Study On Storage And Preservation Of Lotus Sprout Under Low Temperatures

Lotus sprout in storage easily brown and become soft, so it is not easy for storage.This article study on storage and preservation of lotus sprout under low temperatures by the method of freezing and ice-temperature technology, through systematic study of the pretreatment of lotus sprout including blanching, preserving colour, hardening, vacuum penetration of regulation liquid, the freezing process and combination of ice storage and of other preservations, by analyzing the quality changes during storage, the theoretical basis and technical support are expected to provide for the industrializd storage and preservation of lotus sprout. The main research content and the results are as follows:(1) The effect of different blanching methods on the quality of lotus sprout was compared. By comparing the effect of the optimal blanching in boiling water (100℃-1.5min), the best work at low temperature blanching (65℃-3.5min), the best result of microwave blanching (microwave-lmin), and the best craft of steam blanching (Steam-2min), the four methods of blanching on the quality of lotus sprout, The results indicated that steam blanching was an ideal blanching method, and low temperature blanching (65℃-3.5min) followed.(2) Lotus sprout were treated by selected four color fixative and three color-protecting techniques. By comparing the effect of the four color fixative, HI:EDTA (0.25%)+ascorbic acid (0.25%), H2:ascorbic acid (0.25%)+citric acid (0.2%), H3: NaHSO3 (0.05%)+citric acid (0.2%), H4:0.3% L-cysteine and 0.5% citric acid+0.5% NaCl+0.2% ascorbic acid, on the color protectection of lotus sprout, the results showed that, the order of the color-protecting effectiveness was:H4> H2> H3> HI, four color fixative had no significant difference. By comparing the effect of the three color-protecting techniques, color protection first and then blanching (process A), color protection and blanching simultaneously (process B), and blanching first and then color protection (process C), on the color protectection of lotus sprout, the results show that: Process C was the best color protection technology, and showed significant superiority compared with process A andB (p<0.05).(3) The effects of the concentration and processing time of crispness agent (CaCl2) on the texture and color of lotus sprout was studied. The results showed that:the low concentration of CaCl2 for long processing time, or high concentration of CaCl2 for short time can not only improve the texture of lotus sprout effectively, but also can improve the color of lotus sprout. Considering the texture and color comprehensively, the optimal concentration and processing time of CaCl2,were 120mmol/L CaCl2 for 10min.(4) The effect of vacuum infiltration of regulation liquid on protection of lotus sprout during the freezing process was studied, the results showed:sodium alginate (0.5%)-CaCl2 (0.5%) and trehalose (0.5%)-xanthan gum (0.25%) weakened the freezing damage to some extent, but can not fundamentally solve the damage caused by freezing.(5)Freezing curve of lotus sprout at different temperatures were determined, freezing pattern and technology were also studied, it was found out that freezing process was the main reason to cause sharp decline in texture of lotus sprout by observing microscopic cell structure at the different stage of process. Freezing temperature was changed in order to improve the quality of quick frozen lotus sprout, facts proved that:the lower the freezing temperature only reduced the effect of freezing process on the quality of lotus sprout in a very small area. Study on PPO activity, drip loss, nutrition index changes of lotus sprout during frozen storage, results showed that, with the extension of storage time, PPO activity increased and then decreased and showed fluctuations in the overall style, the color kept good, drip loss rates increased, soluble sugar and Vc losses increased.(6) Compared the quality of lotus sprout under four methods of thawed at room temperature (20℃), fridge (4-6℃), running water (15℃) and microwave (750W), results indicated that the thawing at 4-6℃environment was better for lotus sprout, not only kept the texture of lotus sprout, but also maintained nutrition and better color.(7)Research the ice-temperature storage technology and the quality changes during storage. Selected different freezing point regulators to reduce the freezing point of lotus sprout. With comprehensive consideration, it was concluded that, when immersed lotus sprout to 1%CaCl2 for 60min, the freezing point of lotus sprout could drop from-0.8℃to-1.5℃. Packed the treated lotus sprout and stored in-1℃for ice-temperature storage. Compared the preservative effect of ice-temperature storage combined with four treatments including color-protection, modified atmosphere packaging, vacuum packaging and preservation liquid immersion packaging on lotus sprout, results indicates that:Lotus sprout stored at ice-temperature after preservation liquid immersion packaging, the physico-chemical indices were less influenced, that can maintain the quality of lotus sprout to a large extent, and the storage time could be up to 60 days. So it was an ideal storage way.