اثر پراکسید هیدروژن بر کاهش بار میکروبی انواع کشمش منطقه بوانات فارس

تهیه کشمش به روش های مختلفی از قبیل قرار دادن میوه انگور در معرض آفتاب مستقیم و روش های مکانیکی صورت می گیرد. امکان آلودگی انواع کشمش به میکروارگانسیم های مختلف در طول مراحل برداشت و خشک کردن انگور، حمل و نقل و بازاررسانی کشمش وجود دارد. عملیات سنتی تهیه و بسته بندی کشمش در منطقه بوانات (منطقه اصلی تولید کشمش استان فارس)، این محصول را مستعد آلودگی های میکروبی خطرناک برای سلامتی انسان می نماید. این پژوهش به منظور تعیین میزان آلودگی میکروبی انواع کشمش تهیه شده از انگور رقم ’کشمشی بوانات‘ و امکان ضدعفونی آنها اجرا شد. برای این منظور از غلظت های صفر (شاهد) و 0.9 درصد پراکسید هیدروژن به عنوان فاکتور اول و سه نوع کشمش تهیه شده از رقم ’کشمشی بوانات‘ (سایه خشک، کشمش آفتابی و کشمش تیزابی) به عنوان فاکتور دوم در یک آزمایش فاکتوریل 3×2 در قالب طرح بلوک های کامل تصادفی با سه تکرار انجام شد. برای تهیه نمونه های ضدعفونی از هر نوع کشمش 200 گرم در ارلن 1000 میلی لیتری سترون شده قرار داده و به آن 400 میلی لیتر آب مقطر اضافه شد و مقدار 3.6 میلی‌لیتر پراکسید هیدروژن به محتویات ارلن اضافه و به مدت دو دقیقه هم زده شد. سپس آب داخل ارلن دور ریخته شد و برای شستشوی نمونه کشمش ها، 400 میلی‌لیتر آب مقطر داخل این ارلن ها ریخته شد و به مدت 5 دقیقه تکان داده شدند تا سطح نمونه کشمش داخل ارلن کاملاً شسته شود. پس از آن مقدار 50 میلی لیتر از آن به عنوان نمونه کشمش آب شویی و ضدعفونی شده برای بررسی آلودگی میکروبی به آزمایشگاه ارسال شد. برای تیمار شاهد یا نمونه های ضدعفونی نشده، همه این مراحل انجام شد با این تفاوت که در این تیمار از پراکسید هیدروژن برای ضد عفونی استفاده نشد و نمونه ها فقط با آب مقطر سترون شده تیمار شدند. برای هر نمونه شمارش کلی میکروبی، شمارش قارچ ها اعم از شمارش کپک آسپرژیلوس، شمارش باکتری های کلی فرم و اشرشیاکولی انجام شد. نتایج نشان داد که هر سه کشمش عمل‌آوری شده دارای آلودگی‌ میکروبی بودند. آلودگی میکروبی کشمش تیزابی بالاتر از دو نوع دیگر بود. باکتری اشرشیاکولی فقط در کشمش تیزابی وجود داشت. ضدعفونی با پراکسید هیدروژن موجب کاهش قابل توجه آلودگی میکروبی در هر سه روش عمل آوری کشمش گردید. مقدار این کاهش در دو نوع کشمش سایه‌خشک و آفتابی یکسان، اما در کشمش تیزابی کمتر از همه بود. آلودگی به کپک آسپرژیلوس فقط در کشمش تیزابی مشاهده شد و تیمار پراکسید هیدروژن در حذف این آلودگی موثر نبود. این تحقیق نشان داد که برای عاری سازی انواع کشمش از آلودگی های باکتریایی و قارچی می توان از غلظت 0.9 درصد پراکسید هیدروژن (در سطح تجاری) استفاده نمود.

effects of hydrogen peroxide on decreasing microbial contaminations in raisins of bavanat region

 raisins are dried grapes and are prepared from some varieties of grapes (vitis vinifera) in different ways, such as exposing grapes to direct sunlight and mechanical methods. there is a possibility of contamination of various types of raisins with different microorganisms during the stages of harvesting and drying grapes, transportation and marketing of raisins, especially when they are presented in open boxes. the traditional process of preparing and packing raisins in bovanat region (the main raisin production area of fars province) makes this product prone to microbial contamination dangerous for human health. the history of consumption of raisin is very old. the bible provides the first written mention of raisin around 1000 b.c., drying is one of the oldest methods of food preservations; the main purpose of this experiment is reducing the moisture content to level which allows safe storage without spoilage. it has been reported that the use of hydrogen peroxide (h2o2) treatments reduces the microbial contamination loads in dried raisins. moreover, washing with hydrogen peroxide solution can markedly reduce the loads of human pathogens including escherichia coli. primitive methods of making and packaging of raisins in bavanat region contribute to make them vulnerable to microbial contamination and may be harmful for health. this research was conducted in order to determine the initial microbial contamination on the surface of three types of raisins prepared from the keshmeshi grape cultivar and using hydrogen peroxide to reduce these microbial contaminations.materials and methodsthe use of hydrogen peroxide as a potential antimicrobial treatment was investigated for three types of raisins in bovanat region. for this purpose, three samples of raisins (sun-dried, shade-dried and sultana raisins) have investigated. raisins samples randomly were purchased from a local retailer in shiraz (iran). for this experiment, raisin samples with uniform size were selected and damaged or diseased berries were discarded. two concentrations of hydrogen peroxide applied to microbial disinfection were 0% and 0.9%. the raisins that were prepared underwent a treatment process where they were dipped for 5 minutes in solutions containing either 0% or 0.9% hydrogen peroxide. afterward, the raisins were washed with distilled water for 1 minute to remove any residue. a control group was also included, consisting of raisin samples treated with water (0% hydrogen peroxide). for each sample, measurements were taken for microbial count, population of yeasts and other molds, aspergillus, coliform bacteria, and escherichia coli. the experiment was designed as a factorial (2x3) based on a completely randomized block design with 3 replications. the data were analyzed using spss 22.0, and mean data were compared using duncan’s multiple range tests at a 1% probability level. results and discussion the results showed that there was a significant difference (p≤1%) between hydrogen peroxide concentration treatments regarding to microbial contamination. there was also a significant difference (p≤1%) between the raisin samples in terms of microbial contamination. the results also revealed the presence of high amount of microbial infection on surface of all raisin samples. the microbial contamination load of sultana raisins was higher than other raisins. the results also indicate that escherichia coli was not detected in both sun-dried and shade-dried samples, but it was observed in sultana raisins. surface disinfection of sultana raisin samples with 9% of hydrogen peroxide removed escherichia coli infection. hydrogen peroxide was effective in reducing the microbial contamination of all three raisin samples. it seems hydrogen peroxide to be more effective in reducing microbial contamination in sun-dried and shade-dried samples. sultana raisin had highest contamination of mold and yeast while sun-dried and shade-dried raisins were lowest. the effect of hydrogen peroxide on reducing mold and yeast contamination was not the same in all raisin samples, so that the highest effect on reducing mold and yeast contamination was found in sun-dried and shade-dried raisins. the least effect on this contamination was observed in sultana raisins. aspergillus was not detected in sun-dried and shade-dried samples but it was observed in sultana raisins. hydrogen peroxide was not effective against aspergillus. the microbial contamination of all raisin samples which affected by 0.9% hydrogen peroxide was decreased significantly (p≤1%). effect of hydrogen peroxide at 0.9% on removing of microbial infection in sun-dried and shade- dried raisins was similar and it was more than sultana raisins.conclusionall three raisin samples were infected with coliform bacteria, mold and yeast. in the case of escherichia coli infection, it was detected only in sultana samples. hydrogen peroxide was effective in reducing the microbial infection of all raisin samples. it was more effective in reducing the total number of microbes in sun-dried and shade-dried raisins. hydrogen peroxide with a concentration of 0.9% is effective for eliminating the microbial infection of raisins, and the use of hydrogen peroxide with a concentration of 0.9% can be used to disinfect raisins.