Effect of Ultrasonic, Microwave, Chemical, and Osmotic Pre-Treatments on Quality Indexes (Texture, Color, and Rehydration Ratio) of Dried Button Mushroom Slices in Hot Air Drying

Objective: Button mushrooms (Agaricus Bisporus) are among the most widely produced and consumed mushrooms in the world. Generally speaking, mushrooms are of great nutritional value, which due to their high content of moisture and their corruptibility particular attention is required to be paid to their conservation and health. Drying is one of the most important ways to preserve the yields with high content of humidity. Methods: In this study, in order to increase the hold time and quality specifications, different pretreatments including osmotic (NaCl2 with a 10% density ratio), chemical (metabisulfite potassium with concentration 0/5% density ratio), ultrasound (with a frequency of 28 ±0/5 (KHZ)), and microwave (with power 360 watt) were applied. These pretreatments were dried through the hot air method. Osmotic, chemical, and ultrasound pretreatments were used for 2 h, 30 minutes, and 30 minutes, respectively at ambient temperature, while the microwave was employed for 4 minutes. Then effect of various pretreatments on the dried button mushrooms’ quality indexes such as texture, color, and rehydration ratio was investigated. Results: Based on the results, with regard to the tissue of samples under various pretreatments, a highly significant difference at 1% level can be observed for the hardness and adhesiveness indexes, while a significant difference exists for the chewiness index at 5%. After comparison, the maximum hardness was seen in the control sample, and hardness value of the samples under various pretreatments was lower than that of the control. Among the samples with ultrasonic, microwave and osmotic pretreatments, no significant difference was observed and the lowest hardness value belonged to the samples with chemical pretreatment. The samples under chemical pretreatment comprised the lowest chewiness value. Furthermore, no significant difference was observed in the other pretreatment and control samples. The least adhesiveness value belonged to the samples with microwave, osmotic, and ultrasound pretreatments. The sample with chemical pretreatment had the highest adhesiveness. The best color was related to the osmotic samples, and control samples showed a low quality. In general, the samples with pretreatments had better color than the control ones. The lowest rehydration ratio was obtained in the samples under chemical and control pretreatment, respectively. Therefore, application of various pretreatments significantly contributes to the improvement of quality specifications, where chemical pretreatment is of great importance.