مقایسه روش های مختلف انجماد زدایی در ماهی کفال

نوع مقاله : مقاله پژوهشی

نویسندگان

1 گروه صنایع غذایی دانشکده علوم و فنون دانشگاه ازاد تهران شمال

2 گروه صنایع غذایی، دانشکده علوم زیستی، دانشگاه آزاد اسلامی، واحد تهران شمال، تهران، ایران

3 گروه شیلات دانشگاه ازاد اسلامی تهران شمال

چکیده

زمینه مطالعاتی: انجماد تنها روش نگهداری مواد غذایی میباشد که تغییرات ایجاد شده در بافت آبزیان را به حداقل میرساند. بنابراین نگهداری محصول در حالت منجمد یک روش مطمئن برای عملآوری آبزیان دریایی میباشد. هدف: این مطالعه به منظور ارزیابی تاثیر روش‌های مختلف انجمادزدایی (دمای محیط، مایکروویو و یخچال) روی فیله ماهی کفال طلایی (Liza aurata) منجمد انجام شد. روش کار: در این تحقیق، ابتدا فیله کفال طلایی در دمای 35 - درجه سلسیوس منجمد و سپس به مدت 60 روز در دمای 18- درجه سلسیوس نگهداری شده و تاثیر روش‌های مختلف انجمادزدایی شامل انجمادزدایی در دlhd محیط (21 درجه سلسیوس)، مایکروویو (8 درجه سلسیوس) و در دمای یخچال ( 4 درجه سلسیوس ) بر میزان ارزش غذایی و شاخصهای کیفی آن مورد بررسی قرار گرفت. مدت زمان انجمادزدایی در دمای محیط 1 ساعت، دمای مایکروویو 3 دقیقه و در دمای یخچال به مدت 8 ساعت به طول انجامید. نتایج: نتایج حاکی از آن بود که از نظر میزان کاهش اکسیداسیون ثانویه (تیوباربیتوریک اسید) و مواد ازته فرار، پائینترین مقادیر شاخصهای شیمیایی مربوط به تیمار انجمادزدایی شده در دمای یخچال بود و داده‌های آن با دو روش دیگر اختلاف معنیدار داشت (05/0p<). کمترین مقدار pH در تیمار انجمادزدایی شده در دمای مایکروویو مشاهده شد. از نظر حفظ کیفیت ارزش غذایی ماهی (درصد پروتئین، چربی و حفظ رطوبت) روش انجماد زدایی در دمای یخچال و دمای محیط بهتر از دمای مایکروویو بود (05/0p<). همچنین از نظر شاخصهای رنگی، به جز شاخص روشنایی، فیلههای انجمادزدایی شده در دمای محیط از کیفیت و مقبولیت بالاتری نسبت به دو تیمار دیگر برخوردار بودند. نتیجه‌گیری نهایی: بر اساس نتایج حاصل از این تحقیق میتوان بیان کرد که انجمادزدایی آبزیان در دمای یخچال موجب حفظ ارزش غذایی ماده غذایی پس از انجمادزدایی خواهد شد. بنابراین، این روش مناسب ترین روش برای انجمادزدایی فیله کفال طلائی میباشد.

کلیدواژه‌ها


عنوان مقاله [English]

Comparison of different thawing methods quality of mullet fillets (Liza aurata)

نویسندگان [English]

  • babak karami 1
  • Elmira Hajiha 2
  • mohammad kazemian 3
1 department of food science, islamic azad university tehran shomal branch
2 Department of Food Science and Technology, Faculty Biological Sciences, Islamic Azad University, Tehran North Branch. Tehran, Iran
3 department of aquaculture. islamic azad university of tehran shomal branch
چکیده [English]

Introduction: Aquatic products are becoming a vital dietary component in humans’ daily life, due to their high protein and low fat, especially rich in polyunsaturated fatty acids (omega-3 and omega-6). Golden grey mullet, Liza aurata, have a commercial value for fisheries, especially in internal waters. This species usually lives inshore, lagoons and estuaries, and rarely move into freshwater. Additionally, they are widely distributed in the Mediterranean Sea and the Black Sea, Atlantic coasts from the Azores and Madeira northward to the British Isles, and the southern coasts of Norway and Sweden. Many technologies have been used in the food industry to extend the shelf-life of fish for ease of transportation, such as freezing which is the most effective method to ensure food quality and safety. Consequently, the frozen fish should be thawed before further processing. Generally speaking, the quality of frozen food is highly associated with the thawing process. Improper thawing methods have caused unacceptable changes of the chemical and physical properties of frozen fish such as drip loss, enzymatic reaction, lipid and protein oxidation, and inhomogeneity. There are different thawing methods in foods reported, such as air thawing, water thawing, refrigerator thawing, microwave thawing, ultrasonic thawing, high-voltage electric field thawing, high-pressure thawing, and so on. However, each thawing method has its advantages and disadvantages. Therefore, it is necessary to explore a better thawing method that is beneficial for maintaining the quality of frozen fish. The purpose of this study was to evaluate the effects of different thawing methods on the chemical, microbial, sensory, and physical quality of goldfish fillets after thawing.
Material and methods: Twenty live L. aurata weighted 400± 30 g were purchased and were kept in powdered ice in a ratio of 1 to 1 in medium-sized tanks and immediately transferred to the laboratory of the National Center for Aquatic Processing Research. After arrival, the butterfly method was used to wash fishes, then their skin and internal organs were removed. Two back fillets removed from the back. Each fillet was individually packed in a polythene bag to prevent moisture loss and frozen in storage at-35°C and then maintained at -18 °C for 60 days. The fillets were randomly divided into three groups and thawed by different treatments as follows: thawing in the microwave (8°C), ambient temperature )21°C) and refrigerator temperature (4°C). The duration of thawing in each of the above conditions lasted 1 hour, 10 minutes, and 8h, respectively. The experiments were performed at the National Center for Aquatic Processing Research in Bandar Anzali (affiliated to the Iranian Fisheries Research Institute) and at the Food Industry Laboratory of the Azad University of North Tehran Branch in October and November 2016. To determine the approximate amount of protein, fat, moisture, and ash sampling was performed in zero phases (before freezing) and final stage (after 2-months storage) after thawing. For measuring some content of mullet fillets (such as TVB-N and TBA, pH, etc.), color assessment, and weight loss, sampling was done three times during 2-months storage (zero phase, after one month, and after two months). Moisture, ash and protein contents, TVB-N, and pH were measured. Also, fat content and TBA were determined. Moreover, the color assessment was done using a colorimeter (NR60CP Precision Colorimeter, 3nh, China). All experiments were performed in triplicates. The normality of obtained data was checked by Kolmogorov – Smirnov method. All data were presented as mean values ± standard error (SE), which were compared using one-way analysis of variance (ANOVA) following Duncan’s multiple range test. A P-value of less than 0.05 was considered significant. This study was done in the summer of 2018.
Results and discussion: The results indicated that the amount of thiobarbituric acid (TBAs) and volatile nitrogen (TVB-N) and pH were significantly different between treatments. The highest value of the first two parameters and the lowest pH was found in microwave thawing (p<0.05). Also, a significant increase in thiobarbituric acid levels was observed in all three thawing methods. This may indicate increasing the fat oxidation, which may be due to the release of oxidative enzymes and peroxidants from disintegrated cells due to freezing. Regarding the moisture content, crude protein, fat content, and ash content, the results showed that thawing in ambient temperature and refrigerator is better than that thawing in the microwave. It must be due to the formation of drip in the process of thawing and the solubility of ash and protein in drip. Also, it should be related to the high energy of microwaves which causes the removal of intermittent water from fish’s bodies. also, color indices showed that the thawing fillets at ambient temperature had higher quality than at refrigerator and microwave temperature treatment, except for L*, which is the highest in refrigerator temperature.
Conclusion: Based on the results of this research, it can be noted that the freezing of the aquatic environment at refrigerator temperature will maintain the nutritional value of the food after dehumidification, the most suitable method for the thawing of the fillet.

کلیدواژه‌ها [English]

  • Decontamination
  • Quality change
  • Chemical composition
  • Fish fillet