Effect Of Sharp Quenching Processing And Pumping Nitrogen Combined With Nano-packaging On Preservation Quality Of Green Tea

Green tea, a type of popular drink, is increasingly consumed in many countries.China is one of the most important producing country, and over three quarters of greentea prodution is from China. The quality of green tea is subject to deterioration because ofthe oxidation of polyphenols, amino acids and vitamin C, and the decomposition ofchlorophyll during the storage. The reasons for these changes are probably due to theresidual enzymes, ambient moisture, light and oxygen. In order to eliminate the influenceof these factors on the preservation quality of green tea, different storage methods, suchas cold storage, deoxidized packaging, nitrogen packaging and vacuum packaging hadbeen developed. However, most of these techniques are not applied widely, very costeffective and short time-sensitive. Therefore, there is an urgent need to have alternativetechniques to promote the development of the preservation of green tea. Sharpquenching processing (SQP) is a new advanced technology used for tea processing toprotect beneficial ingredients of tea.Moreover, the development and applications ofnew nano-packaging materials have attracted great attentions due to their remarkableeffects on food preservation. Pumping nitrogen technology (PN) has been widelyused to preserve green tea nutrients. In order to further improve the preservationquality of green tea, the techniques of SQP combined with nano-packaging and PNcombined with nano-packaging have been investigated in this study. The main resultswere as follows:The physical and healthful property of the aluminizing nanocompositepackaging(ANP) materials was measured. The lengthwise and crosswise tensilestrength and elongation of aluminizing nanocomposite packaging material were24.3%,19.2%,14.5%and18.6%higher than the normal packaging material,respectively. The water vapor and oxygen permeability of ANP material were46.2%and45.4%lower than the normal packaging material, respectively. These resultsindicated that the ANP material owe better barrier property to H2O and O2than thenormal packaging material. Meanwhile, the healthful property of the ANP materialmet the national standard.The SQP combined with ANP was used to investigate its extensive effect onpreservation quality of green tea (Queshe) during storage at room temperature and35℃. The moisture content of Queshe with SQP/ANP was always increasing moregentle and lower than that of the normal treatment (regular processing withpolyethylene packaging) during the storage. For360-day storage at room temperature,the contents of amino acid, polyphenols, ascorbic acid and chlorophyll in Queshe withSQP combined with ANP (SQP/ANP) were8.83%,9.30%,45.60%and45.70%higher than those with the normal treatment, respectively. For90-day storage at35℃,the contents of amino acid, tea polyphenols, ascorbic acid and chlorophyll were 8.75%,7.86%,17.70%and34.20%higher in Queshe with SQP/ANP than those withthe normal treatment, respectively. Moreover, the sensory quality of Queshe withSQP/NCP storage was also superior to that of Queshe with normal treatment.Therefore, SQP combined with NCP may provide an attractive alternative to keep thepreservation quality of green tea at a higher level during long-term storage.The pumping nitrogen combined with nano-packaging was used to investigate itsextensive effect on preservation quality of green tea (Ruiyi) during storage at35℃for60days. For60-day storage at room temperature, the contents of water extracts,amino acid, polyphenols and chlorophyll in Ruiyi with pumping nitrogen combinedwith nano-packaging were14.65%,10.12%,14.23%and15.16%higher than thosewith the normal treatment (polyethylene packaging), respectively. Especially, thecontent of ascorbic acid was1.6times higher than the polyethylene packaginggroup.Moreover, the reduction of epigallocatechin gallate（EGCG）、epigallocatechin（EGC）、epicatechin gallate（ECG）and gallic acid（GA）were20.48%,21.88%,20.74%and25.35%lower in pumping nitrogen combined with nano-packaging thanthose with the normal treatment, respectively. Meanwhile, the increase of catechin（+C）and epicatechin（EC） in Ruiyi with the normal treatment were16.85%,32.33%higher than those with the pumping nitrogen combined with nano-packaging.The sensory quality of Ruiyi in pumping nitrogen combined with nano-packagingstorage was also superior to that of those with normal treatment by the analysis ofchromatic aberration. Therefore, pumping nitrogen combined with nano-packagingmay provide another comprehensive method to keep the preservation quality of greentea at a higher level during long-term storage.