activity.OsmosisA process by which molecules in a solvent tend to pass through a semi‐permeable membrane from a less concentrated solution into a more concentrated one.OxidationThe act of oxidizing which is brought about by increasing the number of positive charges on an atom or the loss of negative charges.Oxidative RancidityThe deterioration of fats and oils due to oxidation.PackageAny container or wrapping in which a consumer commodity is enclosed for delivery or display to retail purchasers.PanellingDistortion (side wall collapse) of a container caused by development of a reduced pressure (too high vacuum) inside the container.PasteurizationA heat treatment of food usually below 100°C.PathogenDisease producing micro‐organism.PathogenicCapable of producing disease.PatulinA mycotoxin.ppbParts per billion.pHA figure expressing the acidity or alkalinity of a solution on a logarithmic scale on which 7 is neutral, lower values are more acid and higher values more alkaline.Potable WaterDrinkable water / fit for human consumption.ppmParts per million.PreservationAny physical or chemical process which prevents or delays decomposition of foods.PreservativesAny substance capable of retarding or arresting food spoilage or deterioration.Primary SpoilageThat spoilage due to bacterial or chemical action of product packed within the can. See also Secondary Spoilage.Process AuthorityThe person or organization that scientifically establishes thermal processes for low‐acid canned foods or processing requirements for acidified foods.Process, ScheduledThe process selected by the processor as adequate under the conditions of manufacture for a given product to achieve commercial sterility. This process is in excess of that necessary to ensure destruction of micro‐organisms of public health significance.Process TemperatureThe calculated temperature at a particular time (process time) for which a specific can size and food product need to be heated in order to achieve commercial sterility.Process TimeThe calculated time at a particular temperature (process temperature) for which a specific can size and food product need to be heated in order to achieve commercial sterility.PSIGPounds per square inch gauge pressure.PsychrometerAn instrument for measuring the humidity (water‐vapour) content of air by means of two thermometers, one dry and one wet.PutrefactionDecomposition of proteins by micro‐organisms, producing disagreeable odours.RefractometerOptical instrument that measures the percent of soluble solids in solution by the extent to which a beam of light is bent (refracted). Soluble solids scale is based on sugar concentration in a pure sucrose solution (Brix).Relative HumidityThe ratio of actual humidity to the maximum humidity which air can retain without precipitation at a given temperature and pressure. Expressed as percent of saturation at a specified temperature.RetortAny closed vessel or other equipment used for the thermal sterilization of foods.Retort (Retortable) PouchA flexible container in which food is placed to be heated to commercial sterility in a retort or other sterilization system.Rigid ContainerA container whereby the shape or contours of the filled and sealed container are neither affected by the enclosed product nor deformed by an external mechanical pressure of up to 0.7 kg/cm² (10 psig), (i.e. normal firm finger pressure).SalmonellaA genus of bacteria that can cause infections in man that are characteristically gastrointestinal. Destroyed by adequate heating as in the canning process.SalmonellosisInfectious disease caused by bacteria of the genus Salmonella.SanitizerA chemical agent that reduces the number of microbial contaminants on food contact surfaces to safe levels from the standpoint of public health requirements.Secondary SpoilageRusted, corroded and perforated cans (from the outside towards the inside) as a result of product leaking onto them from other spoilt containers. May occur during warehousing or transport.Semi‐rigid ContainerA container whereby the shape or contours of the filled, sealed container are not affected by the enclosed product under normal atmospheric temperature and pressure but can be deformed by an external mechanical pressure of less than 0.7 kg/cm² (10 psig), (i.e. normal firm finger pressure).Shelf‐LifeThe length of time that a container, or material in a container, will maintain market acceptability under specified conditions of storage.SpoilageA process whereby food is rendered unacceptable through microbial or chemical action. See also Primary Spoilage and Secondary Spoilage.SporesSome rod forms of bacteria produce spores. In the spore state, bacteria can survive extremes of cold, heat, drying, and other unfavourable conditions for long periods of time; and when the environment is again favourable, the spores germinate, and the organisms start another cycle of growth. Growing cells are called “vegetative” cells.SpringerSwelled can with only one end remaining out; on pressing this end it will return to normal, but the other end will bulge out.Stack BurnCondition resulting from placing cased cans in piles insufficiently cooled. Food may vary from over cooked to definitely burned flavour and colour. Also, excessive corrosion of interior of container may result.StaphylococciA genus of spherical bacteria (cocci) occurring in pairs, tetrads or irregular, grape‐like clusters.Staphylococcus aureusSpecies of bacteria that are important as a cause of human infections and of food poisoning.SterileFree of living organisms.SterilizationAny process, chemical or physical, which will destroy all living organisms.Sterilization ProcessThe time‐temperature treatment necessary to render canned foods commercially sterile.Sterilization TemperatureThe temperature maintained throughout the thermal process as specified in the scheduled process.Sterilization TimeThe time that lapses between the moment a retort reaches sterilization temperature, until steam is cut off.Sterilization Value (F)The number of minutes at a reference temperature of 121.1°C (250°F) required to kill a known population of micro‐organisms with a z‐value of 10°C (18°F).Still RetortA retort for the sterilization of canned foods in batch amounts, with no agitation.StreptococciA genus of bacteria that are spherical or oval shaped and that divide in such a way that pairs or chains are formed.Superheated SteamSaturated steam that has been heated at constant pressure above its saturation temperature.Swell(1) (Noun) A container with either one or both ends bulged by moderate or severe internal pressure. (2) (Verb) To bulge out by internal pressure, as by gases caused by biological or chemical action.Swell, HardA can of food which has spoiled to the point where both ends are bulged out and show no appreciable yield to thumb pressure.Thermal ProcessThe application of heat to food, either before or after sealing in a hermetically sealed container, for a period of time and at a temperature scientifically determined to achieve a condition of commercial sterility.ThermocoupleA bi‐metallic device to measure temperatures electrically.ThermoduricMicro‐organisms that have the ability to withstand high temperatures, i.e. are highly heat resistant.ThermolabileFairly easily destroyed by heat.Tin PlateSheet steel, usually of special formula and temper, coated on both sides with a controlled thickness of pure tin.ToxinAn organic poison, a product of the growth of an organism. Some toxins are given off as waste products of a micro‐organism, and are called “exotoxins”. Others are contained within the cells, and are liberated only when the cell dies and disintegrates. These are called “endotoxins”.UHTUltra High Temperature. Term used in reference to pasteurization of commercial sterilization of food by heating it for an extremely short period, around 1–2 seconds, at a temperature exceeding 135°C (275°F).Ultraviolet IrradiationA disinfection method that uses ultraviolet (UV) light at sufficiently short wavelength to kill micro‐organisms. It destroys the nucleic acids in these organisms so that their DNA is disrupted.Vacuum PackProducts packed with little or no brine or water, which are sealed under a high mechanical vacuum, and which require maintenance of high vacuum to assure process adequacy.Vegetative CellsStage of active growth of the micro‐organism, as opposed to the bacterial spore.VentingEliminating air from a retort prior to sterilizing canned foods.VentsOpenings controlled by gate, plug, cock, or other adequate valves used for the elimination of air during the venting period.ViscosityThe internal friction or resistance to flow of a liquid. The constant ratio of shear stress to shear rate. In liquids for which this ratio is a function of stress, the term “apparent viscosity” is defined as this ratio.Water Activity (aw)A measure of water availability in food for microbial growth. The ratio of water vapour pressure of a food to the vapour pressure of pure water under identical conditions of temperature and pressure.YeastsMicro‐organisms classified in the kingdom Fungi. They are spherical or more or less elongated cells. Most yeasts break down sugars to carbon dioxide and alcohol. That process is called fermentation.Z‐valueZ‐value is a term used in thermal death time calculations. It is the temperature required for one log reduction in the D‐value for a specific bacteria.
1 History of Thermal Processing
The application of high temperatures is one of the most commonly used methods to kill or control the numbers of micro‐organisms present within foods and on packaging surfaces. Evidence for its importance