Study On The Drying Technology Of Tremella By Solar Assisted Heat Pump Drying System

Tremella, is one of the important medicinal and edible varieties of edible fungi, which is favored by vast number of consumers due to its good nutrition and health value. However, it is easily spoilage after harvested if it wasn’t dehydrated due to high water contents (>80%) in fresh tremella, which would be result in loss of its edible and economic value. Drying is one of the common and effective ways to decrease the high water content in fresh food. Recently, the main drying methods for fruits and vegetable were hot air drying, microwave drying, vacuum freeze drying and so on. However, these methods have the disadvantages of high energy consumption or high investment. So the high efficiency, energy saving and green environmental protection drying method need to be used in fresh tremella. Solar assisted heat pump (SAHP) drying technology was used to dry tremella from Gutian country in Fujian, the effects of drying temperature and loading density were studied during drying process to optimize the technology parameters and conditions. And the storage quality was discussed in different storing temperature to predict the shelf life of tremella products. Finally, HACCP system was established to ensure the quality safety during the processing. The results as follows:(1) The optimized drying parameters of tremella by SAHP were loading density is 1.54 kg/m3, the water content was reached 30% in initial drying temperature 60℃,and then 70℃ was used to continue drying to 13% water content. Under this conditions, the energy consumption was 16260 kJ/kgH2O,20% energy saving less than heat pump drying (19556 kJ/kgH2O), compared to traditional drying,42% energy saving was reached. The tremella products has prefer sensory quality with integrity, uniform light yellow color(L=52.45; b=30.88) and with unique tremlla flavor, which was reached the first class standard according to DB35T 1096-2011. At the same time, the shrinkage rate and rehydrated ration of tremlla products were reached 62.86% and 10, respectively.(2) Effects of storing quality of tremella products was studied in different storing temperature by accelerated experiments. The shelf life of tremella products was predicted according to the principle of the accelerated experiment(Qio). The results showed that the higher storing temperature, the shorter shelf life, the shelflife was achieved 756 days in 25℃.(3)In order to ensure the quality and safety of tremella products, HACCP system of SAHP was established according to the principles of HACCP. The critical control points were acceptance of raw materials, drying conditions, and packing and storing conditions. Critical limits and monitoring measures were also established, the heavy metals and pesticides residues in raw materials would be reached the requirements of GB 7096-2014, if not, raw materials should be rejected. The tremella should be drying in 60℃ for 13 h to reach the 30% water content, and then 70℃ for 2 h was used to continue drying till the water content below 13%. Finally, tremlla products should be storaged in 25℃ with PE package, and water content need to be detected during storing process in order to ensure which was below 13%.