SECTION 5: Food Operations Process Control (Part C)


  • Employee Hygiene
  • Food Contact Surface Cleaning and Sanitizing
  • Food Control - Altering Environmental Conditions
  • Time and Temperature Control - Safe Food Holding Times at Specified Temperatures



    PART B

  • Times at Specified Temperatures for Salmonella Inactivation (Kill)
  • Food Cooling Calculations



    PART C

  • Effective Methods for Cooling Food to 41°F (5°C) Rapidly
  • Food Operations Hazard Analysis and Process Control



    Effective Methods for Cooling Food to 41°F (5°C) Rapidly
            While Juneja et al. (98) suggest that food can be cooled safely with 15 hours continuous cooling, the FDA 1999 Food Code (204) recommends cooling food to 41ºF in 6 hours [from 140°F (60°C) to 70°F (21°C) within 2 hours and 70°F (21°C) to 41°F (5°C) or below within 4 hours].  This requires rapid cooling with either blast coolers, which can cost $10,000, or continuous labor stirring the food in sinks of ice and water.  Figure 5-5 shows the simple ways to cool food rapidly to 41°F (5°C).

    Figure 5-5.  Cooling Methods -- 6 Hours to 41ºF

            Blast chilling.  The simplest way to cool food to 41°F (5.0°C), for example in the FDA-recommended 6 hours or less, is to use a blast chill refrigeration system.  Experiments have shown that the key factors in chilling are:

    1. The velocity of the air across the bottom of the pan [greater than 1,000 fpm (5.1 meters per second)]
    2. The thickness of the food [less than 2 inches (5 cm)]
    3. The temperature of the cooling air system [less than 35°F (1.7°C)].
            Whether the pan containing food is stainless steel, aluminum, or plastic makes little difference in cooling rates.  However, the air velocity across the pan of food must be 1,000 fpm (5.1 meters per second) or greater.  Most fans, if placed 4 inches (10 cm) or less from the side of the pan, can provide adequate air velocity.
            Small-piece cooling.  One way around many cooling problems is to cook ingredients individually and make the sauce separately so that the parts can be cooled easily and the ingredients can be combined when both are cold.  If foods are in small pieces, in thin layers on sheet pans and many sides are exposed (e.g., cubed beef, vegetables for stew), the foods cool very rapidly.  These types of food will cool to 41°F (5.0°C) in approximately 90 minutes in a 35°F (1.7°C) refrigeration unit with air blowing across the pan even at 50 fpm (0.25 meter per second).  This is an effective way to cool ingredients before they are combined into a salad, sauce, or casserole-type dish.  Combining ingredients previously chilled to below 41°F (5.0°C) eliminates the problem of outgrowth of S. aureus from the hands used to mix the salad, because S. aureus does not produce toxin below 50°F (10.0°C).  It is true that if the food is uncovered, it cools about twice as fast.  However, it will become contaminated with mold,  yeast, and other spoilage microorganisms from the refrigerator blower coils, which will grow in the food and cause it to spoil in about 5 days.  If the food is to be used within 2 to 3 days, it can be cooled uncovered.
            Cooling gravies and sauces.  Gravies can be quickly cooled if half of the liquid is omitted during preparation.  When the gravy / sauce has the correct flavor, it can be thickened to a double thick consistency with a roux or starch.  Cooling is accomplished rapidly (3 to 6 minutes) by adding the other half of the liquid as ice (or frozen milk) to chill the gravy or sauce to 35°F (1.7°C).  At the same time, the product is diluted to the correct strength and viscosity.  When individual item pan cooling is combined with this procedure, sauces, gravies, and stocks may be stored at 33 to 35°F (0 to 1.7°C).  To prepare a stew or casserole, the food preparer simply gets the correct amount of refrigerated cubed beef and vegetables and the correct amount of sauce.  The combined product is then reheated in a convection oven or microwave oven in 20 minutes or less.  This system eliminates the hazardous procedure of inadequate cooling and hot holding.
            Solid or liquid carbon dioxide (e.g., dry ice) can also be used to cool sauces.  Carbon dioxide (CO2) is particularly effective, because it does not dilute the liquid.  It also has an excellent inhibiting effect on pathogens, because it forms carbonic acid with water, and the pH of the product declines.  The carbon dioxide may give a sauce or gravy a slightly carbonated flavor when cooled.  However, when the products are reheated, the CO2 vaporizes and the carbonation is no longer evident.  [Note, CO2 should always be used in a ventilated area to prevent asphyxiation.]
            Ice bath cooling. When refrigeration is limited, solid chunks of hot foods such as chicken, beef cubes, pot roast, turkey, potato cubes, macaroni, or rice in perforated pans can be placed into a slush ice bed.  The items should then be covered with a layer of ice and enough water added to make an ice slush.  Most cubed products that are less than 1 inch (2.5 cm) thick can be removed from the ice bath in about 30 minutes when the temperature of the food has dropped to below 35°F (1.7°C).  Large items such as a whole, cooked turkey and roast beef may require 4 hours to cool in an ice bath.  Cold food should be stored covered, in any size container in the refrigerator at 32 to 35°F (0 to 1.7°C).  Products prepared in this manner have a much longer shelf life, because the rapid cooling process also restrains the growth of spoilage microorganisms, and the cooling process avoids much contamination.
            Note, it is very important that the sink or large container containing the slush ice be sanitized prior to using this method in order to prevent any cross-contamination of products.
            Salad preparation.  All ingredients used to prepare cold foods such as salads, which will not receive any further heat treatment, should be cooled to less than 41°F (5.0°C) before ingredients are combined.  An easy way to cool freshly cooked salad ingredients such as macaroni or potatoes is to use the ice bath method.  If all ingredients (including salad dressing) are less than 41°F (5.0°C), it is possible to mix a salad and return it to refrigerator storage before the salad temperature reaches 50°F (10°C).  This prevents the multiplication of S. aureus and proteolytic types of C. botulinum and formation of toxin.

    Food Operations Hazard Analysis and Process Control
            Food operations hazard analysis.  Figure 5-6 presents a summary of the common critical control points in a foodservice operation.  Note, consumer nutrition, consumer allergies, and consumer abuse of the food are included, since they are problems that have been identified in lawsuits.  (If Figure 5-6 does not print properly, click here for separate image.)

    Figure 5-6.  Food Operations Hazard Analysis

    Pasteurized-chilled food process hazard control flow diagram. Figure 5-7 summarizes the standards for the control of chilled food processes. (If Figure 5-7 does not print properly, click here for separate image.)

    Figure 5-7.  Pasteurized-Chilled Food Process Hazard Control Flow Diagram
            First, employees must wash their hands and fingertips using the double hand wash with a fingernail brush.  Insects and rodents must be kept out of the facility, and all food contact surfaces must be cleaned and sanitized between contact with different potentially hazardous raw products.  Assuming that raw food is contaminated, there must be just-in-time delivery of fresh product to assure that there is minimal pathogen multiplication in the wholesale supply system.  Food must be stored before the temperature of the food rises more than 5ºF (2.8ºC).  Damaged packages should be returned, and moldy food should be destroyed.
            Pre-preparation of the food should begin within 24 hours of the time it will be consumed.  The food temperature must kept to less than 50ºF (10.0ºC) during pre-preparation.  Heating the food to above 130ºF (54.4ºC) in less than 6 hours will control the multiplication of C. perfringens.  The food should then be pasteurized to reduce Salmonella 10,000,000 to 1, according to the standards shown.  Leftovers of cooked / pasteurized food should be cooled to 45ºF (7.2ºC) in less than 15 hours in order to control the multiplication of C. perfringens.  If salads are made, they should be mixed at a temperature of less than 50ºF (10.0ºC) in order to control the toxin production by growth of S. aureus and C. botulinum.
            Food held hot on a steam table should be served in less than 30 minutes in order to retain the thermally sensitive nutrients vitamin C, niacin, and thiamin.  Cross-contamination must be controlled.  If hot take-out food is given to a consumer, the consumer must be instructed to eat it within 2 hours, or to begin to cool it immediately to 41ºF (5.0ºC) in 2 hours.  If the consumer cannot do this, then he or she should purchase cold food at 41ºF (5.0ºC) to take home.  Food should be held either below 30ºF (-1.1ºC) or used within the time limits in Table 5-1.
            Reheating food should not be used as a critical hazard control process.  If toxins of S. aureus, B. cereus, and C. botulinum have been produced, they cannot be inactivated by reheating to 165ºF (73.9ºC).
            The following process standards assure that toxins will not be produced after food is cooked.  Keeping food at less than 38ºF (3.3ºC) controls the growth of non-proteolytic C. botulinum and B. cereus.  However, this temperature will allow the growth of L. monocytogenes and Yersinia enterocolitica from cross-contamination.  Therefore, to assure the safety of food, it should be used within the time-temperature constraints of Table 5-1.

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