobial effects of natural preservatives and herbal extracts on the growth of microorganisms in low fat cheese has increased. Interest in consumption of traditional dairy products due to harmful effects of chemical preservatives on human health over Past two decades has increased. Cheese is a fermented milk product with high nutritional value. Traditional cheese has an important role in family meals in Iran and especially in South Khorasan. According to the conditions of production, storage and sale, the possibility of microbial contamination in this product is very high and so it can cause a variety of food borne diseases in consumers (Baniassaddi and Azhdari, 2015). One of the problems of traditional Bot cheese is high microbial contamination. Iran has a very long history in production of a great variety of fermented dairy products, meanwhile cheese is one of the most famous of them. cheese has a large market acceptability due to its excellent taste and flavor. Alternative methods, thus, for manufacturing Sate products as well as using antimicrobial effects of natural preservatives and plant extracts on growth of microorganisms have been increasingly considered. Traditionally, jug (Kope) cheese produced from raw milk in the Northwestern provinces of country and nowadays some of the Kope cheese producers have been used of plastic or metal container as a jug (Sarbazi et al., 2014). Consumer demands have led to a renewed interest in using natural antimicrobial for food products. Biopreservatives such as essential oils have recently gained an increased attention to achieve an enhanced level of product safety and stability in food preservation industry. Herbal essential oils are volatile, natural, complex compounds formed by medicinal plants as secondary metabolites. Nowadays, due to the antioxidant and antimicrobial properties of essential oil and the trend towards the substitution of chemical materials by natural ones, the use of this natural product is prevalent. The essential oil of Pistacia atlantica subsp. kurdica is among essential oils which demonstrate antimicrobial activity against some microorganisms (Tavaria et al., 2003).
Material and methods: In this study to prepare jug cheese, was used with the Raw milk 3% cow fat. In the first stage the raw milk was heated to 37 °C and then cooled to 33-34 °C and 1% vegetable rennet (Caminox, Spain) was added then The pistacia atlantica gum essential oil at the levels 1- 2.5 % based on Jug cheese was added and were mixed in the mixer for 5 minutes. Then coagulation was performed at 30 °C for 20 min and it was poured into a clean cloth and pressed for 15-14 hours at room temperature and then 3.5 % salt was poured to all of the samples equally. Then it was put into the earthenware jars and filled as much as possible with pressure inside the jars so that no air remained finally, the jars were allowed to complete the process at a depth of 1 m under the soil (so that the jar head was downward) for 60 days. After 60 days, the Sample were kept at 4 ° C in the refrigerator until testing (Edalatian Dovom et al., 2013). The prepared samples were evaluated for chemical properties, pH and acidity (Institute of Standards and Industrial Research of Iran 2006), protein (Institute of Standards and Industrial Research of Iran 1965), fat (Institute of Standards and Industrial Research of Iran 1968), Dry matter (Institute of Standards and Industrial Research of Iran 2002), Ash (Institute of Standards and Industrial Research of Iran 1977a) and Salt (Institute of Standards and Industrial Research of Iran 1977b)), Microbial properties (Total of microorganisms (Institute of Standards and Industrial Research of Iran 2014), Coliform (Institute of Standards and Industrial Research of Iran 2008) , Escherichia coli (Institute of Standards and Industrial Research of Iran 2015), Staphylococcus aureus coagulase positive (Institute of Standards and Industrial Research of Iran 2005) and Mold and yeast (Institute of Standards and Industrial Research of Iran 2007) ) and Sensory evaluation (Taste, Smell, Texture and overall acceptability) (Institute of Standards and Industrial Research of Iran 1999) during storage period 60 days of storage.
Results and discussion: The results of this research study showed that different concentrations of pistacia atlantica gum had no significant effects on the variations of protein, fat dry matter, ash and salt contents. Pistacia atlantica gum and its increasing content as well as longer storage time resulted in increased acidity and significant (p < 0/05) decreased in pH value. Use of pistacia atlantica gum and its increased content as well as longer storage time caused. a significant (p < 0/05) decrease in total microorganisms, coliform, mold and yeast, E. coli and congulase –positive S. aureus count. The results of sensory evaluation showed that the added pistacia atlantica gum and its increased is Content had a no significant effect on texture, odor, and taste while at concentrations above 2 %, total acceptance score decreased. Given to exerting no negative effect on physicochemical and sensory properties as well as good indexes such as fat, protein, moisture, total acceptance, and inhibitory effect on microorganisms, treatment A2 (containing pistacia atlantica gum) was selected as the superior treatment. It was demonstrated that a safe jug cheese with desirable quality properties could be produced by using the inhibitory effect of pistacia atlantica gum essence on the microorganisms.
Conclusion: According to the results, there was no significant difference (P>0.05) in sensory properties of treatment containing 2% of pistacia atlantica gum essential oil with control sample and in terms of microbial load less than the control sample and it was within the acceptable range of standards and was selected as a superior treatment.