Heat Preservation and Processing PDF

NFSC 288 TECHNOLOGY OF FOOD PRODUCTS LECTURE 5 HEAT PRESERVATION & PROCESSING  SHORT HISTORY OF CANNING 1809 During the Napoleonic Wars, Nicholas Appert, a French man, was awarded a prize by the French Government for having developed a new, successful mean of preservi...

NFSC 288 TECHNOLOGY OF FOOD PRODUCTS LECTURE 5 HEAT PRESERVATION & PROCESSING  SHORT HISTORY OF CANNING 1809 During the Napoleonic Wars, Nicholas Appert, a French man, was awarded a prize by the French Government for having developed a new, successful mean of preserving foods - Canning 2  SHORT HISTORY OF CANNING  1817 William Underwood established first canning factory in America  1864 Pasteur discovered the relationship between heat and death of microbial cells and food spoilage  1910 Importance of controlling C. botulinum during canning was established 3  HEAT TRANSFER Heat transfer: a transfer of energy from one part of a substance to another by difference in temperature. 4  BOTULISM Clostridium botulinum  Moist, low-acid food  Temperature between 5°C and 50°C  Less than 2 percent oxygen 5  HIGH ACID & LOW ACID FOODS Mild heat required, since spores are inhibited by acid High heat required in order to destroy spores MILD HEAT ACID MILD HEAT HIGH HEAT Spore Spore BACTERIA (with spore) BACTERIA BACTERIA BACTERIA (Vegetative Cell) (with spore) (Vegetative Cell) Fish Corn Meat Peas Asparagus Spinach Green Beans Beets Carrots Tomatoes Apricots Pears Pineapple Cherries Plums Berries pH = 3.0 pH = 4.6 pH = 7.0 HIGH ACID & LOW ACID FOODS  DEGREES OF HEAT PRESERVATION 1. Sterilization 2. Commercial Sterility 3. Pasteurization 4. Blanching 8 1. STERILITY The absence of all organisms which are capable of reproducing. 9  2. COMMERCIAL STERILITY Condition when:  Containers are free of viable microorganisms with public health significance.  Containers are free of microorganisms of non-health significance capable of reproducing under normal conditions of storage and distribution. 10  METHODS OF OBTAINING COMMERCIAL STERILITY  Filling - Closing - Sterilizing: “In-Container Sterilization - Canning” Product sealed inside container, product is heated and cooled in the container. Raw Food Food product Preparation Shelf stable Combine Filling Closing Sterilization product Convert Packaging Package material 11  METHODS OF OBTAINING COMMERCIAL STERILITY  Sterilizing – Filling - Closing: “Out-of-Container Sterilization, In-Flow - Aseptic” Product and container sterilized separately and then product filled into the container in a sterile environment Raw Food Food product Sterilization Preparation Aseptic Combine Filling/ Closing Stable product Convert Packaging material Package Sterilization 12  3. PASTEURIZATION  Pasteurization is less severe in terms of heat treatment than sterilization (< 100ºC ).  Destroys pathogenic microorganisms but not spoilage organisms.  Done to destroy pathogenic microorganisms and to prolong the shelf life of foods. 13  3. PASTEURIZATION  Pasteurization is used with milk, beer, wine, fruit juices, liquid eggs.  Refrigeration needed for pasteurized products vs. shelf stable for sterilized.  Shelf life of milk after pasteurization is 12-14 days at refrigeration temperatures. 14  MILK PASTEURIZATION  Coxiella burnetti (Current Requirements)  Mycobacterium tuberculosis (Previous Requirements) 15  MILK THERMAL PROCESSING Temperature Time Pasteurization: LTLT 63°C 30 min HTST 72°C 15-16 sec Sterilization: UHT 135 to 140°C a few sec 16  Sensor/ Diversion Valve Holding Tube Feed Tank Pump Plate Heat Exchanger Unit 17  4. BLANCHING  Blanching is applied to fruits and vegetables to inactivate natural food enzymes (peroxidase, catalase).  Natural enzymes are still active under freezing, thus the need for blanching before freezing vegetables.  Blanching can also destroy some microorganisms. 18  DEGREES OF HEAT PRESERVATION Mild and Severe Heat Treatments Comparisons Mild Severe Kill pathogens; Kill all bacteria; Aims reduce bacterial count; food will be inactivate enzymes commercially sterile Minimal damage to Long shelf-life; no Advantages flavor, texture, other preservation nutritional quality method is necessary Short shelf-life; Food is overcooked; another preservation Disadvantages major changes in method must be used, texture, flavor, such as refrigeration nutritional quality or freezing Examples Pasteurization; Canning; 19 Blanching UHT Sterilization  HEAT TREATMENT SELECTION Factors to be considered: 1. Heat treatment is as mild as possible. (Quality) 2. Heat treatment is enough to destroy pathogenic microorganisms and toxins. (Safety) 3. Heat treatment is enough to give the needed shelf life. (Storage conditions) 20  HEAT TREATMENT SELECTION In order to select the proper and safe heat treatment, the following needs to be known: 1. Heat penetration characteristics of the food, including the container of food. 2. Time-temperature combination required to inactivate the most heat resistant pathogens and spoilage organisms in a specific food. 21  HEAT PENETRATION CHARACTERISTICS Factors to be considered:  Coldest point (depending on mode of heat transfer)  Can size  Composition of food and consistency  Mode of heat transfer: by conduction or convection 22 COLDEST POINT 23 CAN SIZE 24 COMPOSITION OF THE FOOD 25  EFFECTS OF FOOD CONSTITUENTS  Acid: decrease process time/temperature  Sugar, starch and fat: increase process time/temperature  Wet heating is more efficient than dry heating: Liquid is generally added to canned solid foods 26  CONDUCTION & CONVECTION HEATING Examples: 1. Tomato soup 2. Fruits with sugar syrup 3. Corned beef 27  PROCESS TIME & PROCESS LETHALITY  The time needed to reach the target (final) temperature is called “come-up time” CUT  The cooling phase of sterilization will also involve additional microbial destruction  The total lethality of the process is the summation of lethal effects during the whole process 28  ORDER OF BACTERIAL DEATH  Death of a microorganism is defined as when it has lost its ability to reproduce  When exposed to heat bacterial death is quite orderly  Generally, the number of viable microorganisms reduces exponentially with time of exposure to lethal temperature 29 EXPONENTIAL PHENOMENA 30 31 D-VALUE: DECIMAL REDUCTION TIME  Time in minutes (or seconds) to reduce the population of bacteria by 90% at a specific lethal temperature.  Time required to reduce the population of a certain microorganism by 1 log cycle or by 10 folds at a specific lethal temperature.  Must be based on a pure culture of a single type of a microorganism. 32 33  1 log cycle 10 folds D = 15 minutes 34 Example 1: 35 Example 2: 36  FACTORS INFLUENCING D-VALUE  Species of microorganism  Temperature of the heat treatment  Environment during growth  Nature of heating medium bacteria are suspended in 37  FACTORS INFLUENCING D-VALUE Comparative heat resistance of bacteria ----------------------------------------------------------------------------------------------------------------------------------------------- Approximate Bacterial Group Heat Resistance ----------------------------------------------------------------------------------------------------------------------------------------------- Low-acid and semi-acid foods (pH above 4.5) Thermophiles D250 = D0 Flat-sour group (B. stearothermophilus) 4.0-5.0 Gaseous-spoilage group (C. thermosaccharolyticum) 3.0-4.0 Sulfide stinkers (C. nigrificans) 2.0-3.0 Mesophiles Putrefactive anaerobles C. botulinum (Type A and B) 0.10-0.20 C. sporogenes (including P.A. 3679) 0.10-1.50 ----------------------------------------------------------------------------------------------------------------------------------------------- 38 39  THERMAL DESTRUCTION CURVES Z-values  Reflect the resistance of bacteria to different lethal temperatures.  Numerically equal to the number of ºF or ºC for the thermal destruction curve to transverse one log cycle.  Z-value is the temperature increase that will cause a 10 fold reduction in the lethality time or D-value. 40 TEMPERATURE VS D-VALUES TEMP., ºF D-value (minutes) 230 27.00 240 7.30 250 2.00 259 0.63 268 0.20 41 42  UNIT OF LETHALITY F-value  It is defined as the time required to achieve a certain level of kill.  It is usually a multiple of D-value.  Examples: Pasteurization: 5D or 6D Commercial Sterility: 12D  F-value is expressed as the equivalent minutes at a specified temperature. 43  UNIT OF LETHALITY F0-value Represents the equivalent minutes at 250 ºF (121ºC) at the slowest heating point in the container 44 UNIT OF LETHALITY F-value 45 UNIT OF LETHALITY Example 1: If a food had 10 million organisms and it has been subjected to heat for a time equal to 1 D-value, what will be the population after heat treatment? Example 2: If a food had 1 million organisms and it has been subjected to heat for a time equal to 3 D-values, what will be the population after heat treatment? 46  UNIT OF LETHALITY Example 3: If 100 cans of a food had an initial population of 100 million organisms and received heat for a period equivalent to 6 D values, then what will be the population after heat treatment? 47 ASSIGNMENT 3 48 HEATING BEFORE OR AFTER PACKAGING  Still Retort / Conventional Retort  Agitating Retort After Packaging  Hydrostatic Retort  Aseptic Packaging Before Packaging  Hot Pack-Hot Fill 49 HEATING FOODS AFTER PACKAGING 50 HEATING FOODS AFTER PACKAGING Agitating Retort 51 52  53 Hydrostatic Retort  HEATING FOODS BEFORE PACKAGING  Applied to heat sensitive foods.  Subdividing food and exposing it to a heat exchange surface achieves rapid heating.  Heating foods in container is much slower because of time needed for heat to penetrate the container and reach all points of the food. 54  ASEPTIC PACKAGING  Food is heated outside the container.  Then it is placed into a sterile container and filled and sealed under aseptic conditions.  The package, which is often paper or plastic, is sterilized with heat, or heat and chemicals like Hydrogen Peroxide (H2O2).  This method is mostly suitable for liquid-based food products. 55  ASEPTIC PACKAGING  UHT treatment.  Plate heat exchanger or a tubular heat exchanger for liquid foods.  Up to 150°C for 1-2 seconds.  Food is cooled afterwards using the same system. 56  HOT PACK HOT FILL  The food is filled hot to the container which is not sterile and left at high temperature to sterilize container.  Most effective with high acid foods.  Used with acid juices (orange, grape, tomato) & acid fruits and vegetables (jams, ketchup, pickles, etc.) 57  HOME CANNING  Carefully selecting and washing fresh food  Peeling some fresh foods  Hot packing many foods  Adding acids (lemon juice or vinegar) to foods  Using acceptable jars and self-sealing lids  Processing jars in boiling-water or pressure cooker for correct period of time 58