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Guide to Inspections of Low Acid Canned Food 5

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Preparation - During the preparation of low-acid foods for canning we have to be concerned not only with maintaining the microbiological quality of the food ingredients, to prevent a microbiological load greater than that taken into account during establishment of the thermal process, but also with the physical characteristics of the product which may affect the thermal process.

Sorting - Product size as previously noted may be a factor critical to the thermal process. This can only be determined through process establishment procedures such as heat penetration testing of the product. Larger size products (i.e. large shrimp as compared to small shrimp) may require increased thermal processing times at the same temperature. For some products smaller sizes may allow the product to compact in the container altering the normal heating characteristics of the product. This is especially true of sliced and diced products. If product size is critical to the process the size must be defined in terms that can be measured (i.e. large shrimp = 3 to 5 shrimp per oz). Many firms use mechanical grading as well as grading by plant employees to maintain the desired size range of products. Mechanical grading and sorting may be done by passing product through a rotating drum with different size holes, by passing product over a set of rollers with different spacings or by using other methods which separate out different size products. The size of sliced and diced vegetables may be controlled through the use of fixed blade slicing equipment. The equipment must be evaluated to determine if the correct slice thickness is being provided. It may be critical to the process if excess amounts of product sliced thinner or if excess fines (small particles of product) are being produced. The firms system for controlling fines should be determined during the inspection. The firms system for grading/product size should be evaluated to insure that the size range specified in the firms filed scheduled thermal process is being met.

Grading - Grading of raw materials prior to processing should be designed to insure that the qualities of the raw materials critical to the process are being maintained. An example of product quality that can affect the thermal process is provided by mushrooms. Class 1 or Grade A mushrooms which have a very tightly closed veil may require a shorter process time than Class two or Grade B mushrooms with a more open veil. Grading, sorting and inspection equipment in the cannery should be operated to preclude the addition of microorganisms, filth or physical hazards to the food product. Grading, sorting and inspection equipment should be cleaned at a minimum of once per day, sanitized and washed down prior to use.

Blanching - Blanching of food is performed for several different reasons:

  1. Inhibition of enzymatic action. The high temperature of blanching inactivates the enzymes preventing oxidative and other chemical actions which may alter the taste and/or characteristics of the food.
  2. Expelling of respiratory gases. By driving out the respiratory gases normally found in fresh vegetables & fruits, the effect of these trapped gases on the headspace of the container is minimized, allowing a greater vacuum to be achieved in the container, and minimizing the chances of can buckling. Oxygen, which may be corrosive to the inside of the container and to the product, is driven out of the product prior to packaging.
  3. The food is softened allowing some foods to be packed easier. This may allow for higher fill and drained weights.
  4. Peeling, dicing, cutting and other preparatory steps may be easier to perform.
  5. The natural color of the food may be set.
  6. Raw flavors may be removed from the food.
  7. It may be an added cleaning measure.

Blanching of lacf is normally through the use of hot water or steam. Hot gas blanching has been developed for the blanching of vegetables, partly to reduce the pollution effluent from blanching, however hot gas blanching is not normally encountered.

Thermophilic growth is a major concern with blanchers. Blanchers should be operated at temperatures in the 88-93°C (190 - 200° F) range. Product temperatures at or above 82°C (180°F) helps to control thermophilic growth. Blanchers may be operated at temperatures lower than 82°C (180° F) because of product considerations. These systems should be evaluated for the growth of thermophilic organisms. The product should be rapidly heated and then rapidly cooled if the product is not immediately packed and thermally processed. Products which are to be packed and thermally processed immediately should not be cooled. The water used in blanchers should be changed on a routine basis and the blancher rapidly refilled and reheated. Foam buildup in blanchers should be controlled as the foam may allow for thermophilic growth at temperatures lower than the temperature of the blanching water.

During inspection of lacf manufacturers using blanchers the investigator should obtain the

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