The present invention relates to mushroom growth enhancing materials, and more particularly to a mushroom growth enhancer consisting of a substantially undenatured, sized, and pasteurized particulate soybean product in combination with a preservative agent.
The production and cultivation of the commercial mushroom Agaricus bisporus originated in France at the beginning of the 17th century. At that time, most of the cultivation occurred outdoors. Later, it was discovered that superior results were obtainable by growing the mushroom in caves. The caves provided a cool, consistent environment. As mushroom cultivation techniques developed, the production of A. bisporus using greenhouses increased in popularity. The greenhouses provided a growth environment in which temperature and humidity could be controlled.
Although the biological and chemical systems of the commercial mushroom are complex, agricultural scientists have developed growth methods for improving mushroom yield and quality. The basic stages of mushroom cultivation most commonly used today are as follows:
a. Composting--Composting consists of two stages referred to as phase 1 and phase 2. Phase 1 involves the preparation of compost material for growing the mushrooms. A variety of different materials can be used to make the compost. A preferred compost is prepared by mixing straw materials with protein meal, cottonseed hulls, gypsum, and water and allowing the mixture to ferment by action of the microflora, molds, and bacteria therein. In phase 2, the fermented mixture is placed into trays, and treated to convert free ammonia and other nitrogenous compounds into microbial protein. The treated mixture is then pasteurized to eliminate insects and foreign molds. Preparation of the compost as described above usually takes from 20-30 days.
b. Spawn Run--In this stage, the compost is inoculated with spawn (mushroom seed) and the resulting mycelium allowed to grow for approximately 14 days. The term "mycelium" refers to a mass of branched filaments produced by the growing mushroom.
c. Case Holding--After the spawn run period is completed, a mixture of peat moss, limestone, and water is blended and layered on top of the compost. The mycelium grows up through this casing layer and fruiting is initiated by reducing the temperature and carbon dioxide levels of the growing environment.
d. Production--Once fruiting has started, mushroom production will occur in "breaks" or "flushes" which are usually one week apart. Most mushroom growing facilities will harvest four breaks (28 days) before discarding the compost.
To enhance the above-described mushroom growth process, research has been directed to the formulation of a growth supplement. Testing has shown that supplementation can be undertaken at either the spawn run or case holding phases of growth. Research concerning the supplementation of growing mushrooms was first described by L. C. Schisler and J. W. Sinden in articles entitled, "Nutrient Supplementation of Mushroom Compost at Spawning," Mushroom Science 5, 150-164 (1962) and "Nutrient Supplementation of Mushroom Compost at Casing," Mushroom Science 5, 267-280 (1962.) According to these articles, an increase in mushroom growth is obtainable by incorporating various proteinaceous materials into the compost, including cottonseed meal, soybean meal, and dried skim milk. Increases in yield using these materials are attributed to their relatively high nitrogen concentrations.
Additional research on mushroom supplementation involved the addition of vegetable lipids (fatty materials) to mushroom compost. The following articles describe research in which vegetable lipids were studied as mushroom growth enhancers: Schisler, L. C. and J. W. Sinden, "Nutrient Supplementation of Mushroom Compost at Casing--Vegetable Oils," Can. J. Bot. 44, 1063-1069 (1966); Schisler, L. C., "Stimulation of Yield in the Cultivated Mushroom by Vegetable Oils," Appl. Microbiol. 15, 844-850 (1967); and Schisler, L. C. and T. G. Patton, Jr., "Stimulation of Yield in the Cultivated Mushroom by Vegetable Oils: Effect of Sterols and Ethyl Linoleate," Agric. Food Chem. 18, 1102-1103 (1970).
However, a need remained for a mushroom growth enhancer usable on a large, commercial scale. To be commercially feasible, a growth stimulant must be capable of adding nutrients to the growing mushroom crop without stimulating the growth of competing microorganisms, including bacteria and molds. The growth of competing microorganisms reduces the yield and quality of the mushroom crop. Furthermore, competing microorganisms produce respiratory heat which raises the temperature of the compost to undesirably high levels. High temperatures (approximately 90.degree. F. or above) drastically inhibit the growth of spawn and mushroom mycelium.
To solve this problem, research has been directed to mushroom growth supplements designed to prevent the growth of competing microorganisms. For example, U.S. Pat. No. 3,942,969 to Carroll, Jr. et al. describes a nutrient composition for mushrooms using a denatured proteinaceous material. Preferred proteinaceous materials include fish meal, malt sprouts, brewers yeast products, casein, wheat germ, sunflower seed, corn glutin, cottonseed protein, soybean protein, and peanut protein. In accordance with the patent, the protein may be denatured by heating or by reacting it with formaldehyde, acids, or alkali materials. Denaturation helps prevent competing microorganisms from using the protein as a food source, especially early in the spawn run phase. However, the mushroom mycelium can utilize the denatured protein by resolubizing it from its insoluble, denatured form. The precise mechanism used by the mushrooms to resolubize the protein is not known.
Another nutrient supplement is described in U.S. Pat. Nos. 4,370,159 and 4,421,543 to Holtz. The supplement described in these patents consists of a matrix material having a plurality of chemical growth enhancer droplets embedded therein. A preferred matrix material consists of anhydrous, denatured soybean meal, denaturation being accomplished using formaldehyde and heat. The enhancer droplets preferably consist of a vegetable oil core having an activated soybean protein coat.
The present invention represents an improvement over the above-described inventions. Formaldehyde is an environmentally dangerous and potentially carcinogenic compound. Its use in an agricultural formulation for growing food products is undesirable. By varying and optimizing other factors, including particle size, preparation temperature, and the addition of non-denaturing preservative compounds, the present invention eliminates the need for denaturing the protein supplement using formaldehyde or other methods. As a result, a low-cost, effective, and environmentally safe mushroom growth enhancer is produced, as described in detail below.