Critical Review of Home Preservation Literature and Current
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Literature related to the development of processing schedules for home canned foods was collected and reviewed. An assessment of the origins of the current USDA recommendations was completed through analysis of government technical bulletins, published research reports, state agricultural experiment station publications, and departmental project reports from files at USDA. In addition, a survey tracing the development of scientific research methods as applicable to providing standards for process determinations was complied. As a result of the literature review and meetings with personnel from USDA (CES and ARS) and the National Food Processors Association, a summary of current issues in home canning safety was derived. Finally, process schedules printed by various state Cooperative Extension Services were compared to those in the current Home and Garden Bulletins published by USDA.
The literature reveals that USDA historically has been and presently is a recognized authority and source of home canning recommendations. The majority of current processes have their origins in research conducted by, or in cooperation with, the Bureau of Human Nutrition and Home Economics, USDA, from 1943-1957. Two large contributors on cooperative projects were the Massachusetts and Texas Agricultural Experiment Stations. Research methods developed from findings in the field of bacteriology and the canning industry, beginning about 1920. Unfortunately, no further research was carried out by USDA since 1957 and published processes have not changed in this time period.
The origins and/or safety of a few products remain uncertain. In addition, current issues also include the influence of newer canner construction on process lethality, relationships between headspace, venting and vacuum with current canning equipment, acid-low acid combination products, the use of 15 psig, and the lack of application of newly discovered spoilage organisms in test packs. Steam and oven canning remain issues although literature was found which proves them to be unsafe.
The majority of processes currently published by state Extension services follow USDA guidelines. However, there are major discrepancies in processes for applesauce and tomato products and slight variations for a few other products. There are also many processes offered for products not contained in USDA publications. The majority of these are sugar concentrates (jams, jellies, etc.) and pickles or relishes, but a few states offer additional vegetable and fruit processes. The data to support the validity of these additional recommendations were not reviewed in this paper.