An earnest mushroom hunter can readily develop into an amateur mycologist. He thus becomes a student of the group of plant life known as fungi. He invests some time in studying their features by learning to recognize their size, shape, color, texture, smell, habitat and so on.He learns to recognize several edible and poisonous species. When he is in doubt about their edibiliity, he consults a professional or expert mycologist even before daring to taste them.
We are engaged here with gathering of edible mushrooms like the morel, chanterelle, boletus, russula, puffball, and the ever popular meadow mushroom ( found in all super markets) and preserving them safely as needed. If not eaten fresh as soon as picked or after two days when refrigerated, they can be preserved by drying, freezing, or pickling. A modified pickling method, called acidification, is described here.
Microorganisms of significance to food preservation are molds, yeasts, and bacteria. By far the most important and troublesome are the bacteria. A number of rod shaped bacteria produce spores, a non-vegetative dormant stage in its life cycle. They can survive a wide range of unfavorable conditions. Spores can be compared to plant seeds. They will germinmate and grow when conditions are suitable. Bacterial spores are extremely resistant to heat and cold. Some spores can survive in boiling water for several hours. The same bacterium in the vegetative state will not survive heating to boiling.
Soils or waters from which raw foods are obtained are the
sources of the microorganisms and their spores. Leafy vegetables
such as spinach and other greens which grow close to the soil
harbor high numbers of bacteria and spores. Asparagus and
mushrooms which grow through the soil are always contaminated
with high numbers of spores.
There is a large group of bacteria that grows best at temperatures of 80" to 98"F. Often this is the range of warehouse and some household storage temperatures. All of the bacteria that cause food spoilage grow within this temperature range. The spore-forming organism, Clostridium botulinum, is a member of this group.
Botulism is a food poisoning caused by the toxin produced in foods by the vegetative form of C.botulinum. This is a deadly toxin. Seven types of this bacterium are recognized and classified by the letters A through G. Types A and B are very heat resistant and are able to survive 5 or more hours in boiling water.
There is a term or symbol in chemistry called "pH". It is a measure of the degree of acidity or alkalinity of the food. The scale of pH ranges from zero to 14. The mid-point or neutral point, neither acid nor alkaline, is at ph 7.0 . Distilled water is at pH 7.0 . Most foods are acid but some are much more so than others.
A table can be constructed to show a number of foods ranging in pH from 2.2 to 8.0. Foods with a pH of 4.5 or higher are low acid foods. Those with a pH lower than 4.5 are high acid foods.All fruits are high acid. All vegetables (including mushrooms), meats, seafoods, and milk are low acid.
The pH of a food determines the type of bacteria that will grow in it and whether or not C.botulinum will grow and produce its toxin. Studies have shown that the spores of C.botulinum will not germinate and grow at pH 4.8 and below. Therefore, pH 4.6 has been selected by the Food and Drug Administration as the dividing line between high acid and low acid foods.
The application of mild heat will destroy all non-sporing bacteria and all sporing bacteria in the vegetative state in either low acid or high acid foods. However, in the low acid category high heat must be applied to kill the spores of C.botulinum and the spores of the other food spoilage organisms, hence the need for heat processing under pressure, as in the time-honored pressure cooker. In high acid foods there is no concern with spores of C.botulinum. They are prevented from germinating and growing because of pH 4.6 or below. Since with high acid foods only the vegetative cells need be destroyed, boiling water cooks or hot fill and hold procedures may be used.
Advantage is taken of the inhibition of spore germination and growth of C.botulinum by pH 4.6 or less. There are cartain foods in the low acid category which cannot be processed in a pressure cooker without altering and making the food unappealing and therefore unacceptable as a merchantable product. Such foods are artichoke hearts, peppers, onions, brussel sprouts, and broccoli. When these foods are acidified to pH 4.6 or lower, they can be processed by applying only sufficient heat to destroy molds, yeasts, and non-spore forming bacteria. The spores of C.botulinum have not been destroyed, but are dormant under the unfluence of the acid. In this condition they are harmless. This acidification is a special processing procedure.
An acidified food is defined as a low acid food to which an acid is added to produce a final equilibrium pH 4.6 or less. Foods such as acidified artichoke hearts, bean salads, pimientos, and marinated vegetables as mushrooms, eggplant, beets, and fresh pack pickles are among those considered acidified foods.
According to information gleaned from newsletters from various mushroom clubs in this country and from books on mushrooms which include cooking instructions, many mushroom enthusiasts prefer to preserve mushrooms in olive oil. Evidently, most of these people do not realize that olive oil alone is not a preserving agent, and "preserving" in this manner amounts to a dangerous practice. If preserving in olive oil is really preferred, then this is the way to do it.
Mushrooms are cleaned in cold water,drained, and sliced into fairly large pieces.
In a covered pot, two quarts of a solution combining distilled vinegar and water are brought to a boil. Use one part vinegar to eight parts water. This reduced acidity of pH 3.0 diminishes the effect of the so-called "pickled" taste of foods. Straight commercial vinegar has a pH of 2.2.
One pound of the sliced mushrooms is added to the boiling solution, the pot covered, and boiling is reduced to a simmer.
At the end of 10 minutes the acidified mushrooms are transferred with slotted spoon to sterilized 12 or l6 ounce jars.
Heated olive oil (185") is added to the mushrooms to about one inch above the top of the mushrooms.
Jars are sealed with sterile lids. They are cooled and stored at room temperature. Refrigeration is not necessary. Mushrooms processed in this manner will store indefinitely.
With this procedure the final equilibrium pH of the acidified mushrooms at time of packing in the jars is 4.5 .
Reference: CANNED FOODS. Principles of Thermal Process Control The Food Processors Institute 1401 New York Avenue Washington, DC 20036
Copyright 1995 Michael W. Paparella All Rights Reserved mpaparel@shore.intercom.net
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