Food Structure Volume 3 Number 2 Article 12 1984 Ultrastructural Studies of Raw and Processed Tissue of the Major Cultivated Mushroom, Agaricus bisporus E. M. Jasinki B. Stemberger R. Walsh A. Kilara Follow this and additional works at: https://digitalcommons.usu.edu/foodmicrostructure Part of the Food Science Commons Recommended Citation Jasinki, E. M.; Stemberger, B.; Walsh, R.; and Kilara, A. (1984) "Ultrastructural Studies of Raw and Processed Tissue of the Major Cultivated Mushroom, Agaricus bisporus," Food Structure: Vol. 3 : No. 2 , Article 12. Available at: https://digitalcommons.usu.edu/foodmicrostructure/vol3/iss2/12 This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Food Structure by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. FOOD MICROSTRUCTURE, Vol. 3 (1984), pp. 191-196 07 30-5419/84$1 . 00+. OS SEM Inc. , AMF O'Hare (Chicago), IL 60666 U.S.A. ULTRASTRUCTURAL STUDIES OF RAW AND PROCESSED TISSUE OF THE MAJOR CULTIVATED MUSHROOM, AGARICUS BISPORUS E. M. Jasinski. B. Sternberger, R. Walsh, and A. Kilara Food Science Department, The Pennsylvania State University, 111 Borland Laboratory, University Park, PA 16802 Introduction Commercial mushroom processors currently lose Shrinkage, the loss of weight during process­ approximately 30 percent of the mushroom weight ing (blanching and canning), continues to plaque due to shrinkage during processing (blanchi ng and the mushroom processing industry. Weight losses canning) , resulting in substantial economic loss­ can range as high as 30 percent, which results in es . Microscopy was used to assess the extent and substantial economic losses to the processor (Eby, type of chemical and structural changes induced by 1975) . Shrinkage results from a loss of water and processing mushrooms and causing shri nkage. Scan­ water soluble solids from the mushroom tissue. ning e l ectron microscopy revealed that the Ho we ver, the cause of this loss is not totally processing operations includi ng vacuum hydration , understood. Microscopy can be used in determining blanching , and thermal treatment do not damage the the severity of mushroom processing or in assess ­ integrity of the tissue. Light microscopy re­ ing the effects of processing and/or handling on vealed that the morphology of the tissue, shape the quality of mushrooms . Therefore , an ultra­ and spacing of cells, appear similar for raw and structural examination of raw and processed processed mushroom tissue. However, the intra­ (blanched and canned) mushroom tissue should pro­ cell ular material remained indistinct for both vide insight into the causes of mushroom shrink­ tissue types, and the processed tissue appeared age. distorted. Transmission electron microscopy re­ vea 1ed that commercia 1 mushroom processing caused co~e~2~;~ ~~s c~~ ~{~;~!d (~~~~~~o~i ~~ ~~e t:~r~~jor intracellular damage to the tissue. The heat {Chang, 1980). Information is available on the treatment caused the coagulation of cytoplasmic structure and ultrastructure of raw mushroom material and the disruption of intracellular mem­ tissue; however, minimal information is available branes, resulting in the loss of water holding on the ultrastructure of processed mushroom capacity of the tissue. Therefore, shrinkage of tissue. The general ultrastructure of fungi and processed mushrooms results from "denaturation" of the organelles and the associated loss of water ~::n ~~~;:~;~~~~~r(Br~~ke~;a~~~~~ ~!~k~~~\~a~~ ., holding capacity by those organelles . 1974; Angeli - Papa and Eyme , 1978 ; Alexopoulus and Mims, 1979). These investigations pertain to the stipe elongation mechanism (Craig et al. , 1977a; Craig et al . , 1979), the cell wall structure (Novaes- Ledieu and Garcia-Mendoza , 1981). basidia and septal pore structures (Craig et al . , 1977b; Flegler et al., 1976), cell mem brane development Initial paper received July 14 1984 . (Eyme and Angel i-Couvy, 1975) , the basidiospore Final manuscript received November 8 1984 . structure (Elliott, 1977; Rast and Hollenstein , Direct inquiries to E.M. Jasinski. 1977}. and nuclear distribution (Wanq and Wu, Telephone number: (814) 863-2961. 1974) . However, the relationship of-mushroom ultrastructure to pr ocessing has not been investi­ gated. Mushroom processing operati ons have two major purposes : a) to provide a steri 1 e product and b) to minimize shrinkage of mushroom tissue, to KEY WORDS: Agar icus bisporus, Ultrastructure of maximize canned product yield. Var i ous processes raw mushroom , Ultrastructure of processed mush­ that limit shrinkage have been reported (Go rmley, room, Mushroom, Canning, Transmission electron 1972; Mc Ard le et al ., 1974; Seel ma n and McArdle, m1croscopy, Scanning electron microscopy, Light 1975; Steinbuch, 1979 ). Gormley (1972) found that microscopy . freez ing unblanched mushrooms produced a higher qua lity product than freezing blanched mushrooms . Steinbuc h (1979} found that vacuum packing of 191 E. 1~. Jasinski, B. Sternberger, R. Walsh, et al. unblanched frozen mushrooms showed promise in im­ to 3% glutaraldehyde in the same buffer, post proving mushroom quality and reducing shrinkage. fixed in 1% osmium tetroxide, and treated with Seelman and McArdle (1975) found that post-harvest 0.5% uranyl acetate in 0.1 t~ sodium acetate over­ night. The samples were dehydrated with acetone g~s~rf~~ ~~s~~~o~~ ~~ ~~~~ai~1l~:~~e~~t~~:~ing and embedded in Spurr firm epoxy resin (Spurr, (PSU-3S- Process) or vacuum hydration (SSV - Process) 1969). Samples were sectioned, stained with 1% prior to blanching, increased the canned product toluidine blue for light microscopy or with 3% yield (decreased shrinkage). Increased yields due uranyl acetate in 7. 5% methanol, 0. 2% lead c i­ to storage at elevated temperatures supported the trate (Venable and Coggeshall , 1965), and Reynolds hypothesis that chemical changes within the mush­ lead stain (Reynolds , 1963) for transmission elec­ room tissue caused an increase in water retention tron microscopy. A Leitz- Ortholux 1 ight micro­ by the tissue (Beelman and McArdle, 1975). The scope and an Hitachi HUllE electron microscope higher storage temperatures resulted in an in­ were used . crease in the mushroom tissue's ability to absorb more water before processing and retain more water Results and Discussion during processing (Beelman and McArdle , 1975). These results indicate that a loss of water hold­ Typical conm1ercial mushroom processing 1n ing capacity or water binding capacity of the the United States (F ig. 1) involves washing the mushroom tissue during processing causes shrink­ mushrooms, then cold storage for up to 48 hours, age. and applying a vacuum hydration treatment, which Chemical changes in the protein structure of completes the pre-processing steps . The remain­ the mushroom tissue could produce the increase in ing steps of the process include blanching, fill ­ water holding capacity during storage (Beelman inq, brining, closing, thermal processing, cool­ et al. , 1973). However, the specific chemical and ing, and storage. The major <JOal of this process structural changes that occur during processing to is for the mushroom tissue to absorb as much water cause shrinkage remain unknown. Therefore, this as possible during soaking and vacuum hydration investigation uses microscopy to assess the extent so that the water lost during blanching and ther­ and type of chemical and structural changes in­ mal processing is mostly the absorbed water. duced by processing (blanching and canning) mush ­ Scanning electron, light, and transmission elec­ rooms. tron microscopy were used to determine the effects this process had on mushroom tissue. f~a teri a 1 s and Methods The scanning electron micrographs of the stem, cap , and gills (Figs . 2- 6) show that the Samples absorption of water during vacuum hydration and Raw cultivated mu~hrooms, Agaricus P..!._spor~s subsequent loss of water during blanchinq and (Lange) Sing were obta1 ned from The Pennsylvama thermal processing does not destroy the overall State University Mus hroom Research Center and the integrity of the tissue . Filaments or hyphae com ­ commercially processed samples were canned buttons pose the outer surface of the stem (Fig. 2) and grown and processed in Pennsylvania. Mushrooms the cap (Fig . 4) . The longitudinal filaments in with tightly closed veils and cap diameters rang­ the raw (Fig . 2a) and processed stem (Fig. 2b) ing from 2.8-3.0 em were selected . Seven sections are bunched together. However, the filaments in of raw and processed tissue were prepared for the processed tissue appear deflated or shriveled scanning electron microscopy. These included out­ (Fig. 2b). Monacha (1965) described the stem as side surface, longitudinal, and cross-sectional a combination of wide inflated hyphae and narrow cuts of the cap (pileus) and stem (stipe) and the threadlike filaments. The cross-section a 1 view outside surface of the gills. Five sections of of the stern (Fig. 3) shows the two types of sep­ raw and processed tissue were prepared for light tate hyphae. The compact filaments of the pro­ and transmission electron microscopy. These in­ cessed tissue (Fig . 3b} with gaps between groups cluded cross- section and longitudinal cuts of the of filaments reveal the same distortion seen on cap and stem a nd cross-section of the gills. the outside surface of the stem (Fig . 2b) . Random Scanning Electron