Food Protection Trends - February 2009 - 75

validation study. The details of the validation study depend upon the method of cooking and the product. In many cases, it may be appropriate to consult a statistician to assure that the study fully considers all variables that might significantly affect the adequacy of the final temperature achieved throughout the product during the cooking process. Each product type (including composition, size, shape, components, distribution, or package configuration) should be tested, unless worst-case conditions can be logically applied to cover multiple product variables. In general, testing should be performed with heavier samples in the lot or with maximum-sized pieces (e.g., ones that exceed the product specification by 1/8” in all dimensions). The initial temperature of tested product should be the lowest expected at the time of preparation in a typical consumer’s home. Thus, frozen products, unless they bear clear instructions that thawing is required prior to cooking, should be in their frozen state (0°F - 10°F) when testing begins. Type of cooking device Cooking directions are often provided to the consumer for a variety of cooking devices, such as microwave ovens, conventional or toaster ovens, and stovetops. Because of the fundamental differences in the way foods heat (i.e., the kinetics of heat transfer) in the various cooking devices, especially in microwave ovens, and the impact of the number of units being cooked at a time, the type of cooking device will certainly affect the design of the validation study. The guidelines provide specific information on validation testing for conventional and toaster ovens, fryers, and stovetops. However, validation testing for microwave ovens warrants the greatest attention in the guidelines. Factors to consider for microwave ovens Products bearing microwave cooking instructions are of particular concern, since non-uniform heating of foods in microwave ovens has been implicated as a key factor in undercooked food products resulting in a number of cases of salmonellosis (7, 8, 9). This non-uniform heating leads to cold spots in the product, which may allow the survival of pathogens such as Salmonella potentially present in components of NRTE foods. The guidelines cite microwave oven wattage, rotation of product, magnetron power output, number of units cooked at one time, cold spot determination and heating uniformity in product as key factors to be considered during validation of microwave cooking instructions. Determination of the wattage for each oven used is a fundamental step in validation studies involving microwave ovens. In general, cooking instructions should be validated using a number of ovens that span the range of wattages commonly used by consumers. However, validation studies for microwave cooking instructions can be conducted in several different ways, including running tests with the lowest wattage oven only; conducting tests with a range of consumer microwave oven wattages; and performing tests with the most common wattage used by consumers (~1100 watts). Each method is addressed in the guidelines. The guidelines cover many additional factors to be considered. Ideally, units that do and do not have certain features, such as carousels to rotate product during cooking, should be included in the tests. Any directions provided for manual rotation of the product during cooking should be based on validated test results. Manufacturers should consider the need to provide appropriate instructions on products for which they could reasonably expect consumers to microwave multiple units simultaneously. Examples are provided of various approaches manufacturers can take during validation testing to account for the fact that as the microwave magnetron heats up, the amount of power it generates for cooking decreases (as much as 20% in some cases). Another critical matter addressed in the guidelines is cold spot determination and product heating uniformity. To assure the safety of NRTE foods cooked in a microwave oven, it is necessary to determine that all portions of the product have reached a given temperature for a minimum period of time adequate for the appropriate log reduction of the pathogen(s) of concern. As previously noted, gaining this assurance can be particularly challenging for foods cooked in microwave ovens because of the likelihood of non-uniform heating. Thermal imaging may be useful in identifying cold spots, as well as hot spots. For safety assurance, the product temperature may need to be measured in multiple places in each sample to detect a cold spot. The importance of proper calibration of temperature measuring devices used in the validation study is noted in the guidelines. Clarity of instructions In addition to the critical importance of validating the cooking times and/or temperatures, it is also very important that cooking instructions are written so the consumer can easily follow them. One way to help ensure this is to have a method for consumers to provide feedback, and to monitor this feedback for any indication that the cooking instructions are hard to understand or difficult to use, or that when they were followed, the product was still cold or otherwise not well cooked. Such feedback should be used to review the adequacy/clarity of the cooking instructions. The guidelines acknowledge the value of including visual or other cues, where appropriate, with cooking instructions, especially those for microwave ovens, to help consumers recognize when a product has not been adequately cooked for safety and therefore may require additional cooking time. Examples of such cues could include a statement within the instructions informing the consumer that if the bottom of the tray is cold after the prescribed cooking time, then the product should be cooked for additional increments of time until the tray is warm or hot, or a statement to the effect that when the product is properly cooked, it will be steaming. Although this document deals with the scientific basis for cooking instruction validation, the importance of human factors in cooking instruction communication should not be overlooked. It is critical that the instructions provided to the consumer are clear, complete and well designed. For this reason, this guidance document also refers readers to a complementary document that addresses labeling issues relevant to NRTE food products. This document, “Recommended Guidelines for the Labeling of Microwave Cooking Instructions,” was developed by an American Frozen Food Institute working group (1). The guidelines also contain a table of recommended cooking time and temperatures for various products. In addition, an appendix of generic cooking instruction validation examples is included, along with some approaches to interpretation of results that were provided by GMA members based on their validation protocols. The examples include some approaches FEBRUARY 2009 | FOOD PROTECTION TRENDS 75

Food Protection Trends - February 2009

Table of Contents for the Digital Edition of Food Protection Trends - February 2009