بهینه‌یابی اثر سطوح مختلف استارتر، مخمر و زمان نگهداری بر خصوصیات فیزیکوشیمیایی و میکروبی نوشیدنی کفیر با استفاده از روش سطح پاسخ

نویسندگان
1 فردوسی مشهد
2 گروه علوم و صنایع غذایی، دانشکده کشاورزی، دانشگاه فردوسی مشهد، مشهد، ایران.
چکیده
کفیر نوشیدنی سنتی است که از طریق تخمیر شیر توسط دانه­های کفیر تهیه می­شود، دانه­های کفیر مخلوط پیچیده­ای از باکتری­ها، مخمرها و پلی­ساکارید تولید شده به وسیله این میکروفلور می­باشند. مقدار اولیه دانه کفیر که برای تولید این نوشیدنی تلقیح شده بر کیفیت نهایی آن (مقدار pH، ویسکوزیته و مشخصات میکروبی)، اثر می­گذارد. در این پژوهش اثرات سطوح مختلف استارتر (4، 6 و 8 درصد، حاوی Streptococcus thermophilus، Lactobacillus delbrueckii subsp. bulgaricus، Bifidobacteriumمخمر Saccharomyces cerevisiae (2، 3 و4 درصد) و زمان نگهداری (24، 48 و 72 ساعت پس از تلقیح) بر ویژگی­های فیزیکوشیمیایی و میکروبی نوشیدنی کفیر با استفاده از طرح مرکب مرکزی رویه سطح پاسخ به منظور تولید محصولی با میزان باکتری­های پروبیوتیک بالاتر نسبت به مخمرها، مورد بررسی قرار گرفت. خصوصیات فیزیکوشیمیایی شامل اسیدیته، pH، اتانول، گرانروی ظاهری و پارامترهای رفتار جریان، همچنین شمارش جمعیت میکروبی مورد ارزیابی قرار گرفت. مطابق نتایج حاصل از آزمون­های انجام شده میزان مخمر، بیشترین اثرگذاری را بر گرانروی ظاهری داشته و با افزایش میزان مخمر و در طی زمان نگهداری مقدار گرانروی ظاهری و ضریب قوام کاهش یافت، علاوه بر این با افزایش درصد استارتر بر میزان گرانروی ظاهری افزوده گردید. در خصوص میزان اتانول نیز با افزایش مقدار مخمر میزان اتانول تولید شده افزایش یافته و در طی زمان نگهداری به علت افزایش مقدار مخمر بر میزان تولید اتانول افزوده شد و در نهایت شمارش میکروبی در زمان نگهداری کاهش یافت. نتایج بهینه­یابی نشان داد که نمونه­ حاوی 2 درصد مخمر و 4 درصد استارتر در زمان 38 ساعت پس از تلقیح کمترین میزان اتانول را داشته و از لحاظ خواص رئولوژیکی مناسب می­باشد.
کلیدواژه‌ها

موضوعات


عنوان مقاله English

Optimization of the effects of different levels of starter, yeast and storage time on the physicochemical and microbial properties of kefir beverage through response surface methodology.

نویسندگان English

Soheila Ahmadian Mask 1
Farideh Tabatabayi Yazdi 2
Seyed Ali Mortazavi 2
Arash Kochaki 2
1 Ferdowsi University of Mashhad
2 Department of Food Science & Technology, Faculty of Agriculture, Ferdowsi University of Mashhad, Mashhad, Iran.
چکیده English

Kefir is a traditional beverage that is produced by fermented milk with kefir grains, Kefir grains are complex mixture of bacteria, yeasts, and polysaccharides produced by this micro flora. The initial amount of kefir grains used to produce kefir drinks affects the quality of the beverage in terms of pH, viscosity and microbial characteristics of the final beverage. In this study, the effects of different levels of starter (4, 6 and 8%, containing Streptococcus thermophilus, Lactobacillus delbrueckii subsp. Bulgaricus, Bifidobacterium), yeast Saccharomyces cerevisiae (2, 3 and 4%) and storage time (24, 48 and 72 hours after inoculation) on the physicochemical and microbiological properties of kefir beverage was studied using a central composite design and response surface methodology, in order to produce a product with higher probiotic bacteria than yeast. Physicochemical properties including acidity, pH, ethanol, apparent viscosity and flow behavior parameters, as well as microbial counting was performed. According to the results of the tests, the amount of yeast had the most effect on apparent viscosity and by increasing the amount of yeast and during of storage time, the apparent viscosity and consistency coefficient decreased. In addition, the viscosity increased with increasing starter rates. Regarding the amount of ethanol, the amount of produced ethanol increased by increasing the amount of yeast and during the storage time due to the increase in the amount of yeast and finally the microbial count decreased during storage. Optimization results showed that the sample containing 2% yeast and 4% starter in time 38 hours after inoculation had the lowest amount of ethanol and was suitable for rheological properties.

کلیدواژه‌ها English

Kefir
Starter
Yeast
storage time
Physicochemical properties
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