عوامل موثربر كيفيت نهايي قارچ دكمه اي خشك شده در ايران

Factors inFluencing the quality of dried button mushroom in Iran.

Edible mushroom is one of the agricultural product which has high nutritional value but is extremely perishable and has a short shelf life period. This study was conducted to extend the shelf life of A. bisporus by hot air drying method, novel chemical and heat treatment (blanching). Colour change percentage and ratio of rehydration, protein content and microbial count were used as primary criteria for the evaluation of the quality of the dried mushroom slices under optimum condition. Below factors which change the quality of dried product were studied; Chemical treatments by H.Cl.Ca, citric acid, EDTA, metabisulphite (M.B.S.) and combination of M.B.S with other chemicals, Pre-treatment blanching with steam or boiling water, different strains of A. bisporus, number of break or flush, best time of drying (from harvest to processing time), differents condition of culture, determine shelf life of the products. Results indicated that different treatments and levels were affected significantly (p<0.0001). Chemical treatment with chlorine solution at 50 ppm reduced the microbial count. Citric acid slightly improved the colour and microbial load at 500 and 600 ppm in comparison with the control. Effect of metabisulphite with 400 and 500 ppm improved colour while EDTA had no change on colour of the dry product as compared to the control. On the other hand using M.B.S plus EDTA produced superior dehydrated product from the consumer point of view. M.B.S with cholorine solution effectively decreased the microbial load. Combination of M.B.S with citric acid caused a slight pale-yellow colour. This colour change was increased as acid quantity, increased and turned completely yellow. Blanching reduced the attractiveness of dried mushroom compared to the control. Unblanched dried mushroom had higher rehydration value and lower protein content than blanched dried mushroom. Treatment of mushroom by blanching (steam or boiling water) reduced the microbial count. Similar results were obtained by either boiling water or steam blanching. This reduction also was similar in either boiling water or steam of blanching. Cultivation conditions of mushroom farms had very important effect on the colour, texture, percentage and ratio of rehydration as well as on nutritional value and microbial contamination of the quality of the dried products. Strains of Agaricus bisporus such as U1, U3, X1, 413 and A-5 on the same cultivation condition had a slight effect on colour and texture but not the total microbial count. The best colour of the dried mushroom were obtained from the 1st and 2nd flushes. Increasing the number of flushes, colour changes also increased. Result showed that harvested fresh mushroom should not be immediately processed, processing should take place after 48, 72 and 96 hours post harvest.