| Pleurotus eryngii is rich in proteins, vitamins, amino acids, polysaccharides, mineral substance, and many other nutrients and bioactive substances, which has high nutritive value and medicinal value. It can improve human’s immunity by frequently consumption. Because of the high moisture content and the delicate tissue, the poor storage property and the browning are serious in the manufacturing process. These seriously affect sensory quality and shelf life. The traditional drying methods are mainly solarization and hot-air drying, which make the products has poor color, low-rehydration and high nutrients loss. Therefore, the study on color protection technology and the best drying methods of Pleurotus eryngii in the drying process have great significance.Microwave vacuum drying and vacuum frying technology were used in the process of Pleurotus eryngii drying in this paper. Color protection technology with non-sulfites as inhibitors and soaking with ultrasonic were studied. Meanwhile, technology parameters were optimized, and the influence of different drying methods on quality characteristics were also investigated. The purpose is to provide a technical guarantee for energy-saving processing and high quality products. The main research results were as follows:1. In order to solve the browning problem in the process, Pleurotus eryngii was treated by five browning inhibitors with different concentrations. Through orthogonal optimization test, the optimum technological parameters were:calcium chloride concentration was0.4%, citric acid concentration was0.8%, ascorbic acid concentration was0.15%, and L-Cysteine concentration was0.09%. The results indicate that L-Cysteine had significant effect the on L-value of Pleurotus eryngii slices (P<0.05).2. Effects of different factors, including comparison of impregnating solution, different concentrations, dipping time and methods were investigated respectively. The optimum technological parameters for impregnating were:solid-liquid ratio was1:4, mass fraction of maltodextrin was10%, mass fraction of maltose was5%, and soaking time was15min with ultrasonic.3. Effects of microwave power, loadage and vacuum degree on the drying rate by microwave vacuum drying were investigated, from which the rule of water changes during the process was obtained. The drying process of MVD was divided into two stages, called accelerated phase and decelerated phase. During the drying, the higher the microwave power, the higher vacuum degree, the higher prower intensity and the less loadage was the greater dehydration rate and the shorter the drying time required.4. The optimum technology parameters were obtained by L9(34) orthogonal test, with the factors of dehydration rate, microwave power and loadage, which were evaluated by L-value, expansion rate and rehydration rate. The optimum parameters for AD-MVD were:microwave power was900W, loadage was50g and rehydration rate by hot-air drying was70%or80%.5. Effects of four drying methods, including vacuum freeze drying (FD), microwave vacuum drying (MVD), combination drying of hot-air and microwave vacuum (AD-MVD) and hot-air drying (AD), were investigated respectively which evaluated by color, appearance, rehydration rate and Vitamin C content. The results showed that AD-MVD take the shortest drying time and the lowest energy consumption. And the energy consumption by AD-MVD was81.9%lower than by MVD. The overall quality of Pleurotus eryngii drying by AD-MVD and MVD was very close (P<0.05), which was much greater than AD’s and litter worse than FD’s. But FD took the longest time and the highest energy consumption, those more than6.3times and8.87times higher than AD-MVD’s.6. The optimum technology parameters for vacuum frying were obtained by L9(34) orthogonal test, with the factors of pre-drying time, frying temperature and frying time, which evaluated by oil content and sensory quality. The optimum parameters:the thickness was2mm, float time was90s at80℃, solid-liquid ratio was15mL/g, mass fraction of maltodextrin was10%, soaking time was15min with ultrasonic, predrying for20min under60℃hot air, vacuum frying at80℃-90℃for10min, vacuum degree was0.08MPa-0.09MPa and rotary de-oiling for10min with350r/min. |
PDF Full Text Request