Study On Lossing Kinetic And Pathway Of β-carotene In Carrot When Drying With N₂Source Heat Pump

The carrot is one kind of vegetable with highest content of carotene in humandietary.The main one is β-carotene.Carotene have many functions.The content ofcarotene is the main reason to effect the quality of carrot and its products.In thispaper,we dried the carrot using N₂source heat pump with different dryingtemperature、 medium velocity and oxygen levels.The effect on β-carotene retentionrate with drying temperature and oxygen levels is the key point to study. Then westudied the lossing kinetic of β-carotene in carrot during N₂source heat pump dryingprocess and detected the oxidation products of β-carotene by HPLC-DAD-MS.Theoxidation products of β-carotene were got by chemical oxidation and auto-oxidationduring drying process.At last,we explored the pathway of β-carotene lossing whencarrot was drying by N₂source heat pump.The retention of β-carotene in carrots is related to the drying method andparameters during drying process.There is no loss when drying at vacuum freezedrying; When the carrots were dried at vacuum drying,the retention rate of β-carotenewas depending on the drying time and temperature.There is a serious loss of β-carotene when carrots were drying at hot air. The degree of loss is related to the dryingtemperature.When carrots were drying at N₂source heat pump,the retention of β-carotene was increasing when the oxygen content descending;The retention rate of β-carotene is equal compared with the best level of vacuum drying when the dryingtemperature is40℃and the oxygen level is5%,but more timesaving.The results ofstatistical method showed that oxygen levels affect the β-carotene retention rate wasmore significant compared with temperature.When the carrots dried at hot air with different oxygen levels and differenttemperature,the lossing pattern of β-carotene is fitting with first-order kinetics.The degradation rate increased when the temperature was increasing.The relationshipbetween degradation reaction rate constant and temperature is fitting with Arrheniusequation, the activation energy is50.7154²37.7804kJ·mol-1.The reaction rateconstants of β-carotene lossing increased with the same drying temperatureconditions;At the same time, Q10increases when improving the oxygen level,indicating that oxygen reduces the sensitivity of β-carotene on temperature.We foundthat the β-carotene content changes,the color changes either. The correlationcoefficient is between0.5⁰.9.When β-carotene was oxidation by MCPBA with different addition and reactiontime,there was no significant effect on production mode.And the reaction products didnot cumulate with the increasing of dose or duration;The oxidation products of β-carotene by MCPBA are mainly isomers and epoxidation products,such as9-cis-β-carotene,13-cis-β-carotene,9-cis-5,8-epoxy-β-carotene,all-trans-5,6-epoxy-β-caroteneand5,6-5,8-epoxy-β-carotene.When β-carotene was oxidation by KMnO₄,isomers and epoxidation products arethe early products during the oxidation process.The ending products are5,6,5′,6′-β,β-tetracarbonyl-carotene, All-trans-5,6-dicarbonyl-β,β-carotene-14′-al,5,6-dicarbonyl-β,β-carotene-12′-al,5,6-dicarbonyl-β,β-carotene-10′-al,5,6-dicarbonyl-β,β-carotene-8′-al and their monohydroxy derivatives.The cis-isomers of the ending products areaslo existing.Then we can see that the pathway of the products is oxidation at β-iononeand double bond in carbon chain.The auto-oxidation products of β-carotene are isomers and epoxidation productswhen carrots were dried by N₂source heat pump.The products are13-cis-5,6-epoxy-β-carotene,13-cis-β-carotene and9-cis-β-carotene respectively.There were nooxicracking products to be detectived.