تعیین خاصیت ضداکسیدانی، محتوای پلی‌فنل کل و شمارش کلی بار میکروبی شیر ‌‌طعم‌دارحاوی عصاره پوست انار و شهد خرما طی نگهداری در سرما

پوست انار بخش غیرقابل خوردن حاصل از فرآیند آبگیری میوه انارو منبع غنی از تانن‌ها، فلاونوئید‌ها و ترکیبات فنولی دیگر می‌باشد. شهد خرما، نیز طعم و بوی منحصر به فردی دارد؛ و می‌تواند بعنوان شیرین‌کننده طبیعی کاربرد داشته باشد. امروزه، توجه مصرف‌کننده به سوی غذاهای سلامتی بخش معطوف شده است و ترکیبات فنلی موجود در انار و پوست آن می‌توانند چنین نقشی را ایفا کنند؛ علاوه بر آن، دارای خواص ضدباکتریایی بالایی هستند. در این مطالعه، تاثیر افزودن عصاره آبی پوست انار در مقادیر 10، 20 و 30 درصد حجمی/ حجمی همراه با شهد خرما در مقادیر 2، 4 و 6 درصد حجمی/ حجمی بر خاصیت ضداکسیدانی، محتوای پلی‌فنل کل و شمار شکلی بار میکروبی شیر‌ طعم‌دار فراسودمند در طول 21 روزنگهداری در سرما مورد بررسی قرار گرفت. برای تولید نمونه‌‌های شیرطعم‌دار، پیش گرم کردن شیر تا دمای 50 درجه سانتی‌گراد انجام پذیرفت؛ شهد خرما و عصاره پوست انار به شیر اضافه و به مدت 5 دقیقه مخلوط شدند؛ سپس، مخلوط در دمای 75 درجه سانتی‌گراد به مدت 15 دقیقه حرارت داده شد. نمونه‌های شیرطعم‌دار فراسودمند، پس از خنک شدن تا دمای 25 درجه سانتی‌گراد، در دمای 4 درجه سانتی‌گراد نگهداری شدند. بر اساس پژوهش حاضر، با افزودن عصاره پوست انار،فعالیت ضداکسیدانی و محتوای پلی‌فنل کل افزایش یافتند (p<0/01). علاوه بر این، افزودن عصاره پوست انار باعث کاهش شمارش کلی بار میکروبی شیرطعم دار شد (p<0/01). با افزودن شهد خرما، فعالیت ضداکسیدانی و محتوای پلی فنل کل شیرطعم دار افزایش یافت (p<0/01). با افزودن مقادیر مختلف شهد خرما، تغییریدر شمارش کلی بار میکروبی نمونه های شیر طعم دار مشاهده نشد (p>0/05)

The determination of antioxidant activity, total polyphenols and microbial total count of functional flavored milk containing pomegranate peel extract and date datesyrup during cold storage

Introduction: Flavored milk is a healthy beverage, nutritious, delicious and thirst elimination by a large group of people, especially children consumed. Therefore, the need to find different ways to enhance the nutritional value of milk and its products is of many researchrs’ interest.Pomegranate fruits peel is an inedible part obtained during processing of pomegranate juice. Pomegranate peel is a rich source of tannins, flavonoids and other phenolic compounds;which is currentlybeingwidely used in medicine and food industry. Moreover, consumers prefer to use natural antioxidants rather than synthetic ones. The datedatesyrup has unique odor and taste; it has high potential to be a new sweetener which is natural and chemicalfree. Datesyrup hasa natural sweetness and is considered easy to digest. Also, it has low fat, no cholesterol and saturated fat and a good source of dietary fiber is considered. In this study, the effect ofaqueous extract of pomegranate peel adding at levels 10%, 20%, 30% and datedatesyrup adding at levels 2%, 4% and 6% on antioxidant property, total polyphenols contents andmicrobial total countof functional flavored milk was investigated during 21day cold storage. Materials and method: Raw milk from Deniz factory (Iran), date syrup with Brix ° 83 from Dombaz company (Iran), Reagent Folin Ciocalteau, reagent 2,2Di Phenyl1Picryl Hydrazyl(DPPH) and gallic acid monohydrated from Sigma (America) were prepared. Other laboratory chemicals and PCAGARCulture media from Merck (Germany) was purchased.Also, pomegranate variety of Shiraz Black Tail (Iran) was used.Preparation ofAqueous extract of pomegranate peelFresh pomegranate was washed and peeled and stored at room temperature away from sunlight for a week. 50gr of powdered pomegranate peelwas mixed with 500 ml of distilled water with temperature of 30°Cand was maintained at 30°C for 12 hours.Preparation of flavored milkThe milk used for producing functional flavored milk samples was preheated at 50ºC, then date syrup was addedat levels of 2%, 4% and 6% and aqueous extract of pomegranate peel was also added at levels of 10%, 20% and 30% to milk and the whole mixture was mixed for 5 minutes; The mixture was then heated to75ºCfor 15 minutes. After cooling at 25°C, flavored milksamples were refrigeratedat 4ºC.Determination of antioxidant activityThe antioxidant activityof flavored milk samples was measured according to Elfalleh et al. (2012) method using model CARY 50spectrophotometer,Australia, at 517 nm by a Radical Scavenging Activity (RSA) and DPPH reagent .Determination of total polyphenolsThe total polyphenolsof flavored milk samples were measured according to Elfalleh et al. (2012) method usingmodel CARY 50spectrophotometer,Australia, at 765 nm by Folin Ciocalteu reagent. The amount of phenol content was calculated by standard curve of gallic acid .Microbial total countMicrobialtotal count was determinedin plate count agar according to Iranian National Standard no.5484. Sample plates were incubated in model zn1434incubator, Iran, at 31 ° C for 72 hours.Experimental designIn this study, A completely randomized design was employed usng SAS software (version 9.1) to determinate the antioxidant activity, total polyphenols and microbial count. The experiment was consisted of three factors including pomegranate peel extract (in three levels 10, 20 and 30%), date syrup factor (in three levels 2, 4 and 6%) and time (in four days 0, 7, 14 and 21).Results and Discussion: According to present research, with adding pomegranate peel extract percentage of free radical scavenging and total polyphenols content increased (p