بررسي اثرات انجماد كند و سريع بر روي اسيدهاي چرب و بار ميكروبي فيله ماهي تيلاپيا نيلي (Oreochromis niloticus)

The Effect of Slow and Quick Freezing on Fatty Acid and Total Count of Nile Tilapia (Oreochromis niloticus) Fillets

در اﯾﻦ ﭘﮋوﻫﺶ اﺛﺮ اﻧﺠﻤﺎد ﮐﻨﺪ و ﺳﺮﯾﻊ ﺑﺮ روي اﺳﯿﺪﻫﺎي ﭼﺮب و ﺑﺎر ﻣﯿﮑﺮوﺑﯽ ﻣﺎﻫﯽ ﺗﯿﻼﭘﯿﺎي ﻧﯿﻠﯽ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺘﻪ اﺳﺖ. ﺑﺮاي اﯾﻦ ﻣﻨﻈﻮر ﻓﯿﻠﻪ ﻫﺎي ﻣﺎﻫﯽ ﺗﯿﻼﭘﯿﺎ ﻧﯿﻠﯽ )Oreochromis niloticus( ﺑﻪ دو روش اﻧﺠﻤﺎد ﮐﻨﺪ و ﺳﺮﯾﻊ ﻣﻨﺠﻤﺪ، ﺑﺴﺘﻪﺑﻨﺪي و در دﻣﺎي 18- درﺟﻪ ﺳﻠﺴﯿﻮس ﺑﻪ ﻣﺪت ﺷﺶ ﻣﺎه ﻧﮕﻬﺪاري ﺷﺪﻧﺪ. ﺗﻐﯿﯿﺮات اﺳﯿﺪﻫﺎي ﭼﺮب و ﺑﺎر ﻣﯿﮑﺮوﺑﯽ ﻓﯿﻠﻪ ﻫﺎ ﺑﻪ ﺻﻮرت ﻣﺎﻫﺎﻧﻪ ﻣﻮرد ﺑﺮرﺳﯽ ﻗﺮار ﮔﺮﻓﺖ. ﻧﺘﺎﯾﺞ ﻧﺸﺎن داد ﮐﻪ درﺻﺪاﺳﯿﺪﻫﺎي ﭼﺮب در زﻣﺎن ﻧﮕﻬﺪاري در ﺳﺮدﺧﺎﻧﻪ در ﺗﻤﺎﻣﯽ ﻧﻤﻮﻧﻪ ﻫﺎ دﺳﺘﺨﻮش ﺗﻐﯿﯿﺮات ﺷﺪ. در ﻧﻤﻮﻧﻪ ﻫﺎي ﺗﺎزه ﺗﯿﻼﭘﯿﺎ ﻧﯿﻠﯽ ﺑﻪ ﺗﺮﺗﯿﺐ درﺻﺪاﺳﯿﺪﻫﺎي ﭼﺮب اﺷﺒﺎع )SFA( 24/84 درﺻﺪ، اﺳﯿﺪﻫﺎي ﭼﺮب ﻏﯿﺮ اﺷﺒﺎع داراي ﯾﮏ ﺑﺎﻧﺪ دوﮔﺎﻧﻪ )MUFA( 36/14 درﺻﺪ و اﺳﯿﺪﻫﺎي ﭼﺮب ﻏﯿﺮ اﺷﺒﺎع داراي ﭼﻨﺪ ﺑﺎﻧﺪ دوﮔﺎﻧﻪ )PUFA( 38/62 ﺑﻮد. در ﻣﺎه آﺧﺮ ﻧﻤﻮﻧﻪﺑﺮداري، درﺻﺪ SFA و MUFA ﺑﻪ ﺻﻮرت ﻣﻌﻨﺎدار اﻓﺰاﯾﺶ و درﺻﺪ PUFA ﮐﺎﻫﺶ ﯾﺎﻓﺖ)p<0.05(. در ﺗﯿﻼﭘﯿﺎي ﻧﯿﻠﯽ ﺑﺎ اﻧﺠﻤﺎد ﮐﻨﺪ و ﺳﺮﯾﻊ ﺑﻪﺗﺮﺗﯿﺐ درﺻﺪ SFA ﺑﻪ 28/90 و 27/38،درﺻﺪ MUFA ﺑﻪ 39/55 و 38/21 و درﺻﺪ PUFA ﺑﻪ 30/56 و 35/22 رﺳﯿﺪ. ﻣﯿﺰان اﯾﻦ ﺗﻐﯿﯿﺮات ﺑﺮاي ﻧﻤﻮﻧﻪ ﻫﺎي ﺣﺎﺻﻞ از اﻧﺠﻤﺎد ﺳﺮﯾﻊ ﻧﺴﺒﺖ ﺑﻪ اﻧﺠﻤﺎد ﮐﻨﺪ ﮐﻤﺘﺮ ﺑﻮد)0.05

This study is designed to investigate the effects of slow and quick freezing on fatty acids and microbial load of Oreochromis niloticus. Fillets were prepared in groups of slow and quick freezed and were preserved in -18ᵒ centigrade for six months. Changes in Fatty acids amounts and microbial load were monitored every month. Our results indicate statistically significant changes in fatty acid amounts during cold-room preservation in all tested samples. Fresh fillets of O.niloticus contain 24.84 percent of sutured fatty acids (SFAs), 36.14 percent of mono unsutured fatty acids (MUFAs) and 38.62 percent of poly un-sutured fatty acids (PUFAs). However, in the last month of sampling, SFA and MUFA levels significantly increased; whereas PUFA level decreased (p<0.05). In slow and quick freezed O.niloticus, SFA increased to 28.90% and 27.38%, MUFA reached 39.55% and 38.21%, and PUFA decreased to 30.56% and 35.22%, respetively. Changes in fatty acid levels were significantly less severe in fillets with quick freezing method (p<0.05). The results of total count indicate that quick freezed samples had lower numbers of microbial load in comparison with slow ones (p<0.05).