با همکاری انجمن علوم و صنایع غذایی ایران
نوع مقاله : مقاله پژوهشی
نویسندگان
گروه علوم و مهندسی صنایع غذایی، دانشکده کشاورزی، دانشگاه فردوسی مشهد، مشهد، ایران
کلیدواژهها
عنوان مقاله English
نویسندگان English
Introduction
In recent years, consumer interest in traditional and natural dairy products has increased due to their perceived health benefits, cultural value, and unique sensory properties. Among traditional Iranian dairy products, sarshir is widely consumed and valued for its rich taste and high energy content. Sarshir is a traditional Iranian high-fat dairy product obtained through heat-induced creaming of milk. However, its industrial production faces several challenges, including long processing time, low yield, high susceptibility to lipid oxidation, and variability in texture and quality. Milk protein concentrate (MPC), rich in casein and whey proteins, is widely used in the dairy industry due to its functional properties such as emulsification, gelation, and texture enhancement. Therefore, the incorporation of MPC into sarshir formulations may improve structural stability, enhance sensory properties, and potentially enable partial fat reduction. Accordingly, this study aimed to evaluate the effects of different cream fat levels (50%, 60%, and 70%) and MPC concentrations (0%, 1%, and 2%) on the physicochemical, textural, sensory, yield, and shelf life of Sarshir, and to determine and introduce an optimal formulation for industrial production.
Materials and Methods
Raw milk was obtained from Sepidan Shir Company (Mashhad, Iran), and milk protein concentrate (MPC-80) was supplied by Pegah Isfahan Company (Isfahan, Iran). Sarshir samples were prepared by standardizing milk fat content to 50, 60, and 70% (w/w) using cream, along with MPC addition at 0, 1, and 2% (w/w). Raw milk was heated to 40–45 °C and centrifuged (7000 rpm) to obtain cream fractions, which were recombined with skim milk based on mass balance calculations. MPC was hydrated at 40 °C for 20 min under stirring. The mixtures were then heated to 90 °C and incubated at 43 °C for 3 h, followed by cooling at 5–6 °C for 24–48 h to form the sarshir layer. The sarshir layer was separated and analyzed for different properties. Shelf life was evaluated at 4–5 °C every 2 days based on sensory acceptability.
Results and Discussion
The highest dry matter and fat contents were observed in the samples containing 70% fat and 2% protein (68.03 g/g and 72.50%, respectively), whereas the lowest values were recorded in the control treatment (50% fat and 0% protein). The increase in MPC significantly affected the physicochemical properties, particularly pH and acidity (p< 0.05), with higher pH and lower acidity observed in formulations with higher fat and protein levels. The highest protein content (5.44%) was also recorded in samples containing 50% fat and 2% protein. Texture profile analysis indicated that increasing fat content from 50% to 70% significantly reduced hardness (61.00 to 21.00 g), consistency (5.00 to 1.75 g·s), and adhesiveness (25.50 to 9.50 g·s). In contrast, MPC addition generally increased textural parameters, suggesting a strengthening effect of milk proteins on the gel structure, while fat had a softening effect on product consistency. Accordingly, the lowest textural values were observed in the 70% fat and 2% protein treatment, whereas the highest hardness was associated with the control sample. Production yield was significantly influenced by formulation (p< 0.05), reaching a maximum in the 70% fat and 2% protein treatment (approximately 58%) and a minimum in the control sample (approximately 30%). However, storage time showed an inverse trend, decreasing with increasing fat and MPC levels, with the shortest storage time (7 days) observed in the 70% fat and 2% protein sample and the longest (16 days) in the control. Sensory evaluation revealed that although high-fat/high-protein samples showed improved creaminess and mouthfeel, the formulation containing 50% fat and 2% protein received the highest overall sensory scores, particularly for flavor intensity, dairy flavor, and creamy mouth feel aftertaste.
Conclusion
The results indicated that the addition of milk protein concentrate (MPC) significantly influenced the physicochemical, textural, and sensory properties of sarshir. Increasing both fat and MPC concentrations improved total solids, fat content, production yield, and textural attributes; however, such increasing trend was associated with a reduction in shelf life. The sample containing 50% fat and 2% MPC demonstrated the highest sensory acceptability. Overall, this formulation achieved an optimal balance between quality and stability, and is therefore recommended for industrial production.
کلیدواژهها English
Authors retain the copyright. This is an open access article distributed under Creative Commons Attribution 4.0 International License (CC BY 4.0).
