In home canning, pack is a term that describes the method used for preparing and placing food in a jar prior to sealing the jar for processing.
Pack is actually a word that comes from the commercial canning industry, thus they were often called “packers.”
How a food item is packed into a jar is important. The size of the pieces, etc, help determine heat transfer. “The method of packing the jars also plays an important role in heat transfer through the product.” [1] Harrison, Judy A. Canning Foods at Home: The Basics. Powerpoint presentation, Slide 16. Cooperative Extension: University of Georgia. Accessed December 2014.
Methods of packing
There are two broad categories of packing: raw pack, and hot pack.
The National Center for Home Food Preservation (NCHFP) says,
There are two methods for packing foods into jars for canning. These are the raw pack and the hot pack. In some cases, either method may be suitable for a particular product. Other products may work best with only one of the methods.” [2] National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Methods of Pack. Accessed March 2015.
Some foods can be processed either via raw pack or hot pack. Putting Food By says,
Many foods may be packed in their containers either Raw (in some manuals they used to be designated as “Cold”) or Hot. The food is trimmed, cleaned, peeled, cut up, etc., in the same manner for both packs.” [3] Hertzberg, Ruth; Greene, Janet; Vaughan, Beatrice (2010-05-25). Putting Food By: Fifth Edition (p. 73). Penguin Publishing Group. Kindle Edition.
A tested recipe will always tell you which pack type to use. Sometimes you will have a choice, but other times, no. If there are only recommendations for hot pack, then only do hot pack. That means that the processing times given are valid for hot pack only, and that safe processing times for raw pack are not known. “If directions only list hot pack instructions, then hot pack!” [4] Harrison, Judy A. Canning Foods at Home: The Basics. Powerpoint presentation, Slide 17. Cooperative Extension: University of Georgia. Accessed December 2014.
How pack methods were decided upon
Most times, the packing method that the recipe writers decided upon was the method that they deemed to deliver the best quality end product. “The offering of hot and/or raw packs is usually based on quality issues with the finished product.” [5] D’sa, Elaine M. and Elizabeth L. Andress. Heat Processing of Home-canned Foods. National Center for Home Food Preservation. 22 December 2005. Accessed March 2015 .
Sometimes, it’s just that the researchers who developed the process made an arbitrary call, and / or didn’t have the funding or goal to test different variations for the same thing. “Sometimes it has been the choice of the researchers who developed the process recommendation to only use one method.” [6] D’sa, Elaine M. and Elizabeth L. Andress. Heat Processing of Home-canned Foods. National Center for Home Food Preservation. 22 December 2005. Accessed March 2015.
Raw Pack
Elizabeth Andress of the NCHFP says, for a raw pack, “food is washed, peeled, cut, etc but just not blanched or pre cooked in any way.” [7] Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” 1:02 Webinar. 27 February 2013. Accessed January 2015.
Judy Harrison of the University of Georgia says,
In a raw pack, raw food is placed directly in the jars. Then hot, boiling liquid is poured over the contents. Pack firmly, but do not crush. Free the bubbles or trapped air between the pieces of food.” [8] Harrison, Judy A. Canning Foods at Home: The Basics. Powerpoint presentation, Slide 16. Cooperative Extension: University of Georgia. Accessed December 2014.
The USDA Complete Guide says, basically, that raw pack seems to be more suited for vegetables (when the recipe gives you a choice):
Raw-packing is more suitable for vegetables processed in a pressure canner.” [9] United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-12.
If you are raw packing, generally you need to pack the food tightly into the jars because raw packed food will shrink:
Fruits and most vegetables packed raw should be packed tightly because they will shrink during processing. The exceptions are lima beans, corn, potatoes and peas. These expand during processing and should be packed loosely.” [10] National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Methods of Pack. Accessed March 2015.
When you are raw packing, don’t have the water in the canning pot too hot or you may crack the jars.
- For water bath: “If the product is raw packed, the water in the canner should be warm to hot when the jars are placed in the canner. Following these guidelines will help to prevent jar breakage.” [11] National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Boiling Water Processing. Accessed March 2015.
- For pressure canning: “Place 2 to 3 inches of water in the canner….. If the product is raw-packed, have the water in the canner warm to hot.” [12] National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Pressure Canner Processing. Accessed March 2015.
In very old canning books, you may see raw pack referred to as “cold pack.” That term is now discouraged, because it’s used in too many ways. [13] Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” 1:02 Webinar. 27 February 2013. Accessed January 2015.
Raw pack quality issues
Because raw-packed food hasn’t been blanched, with subsequent shrinking owing to air exiting from the food during the blanching, you will be able to fit less of that food in a jar. And, after processing, you will notice a lot of empty space in the jar because the food did its shrinking instead during processing. “The food level and liquid volume of raw-packed jars will be noticeably lower after cooling. Air is exhausted during processing and food shrinks.” [14] United States Department of Agriculture (USDA). 2015. Complete guide to home canning. Agriculture information bulletin No. 539. Page 1-20
And, “Raw-packing is the practice of filling jars tightly with freshly prepared, but unheated food. Such foods, especially fruit, will float in the jars. The entrapped air in and around the food may cause discoloration within 2 to 3 months of storage.” [15] United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-12.
Hot Pack
The food is washed, peeled, cut, then preheated. Usually the cooking water can be poured over the food, but sometimes they will call for fresh water (for potatoes and dried beans, for instance, because they don’t want the excess starch in the cooking water.) [16] Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” 1:02 Webinar. 27 February 2013. Accessed January 2015 at https://nchfp.uga.edu/multimedia/video/nchfp.wmv
The USDA says, “Hot-packing is the practice of heating freshly prepared food to boiling, simmering it 2 to 5 minutes, and promptly filling jars loosely with the boiled food…” and “Hot-packing is the best way to remove air and is the preferred pack style for foods processed in a boiling-water canner.” [17] United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-12.
Don’t let food prepared for “hot pack” processing cool in the jars before placing it in the canner for processing. “The heat curves are based on the food being hot at the beginning of the processing. The product could be under-processed.” [18] Brennand, Charlotte P. Avoiding Common (Major and Minor) Canning Mistakes. (Originally published 1999 as Food Canning-Major Canning Sins”. Food and Health. Paper 31. September/October 2011 revision) USU Extension • Utah County. Office . Page 5. Accessed March 2015 at https://extension.usu.edu/utah/files/uploads/Newsletters/Avoiding%20Canning%20Mistakes.pdf.
Advantages of hot pack
Pre-cooking food before canning helps remove some of the oxygen that would otherwise be trapped inside the jars and spoil food quality. [19] National Center for Home Food Preservation Self Study Course. Module 1. Intro. to Food Preservation: Major Causes of Food Spoilage. Accessed March 2015.
The food will retain its flavour and colour longer in storage. The USDA says,
How long canned food retains high quality depends on how much air is removed from food before jars are sealed…. At first, the color of hot-packed foods may appear no better than that of raw-packed foods, but within a short storage period, both color and flavor of hot-packed foods will be superior.” [20] United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-12.
Judy Harrison of the University of Georgia says,
The preferred method of pack for most foods is the hot pack. In a hot pack, foods are cooked in liquid before packing. Then the cooking liquid is poured over the food in the jar. The advantages of this method are that fewer jars are needed, there is less floating of the food because air has cooked out of it, the color and flavor are better retained, and the foods are easier to pack in the jars because they are more pliable. Always follow directions for the specific type of pack called for.” [21] Harrison, Judy A. Canning Foods at Home: The Basics. Powerpoint presentation, Slide 17. Cooperative Extension: University of Georgia. Accessed December 2014.
With a hot pack, you also need fewer jars because the food items will have lost some liquid during blanching and shrunk. This also makes it easier to fit the food into jars, because it’s softer.
The NCFHP says,
Hot pack means heating the food to boiling or cooking the food for a specified amount of time and then packing the hot food into the jar and adding boiling liquid to cover the food. Since shrinkage will already have occurred, the food should be packed loosely.” [22] National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Methods of Pack. Accessed March 2015.
Nancy Hudson, an extension agent in Greene County, Ohio, explained:
The reason USDA recommends all foods be hot packed is the amount of food which you can place in the jar. Some products will shrink only 5 percent after processing. However, products such as apples and peaches will shrink 25 to 30 percent and mushrooms as much as 40 percent after pressure canning. Be sure to hot pack. Hot packing foods also makes a difference in preserving nutritional value and quality over a long storage period.” [23] Hudson, Nancy. New research gives tips on using jars and lids. Xenia, Ohio: Daily Gazette. 7 April 1986. Page 6.
There will be fewer awkward-looking floating vegetables or fruits in your jars, because during blanching some air will have already left the pieces of food. The USDA guide says, “Many fresh foods contain from 10 percent to more than 30 percent air.” [24] United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-12.
A hot pack is more work, certainly. But Angela Fraser of Clemson University says,
A hot pack takes more time but has been found to result in higher quality canned foods.” [25] Fraser, Angela. Associate Professor/Food Safety Education Specialist. How Canning Preserves Food. Clemson University, Clemson, SC. Accessed March 2015 http://www.foodsafetysite.com/consumers/resources/canning.html.
University of Georgia video
Understanding some of the rational
For some items there’s a definite rational as to why one pack is recommended over the other. For instance, potatoes are always packed hot. The blanching of the potatoes in the hot-pack prep helps leech out some of the starch that would come out in the jar otherwise. So they are blanched, and then packed into jars with fresh boiling water. If excess starch leeched out into the jar later, it could raise heat transfer safety concerns, as well as gelatinizing in the jar, and making the jar really cloudy. [26] D’sa, Elaine M. and Elizabeth L. Andress. Heat Processing of Home-canned Foods. National Center for Home Food Preservation. 22 December 2005. Accessed March 2015.
Another safety example involves many chunky pickled products such as relishes and chutneys. They are hot packed because heating them helps to drive acid into food particles, giving the product a good head start on safety. [27] D’sa, Elaine M. and Elizabeth L. Andress. Heat Processing of Home-canned Foods. National Center for Home Food Preservation. 22 December 2005. Accessed March 2015.
Raw pack processing times
Sometimes processing times are different for raw pack and hot pack; sometimes they are the same. [28] Andress, Elizabeth. “History, Science and Current Practice in Home Food Preservation.” 1:02 Webinar. 27 February 2013. Accessed January 2015.
The USDA Complete Guide says,
When canning in boiling water, more processing time is needed for most raw-packed foods and for quart jars than is needed for hot-packed foods and pint jars.” [29] United States Department of Agriculture (USDA). Complete guide to home canning. Agriculture information bulletin No. 539. 2015. Page 1-11.
If it is longer, the recipe will tell you.
If the processing times given for either raw or hot pack are the same, it’s because both methods have been researched and tested separately, and the required processing times for both methods may have ended up the same.
Other times, it may be that in the lab the hot pack might have been, say, 11 minutes and the raw pack 14 minutes, but because all process times are rounded up to the next 5 minutes, they both end up being recommended as 15 minutes. [30]”Why are hot and raw pack processing times sometimes the same?” D’sa, Elaine M. and Elizabeth L. Andress. Heat Processing of Home-canned Foods. National Center for Home Food Preservation. 22 December 2005. Accessed March 2015.
Debating which way to go when you have a choice
Some people feel that when a tested recipe gives you a choice of using a raw pack, that it is best primarily reserved for foods that could lose shape easily during a pre-blanching.
The National Center for Home Food Preservation says,
When selecting a method of pack, always use the one specified for a particular product. If given a choice, the hot pack method results in better color and flavor (especially in boiling water canning) and less floating of foods in the jars. Hot packed foods are easier to pack than raw packed foods because they are more pliable. Fewer jars are needed when a food is hot packed. Raw packs are especially useful when working with foods that lose shape when cooked.” [31] National Center for Home Food Preservation Self Study Course. Module 2. General Canning: Methods of Pack. Accessed March 2015.
Bernardin points out that even though there’s a raw pack option for many fruits, it may not be the best choice:
Fruit has very porous tissue. While these pores contain the juice we love, they also hold air that, if not exhausted from the fruit, can cause discolouration as well as floatation. Hot packing fruit helps exhaust this air. Hot packing requires prepared fruit to be heated to a boil in the hot canning liquid. Raw packing skips this heating step and often results in an inferior product. One of the goals of home canning is the removal of excess air — also prevents fruit from floating to the top of the jar, increases the vacuum in sealed jars and improves shelf-life.” [32] Bernardin Guide to Home Preserving. Toronto, Canada: Bernardin Ltd. 2013. Page 36.
You may notice that the USDA gives hot or raw pack option for some fruits, though recommending the hot pack as best quality. If you have a Presto manual, and compare the fruit canning directions, you will see that they are essentially USDA directions but with raw pack options dropped. The Presto test kitchens presumably decided against carrying forward the option for the “lower-quality” option.
Despite all that, some long-time canners still feel that some fruits such as peaches and some varieties of apples are just too delicate to survive hot-packing, and opt to raw pack them instead. This is one of those instances where it definitely is down to your discretion.
Sugar-free fruit canning note
If you are not using sugar in canning your fruit, you need to hot pack only. Do not exercise the raw-pack choice. Ball says,
Hot Pack: This method is preferred when the food to be canned is relatively firm and handles well. Whole or cut food is first cooked in brine, syrup, fruit juice, or water. It may be removed from the cooking liquid and placed into the jar without crushing. Hot brine, syrup, fruit juice or water is added just to cover or as stated in the recipe. The hot pack method is preferred for nearly all vegetables, meats, poultry, seafoods, and many fruits. Fruit canned without a sweetener is always hot packed.” [33] Ball Blue Book. Muncie, Indiana: Healthmark LLC / Jarden Home Brands. Edition 37. 2014. Page 12.
Fancy packs
The National Center for Home Food Preservation doesn’t want you trying to get fancy with how you pack food in a jar. Elizabeth Andress, the head, says:
Fancy packs are generally discouraged. Vertical or horizontal layering can not only be impractical, but can interfere with intended heat penetration during the canning process. (i.e., the product may be underprocessed.)” [34] Andress, Elizabeth L. and Allison M. Oesterle. Judging Home Preserved Foods. National Center for Home Food Preservation. Publication FDNS-E-90. August 2003. Page 26. Accessed March 2015.
Further reading
Development of Raw Packs for Low-Acid Vegetables. Andress, Elizabeth L and Gerald Kuhn. Critical Review of Home Preservation Literature and Current Research. Athens, GA: University of Georgia, Cooperative Extension Service. 1998.
Hot Packs and Raw Packs. In: Andress, Elizabeth L and Gerald Kuhn. Critical Review of Home Preservation Literature and Current Research. IV. Equipment and its Management – History and Current Issues. Athens, GA: University of Georgia, Cooperative Extension Service. 1998.
Video discussion on impact of pack types
References
Leave a Reply