Quality Change And Control During The Concentration Of Coconut Jam

As a typical tropical fruit,coconut has high nutritional value and unique taste,which is deeply loved by consumers.In mature coconuts,the physical and chemical properties of coconut pulp make this food suitable for consumption under natural conditions.Therefore,coconut pulp is an excellent raw material for making jam.As one of the deep-processed products of fruits,jam can enrich the types of coconut products,improve the quality and utilization of coconuts,and extend the shelf life.In this paper,HS-SPME/GC-MS,LC-MS,rheometer and texture analyzer were used to measure and analyze the quality change of coconut jam during the concentration process.Therefore,some guiding suggestions were put forward for the industrialized production of coconut jam.The main research results of this paper are as follows:The volatile components and markers of coconut jam were characterized by HSPME/ GC-MS.Principal component analysis revealed the concentration process of coconut jam can be divided into three stages.In the first stage,esters and alcohols were the two main contributors to the aroma of the coconut jam.Next,a caramel smell was gradually formed during the second stage,which was mainly derived from aldehydes,ketones and alcohols.The concentration of aldehydes increased gradually at this stage,which may be the result of a combination of the Maillard reaction and the caramelization reaction.In the final sterilization stage,the ‘odor intensity’ of caramel reached the maximum level and a variety of aroma compounds were produced,thereby forming a unique flavor for the coconut jam.Finally,furfural fit a logistic model with a regression coefficient(r2)of 0.97034.Therefore,furfural can be used as a marker substance for monitoring the concentration of coconut jam.The 5-hydroxymethyl furfural,sucrose,glucose,fructose and corresponding physical and chemical indicators in the coconut jam processing process were determined and analyzed by LC-MS and other technologies.The result analysis shows that the main ways of 5-hydroxymethyl formation were Maillard reaction and caramelization reaction.During the processing and concentration of coconut jam,reducing sugar,total phenols,soluble solids,and browning index all showed an upward trend.Coconut jam had the highest sucrose content,followed by fructose,and finally glucose.In the analysis of amino acids,it was found that the content of norvaline was the highest,and the contents of lysine and proline were continuously decreasing,which had a positive effect on the browning of coconut jam.Correlation analysis showed that the concentration of 5-hydroxymethyl was significantly negatively correlated with the concentration of proline(r=-0.926).According to the above conclusions,the formation mechanism of 5-hydroxymethy during the processing and concentration of coconut jam can be speculated.There are three ways to produce 5-hydroxymethyl during the processing and production of coconut jam.First,glucose interacts with free amino acids to generate a Schiff base to produce 5-hydroxymethyl.Second,glucose and fructose undergo 1,2 enolization and dehydration to produce 3-deoxyketone and further produce5-hydroxymethyl.Third,the glycosidic bond of sucrose is cleaved under hightemperature conditions to generate fructofuranosyl cations and further dehydrated to form 5-hydroxymethyl.Therefore,a better understanding of the changes of parameters related to the formation of 5-hydroxymethyl can provide reasonable guidance and suggestions for the safety management of industrial production of jam.Through sensory evaluation,rheology and texture analysis,the quality of coconut jam with different sugar concentrations was analyzed.The result analysis revealed when fructose syrup and sucrose are added at 12%-18%,sugar-free crystals are precipitated.Under the premise of ensuring consumer acceptance,the maximum addition of coconut jam fructose syrup or sucrose accounts for 24%,and a very few sugar crystals are precipitated at this time.Therefore,the amount of fructose syrup and sucrose added needs to be controlled within 12%-24%.Coconut jam with fructose syrup as the main sweetener,as the concentration of fructose syrup continues to increase,its viscosity index,adhesion,strength and hardness all show a downward trend.On the contrary,coconut jam,which uses sucrose as the main sweetener,shows an upward trend in viscosity index,adhesion and hardness as the concentration of sucrose continues to increase.The linear amplitude scanning viscoelastic zone analysis of coconut jam showed that the linear viscoelastic zone of coconut jam with fructose syrup and sucrose as the main sweeteners was in the range of 0.01%-10%.Sweep analysis of the coconut jam oscillation frequency showed that changes in the concentration of fructose syrup and sucrose will not affect the deformation resistance of the coconut jam,and can allow the coconut jam to maintain its own structure.Viscosity test analysis showed that the coconut jam with fructose syrup and sucrose as the main sweeteners,with the continuous increase of the shear rate,the viscosity continued to decrease.The jam sample has the phenomenon of shear dilution,and the coconut sauce sample behaves as a non-Newtonian fluid.In summary,during the processing and concentration of coconut jam,furfural can be used as a labeling substance to achieve the purpose of monitoring the concentration of coconut jam.The amount of 5-hydroxymethyl furfural produced during the concentration of coconut jam is lower than the national standard and meets the safety index.When the addition of fructose syrup and sucrose in coconut jam is controlled at12%-18%,sugar-free crystals are precipitated.