A Guide to Calculating Shelf Life of Foods PDF

A Guide to Calculating the Shelf Life of Foods Information Booklet for the Food Industry 8204_Shelf Life 1.2.indd 1 21/3/05 12...

A Guide to Calculating the Shelf Life of Foods Information Booklet for the Food Industry 8204_Shelf Life 1.2.indd 1 21/3/05 12:15:59 PM  Published in February 2005 by New Zealand Food Safety Authority PO Box 2835, Wellington, New Zealand ISBN 0-478-07865-X This document is available on the New Zealand Food Safety Authority’s web site: http://www.nzfsa.govt.nz Disclaimer Every effort has been made to ensure the information in this publication is correct. NZFSA does not accept any responsibility or liability whatsoever for any error of fact, omission, interpretation or opinion that may be present, however it may have occured. 8204_Shelf Life 1.2.indd 2 21/3/05 12:16:02 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods A Guide to Calculating the Shelf Life of Foods Information Booklet for the Food Industry 1 8204_Shelf Life 1.2.indd 1 21/3/05 12:16:02 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s Foreword The New Zealand Food Safety Authority (NZFSA) and Health Protection Officers regularly deal with enquiries on the shelf life and date marks on foods. This Guide to Calculating the Shelf Life of Foods contains background information on the factors that influence shelf life and a procedure to assist you to calculate the shelf life of foods. Although the shelf life and date mark requirements are detailed in legislation, the guide provides assistance to meet these requirements and should be read in conjunction with the Australia New Zealand Food Standards Code. Traditional sectors of the food industry have gained valuable experience in calculating the shelf life of perishable foods but with changes in legislation and the expanding range of ready-to-eat, short shelf life foods there are increasing numbers of foods requiring date markings and specific storage conditions. The increased availability of ready-to-eat foods with extended refrigerated shelf lives has resulted in the need for the food industry to employ measures to minimise the potential for microorganisms such as Listeria monocytogenes and Clostridium botulinum to be present in foods in numbers that result in a hazard to health. This updated guide contains sections on points that should be considered when determining the shelf life of foods that are capable of supporting growth of these organisms. Calculating a realistic shelf life and date mark for food helps ensure the safety and quality of food sold Who is this Guide intended for? This guide was written to assist anyone who is providing information on the shelf life of food. It provides relevant background information on shelf life and outlines several approaches that can be used to determine it. 2 8204_Shelf Life 1.2.indd 2 21/3/05 12:16:02 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods Contents What is shelf life? 4 Is the shelf life of food related to food safety? 4 What are the regulations relating to shelf life? 4 Who is responsible for calculating a shelf life? 5 Who influences the shelf life? 6 Factors influencing the shelf life of a product 7 What is a shelf life study? 8 Step by step determination of shelf life 9 by the direct method What are indirect methods? 13 What is challenge testing? 14 Appendix 1: Guidelines for microbiological 14 examination of ready-to-eat foods Appendix 2: Determination of shelf life of foods 18 capable of supporting Listeria monocytogenes Appendix 3: Extended shelf life foods and 25 Clostridium botulinum Appendix 4: Contacts 27 Appendix 5: Publications 28 Appendix 6: Further reading 29 3 8204_Shelf Life 1.2.indd 3 21/3/05 12:16:03 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s What is shelf life? Shelf life is a guide for the consumer of the period of time that food can be kept before it starts to deteriorate, provided any stated storage conditions have been followed. The shelf life of a product begins from the time the food is prepared or manufactured. Its length is dependent on many factors including the types of ingredients, manufacturing process, type of packaging and how the food is stored. It is indicated by labelling the product with a date mark. Is the shelf life of food related to food safety? Shelf life testing describes how long a food will retain its quality during storage. Controlling the pathogen content (safety) of foods should be achieved by using a Hazard Analysis Critical Control Point (HACCP) system. Predictive modelling or challenge testing can be used to assess pathogen growth. However, food safety and product shelf life are inextricably linked. During the shelf life of a food it should: Remain safe to eat Keep its appearance, odour, texture and flavour Meet any nutritional claims provided on the label. What are the regulations relating to shelf life? The Australia New Zealand Food Standards Code defines composition and labelling requirements for all food sold in New Zealand. The shelf life is defined in Standard 1.2.5, which requires that any packaged food with a shelf life of less than two years be labelled with a date mark. The Code requires food to be safe up to, and including, the date marked. One of the following options must be used: A “Use by” date. This is used for highly perishable foods that will present a safety risk if consumed after this date. A food must not be sold if it is past its “Use by” date, nor should it be consumed. A “Best before” date. This is used for foods other than those specified above. It is not illegal to sell food that has reached its “Best before” date. 4 8204_Shelf Life 1.2.indd 4 21/3/05 12:16:03 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods “Baked on” and “Baked for” date marks can be used on bread products with a shelf life of less than 7 days. The “Baked for” date must be no later than 12 hours after the bread was baked. What does the date mark look like? The words “Use by”, “Best before”, or “Baked on” must be followed by a date or a reference to where on the package the date is located. The date must have: At least the day and the month for products with a shelf life of up to three months e.g. Best before 24 Jan At least the month and the year for products with a shelf life over three months e.g. JAN 05 The dates must be expressed numerically and chronologically (day month year) but the month can be expressed in letters. These must be uncoded. “Packed on” dates or packer’s codes can be used but only in addition to the date marks described above. The Code also states: Specific storage instructions must be included on the label where these are necessary to ensure the food will keep for the specified period indicated by the date marking. Storage conditions must be achievable in the distribution and retail systems and in the home. The seller must store the food according to stated storage instructions. Consideration also needs to be given to providing directions for use and storage after opening. This is particularly important for foods preserved by modified atmospheres or under vacuum where the sealed packaging has a significant influence on the product’s shelf life. For example, sliced ham in vacuum packaging may have a one month refrigerated shelf life, however, once the package is opened it should not be held for longer than 3-4 days. Who is responsible for calculating a shelf life? Anyone who packages and sells food that is required to be date marked is legally responsible for calculating how long their product can reasonably be expected to keep, without any appreciable change in quality. The food label is required to detail the shelf life and the storage instructions to meet that shelf life. In most cases, this is the responsibility of the food manufacturer, but it can also be repackers, secondary processors, food retailers and supermarkets. 5 8204_Shelf Life 1.2.indd 5 21/3/05 12:16:04 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s Who influences the shelf life? Growers/Producers Other suppliers Manufacturers Distributors Retailers Consumers Everyone in this food production chain has an influence on food quality and safety. It is not possible to be confident that food is safe unless a food control plan is in place that identifies and controls hazards throughout the food chain. The role of each person in the food chain should be considered. GROWERS AND PRIMARY PRODUCERS… provide the raw materials. Variable quality of these can make production of a consistent final product difficult. Consistent quality can be maintained by developing raw material specifications. OTHER SUPPLIERS… for example, of packaging materials or ice for chilling also have a responsibility to supply safe and consistent materials. They may also provide advice about different materials and their effect on shelf life. MANUFACTURERS… are responsible for determining a suitable shelf life for their products. This should be based on a study that considers all stages of the production chain. DISTRIBUTORS… transport the food product from the manufacturer to the retailer. It is essential that food is stored safely and securely in the warehouse, transported at the correct temperature, delays are avoided, and packaging is not damaged. Consideration should also be given to the possibility of contamination of the food from other goods carried in the vehicle. RETAILERS… store and handle the product immediately before it reaches the consumer. They must store products according to directions that the manufacturer supplies. CONSUMERS… are the final link in the chain and it is important that they are provided with the correct information on storage conditions. 6 8204_Shelf Life 1.2.indd 6 21/3/05 12:16:04 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods Factors influencing the shelf life of a product How long a shelf life should my product have? There is no simple answer to this question. All foods spoil with time, but there is considerable variation in spoilage rates. Some of the factors involved in loss of quality are explained below. MICROBIAL GROWTH… the growth of some bacteria, yeasts and moulds in food may lead to either food spoilage or food poisoning. The time taken for microorganisms to affect foods will depend on their levels in the food when it is produced, as well as any further contamination the food may suffer during packing, storage and other handling. The temperature and time of storage, as well as the type of food, are also important factors. Moist foods will usually spoil faster than dry foods. Definition of the end of shelf life is usually based on numbers of microorganisms present or on recommended guidance (FSANZ criteria are detailed later in this booklet). In other cases, the end of shelf life may be determined by sensory or biochemical deterioration. NON-MICROBIAL SPOILAGE… there are many other ways in which quality and nutrients can be lost. They may not necessarily result in the product being harmful but can mean that it is no longer of an acceptable standard. Moisture gain/loss can result in loss of nutrients, browning and rancidity. Dry foods can become vulnerable to microbial spoilage if they take on moisture. Chemical change can result in off flavours, colour changes, browning and loss of nutrients. Light induced change can cause rancidity, vitamin loss and fading of natural colours. Temperature changes increase or decrease the speed of other forms of spoilage. Physical damage to food can result in spoilage, for example bruising of fruit and vegetables. Damage to food packaging can make the food vulnerable to both microbial and non-microbial spoilage. For example, pin holes in cans or tears in plastic bags allow microorganisms to enter the food and moisture to be lost from the food. Other Spoilage by rodents and insects Flavours and odours from storing food near other strongly smelling products Product tampering. 7 8204_Shelf Life 1.2.indd 7 21/3/05 12:16:05 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s What is a shelf life study? A shelf life study is an objective, methodical means to determine long a food product can reasonably be expected to keep for, without any appreciable change in quality. A separate study needs to be carried out for each type of product. The two main methods used are: 1. Direct method This is the one most commonly used. It involves storing the product under preselected conditions for a period of time longer than the expected shelf life and checking the product at regular intervals to see when it begins to spoil. The exact procedure is unique for each product. Details of the steps required and types of decisions to be made are discussed in the following pages. 2. Indirect method This approach uses accelerated storage and/or predictive microbiological modelling to determine a shelf life. A brief outline of these is given later. Steps involved in Calculating Shelf Life by the Direct Method Before product on market Identify what may cause the food to spoil or become unsafe Decide which tests to use Plan the shelf life study Determine the shelf life Once product on market Continue to monitor shelf life 8 8204_Shelf Life 1.2.indd 8 21/3/05 12:16:05 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods Step by step determination of shelf life by the direct method There are a number of decisions that need to be made during the study, where it may be necessary to seek expert advice STEP 1. Identify what may cause the food to spoil or become unsafe. Each product will have its own set of factors that may limit its shelf life. Use the following lists as a starting point to help identify all the possible ways that the product may deteriorate in quality and/or safety. At the same time, identify the factors that help prolong the shelf life. Do not forget to consider the entire process, from the purchase of ingredients and packaging materials right through to the end use by the consumer. You may also need to consider the time of year, as some products will deteriorate faster in summer than in winter due to higher temperatures. PRODUCT RELATED SPOILAGE: Raw materials. The quality, consistency, level of contamination and storage of raw materials will all affect the final product. Product make-up. Which ingredients you use, and how they behave when combined, influences what type of and how many spoilage organisms can grow. Any changes to the proportions of ingredients, or the ingredients themselves, may affect the shelf life. Water activity. This is the amount of water in a food that that is available to be used by microorganisms. Microorganisms need water to grow. Water activity can be reduced by the addition of salt, sugar and some other ingredients. Jam is a moist food but the large amounts of sugar it contains mean only a small amount of this water can be used by microorganisms. pH. This is a measure of acidity or alkalinity. The pH will influence which microorganisms will survive and grow in a food. For example, fresh mussels have a very short shelf life whereas mussels in vinegar (acidic) marinades have much longer shelf lives as the acidic environment limits most microbiological growth. Oxygen availability. By removing air from around food, or using vacuum packaging, or modified atmosphere packaging, the food’s shelf life may be extended. However, some microorganisms can grow in environments without oxygen so production processes need to control these microorganisms as well. 9 8204_Shelf Life 1.2.indd 9 21/3/05 12:16:05 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s High standards of hygiene are still important as these packaging methods only limit the growth of spoilage organisms that need oxygen - they do not kill them or limit the growth of organisms that grow in the absence of oxygen; for example the bacteria that cause slime, botulism or listeriosis. Chemical preservatives. When used correctly preservatives help to control the growth of microorganisms. Some have more than one role; for example sulphites slow spoilage and also prevent browning in dried fruits. The types and amounts of preservatives that can be used are detailed in the Australia New Zealand Food Standards Code. PROCESS RELATED SPOILAGE: Processing. Processes include anything from mixing, salting, smoking, fermenting, heating, cooling and chilling to dehydration, freezing and heat sterilisation. The choice of process can alter the shelf life of the final product. For example, UHT milk is a sterilised product and has a longer shelf life than pasteurised milk as the heat treatment is much greater. To achieve a consistent product with the same appearance, flavour, shelf life, etc., it is important that the ingredient quantities, quality and the processing steps are always the same. A written recipe or flow chart that gives exact details of what needs to be done at each step, particularly times and temperatures, will ensure this. You cannot apply someone else’s shelf life without knowing that all the steps in their process (i.e. growing, manufacture, distribution and sales) are the same as your own. Minor variations in the time or temperature can result in a failure to destroy spoilage and food poisoning organisms. Packaging. Packaging must protect the product from contamination during all subsequent steps including distribution, sale and domestic storage. Packaging can also be a source of contamination if it is not produced and stored hygienically. Storage. Temperature of storage is important as it can slow down the growth of the microorganisms that are important to food safety and quality. Other factors to consider are humidity, light, physical handling, placement near other products that could taint the food and protection from rodents, birds and insects. Use temperature data loggers to ensure correct controls are maintained as fluctuating temperatures can affect the shelf life of perishable products. By now you should have identified all the possible ways the product could deteriorate and the factors involved should have been identified. STEP 2. Which tests to use? You need to select suitable tests for determining the safety and quality of the product. All tests are not appropriate for all products. For example, you may test raw meats for numbers of lactic acid bacteria but you wouldn’t test fermented raw meats (salami) for these organisms. It may also be important to test for food poisoning organisms such as Listeria in order to verify product safety. 10 8204_Shelf Life 1.2.indd 10 21/3/05 12:16:06 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods If laboratory tests are needed, check that the laboratory is accredited for those tests with IANZ. If a laboratory is carrying out storage trials on your behalf you need to see records of storage temperature stability. In general, tests can be divided into the following four categories: 1. SENSORY EVALUATION Sensory evaluation assesses a food’s smell, appearance, flavour, and texture. It can be used to monitor and record obvious changes that occur over time, and is therefore, useful when determining the shelf life of a food. The food should be assessed under the conditions at which it is designed to be stored and consumed. Ideally, this should be done by a trained panel using recognised evaluation methods. Always check the food is safe to eat before using a taste panel. If possible, without destroying the texture or other properties of the food, freeze samples at the beginning of the study. These can then be used as a comparison at each testing session. If the food cannot be frozen, use a freshly prepared sample as a comparison. 2. MICROBIOLOGICAL These tests can be used to evaluate both food quality and safety. Tests may be done to estimate changes in the number and type of spoilage organism (yeasts, moulds or bacteria) occurring over time. Table 1 in Appendix 1 provides examples of standard plate count levels that apply to various ready-to-eat food groups. If a specific food is not included in the table, use your judgement to determine where it would fit. Identification of any food poisoning organisms present is important for food safety. Tests required will depend on the particular product. Microbiological standards and guidelines give guidance on the types of organisms and their number that can be considered acceptable, or unsafe, in a food. The following criteria apply to testing of foods in New Zealand: Standard 1.6.1 Microbiological Limits for Food Microbiological guideline criteria Guidelines for the microbiological examination of ready-to-eat foods These documents are available on the FSANZ website http://www.foodstandards.gov.au/ It is unlawful to exceed limits set out in Standard 1.6.1. The other criteria listed above provide guidance to the food industry in setting acceptable levels of microorganisms. NZFSA recommends that industry set their own, more stringent, microbiological standards. Some European countries are preparing standards that set microbiological criteria for L. monocytogenes at end of shelf life (Anon, 2004). A separate section has been included in this guide to provide assistance when determining the shelf life of foods capable of supporting growth of L. monocytogenes (Appendix 2) 3. CHEMICAL Chemical tests can detect changes in the product’s quality throughout its shelf life. Examples of instrumental chemical tests include pH, headspace gas analysis, free fatty acids and total volatile nitrogen. 11 8204_Shelf Life 1.2.indd 11 21/3/05 12:16:07 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s 4. PHYSICAL These include tests for measuring product texture, examination of packaging, ‘travel tests’ and determining the best, worst and average retail conditions. A ‘travel test’ helps to identify any hazards involved in transport and handling. It involves transporting the product through the expected distribution and storage chain. An examination of the product at various points, and at the end of the chain, is required. A data logger may be used to record the temperature at preset times for later analysis. Experimental design should attempt to mimic real life practices e.g. include predicted transport temperatures to retail outlets, during commercial control, consumer purchase and transport, and consumer storage. By now you should have selected the tests to be used in the shelf life study. STEP 3. Plan the shelf life study Consider the following points when preparing your detailed shelf life study plan: 1. What tests need to be carried out? 2. How long will the study run for, and how often will the tests be carried out? Include the actual sampling dates in your plan. It is suggested that sampling be carried out at the beginning, at the target end point and at about three occasions in between. Another sampling should be carried out beyond the target to confirm the end point selection. 3. How many samples will be tested each time? At least triplicate packs of product should be tested at each sampling, 4. How many samples will be needed for the whole study period? 5. When will the study be run? Ideally it should be carried out in the season most likely to cause problems, usually summer. The study should be carried out more than once to take account of variability of the product. The product, process and packaging should be the same as you intend to use for the final product. Keep written records of everything you use or do, as these can be helpful when interpreting results. Now the study is fully planned and timetabled. STEP 4. Run the shelf life study During the study samples should be stored under the same conditions as your normal production samples, from manufacture through to consumption. If this is not possible the samples should be stored at a known temperature and humidity. These need to be checked and recorded regularly. At the times set out in Step 2, samples are selected and tested as per the tests decided in Step 1. Do not forget to record the test results, and anything else you think may be helpful later. STEP 5. Determine the shelf life Eventually a point is reached when the product no longer meets the quality standard. Using all the information you have recorded and observed, decide how long the product can be kept and still be of an acceptable quality and safety. Maximum storage times for quality and safety may not be the same. The shelf life of a product should be which ever is shortest. Look at the test results and if any of them don’t make sense, repeat them. If the results still don’t make sense or are variable, check that the ingredients, their quality and the processing are the same for all batches. Determine what is causing the variability; fix it, then repeat the sampling and tests. 12 8204_Shelf Life 1.2.indd 12 21/3/05 12:16:08 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods Now you have an estimated shelf life that is based on ideal storage conditions, so you need to make allowance for the ‘real world’ where storage conditions may be variable, and product abuse can occur. The shelf life you select for your product should be reasonable, not ideal, and you should allow a safety margin. You can limit the possibility of product abuse to some extent by specifying the storage conditions for the product and limiting its distribution. Now you have calculated the working shelf life. STEP 6. Monitoring the shelf life Samples should be tested for the factors that the shelf life study indicated were the most important for that product, e.g. acidity, loss of flavour, level of spoilage organisms etc. Samples could also be taken from various points within the distribution and retail system. If this testing shows that the preliminary shelf life is inappropriate, it should be adjusted. It is also critical that the shelf life study is repeated after any changes have been made in the production or the processing environment. A longer shelf life may be developed by identifying the limiting factors in the shelf life study, modifying them and repeating the study. Investigating customer complaints relating to product failure before the expiry date may help to identify a recurring problem and indicate a need to recalculate the shelf life. The records you made while designing and carrying out the shelf life study will assist you in the evaluation of customer complaints, trouble shooting, production and distribution problems and in reviewing the shelf life of the product. It is important that all test results are written down and that these records are kept in a safe, but accessible, place. Continue to monitor the product to ensure it is safe and of good quality throughout its whole shelf life. What are indirect methods? Indirect methods attempt to predict the shelf life of a product without running a full length storage trial; hence, they can be useful for products with long shelf lives. The two most common indirect methods are: 1. ACCELERATED SHELF LIFE STUDIES The trial period is shortened by deliberately increasing the rate of deterioration. This is usually done by increasing the storage temperature. The results are then used to estimate the shelf life under normal storage conditions. 2. PREDICTIVE MODELLING Predictive models are mathematical equations which use information from a database to predict bacterial growth under defined conditions. Predictive models can be used to calculate the shelf life of a food. Information on the changes that occur in the product when it deteriorates, the properties of the product and packaging is required for the calculations. Most predictive models are specific to particular types of organisms. 13 8204_Shelf Life 1.2.indd 13 21/3/05 12:16:08 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s Some examples of predictive modelling systems are the United States Department of Agriculture (USDA) Pathogen Modelling Program (available to download from the internet), Growth Predictor and FORECAST (a paid service by Campden and Chorleywood Food Research Association (CCFRA)). Models are useful as a first step in the evaluation of a product’s shelf life. However, information from modelling programmes needs to be verified by challenge testing or a shelf life trial. Food safety and technology consultants should be able to assist with specific predictive modelling trials or problems. A list of consultants is available on NZFSA’s website. See Appendix 4 for contact details. What is challenge testing? Challenge testing is used to assess whether a product formulation and storage conditions of a food can control the growth of pathogens, if present, during the designated shelf life. The procedure involves inoculation of the product with relevant microorganisms and incubation of the product under controlled environmental conditions in order to assess the risk of food poisoning, or to establish product stability. When should you use challenge testing? In many foods, a combination of factors contribute to the preservation effect, none of which is sufficient to control the safety of the food on its own. Where the effect of such food control systems on specific pathogenic microorganisms cannot be predicted from the literature, it may be necessary to use challenge testing to evaluate the safety of the product. Appendix 1: Guidelines for microbiological examination of ready-to-eat foods TABLE 1: EXAMPLES OF STANDARD PLATE COUNT LEVELS APPLICABLE TO READY-TO-EAT FOOD GROUPS Food group Examples of products SPC Level to apply* Meat Brawn 2 Cold meat and poultry 2 Kebabs (without salad) 1 Minced patties (cooked) 1 Sausages, frankfurters, saveloys (pre-cooked 1 Sliced meat (ham, corned silverside, luncheon, etc) 2 Sliced salami and other fermented meats 3 Smoked meats (pastrami, hot pork, chicken) 2 14 8204_Shelf Life 1.2.indd 14 21/3/05 12:16:09 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods Food group Examples of products SPC Level to apply* Seafood Crustaceans (shrimps, prawns, crab meat – cooked) 1 Crustaceans and molluscs (cooked and marinated) 1 Fish products (battered, crumbed – cooked) 1 Fish and molluscs (smoked) 2 Fish-based and seafood paté 1 Herrings, roll mop and other raw pickled fish 1 Molluscs and other shellfish (cooked) 1 Surimi, crab sticks, and flavoured fish paste products 1 Dessert Cakes, pastries, slices and desserts (with fresh cream) 2 Cakes, pastries, slices and desserts (without fresh cream) 1 Cheesecakes (baked) 1 Cheesecakes (unbaked) 3 Cooked fruit 1 Fruit salad (fresh) 3 Tarts, flans and fruit pies 1 Savoury Cheese-based bakery products 1 Curried eggs, mashed egg 2 Dumplings, dim sims, won tons. spring rolls 1 Flan/quiche 1 Hummus, dips 2 Meat and savoury pies 1 Paté, terrines (sliced) 2 Samosa, curry puffs 1 Satay 1 Sushi 3 Sausage rolls, hot dogs 1 Fermented foods 3 Vegetable Coleslaw 3 Fruit and vegetables (dried) 1 Fruit and vegetables (fresh) 3 Mixed salads, tossed salads 3 Rice and rice based salads (cooked) 2 Vegetables and vegetable meals (cooked) 1 Vegetarian paté 1 Dairy Cheese 3 Cream freeze 2 Iceblocks, flavoured shaved ice, sorbets 2 Ice cream on cone (dairy and non-dairy) 2 Milkshakes 2 Continued overleaf… 15 8204_Shelf Life 1.2.indd 15 21/3/05 12:16:09 PM A Gui de t o Cal c ul at i ng t he S h e l f L i fe o f F o o d s Food group Examples of products SPC Level to apply* Ready-to-eat meals Pasta/pizza 1 Meals (others) 1 Bread products Sandwiches and filled rolls (with salad) 3 Sandwiches and filled rolls (without salad) 2 Sandwiches and filled rolls (with cheese) 3 *Application of Standard Plate Count (30ºC/72hr) levels (see next page) Level 1 – applies to RTE foods in which all components of the food have been cooked in the manufacturing process/preparation of the final food product and, as such, microbial counts should be low. Level 2 – applies to RTE foods which contain components that have been cooked and then further handled (stored, sliced and mixed) prior to preparation of the final food or where no cooking process has been used. Level 3 – SPCs not applicable. This applies to foods such as fresh fruits and vegetables (including salad vegetables), fermented foods and foods incorporating these (such as sandwiches and filled rolls). It would be expected that these foods would have an inherent high plate count because of the normal microbial flora present. NOTE: If a specific RTE food is not included in the examples, use you professional judgement to decide where the product would fit based on the type of product and the processing it has received The following table has been extracted from the FSANZ Guidelines for the microbiological examination of ready-to-eat foods. The full document is available at the following address: www.foodstandards.gov.au/mediareleasespublications/publications/guidelinesformicrobi1306.cfm 16 8204_Shelf Life 1.2.indd 16 21/3/05 12:16:09 PM  A Guide t o Ca lcula t ing t he She lf Lif e of Foods TABLE 2: GUIDELINE LEVELS FOR DETERMINING THE MICROBIOLOGICAL QUALITY OF READY-TO-EAT FOODS Microbiological Quality (cfu per gram) Potentially Test Satisfactory Marginal Unsatisfactory Hazardous Standard Plate Count (30ºC/72hrs) Level 1