Technologists producing acidic foods such as pickles and sauces often find it difficult to get information on the processing conditions required to obtain commercial sterility or how to calculate the processing time at a higher temperature. Following the experience of working with processors experiencing technical issues, including spoilage problems and difficulties in exporting products, I have produced a concise Ebook (Thermal processing of acid fruit and vegetable products. Significant microorganisms, recommended processing time / temperatures, and public health significance of spoilage) that may be helpful. Currently the Ebook (figure 1):
1) Identifies the potential spoilage organisms of acidic foods
2) Discusses the decimal reduction times and Z-values of the major spoilage organisms of acid foods
3) Lists F or P values and reference temperatures for ensuring the production of commercially sterile acid foods
4) Explains how to calculate F values and the number of log reductions of spoilage organisms following processing
5) Explains how to calculate equivalent processes e.g. at higher temperatures using published data
5) Explains the importance of measuring pH over the shelf life of acidified products
6) Provides a summary of the major causes of spoilage of acidic foods and their control
7) Lists literature, including a free On Line database containing around 6000 D-values, concerning the manufacture and control of acid foods.
The booklet can also be used on an iPhone or Android device that can view PDF files.
This Ebook currently contains 17 pages, 5 tables and 19 references (the table of contents is shown in figure 2). Worked examples are provided and the author is prepared (within reason) to help users having problems, providing they are posted on the forum.
The Ebook was updated to version 1.3 on the 30th June 2012 and can be downloaded using the original download URL.
The next update, version 1.4, has been written and will be uploaded to the site by the end of March, 2017 following peer review. This is a major revision and includes more information on factors affecting heat sensitivity, use of acidulants, P values, potential for growth of Clostridium botulinum and the limitations of pasteurization when dealing with vegetables or ingredients containing high spore loads. Zapateria spoilage of olives and its prevention by thermal processing has also been included. In addition, unlocked Excel-spreadsheets will be provided for all thermal processing calculations.
In the meantime any past or current purchasers of earlier versions can request a free unlocked Excel spreadsheet illustrating any of the thermal processing models in the Ebook.
The Ebook will continue to be updated periodically and donors will be advised of updates through the News Section of the website. Updates will be available at no cost.
Note the Ebook should also be of use to manufacturers of pasteurized, acidic beverages, including 'health foods' and some pharmaceutical products such as mouthwashes.
Figure 2. Table of contents of the thermal processing report.
The Ebook is available as an immediate download following a donation of £40.00 (about $49 or 46 Euros) to the Diary Science and Food Technology website. Only make this donation if you understand that you are receiving an educational aid to help you understand the scientific and technological factors influencing the production of commercially sterile acid and acidified foods.