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Guide to Inspections of Low Acid Canned Food 7

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finished product. When the firms filed scheduled process list an aw greater than 0.85 but less than the aw that would allow the growth of spores of public health significance (i.e. Clostridium botulinum is inhibited by a water actively less than 0.93) there must be in place sufficient controls to insure that both the water activity and the thermal process are controlled.

Water activity in food products may be controlled through the addition of salts, sugars and other chemicals. Salt is a common ingredient used for the preservation of caviar and other fish products. If the product is to be packaged in hermetically sealed containers and stored at non-refrigerated temperatures, the control of the amount of salt present in the product may be critical to the thermal processing of the product. Salt content is normally expressed as percent water phase salt. When the percent water phase salt is part of the firms filed scheduled process the salt content must be measured and recorded for each batch of product produced.

A recognized method for water phase salt should be used:

Moisture Content (Total Solids)-AOAC, *16th edition, 952.08. Section 35.1.13, *Note: Substitute pumice or sand for asbestos.

Water Phase Salt-AOAC, *16th edition, 937.09, section 35.1.18, *volumetric method.

The formula for calculating water phase salt, i.e., salt concentration expressed as percent of salt in aqueous phase:

It is suggested that the firm use a check off system to document formulation control. The established process may have to be reevaluated (e.g. heat penetration tests may have to be performed) to determine if formulation changes are significant. If formula changes exceed the limits established in the process (e.g. flour changed from 3.5% to 5% of formula), the formula should be reviewed by the firms processing authority, and documented by the firm.


The packing medium for lacf is normally thought of as the liquid portion(s) of the product which is added over or to the solid portion(s) of the product. Packing medium for lacfs varies with the product being canned and include: water, salt brines, sugar solutions, starch solutions, tomato sauces, mustard sauces and other formulated liquid coverings.

Preparation and handling of the packing medium may be critical to the thermal process. This is especially true for covering liquids containing starches for the reasons mentioned in the product formulation section. Consistency/viscosity of starch solutions is normally specified in the filed scheduled process. The consistency/viscosity of a starch solutions can be measured using a variety of equipment including: the Bostwick Consistometer, capillary viscometers, Brabender consistometer and the Brookfield consistometer. The method of determining the consistency/viscosity should be listed in the filed scheduled process. When sugar syrups are used as covering liquids, the percent sugar (Brix) of the syrup may be critical to the process. Percent sugar is measured on a Brix scale using a hydrometer for sugar solutions graduated so that its readings at a specified temperature represent percentages by weight of sugar in the solutions. Not only is it important to formulate the syrup to the correct brix, but it is important to maintain this brix prior to addition of the liquid to the container. In systems using holding tanks to hold the syrup prior to and during addition to the container, holding of the syrup at elevated temperatures over a long time period may drive off water from the syrup and raise the sugar content of the syrup. A covering liquid with a higher brix than that used during the establishment of the thermal process may cause the product to receive a thermal process less than that established for the product. When the covering liquid for lacfs contains starch or sugars the manufacturer is responsible for ensuring that the covering liquids comply with the requirements of the firms filed scheduled process.

For some products the packing medium may be critical to the process because of its heating characteristics. A good example of this is the production of sardines, which may be packed in many different packing mediums including, oil, ketchup, and mustard sauces. The heating properties of these 3 liquids vary. Normally oil is expected to be the slowest heating of the three sauces; however the slowest heating packing medium will have to be determined by heat penetration or other process establishment studies. Some firms will establish the slowest heating covering liquid, where more than one type of covering liquid is used on the same product. The filed scheduled and operating processes for the product will then be based on the slowest heating covering medium and used for all other covering mediums on the same product. Other firms will establish a separate thermal process for each packing medium.

The growth of thermophilic bacteria is a concern

% salt aqueous phase =

% salt x 100

%water & % of salt

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