Food Storage FAQ by Alan T. Hagan Part IX

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Preventing Mold Growth In Stored Grains and Legumes


The easiest method to prevent mold growth in your stored grains and legumes is simply to keep them too dry for the mold to grow. The Aspergillus and Fusarium molds require moisture contents of 18% and above to reproduce. This is subject to some variability, but in all grains and soybeans, they must have a moisture content of that level. If you are storing raw (not roasted) peanuts, in the shell or shelled, you want to get the moisture content to less than 8% as peanuts are particularly susceptible to mold growth. The recommended moisture content for all other grain and legume storage is no more than 10%. (Please see part 2.A.3.1 Grains and Legumes for a method to determine moisture content.) At 10% moisture, it is simply too dry for fungi to grow. (Please see Storing Grains and Legumes for a suitable packaging technique.)


Bacterial Spoilage


Just like the fungi, bacteria are everywhere. They’re in the water, soil, air, on you, your food and your food storage containers. Fortunately, the vast majority of the bacteria we encounter are relatively harmless and only a few represent a danger to us and our stored foods.


    Bacteria can be very much more difficult to kill off than molds and insects. Some of them are capable of continued growth at temperatures that would kill other spoilage organisms. When conditions are such that they are unable to grow, some bacteria can go dormant and form spores. These spores can be quite hardy, even to the point of surviving a rolling boil.


    In order to grow, bacteria need moisture, some as little as a 20% moisture content. For dry grains, legumes, powdered milk and other low moisture foodstuff bacterial spoilage will seldom be a problem so long as the moisture level in the foodstuff remains too scant to support its growth. For this reason, it is imperative that such products be drier than 20% and preferably below 10% to ward off mold growth as well. The botulism bacteria need moisture in the 35% range to grow. Thus, using desiccants in your food packaging is also an excellent idea.


    WARNING: It is in wet pack canned goods (where the container has free liquid in it) and fresh foods we must be the most concerned about spoilage bacteria. It is here that a little bad luck and a moment’s inattention to what you are doing could kill or seriously injure you or some other person who eats the foods you’ve put by. In both home-canned and commercially-canned goods, IF THE CAN IS BULGING, LEAKING, SMELLS BAD, OR SPEWS LIQUID WHEN YOU OPEN IT THEN THROW IT OUT! But, throw it out safely so that children and animals cannot get into it.




    Clostridium botulinum is one of the oldest types of life forms found on the planet. Like the gangrene bacteria, it is an anaerobic organism meaning it lives and grows in the absence of free oxygen. It forms spores when conditions are not suitable for it to grow and it is commonly found in the soil. This means it can be brought into your life on raw produce, tools, hands or anything else that came into contact with dirt. To further complicate matters, botulinum spores are extremely heat-hardy. The bacteria itself can be killed by exposing them for a short time to boiling water (212 F AT SEA LEVEL PRESSURE), but their spores can not. To kill them, the food product and container must be exposed to temperatures of 240 F (AGAIN AT SEA LEVEL PRESSURE) for a long enough period of time to allow all of the food in each container to come completely up to the proper temperature. Only a pressure canner can reach the necessary temperature.


It’s not the bacteria or its spores which are directly deadly, but the toxin the bacteria creates when it grows and reproduces. In its pure form, botulism toxin is so potent that a mere teaspoon of it would be enough to provide a fatal dose to hundreds of thousands of people. It is this lethality that is why every responsible book on canning, food preservation, food storage, and the like hammers constantly on the need for care in technique and method and why spoilage must be taken so seriously.


C. botulinum, like any other life form, must have suitable conditions for it to grow and become a danger to you. One of the conditions it must have is a suitable pH range in its environment. pH is the measure of the acidity or alkalinity of a substance and is measured on a scale of 1-14 with anything above 7 being considered alkaline and everything below 7 being considered acid. If the pH of your wet pack food is BELOW 4.6 then botulism is unable to grow. Keep in mind pH is not eternal in foods and it is possible for it to change. If it should change to a lesser acidity than 4.6 pH your previously botulinum-proof food may start allowing the lethal spoiler to grow (see molds in canned goods). This is why it is vital to use proper technique, even for acid foods like tomatoes. It has been found that when this occurs and botulinum becomes active and produces its lethal toxin it also produces minute amounts of acid which can lower the pH of the poisoned food back into what should have been the safe zone had the pH not jumped up and allowed the bacteria to grow. Again and again -- use good technique and pay attention to what you are doing.


Botulinum toxin, unlike fungal mycotoxins, can be destroyed by boiling the food briskly in an open vessel for fifteen minutes. Because of this, if your canned food shows any safety problems you should follow this procedure. If the food shows even the slightest mold growth, keep in mind that mycotoxins are not for the most part broken down by heat and dispose of the food safely.


I don’t intend to go into the hows of home canning here. For that I strongly recommend that you read sections 1, 4, and 5 of the r.f.p. FAQ and most especially the book Putting Food By for in depth information on this subject.


Other Bacterial Spoilers


This section will be in a future version of this FAQ.


Enzymatic Action In Food Spoilage




Every living organism uses enzymes of many sorts in its bodily functions as part of its normal life cycle. Enzymes are used in creating life. After death, enzymes play a role in the decomposition of once living tissue. The enzymes in a tomato help it to ripen and enzymes produced by the tomato and whatever fungal and bacterial spoilers are on it cause it to decay.


Fortunately, slowing down or stopping the action of a food’s enzymes is much easier to do than slowing or stopping some of the bacterial spoilers mentioned above. Enzymes are most active in a temperature range between 85 to 120 F and begin to be destroyed when the temperature goes above 140 F. Cold also slows down the action of enzymes, which is why fresh tomatoes last longer in the refrigerator than they do on the kitchen table. Most enzymatic action also requires moisture to occur. In foods stored at 10% moisture or less, there is not enough moisture for most enzymes to be active.


Specific Equipment Specifications


  OK, I’m ready to start my food storage program. What should I put the food in?


You should use food grade containers for storing anything you intend to eat. A food grade container is one that will not transfer non-food chemicals into the food and contains no chemicals which would be hazardous to human health. If you are uncertain whether a container is food-grade or not then contact the manufacturer and ask if a particular container is approved for food use. Many manufacturers are beginning to indicate on the container label if it is approved for food use.


Plastic Containers


What makes a bucket or plastic bag “food grade”? And where can I find them?


Plastic films and containers of food grade quality are made from polycarbonate, polyester or polyethylene. Their characteristics in terms of density, permeability and strength vary. To limit permeability to moisture and oxygen, films of the above plastics are sometimes laminated together, frequently with a metallic layer. Military food packaged in just such a metallized polyester, polyethylene wrap has a long shelf life (5+ years) if kept cool.


OK, I’ve got some used food grade containers, but they’re pickle buckets. How do I get the smell out?


I’ve had fairly good luck doing it this way. Since vinegar is the primary smell in pickles and it’s acidic, we used a base to counteract it. First we scrubbed the bucket well, inside and out, with Dawn dish detergent. I imagine most any sort will do. Then we filled the buckets with hot water and dissolved a cup of baking soda in each. Stir well, get the bucket as full as you can and put the top on. Put the bucket in the sun to keep it warm so the plastic pores stay open as much as possible. In a couple of days come back and empty the buckets. Rinse them out, fill with warm water again and add about two cups of bleach and reseal. Put back in the sun for another couple of days. Empty out and let dry with the tops off. We completely eliminated the vinegar smell this way. It might be possible to cut the time down a lot, but we haven’t experimented that much since we can’t get that many pickle buckets.


Metal Cans


The metal cans used by the canning industry for wet-pack canning are designed to last only a few years. Most losses of canned foods occur due to the breakdown of the can rather than extensive deterioration of the food under normal storage conditions.


The major disadvantages of metal cans for putting up your own food are that the cans are hard to come by, they take specialized equipment to use (but so do glass jars) and they can only be used once to seal in food. Not being reusable is the flaw that has largely made them unpopular for home canning use. Since they’re not interested in reusing the containers, metal cans make great sense for the commercial canning industry. The cans are both cheaper (for them) and lighter than glass jars and this adds to the economy of scale that makes canned foods as cheap as they are in the grocery store.


For home canners, glass jars are better because even the smallest of towns will usually have at least one store that carries pressure and boiling water canners along with jars, rings and lids. With tin cans, however, a can sealer is necessary and that usually has to be ordered from its manufacturer.


    Tin cans are not really made of tin. They’re actually steel cans with a tin coating on the inside and outside. Some kinds of strongly colored acidic foods will fade in color from long exposure to tin so a type of enamel liner called “R-enamel” is used to forestall this. Certain other kinds of food that are high in sulfur or that are close to neutral in pH will also discolor from prolonged contact with tin. For those foods, cans with “C-enamel” are used.


 The excellent food preservation book, *Putting Food By* Chapter 6 (see reference list) has a section on the use of tin cans for wet packed foods.


The Church of Jesus Christ of Latter Day Saints:

There is one way that metal cans do make economic sense to use and that is by pooling community resources to purchase the can sealer and the cans. The LDS church does just this in their family canneries and have, in fact, almost exclusively gone over to using metal cans from all other containers. This is done primarily for dry-pack canning. Those areas that do wet-pack canning primarily use canning jars. By sharing the cost of the equipment and purchasing the cans in bulk quantities to reduce cost to the lowest possible level, the advantage of metal cans over plastic containers can then begin to outweigh the disadvantages.


If properly protected from corrosion, metal cans are gas-impervious and immune to rodent attack, qualities that plastic containers are weak on. The cans still aren’t resealable, other than with a plastic lid, after they’re opened, but for a one time use they’re pretty tough. Of course, there is still the oxygen and moisture that is trapped inside to deal with, and the heat of the storage area they’re kept in, but this is common to all food storage regardless of the container.


It may not be necessary to form your own community to purchase a dry-pack can sealer and bulk quantities of metal cans. If you live in the right area your local LDS church may have facilities they will allow you to use and perhaps even suitable food products they will sell you.


 Most facilities will be located at one of the LDS Bishop’s Storehouses located in various places around the country, but some churches also have their own local facilities. The easiest means of finding out is simply to ask the LDS church member you know. If they don’t themselves know, or you don’t know any Mormons then a little phone book research will be necessary. Find your nearest local Mormon church and ask about speaking with the local Bishop of the Ward or Relief Society president. Either one of those two individuals will be able to give you the information you seek.


IMPORTANT NOTE: Please do keep in mind that the individuals responsible for the family canneries are all volunteers with demands on their time from many areas. Be courteous when speaking with them and, if there are facilities for use, flexible in making arrangements to use them. You will, of course, have to pay for the supplies that you use, cans and lids at the least, and any food products you get from them.


Any food products you want to have sealed in cans will need to fall within their guidelines of suitability for that type of packaging. This is for reasons of spoilage control since many types of foods just aren’t suitable for just sealing in a container without further processing. If you purchase food products from them, they will already be within those guidelines.


I’ve corresponded with many LDS members and have even contacted the LDS headquarters in Salt Lake City to get the official word. Keeping in mind that not every area may have facilities for use and that the family canneries are run by volunteers, they are quite earnest about allowing non-church members to use their facilities. It’s worth investigating.