A revamp of one of my previous posts, On Preserving Food. This time I seriously overanalyzed a series of college and university-level documents regarding the spoilage process and how certain consumables would be affected and how measures could be taken to prolong the shelf life. Links to all sources used will be provided at the bottom of my post.
Let us begin by categorizing the various types of foods based on their shelf life. Based on this I have found three major categories:
These have a shelf life ranging from several days to a maximum of three weeks without any form of preservatives or preservation techniques. Examples include meat and dairy products including but not limited to meat, poultry, eggs, and seafood.
These items can be preserved for up to six months under proper storage conditions, these include vegetables, certain types of cheese, and most types of fruit.
This final category covers all natural and processed foods that have a shelf life of several years or cannot spoil. Dried nuts and beans, sugar, honey, peanut butter and any type of canned or pickled food falls into this category.
However, classification based on shelf life is not enough, and therefore I shall introduce the secondary classification based on the extent and purpose of processing.
Unprocessed or minimally processed foods
No processing or mostly physical processes used to make single whole foods more available, accessible, palatable, or safe. These include raw, chilled, frozen, vacuum-packaged, and dried foods.
Processed culinary or food industry ingredients
These include extracts and purified components of foods, resulting in producing ingredients used in the preparation and cooking of dishes and meals, or in the formulation of ultra-processed foods, such as butter, milk cream, sweeteners, raw pastas and noodles, flour, sugar, etc.
Ultra-processed food products
Processing of a mix of process culinary, or food industry ingredients and processed or minimally processed foodstuffs in order to produce accessible, convenient, palatable, ready-to-eat or to-heat food products with longer shelf life. These include breads, biscuits, cakes and pastries; processed meat products such as sausage and luncheon meat; all types of soft drinks; as well as anything that is salted, smoked, cured, pickled, and/or canned.
Food spoilage is affected by a variety of three major factors; physical, microbial, and chemical. This goes really deep, so I’ll just summarize it and spare you the details.
Physical spoiling encompasses any physical change or instability, such as water loss, food going stale, slow ripening of fruits, and chilling injury, such as when certain fruits and vegetables, especially those accustomed to tropical or subtropical climates, are exposed suddenly to sub-zero and freezing temperatures.
Microbial spoilage includes any type of spoiling associated with either molds, yeasts, and bacteria, but for the sake of simplicity I’ll cut out yeasts. These have the highest chance of causing disease and foodborne illnesses. Molds typically affect fermented foods, bottles, etc, and is temperature sensitive, meaning high or low temperature extremes can easily kill mold. Bacteria, however, is more problematic and affects a wide range of consumables. These can be killed by cooking or prevented from forming with certain preservation techniques.
Chemical spoilage occur naturally within foods and is often interrelated with microbial spoilage, which causes certain chemical processes to occur. These include simply rotting foods to an increase in ammonia content in raw seafood, especially when left in the open for too long. These can cause serious physical reactions as for example high ammonia amounts are toxic.
Now, onto the meat and potatoes of the topic: the actual preservation methods. These can be further divided into two generalized categories; physical, which relies on actual physical factors to slow or eliminate spoilage, and chemical, which relies on chemical preservatives to kill microbes.
Simple enough, yeah? Drying reduces or eliminates the water content necessary for microorganisms to thrive, and also reduces the mass and volume of certain foods. It is also the cheapest and easiest way to preserve food. Salting and sugaring both fall into this as they reduce water content. Smoking also falls into this category, but is usually limited to just meat and fish.
Almost just as simple as drying. In this, the food or liquid is heated to kill all microbes that can possibly cause spoilage, thus prolonging its shelf life. This process is most commonly used with liquids such as milk, fruit juice, butter, and sour cream.
Freezing reduces biochemical reactions by reducing water content and heat transfer, which then inhibits microbial growth.
Some foods, such as many cheeses, wines, and beers, use specific micro-organisms that combat spoilage from other less-benign organisms. These micro-organisms keep pathogens in check by creating an environment toxic for themselves and other micro-organisms by producing acid or alcohol.
Pickling is a method of preserving food in an edible, antimicrobial liquid. Pickling can be broadly classified into two categories: chemical pickling and fermentation pickling. In chemical pickling, the food is placed in an edible liquid that inhibits or kills bacteria and other microorganisms. Typical pickling agents include brine, vinegar, alcohol, and vegetable oil.
Canning involves cooking food, sealing it in sterilized cans or jars, and boiling the containers to kill or weaken any remaining bacteria as a form of sterilization. Oftentimes this is combined with a natural preservative such as vinegar, brine, or vegetable oil.
Food may be preserved by cooking in a material that solidifies to form a gel. Such materials include gelatin, agar, maize flour, and arrowroot flour. Some foods naturally form a protein gel when cooked, such as most meats and fish.
The process of stewing the meat in a covered earthenware jug or casserole with brine or alcohol. A popular method of preserving meats up until the mid-twentieth century.
Seals food inside an airtight plastic bag which preserves it nearly indefinitely, but requires a source of suction such as a vacuum cleaner.
Visual graph comparing various preservation techniques versus the same untreated food