غیرفعال سازی آنزیم پکتین متیل استراز موجود در آب هویج- کیوی طی فرایند حرارتی

ﺳﺎﺑﻘﻪ و ﻫﺪف: ﮐﺪورت در ﺑﺴﯿﺎری از آب ﻣﯿﻮهﻫﺎ ﻣﺎﻧﻨﺪ آب ﻫﻮﯾﺞ- ﮐﯿﻮی ﯾﮏ وﯾﮋﮔﯽ ﻣﻄﻠﻮب ﺑﻪ ﺷﻤﺎر ﻣﯽرود ﮐﻪ ﭘﮑﺘﯿﻦ ﻣﻮﺟﻮد در ﻋﺼﺎره ﻣﻬﻢﺗﺮﯾﻦ ﻋﺎﻣﻞ اﯾﺠﺎد آن اﺳﺖ. آﻧﺰﯾﻢ ﭘﮑﺘﯿﻦﻣﺘﯿﻞاﺳﺘﺮاز ﺑﺎ ﺗﺠﺰﯾﻪ ی ﭘﮑﺘﯿﻦ، ﻣﻮﺟﺐ از ﺑﯿﻦ رﻓﺘﻦ ﮐﺪورت ﻣﺤﺼﻮل ﻣﯽ ﺷﻮد. ﻓﺮاﯾﻨﺪ ﺣﺮارﺗﯽ ﻣﺮﺳﻮمﺗﺮﯾﻦ روش ﺟﻬﺖ ﻏﯿﺮﻓﻌﺎلﺳﺎزی اﯾﻦ آﻧﺰﯾﻢ اﺳﺖ. از اﯾﻦ ﺟﻬﺖ ﻫﺪف از اﯾﻦ ﭘﮋوﻫﺶ، ﺑﺮرﺳﯽ ﺳﯿﻨﺘﯿﮏ ﻏﯿﺮﻓﻌﺎلﺳﺎزی ﭘﮑﺘﯿﻦﻣﺘﯿﻞاﺳﺘﺮاز ﻣﻮﺟﻮد در آب ﻫﻮﯾﺞ- ﮐﯿﻮی ﻃﯽ ﻓﺮاوری ﺣﺮارﺗﯽ در دﻣﺎﻫﺎی ﻣﺨﺘﻠﻒ ﺑﻮد. ﻣﻮاد و روشﻫﺎ: ﺑﻪ ﻣﻨﻈﻮر ﻣﻄﺎﻟﻌﻪی ﺳﯿﻨﺘﯿﮏ ﻏﯿﺮﻓﻌﺎلﺳﺎزی آﻧﺰﯾﻢ ﭘﮑﺘﯿﻦﻣﺘﯿﻞاﺳﺘﺮاز، اﺑﺘﺪا آب ﻫﻮﯾﺞ-ﮐﯿﻮﯾﯽ در ﺣﻤﺎم آب ﮔﺮم در دﻣﺎﻫﺎی 60، 70، 80 و 90 درﺟﻪ ﺳﻠﺴﯿﻮس در ﺑﺎزهﻫﺎی زﻣﺎﻧﯽ ﻣﺨﺘﻠﻒ )ﻣﺘﻨﺎﺳﺐ ﺑﺎ دﻣﺎ( ﺣﺮارت دﻫﯽ ﺷﺪ . ﺷﺎﺧﺺ d و z و ﭘﺎراﻣﺘﺮﻫﺎی ﺳﯿﻨﯿﺘﮑﯽ واﺑﺴﺘﻪ ﺑﻪ دﻣﺎ ﺷﺎﻣﻞ اﻧﺮژی ﻓﻌﺎلﺳﺎزی واﮐﻨﺶ (ea)، اﻧﺘﺎﻟﭙﯽ (h∆)، اﻧﺘﺮوﭘﯽ (s∆) و اﻧﺮژی آزاد ﮔﯿﺒﺲ (g∆) ﻣﺮﺑﻮط ﺑﻪ ﺗﺨﺮﯾﺐ ﺣﺮارﺗﯽ ﭘﮑﺘﯿﻦﻣﺘﯿﻞاﺳﺘﺮاز ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﯾﺎﻓﺘﻪﻫﺎ: ﺑﺮ اﺳﺎس ﻧﺘﺎﯾﺞ ﺑﻪ دﺳﺖ آﻣﺪه، ﻣﯿﺰان ﺷﺎﺧﺺ z اﻧﻮاع ﺣﺴﺎس و ﻣﻘﺎوم ﺑﻪ ﺣﺮارت آﻧﺰﯾﻢ ﭘﮑﺘﯿﻦﻣﺘﯿﻞاﺳﺘﺮاز ﻣﻮﺟﻮد در آب ﻫﻮﯾﺞ-ﮐﯿﻮی ﻃﯽ ﻓﺮاوری در دﻣﺎﻫﺎی 60، 70، 80 و 90 درﺟﻪ ﺳﻠﺴﯿﻮس ﺑﻪ ﺗﺮﺗﯿﺐ ﻣﻌﺎدل 17/85 و 22/27 درﺟﻪ ﺳﻠﺴﯿﻮس ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻣﯿﺰان ea ﻣﻮرد ﻧﯿﺎز ﺟﻬﺖ ﺷﺮوع ﻏﯿﺮﻓﻌﺎلﺳﺎزی اﻧﻮاع ﺣﺴﺎس و ﻣﻘﺎوم ﺑﻪ ﺣﺮارت اﯾﻦ آﻧﺰﯾﻢ ﻣﻮﺟﻮد در آب ﻫﻮﯾﺞ ﮐﯿﻮی ﺑﻪ ﺗﺮﺗﯿﺐ ﻣﻌﺎدل 356/83 و 257/17 ﮐﯿﻠﻮ ژول ﺑﺮ ﻣﻮل ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻫﻤﭽﻨﯿﻦ ﻣﯿﺰان اﻧﺘﺎﻟﭙﯽ ﻏﯿﺮﻓﻌﺎلﺳﺎزی اﻧﻮاع ﺣﺴﺎس و ﻣﻘﺎوم ﺑﻪ ﺣﺮارت ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺮاﺑﺮ 354/1 ﺗﺎ 353/8 ﮐﯿﻠﻮ ژول ﺑﺮ ﻣﻮل و 254/4 ﺗﺎ 254/1 ﮐﯿﻠﻮ ژول ﺑﺮ ﻣﻮل ﺗﺨﻤﯿﻦ زده ﺷﺪ . ﻃﯽ ﻓﺮاوری ﺣﺮارﺗﯽ آب ﻣﯿﻮه، ﻣﯿﺰان اﻧﺘﺮوﭘﯽ ﻣﺮﺑﻮط ﺑﻪ ﻏﯿﺮﻓﻌﺎلﺳﺎزی دو ﻧﻮع ﺣﺴﺎس و ﻣﻘﺎوم ﺑﻪ ﺣﺮارت آﻧﺰﯾﻢ ﺑﻪ ﺗﺮﺗﯿﺐ ﺑﺮاﺑﺮ 0/79 ﺗﺎ 0/73 و 0/47 ﺗﺎ 0/43 ﻣﺤﺎﺳﺒﻪ ﺷﺪ. اﻧﺮژی آزاد ﮔﯿﺒﺲ ﻣﺮﺑﻮط ﺑﻪ ﻏﯿﺮﻓﻌﺎلﺳﺎزی اﻧﻮاع ﺣﺴﺎس ﺑﻪ ﺣﺮارت ( 91/1 ﺗﺎ 87/3) و ﻣﻘﺎوم ﺑﻪ ﺣﺮارت ( 97/9 ﺗﺎ 97/0) اﯾﻦ آﻧﺰﯾﻢ ﻧﯿﺰ ﺗﺨﻤﯿﻦ زده ﺷﺪ. اﯾﻦ ﻧﺘﺎﯾﺞ ﻧﺸﺎندﻫﻨﺪهی اﺛﺮ ﺗﻐﯿﯿﺮ دﻣﺎ ﺑﺮ ﺳﺎﺧﺘﺎر ﭘﺮوﺗﺌﯿﻨﯽ اﯾﻦ آﻧﺰﯾﻢ اﺳﺖ. ﻋﻼوه ﺑﺮ اﯾﻦ، ﻣﯿﺰان درﺻﺪ ﻣﻮﺛﺮ ﻣﺮﺣﻠﻪی اﻓﺰاﯾﺶ دﻣﺎی ﻣﺤﺼﻮل در ﺗﺨﺮﯾﺐ ﺣﺮارﺗﯽ اﻧﻮاع ﺣﺴﺎس و ﻣﻘﺎوم ﺑﻪ ﺣﺮارت ﭘﮑﺘﯿﻦﻣﺘﯿﻞاﺳﺘﺮاز ﻣﻮﺟﻮد در آب ﻫﻮﯾﺞ-ﮐﯿﻮی ﻣﺤﺎﺳﺒﻪ ﺷﺪ. ﻧﺘﯿﺠﻪ ﮔﯿﺮی: ﺑﺎ در ﻧﻈﺮ ﮔﺮﻓﺘﻦ درﺻﺪ ﻣﻮﺛﺮ ﻣﺮﺣﻠﻪی اﻓﺰاﯾﺶ دﻣﺎی ﻣﺤﺼﻮل و ﻣﻘﺎوﻣﺖ ﺣﺮارﺗﯽ ﻧﻮع ﺣﺴﺎس ﺑﻪ ﺣﺮارت اﯾﻦ آﻧﺰﯾﻢ، زﻣﺎن ﻣﻮرد ﻧﯿﺎز ﺟﻬﺖ ﭘﺎﺳﺘﻮرﯾﺰاﺳﯿﻮن ﺣﺮارﺗﯽ آب ﻫﻮﯾﺞ- ﮐﯿﻮی در دﻣﺎﻫﺎی 75، 80، 85، 90 و 95 درﺟﻪ ﺳﻠﺴﯿﻮس ﺑﻪ ﺗﺮﺗﯿﺐ 22/14، 11/61، 6/09، 3/19 و 2/01 دﻗﯿﻘﻪ ﺗﺨﻤﯿﻦ زده ﺷﺪ.

Inactivation of Pectin methylesterase in carrot-kiwi juice during thermal processing

Background and objectives: In this study, the mixture of carrot and kiwi juice is introduced as a new food product with high nutritional value. Turbidity is considered as a desirable property in carrot kiwi juice that is influenced by the presence of released pectin into the extraction. Pectin methylesterase (PME) desterified the pectin that resulted in the turbidity loss in the juice. Thermal processing is known as the most common method to PME inactivation. The aim of this study is to investigate the PME inactivation during carrot kiwi juice thermal processing at different temperature. Materials and methods: To study the inactivation of pectin methylesterase, at first the carrot kiwi juice was heated at 60, 70. 80 and 90 ℃ in different time (proportional to the temperature). Using a thermocople, the changes in the temperature of the sample were recorded and reported in a second. During thermal processing, the activity of the enzyme was measured according to Kimball (1991) method. Dvalue, Zvalue and also thermodynamic parameters of the thermal destruction of PME were calculated. Results: Based on the obtained results, Zvalue of heat labile and stable isoforms of PME in the juice were estimated 17.85℃ and 22.27℃, respectively. The required activation energy to inactivate the heat labile and stable isoforms of PME in the carrot kiwi juice were calculated 356.83 kJ/mol and 257.17 kJ/mol, respectively. Enthalpy for inactivation of the heat labile (354.1 to 353.8 kJ.mol1) and stable (254.4 to 254.1 kJ.mol1) isoforms were estimated. During the carrot kiwi juice processing, the entropy of the inactivation of the heat labile and stable isoforms were calculated 0.79 to 0.73 K1.kJ.mol1 and 0.47 to 0.43 K1.kJ.mol1, respectively. Also, the free energy related to the inactivation of the heat labile (91.1 to 87.3 kJ.mol1) and stable (97.9 to 97.0 kJ.mol1) isoforms of PME was measured. These results represent the effect of temperature on the protein structure of the enzyme. In addition, the effectiveness percentage of the come up time (CUT) on inactivation of the heat labile (5522%) and stable (6622%) isoforms of PME in the carrot kiwi juice were computed. Conclusion: The overheating of the product and also loss of nutritional value, organoleptic and qualitative properties and also energy wasting could be prevented by reducing the required thermal processing temperature of the carrot juice by its combination with the kiwi fruit that resulted in pH adjustment and also study the effect of CUT on the PME inactivation.