Additional Processing Information

Processing Concerns

Concerns related to processed foods in jars: The National Center for Home Food Preservation website has explanations and information regarding processing of food at home that also applies to food products processed for retail sale.

There are several factors that affect the way in which heat is distributed through the food in a jar during the canning process. It is this variation in heat penetration that determines the position of the “cold spot” (the slowest heating area) of the jar, which can be different for different jar sizes and shapes as well as different foods. The heating rate at the cold spot determines how long the process time needs to be. In the case of low-acid foods, this is to ensure that the food receives the heat necessary to kill Clostridium botulinum spores. Left alive inside a sealed jar of low-acid food at room temperature, the spores become bacterial cells that multiply and produce the toxin that causes botulism poisoning.

The time and temperature combinations at which C. botulinum, its spores and other bacteria are killed are established under certain conditions. However, the substrate (food) in which these bacteria are found is an important variable factor in the rate of destruction. The food factors that will influence the amount of heating needed to kill bacteria include: the consistency of the food; the pH (acidity); and, the presence of nutrients that are “protective” for bacteria (e.g., high protein and sugar levels). Other influences on the amount of heat delivered to the food in the jar are: the shape and size of the jar; the size, shape and texture of food pieces; the solid to liquid ratio; the temperature of the food at the beginning of the process; and, the temperature inside the canner. For example, heat penetration through a mass of liquid (faster) will be very different from heat penetration through puréed or mashed food (slower). This is apparent during stove-top cooking too, where different foods heat up differently based on their composition and consistency.

Canning at High Altitude: At high altitudes above 3,000 feet, preparation of food may require changes in time, temperature or recipe. The reason is the lower atmosphere pressure due to a thinner blanket of air above. At sea level, the air presses on a square inch of surface with 14.7 pounds pressure; at 5,000 feet with 12.3 pounds pressure; and at 10,000 feet with only 10.2 pounds pressure — a decrease of about 1/2 pound per 1,000 feet.  This decreased pressure affects food preparation in two ways.  First, water and other liquids evaporate faster and boil at lower temperatures.  Secondly, Leavening gases in breads and cakes expand more.

All home-canned foods should be canned according to USDA or USDA-endorsed recommendations. Low-acid and tomato foods not canned using these methods present a risk of botulism. If there is a possibility that any deviation from the USDA-endorsed methods occurred, boil low-acid and tomato foods in a saucepan before consuming to prevent the risk of botulism. At altitudes below 1,000 feet, boil foods for 10 minutes. Add an additional minute of boiling time for each additional 1,000 feet elevation (for example, at 3,000 feet, boil for 12 minutes). For more information regarding high altitude cooking.

If the food is thick, puréed, or mashed; if there are large pieces of food in the jar, which is common with salsa recipes; or, if the food is packed in too tightly, heat penetration can be slower than in more liquid or loosely packed foods. If a specific heat process is not calculated for each food and style of pack, the heating may not be adequate, and the food will be under processed.

How the processing time for a food can be determined experimentally: Heat penetration experiments, which are necessary for all low-acid foods and some acid foods, are carried out in a properly equipped laboratory. The food prepared by specific procedures is filled into jars and thermocouples (temperature measuring devices) are inserted through the lid, jar or can into the food in the jar. These are connected by wires to a monitor, and the temperature at the end of each thermocouple is recorded throughout the time the canner comes up to processing temperature, during a process at that temperature (e.g., boiling water or 240°F under pressure), and during at least some of the cooling period.

Determining the process time is a two-step procedure. The first step is to put thermocouples in several areas of the jar to determine the “cold spot” (slowest-heating location) of the jar. Once that spot is located, more data is collected at the cold spot to have enough information to calculate the process time for this food under these specific conditions – i.e., in a particular jar type in this canner. The process time is the time needed to achieve a certain level of “lethality”, or killing of a number of target pathogens or spoilage organisms for that food.

In the case of low-acid foods, the processing time needs to ensure that the minimum temperature and time combination to destroy spores of C. botulinum is reached, so that the food will be safe when stored on the shelf. In the case of acid foods, such as acidified salsa recipes, the target microorganisms will be those likely to make someone sick or spoil the food.

This process has to be done separately with each food, as well as any variation that alters pH, consistency, texture, distribution of solids and liquids, or other factors that result in a “new’ product”. Experimentally determining safe processing times for home-canned foods is thus a lengthy, expensive and time-consuming process, which explains why there are fewer home-canned processes available than many people would like. In short, there is no easy formula to work out processing times without experimentation and analysis that take into account how each food product heats in a particular canning situation.

The commercial food manufacturing industry puts a lot of time and expense into research for their own safely canned products (they do not have a ‘blanket processing’ method or formula for adjustments, without collecting heat penetration data, either). Also, just because a canned food is made commercially and found on a store shelf does not mean a home canning process is available for the same or similar item. The heating characteristics under home preparation methods and canning procedures would have to be studied to come up with a home-canning process. The commercial canning industry also has more resources and methods at its disposal for controlling the consistency and maturity of raw ingredients going into a canned food. There will be more variability to take into account when researching a home-canning process to cover all the potential variables.

Adapted with permission from: The National Center for Home Food Preservation

Colorado Labs that Perform Food Product Testing

Information about Food Testing in Colorado, Colorado Department of Public Health & Environment: (303) 692-3090

Commercial Kitchens

A limited list of food items, called cottage foods, may be prepared in a private home kitchen and sold for public consumption. See Cottage Foods.

All other types of foods made for public consumption must be obtained from approved sources and prepared in a licensed commercial kitchen. Commercial kitchens may be located in a private home only if they are constructed to meet the requirements of the Colorado Retail Food Rules and Regulations and the kitchen is used for no other purpose.

The kitchen must be approved by the local health department or the Colorado Department of Public Health and the Environment (CDPHE).  Non-profit, charitable organizations may be exempt.  Contact the CDPHE (303) 692-3620 or the local health department in your county.

To make organic products you do not have to work in an organic only kitchen, but it is important to keep all organic and non-organic ingredients separate.

To make gluten-free products you do not have to be in a gluten-free kitchen, but it is important to take steps to protect your gluten-free foods from contact with gluten. Here are a few tips:

  • Use a separate colander/strainer for gluten-free pasta. Colanders are too hard to clean to completely remove gluten. Color coding with a permanent marker can help keep all kitchen utensils separate.
  • Clean counter tops and cutting boards often to remove gluten containing crumbs.
  • Clean cooking utensils, knives, pans, grills, thermometers, cloths, and sponges carefully after each use and before cooking gluten-free foods.
  • Store gluten-free foods above gluten-containing foods in your refrigerator and cupboards.
  • Use pure spices rather than blends.
  • If you bake with gluten-containing flours, put away or cover your gluten-free foods when you bake. Flour dust can float in the air for several hours and contaminate your gluten-free products.
  • Avoid purchasing staples from bulk bins.

Consult Colorado State University Extension: Gluten Free Diet Guide and Colorado State University Extension: Gluten Free Baking for more information.

The importance of using a commercial kitchen: According to the Centers for Disease Control and Prevention (CDC) there are over 200 different types of microrganisms known to cause foodborne illness.  The best method, often the only method, we have to protect ourselves, food workers, and our customers from exposure to the organisms that cause foodborne illness, is prevention of food contamination.   A clean food processing environment is essential and the best situation to limit food contamination of food products sold to the public is the use of commercial kitchens.  These establishments must adhere to a standard set of regulations including the exclusion of pets, ill persons, and toxic substances and the proper use of sanitizing procedures. Understandably, home kitchen environments cannot always abide by these same regulations and routine inspections by local authorities is not feasible. Immunity to disease-causing microorganisms varies between individuals, depending on health status and exposure history. Bacteria or parasites in your home kitchen may not be a health hazard for you but could cause severe illness for someone else. As an example, in some homes living with pet cats in the kitchen is common but baked goods from that home may cause an illness to a immune-compromised person that consumes those food products.  The best solution for the protection of producers and consumers of locally made products is to require the use of commercial kitchens for processing retail products.  We are very fortunate to live in a public-health minded state that long-ago adopted this requirement.

Colorado Co-Pack Directory (including kitchens to rent)

The Colorado Co-Pack Directory was prepared by the Colorado Department of Agriculture to encourage the growth of existing businesses and the establishment of start-up businesses. The directory lists commercial kitchens to rent as well as professional co-packing companies willing to contract manufacture food products.