Study On Preparing High Concentration Natural Apple Essence

China produces the largest quantities of apple juice concentrate in the world. As the byproduct of apple juice concentrate, natural apple essence is recycled, and adds substantial profits to the producers. The security of natural apple essence is incomparable better than the artificially synthesized apple essence. In order to save the transportation and storage cost, the demand of high time natural apple essence (hereinafter referred to as apple essence) becomes larger and larger. In this paper,200time apple essence was employed to study the preparation of high time apple essence. First, Headspace Solidphase Microextraction (HS-SPME) coupled with gas chromatograph-mass spectrometer (GC-MS) were used to detect the volatile compounds of apple essence, and quantities of14main volatile compounds were obtained by internal standard method. Second, the atmospheric distillation were studied for preparing high time apple essence, and the process parameters were optimized. Third, reverse osmosis parameters were studied and optimized to prepare high time apple essence. The component changes were explored by GC-MS for both preparing methods. Conclusions were gained as follows:1. In total,53volatile compounds were detected in apple essence, namely24esters,13alcohols,8aldehydes,5acids,2ketones, and1benzene derivative, including aromatic compounds such as (E)-2-hexenal, hexanal, hexanol, butyl acetate, butanol, ethyl butyrate, hexyl acetate. Quantities differ greatly among these volatile compounds, alcohols were the compound class with the largest peak area, followed by aldehydes and esters.2. Optimal HS-SPME condition was gained by response surface design experiments. The best SPME fiber is85μmPA, the added apple essence volume is2mL, the NaCl concentration is0.4g/mL, the extracting time is30min, the extracting temperature is40℃. The optimal GC split ratio is60:1.3. The R2of14chemical standard curves created by the internal standard method ranged96.79%-99.68%. RSD of compound content determination experiments ranged1.20%-3.60%. The recovery ratio of the chemical standards ranged93.44%-107.42%.4. The atmospheric distillation process for preparing high time apple essence was fully studied. The optimal process is divided into two steps. First,200time apple essence is concentrated to800time, the heating temperature is160℃, the condensing temperature is-6℃. The concentration of concentrated essence was73918.33μg/g. The concentration of residual essence was303.89μg/g. The concentrating ratio was84.67%, and residual ratio was1.04%. Second,800time apple essence is concentrated to3200time. The heating temperature is160℃, the condensing temperature is-15℃. The concentration of concentrated essence was304179.98μg/g. The concentration of residual essence was6083.29μg/g. The concentrating ratio was81.49%, and residual ratio was4.89%.5. Reverse Osmosis (RO) was studied to concentrated apple essence using AFC99(NaCl rejection rate99%) and AFC80(NaCl rejection rate80%) membrane. The optimal RO process parameters were gained. The optimal membrane is AFC99; the optimal feed temperature is15℃; and the cross-membrane pressure is3MPa. Under the optimal condition, the average concentrating ratio was69.91%, the average permeate ratio was13.15%when200time apple essence was concentrated to800time. The average concentrating ratio was62.46%, the average permeate ratio was11.72%when800time apple essence was concentrated to1600time.6. In total,34volatile compound was detected in the original apple essence sample;28, and11in140℃concentrated essence, and residual essence;24and11in200℃concentrated essence, and residual essence. Atmospheric distillation under high heating temperature causes substantial aroma loss,12volatile compounds were not detected after distillation.11new compounds were detected after distillation, which may either be newly synthesized or concentrated to a higher concentration.7. In Reverse Osmosis process, the compound number for each compound class was higher in original apple essence than in concentrated essence and permeate essence.23,21volatile compounds were detected in concentrated essence, permeate essence using AFC99; and18,23volatile compounds were detected in concentrated essence, permeate essence using AFC80. Reverse Osmosis process causes substantial aroma loss,12volatile compounds were not detected after the process.3new compounds were detected after concentrating, which may be concentrated in this process. Except terpenoids and benzene derivatives, other compound family had larger peak area in AFC99concentrated apple essence than in AFC80, had smaller number and peak area in residual essence.