《肉制品冷冻技术》（英文版） Part 12 Consumer handling

Consumer handling Since the mid-1980s there has been a considerable increase in legislation defining maximum temperatures during the production, distribution and retailing of chilled food. However, as soon as the food is purchased by the consumer, it is outside of any of these legislative requirements. Increasingly food poisoning incidents have been found to be due to mishandling of food in the home with insufficient refrigeration or cooling being the most fre uent factor causing disease(WHO, 1992). Of the 1562 cases of food poi- soning reported during 1986-1988, 970(62%)were caused in the home. Consumer handling of products may not be as intended or envisaged by the manufacturer. Many chilled products are purchased on the basis of the "fresh image, but then frozen at home(Brown, 1992) After a chilled or frozen product is removed from a retail display cabinet it is outside a refrigerated environment whilst it is carried around the store and then transported home for further storage. In the home it may be left in ambient conditions or stored in the refrigerator/freezer until required. There are few published data on consumers'attitudes to chilled food and their handling procedures in the home. The majority of the data quoted here have been obtained from a survey of 252 households which was funded by the Ministry of Agriculture Fisheries and Food(MAFF)in the UK(Evans et aL., 1991). As part of the survey, participants were asked questions to ssess their attitude to food poisoning, shopping habits and the length of ime they stored chilled foods in the home Monitoring was then carried out to determine the length of time and temperature foods were stored at in the home. These data were augmented with experimental data from labo- ratory studies on the performance of refrigerators and temperature changes during transportation to the home

12 Consumer handling Since the mid-1980s there has been a considerable increase in legislation defining maximum temperatures during the production, distribution and retailing of chilled food. However, as soon as the food is purchased by the consumer, it is outside of any of these legislative requirements. Increasingly food poisoning incidents have been found to be due to mishandling of food in the home with insufficient refrigeration or cooling being the most fre￾quent factor causing disease (WHO, 1992). Of the 1562 cases of food poi￾soning reported during 1986–1988, 970 (62%) were caused in the home. Consumer handling of products may not be as intended or envisaged by the manufacturer. Many chilled products are purchased on the basis of the ‘fresh image’, but then frozen at home (Brown, 1992). After a chilled or frozen product is removed from a retail display cabinet it is outside a refrigerated environment whilst it is carried around the store and then transported home for further storage. In the home it may be left in ambient conditions or stored in the refrigerator/freezer until required. There are few published data on consumers’ attitudes to chilled food and their handling procedures in the home.The majority of the data quoted here have been obtained from a survey of 252 households which was funded by the Ministry of Agriculture Fisheries and Food (MAFF) in the UK (Evans et al., 1991). As part of the survey, participants were asked questions to assess their attitude to food poisoning, shopping habits and the length of time they stored chilled foods in the home. Monitoring was then carried out to determine the length of time and temperature foods were stored at in the home. These data were augmented with experimental data from labo￾ratory studies on the performance of refrigerators and temperature changes during transportation to the home

252 Meat refrigeration Bacon Sausages Cook-chill foods Me Pouitry-raw 0102030405060708090100110 Number of occurrences Fig 12.1 Meat products considered a food poisoning risk(source: Evans et al. 1991) 12.1 Consumer attitudes to food poisoning In the survey consumers were initially asked about their concern about food poisoning. The greatest number of participants (56.7%) were either only slightly concerned or not at all concerned about food poisoning. However, 31.7% of participants were concerned or very concerned about food poi soning(answers were restricted to concern about food from shops and did not include concern about food poisoning due to restaurant or fast food type meals or food) When asked to name foods that they considered might constitute a food poisoning risk most of the respondents(73%)considered poultry to be a problem. Raw poultry was considered to be a greater risk than cooked poultry Meat was also considered likely to cause food poisoning with 66.7% of participants mentioning either raw or cooked meat as a potential problem(Fig. 12.1) 12.2 Shopping habits and transport from retail store to e nte The frequency of shopping governs the length of time chilled food is stored n the home. Most consumers, 99. 2% of the survey population, shopped on at least one day a week and few(16.3%)less than twice a week for chilled food. The greatest number(33.7%) shopped for food 3-4 days per week, closely followed by 26.2% who shopped 5-7 days per week and 23.8% who shopped on two days. Generally shopping was divided into trips for large quantities(defined as greater than one bag)and small amounts of food (less than one bag). The majority of households(84.5%)shopped for small quan tities of chilled food on a variable basis as required

12.1 Consumer attitudes to food poisoning In the survey consumers were initially asked about their concern about food poisoning. The greatest number of participants (56.7%) were either only slightly concerned or not at all concerned about food poisoning. However, 31.7% of participants were concerned or very concerned about food poi￾soning (answers were restricted to concern about food from shops and did not include concern about food poisoning due to restaurant or fast food￾type meals or food). When asked to name foods that they considered might constitute a food poisoning risk most of the respondents (73%) considered poultry to be a problem. Raw poultry was considered to be a greater risk than cooked poultry. Meat was also considered likely to cause food poisoning with 66.7% of participants mentioning either raw or cooked meat as a potential problem (Fig. 12.1). 12.2 Shopping habits and transport from retail store to the home The frequency of shopping governs the length of time chilled food is stored in the home. Most consumers, 99.2% of the survey population, shopped on at least one day a week and few (16.3%) less than twice a week for chilled food. The greatest number (33.7%) shopped for food 3–4 days per week, closely followed by 26.2% who shopped 5–7 days per week and 23.8% who shopped on two days. Generally shopping was divided into trips for large quantities (defined as greater than one bag) and small amounts of food (less than one bag).The majority of households (84.5%) shopped for small quan￾tities of chilled food on a variable basis, as required. 252 Meat refrigeration Bacon Sausages Pies Cook-chill foods Pâté Meat – raw Poultry – cooked Meat – cooked Poultry– raw 0 10 20 30 40 50 60 70 80 90 100 110 Number of occurrences Fig. 12.1 Meat products considered a food poisoning risk (source: Evans et al., 1991)

Consumer handling 253 Most participants in the survey carried out their main shopping between 1 and 5 miles from their homes and few householders travelled more than 5 miles to shop. Most people(85.3%)used a car to transport their main hopping home. Small quantities of food were generally bought close to the home, reflecting the availability of shops in the towns surveyed. Most house holders(87.6%)who bought small quantities of food transported it home either on foot or by car. Unprotected chilled food will warm up during transportation. Survey results showed that consumers took on average 43 min to bring meat, fish or dairy items home from the shops and place them in a refrigerator. The greatest number of items were transported home and placed in a refriger ator within 13 min. Although most people bought food home well within 60min there were a number of items which took far longer to be bought home(up to 2 days )and placed in a refrigerator. Although insulated bags and boxes are widely sold, only a small per centage of consumers(12.7%)used them to transport some of their food home. The vast majority(87.3%)of people did not use any means of pro- tecting food from temperature gain during transportation Increases in product temperatures during transportation can be consid erable. In investigations, the temperatures of 19 different types of chilled product (including a variety of meat products) were monitored during a simulated journey from the supermarket to home (James and Evans, 1992a). One sample of each product was placed in a precooled insulated box containing eutectic ice packs and the second left loose in the boot of he car. The car was then driven home and the product removed and placed a domestic refrigerator after a total journey time of 1h. Additional investigations looked at 9 types of frozen product, including frozen chicken, meat pie, lasagne and pizza(Evans, 1994). Products were purchased and transported to the research Centre where the products were tempered and temperature sensors inserted into the geometric centre of each food and where possible a second sensor inserted just below the surface of the sample. The products were then refrozen to a temperature of ca.-25C and then transferred to a car where the above procedure was repeated. After a journey time of l h the products were placed in the freezer ection of a domestic refrigerator. The ambient temperature during both urneys ranged from 23 to 270 Initial product temperatures of the chilled meats measured when the food reached the car ranged from 4C to over 20'C(Table 12.1). Some of the meat product temperatures in samples placed in the boot rose to around 30C during the 1 h car journey whilst most of the samples placed in the insulated box cooled during the car journey except for a few at the top of the box which remained at their initial temperature. Product temperatures in the frozen foods were close to -25C when placed in the car. Temperatures of products placed in both the cold box and at ambient temperature rose during the l h journey. Temperatures of

Most participants in the survey carried out their main shopping between 1 and 5 miles from their homes and few householders travelled more than 5 miles to shop. Most people (85.3%) used a car to transport their main shopping home. Small quantities of food were generally bought close to the home, reflecting the availability of shops in the towns surveyed. Most house￾holders (87.6%) who bought small quantities of food transported it home either on foot or by car. Unprotected chilled food will warm up during transportation. Survey results showed that consumers took on average 43 min to bring meat, fish or dairy items home from the shops and place them in a refrigerator. The greatest number of items were transported home and placed in a refriger￾ator within 13 min. Although most people bought food home well within 60 min there were a number of items which took far longer to be bought home (up to 2 days) and placed in a refrigerator. Although insulated bags and boxes are widely sold, only a small per￾centage of consumers (12.7%) used them to transport some of their food home. The vast majority (87.3%) of people did not use any means of pro￾tecting food from temperature gain during transportation. Increases in product temperatures during transportation can be consid￾erable. In investigations, the temperatures of 19 different types of chilled product (including a variety of meat products) were monitored during a simulated journey from the supermarket to home (James and Evans, 1992a). One sample of each product was placed in a precooled insulated box containing eutectic ice packs and the second left loose in the boot of the car. The car was then driven home and the product removed and placed in a domestic refrigerator after a total journey time of 1 h. Additional investigations looked at 9 types of frozen product, including frozen chicken, meat pie, lasagne and pizza (Evans, 1994). Products were purchased and transported to the Research Centre where the products were tempered and temperature sensors inserted into the geometric centre of each food and where possible a second sensor inserted just below the surface of the sample. The products were then refrozen to a temperature of ca. -25 °C and then transferred to a car where the above procedure was repeated.After a journey time of 1 h the products were placed in the freezer section of a domestic refrigerator. The ambient temperature during both journeys ranged from 23 to 27 °C. Initial product temperatures of the chilled meats measured when the food reached the car ranged from 4 °C to over 20 °C (Table 12.1). Some of the meat product temperatures in samples placed in the boot rose to around 30 °C during the 1 h car journey whilst most of the samples placed in the insulated box cooled during the car journey except for a few at the top of the box which remained at their initial temperature. Product temperatures in the frozen foods were close to -25 °C when placed in the car. Temperatures of products placed in both the cold box and at ambient temperature rose during the 1 h journey. Temperatures of Consumer handling 253

254 Meat refrigeration Table 12.1 Maximum temperatures(C)measured in meat products after being transported for I h in the boot of a car without protection or within a cooled insulated container Product Unprotected Smoked ham Beef pie 954726 Lasagne Source: Evans et al. 1991 te centre Cool box pate surface Fig. 12.2 Temperature chasse prans te during domestic transportation(source chickens and meat pies placed at ambient temperature reached tempera- tures approaching 10C. Frozen meat products in the cold box kept below 10C for the period of the journey Thin sliced chilled products showed the highest temperature char luring transport, whereas temperature gains in thicker products such hicken and pate(Fig. 12.2)were smaller. A similar trend was seen with the frozen products. After being placed in the domestic refrigerator, warm hilled products required ca 5h before the temperature at the surface was educed below 7C.Warm' frozen products placed in a domestic freezer required at least 5 h to reduce centre product temperatures to below -15C Predictions made using a mathematical model that calculated bacterial growth from temperature/time relationships indicated that increases of up to 1.8 generations in bacterial numbers(Table 12.2) could occur in the chilled foods during this transport and domestic cooling phase. The model assumed that bacteria required a time to acclimatise to the change in tem perature(the lag phase)and that no acclimatisation had occurred during

chickens and meat pies placed at ambient temperature reached tempera￾tures approaching 10°C. Frozen meat products in the cold box kept below -10 °C for the period of the journey. Thin sliced chilled products showed the highest temperature changes during transport, whereas temperature gains in thicker products such as chicken and pâté (Fig. 12.2) were smaller. A similar trend was seen with the frozen products. After being placed in the domestic refrigerator, ‘warm’ chilled products required ca. 5 h before the temperature at the surface was reduced below 7 °C. ‘Warm’ frozen products placed in a domestic freezer required at least 5 h to reduce centre product temperatures to below -15 °C. Predictions made using a mathematical model that calculated bacterial growth from temperature/time relationships indicated that increases of up to 1.8 generations in bacterial numbers (Table 12.2) could occur in the chilled foods during this transport and domestic cooling phase. The model assumed that bacteria required a time to acclimatise to the change in tem￾perature (the lag phase) and that no acclimatisation had occurred during 254 Meat refrigeration Table 12.1 Maximum temperatures (°C) measured in meat products after being transported for 1 h in the boot of a car without protection or within a cooled insulated container Product Unprotected Cool box Minced beef 18 9 Sausage (raw) 28 15 Smoked ham 30 14 Beef pie 24 7 Sausage roll 28 12 Lasagne 21 6 Source: Evans et al., 1991. 0 60 120 180 240 300 360 Time (min) 0 5 10 15 20 25 30 Temperature (°C) Ambient pate centre Ambient pate surface Cool box pate centre Cool box pate surface ˆ ˆ ˆ ˆ ´ ´ ´ ´ Fig. 12.2 Temperature changes in paté during domestic transportation (source: Evans et al., 1991)

Consumer handling Table 12.2 Maximum temperature measured and increase in bacterial numbe in chilled foods during 1 h in car followed by 5h in a domestic refrigerator Product Conditions Maximun Pseudomonas temperature (generations) (generations) C Pate Ambient. car Cool box car <04 Chicken-raw Ambient. car 1.6 Cool box car Ambient. car 1.8 cooked Cool box car 344827 Prawns Ambient car 13 Cool box car 0.0 Source: Evans et al.. 1991 display. If this rather optimistic assumption was not made then up to 4.2 doublings of pseudomonas and growth of both salmonella and listeria were predicted. Only very small increases in bacterial numbers(<0. 4 genera- tions)were predicted in products transported in the insulated box, owing to the maintenance of lower product temperatures. Although it was unable to prevent bacterial growth, the cold box did ensure that bacterial growth was minimal and was substantially less than if transported in ambient conditions 12.3 Refrigerated storage in the home The length of time consumers store chilled foods after purchase will affect their safety. In the survey consumers thought that the majority of meat and meat products (raw meat, cooked meat, raw poultry, cooked poultry, pre pared meals, pizza/quiche, cold pies and sausages) would store well for 2 days. However, a number of people considered that these foods could be stored for more than 7 days and sometimes as long as 30 days. Most par ticipants thought that products such as bacon and pate could be stored for up to a week, although a few people considered that storage of up to 30 days was acceptable. Fresh fish was generally considered to store less well, ith most participants stating that they would only store fish for 1 day or less o The range in anticipated storage life for different food types varied con- derably Opinions on the storage lives of individual foods ranged from 0.5 o 7 days(range 6.5 days)for cold pies and sausages to between 0.5 to 30 days(range 29.5 days) for pate and bacon. The minimum storage life for all meats and meat products was either a quarter or half a day. A small number of householders thought that they could store chilled foods for periods of up to 30 days. Bacon and pate were both thought to be acceptable after this

display. If this rather optimistic assumption was not made then up to 4.2 doublings of pseudomonas and growth of both salmonella and listeria were predicted. Only very small increases in bacterial numbers (<0.4 genera￾tions) were predicted in products transported in the insulated box, owing to the maintenance of lower product temperatures. Although it was unable to prevent bacterial growth, the cold box did ensure that bacterial growth was minimal and was substantially less than if transported in ambient conditions. 12.3 Refrigerated storage in the home The length of time consumers store chilled foods after purchase will affect their safety. In the survey consumers thought that the majority of meat and meat products (raw meat, cooked meat, raw poultry, cooked poultry, pre￾pared meals, pizza/quiche, cold pies and sausages) would store well for 2 days. However, a number of people considered that these foods could be stored for more than 7 days and sometimes as long as 30 days. Most par￾ticipants thought that products such as bacon and pâté could be stored for up to a week, although a few people considered that storage of up to 30 days was acceptable. Fresh fish was generally considered to store less well, with most participants stating that they would only store fish for 1 day or less. The range in anticipated storage life for different food types varied con￾siderably. Opinions on the storage lives of individual foods ranged from 0.5 to 7 days (range 6.5 days) for cold pies and sausages to between 0.5 to 30 days (range 29.5 days) for pâté and bacon. The minimum storage life for all meats and meat products was either a quarter or half a day.A small number of householders thought that they could store chilled foods for periods of up to 30 days. Bacon and pâté were both thought to be acceptable after this Consumer handling 255 Table 12.2 Maximum temperature measured and increase in bacterial numbers in chilled foods during 1 h in car followed by 5 h in a domestic refrigerator Product Conditions Maximum Pseudomonas Clostridium temperature (generations) (generations) (°C) Pâté Ambient, car 25 1.5 0.4 Cool box, car 13 <0.4 0.0 Chicken – raw Ambient, car 24 1.6 0.2 Cool box, car 4 0.0 0.0 Chicken – Ambient, car 28 1.8 0.7 cooked Cool box, car 12 0.0 0.0 Prawns Ambient, car 37 1.3 1.6 Cool box, car 14 0.0 0.0 Source: Evans et al., 1991

256 Meat refrigeration Meat-cooked Bacon ■ Maximun Pizza/quiche 口Mode Prepared meal 0246810121416182022 Fig 12.3 Minimum, modal and maximum storage lives of chilled meat and meat products stated by householders(source: Evans et aL., 1991) period by a small proportion of participants. Cooked meat and poultry were also thought to store for up to 21 days by a few householders(Fig. 12.3) It was interesting to note that although poultry and meat were con sidered a likely cause of food poisoning, participants did not necessarily consider that these foods had short storage lives. It is therefore possible that people do not associate storage time as being related to any food poison- ng problem. Consumers do not always 'practice what they preach. When the food stored in consumers' refrigerators was examined, actual storage times were generally greater than storage times stated in the questionnaire. Almost 67% of the food was kept for longer periods. Actual storage times were greater than the stated storage time for all meat, fish and dairy items except pies which were thought to have an acceptable storage life of 3.3 days and were stored for 3.2 days(Table 12.3) 12.4 Temperatures in domestic food storage The refrigerator is a common household device and very few households in the uk do not own a refrigerator or fridge-freezer for storage of chilled foods. Fridge-freezers have become increasingly popular in the last 20 years in the UK and now provide almost 50% of the market(Anon, 1990). These

period by a small proportion of participants. Cooked meat and poultry were also thought to store for up to 21 days by a few householders (Fig. 12.3). It was interesting to note that although poultry and meat were con￾sidered a likely cause of food poisoning, participants did not necessarily consider that these foods had short storage lives. It is therefore possible that people do not associate storage time as being related to any food poison￾ing problem. Consumers do not always ‘practice what they preach’. When the food stored in consumers’ refrigerators was examined, actual storage times were generally greater than storage times stated in the questionnaire. Almost 67% of the food was kept for longer periods. Actual storage times were greater than the stated storage time for all meat, fish and dairy items except pies which were thought to have an acceptable storage life of 3.3 days and were stored for 3.2 days (Table 12.3). 12.4 Temperatures in domestic food storage The refrigerator is a common household device and very few households in the UK do not own a refrigerator or fridge-freezer for storage of chilled foods. Fridge-freezers have become increasingly popular in the last 20 years in the UK and now provide almost 50% of the market (Anon, 1990). These 256 Meat refrigeration 0 2 4 6 8 10 12 14 16 18 20 22 24 26 28 30 Prepared meal Pizza/quiche Pie Pate Sausage Bacon Burger Poultry – cooked Poultry – raw Meat – cooked Meat – raw Days Maximum Mode Minimum ˆ ´ Fig. 12.3 Minimum, modal and maximum storage lives of chilled meat and meat products stated by householders (source: Evans et al., 1991)

Consumer handling 257 Table 12.3 Mean actual and perceived storage life Food storage life(days) storage life( days) Meat-raw cooke Bacon 3.3 ource: Evans et aL. 1991 igures were almost replicated in the survey where only 3 of the households did not own a working refrigerator and 49.4% owned a fridge-freezer. Almost 32% owned an ice box type refrigerator and the rest larder refrigerators. The temperature at which a refrigerator operates is critical for the safe storage of chilled food. Recommendations concerning the microbiological safety of foods advise that maximum temperatures in domestic refrigera tors should not exceed 5C(Richmond, 1991) Consumers in the survey were therefore asked what temperature they tried to operate their refrigerator. Nearly all participants were unable to name actual temperatures and gave answers based on the method they used to set the temperature dial (Fig. 12. 4). A large number of people (32.8%) set their refrigerators according to the weather, setting the refrigerator to a lower temperature(higher setting) in the summer. It was interesting to note that although 38 participants had a thermometer in their refrigerator only 30 actually used the information to set their refrigerator temperature. To evaluate temperatures within each refrigerator, a miniature data logger with 3 air and 2 product sensors was placed into the refrigerator to monitor temperatures every &s and to record mean temperatures every 5min for a period in excess of 7 days. Air temperature sensors were posi tioned in the top, middle and bottom sections of the refrigerator and a sim- ulated food product(87 mm diameter by 28 mm high disc of, a food substitute, in a petri dish) placed on the middle shelf. Sensors were placed in the geometric centre and centrally on the surface of the Tylose disc(Fig 125 Results showed that the mean temperature over 7 days(evaluated from top, middle and bottom sensors)ranged from-1 to 11C. The overall mear air temperature for all the refrigerators in the survey was 6C, with 70% of refrigerators operating at average temperatures above 5C(Fig. 12.6).An investigation carried out in Northern Ireland found similar results with 71% of refrigerators having a mean internal temperature above 5C(Flynn

figures were almost replicated in the survey where only 3 of the households did not own a working refrigerator and 49.4% owned a fridge-freezer. Almost 32% owned an ice box type refrigerator and the rest larder refrigerators. The temperature at which a refrigerator operates is critical for the safe storage of chilled food. Recommendations concerning the microbiological safety of foods advise that maximum temperatures in domestic refrigera￾tors should not exceed 5 °C (Richmond, 1991). Consumers in the survey were therefore asked what temperature they tried to operate their refrigerator. Nearly all participants were unable to name actual temperatures and gave answers based on the method they used to set the temperature dial (Fig. 12.4). A large number of people (32.8%) set their refrigerators according to the weather, setting the refrigerator to a lower temperature (higher setting) in the summer. It was interesting to note that although 38 participants had a thermometer in their refrigerator only 30 actually used the information to set their refrigerator temperature. To evaluate temperatures within each refrigerator, a miniature data logger with 3 air and 2 product sensors was placed into the refrigerator to monitor temperatures every 8 s and to record mean temperatures every 5 min for a period in excess of 7 days. Air temperature sensors were posi￾tioned in the top, middle and bottom sections of the refrigerator and a sim￾ulated food product (87 mm diameter by 28 mm high disc of ‘Tylose’, a food substitute, in a petri dish) placed on the middle shelf. Sensors were placed in the geometric centre and centrally on the surface of the Tylose disc (Fig. 12.5). Results showed that the mean temperature over 7 days (evaluated from top, middle and bottom sensors) ranged from -1 to 11°C. The overall mean air temperature for all the refrigerators in the survey was 6 °C, with 70% of refrigerators operating at average temperatures above 5°C (Fig. 12.6). An investigation carried out in Northern Ireland found similar results with 71% of refrigerators having a mean internal temperature above 5°C (Flynn Consumer handling 257 Table 12.3 Mean actual and perceived storage life Food Actual mean Perceived mean storage life (days) storage life (days) Meat – raw 3.9 2.4 Meat – cooked 5.4 4.5 Poultry – raw 3.3 2.5 Poultry – cooked 3.9 2.4 Bacon 8.2 6.6 Sausages 5.6 4.1 Paté 10.3 4.1 Pies 3.2 3.3 Source: Evans et al., 1991

258 Meat refrigeration Manufacturers Other refrigerator ecommended 12% Recommendatio 328% Same setting all the time Fig 12.4 Methods used to set refrigerator temperature (source: Evans et aL., 1991) Freezer placed in ttom of refrigerator Door Simulated food product 3 Fig. 12.5 Position of miniature data logger and sensors within refrigerator(source Evans et al, 1991) et aL., 1992). A US study of food discard patterns and reasons found 21% of refrigerators were at or above 10.C (Van Garde and woodburne, 1987) An analysis of percentage time spent between certain temperatures, calculated for all refrigerators, showed that the greatest proportion of time

et al., 1992). A US study of food discard patterns and reasons found 21% of refrigerators were at or above 10 °C (Van Garde and Woodburne, 1987). An analysis of percentage time spent between certain temperatures, calculated for all refrigerators, showed that the greatest proportion of time 258 Meat refrigeration 17.2% Refrigerator ‘feels’ cold 12% Recommendation on thermometer 2% Other 28% Same setting all the time 32.8% According to weather 0.25% No setting on refrigerator 7.6% Manufacturers recommended setting Fig. 12.4 Methods used to set refrigerator temperature (source: Evans et al., 1991). Simulated food product with thermistor probes at the surface and centre Data logger 1,2 and 3 – thermistors placed in air at top, middle and bottom of refrigerator Crisper 3 2 1 Door Freezer Fig. 12.5 Position of miniature data logger and sensors within refrigerator (source: Evans et al., 1991)

Consumer handling 259 14-149°C 13-13.9°c 12-129°C 11-119°C 10-109° 9-9.9°c 8-89°c 7-79°C 6-69°C 5-59°C 4-4.9°C 1-19°c 1to-0.1° 1°C Fig. 12.6 Overall mean temperatures for all refrigerators in survey(source: Evan a.,1991) Table 12.4 Position of highest temperature within re Highest mean Lowest mean temperature temperature Middle 45. Bo 22.0 34.6 Source: Evans et aL, 1991 (80.3%)was spent between 3 and 8.9C. Only small amounts of time were spent above 9C(Fig. 12.7). However, only 4 refrigerators(1.6%)in the whole survey operated below 5C during all the monitoring period and 33.3% of refrigerators spent all their time above 5C. A further analysis showed that in 69.9% of refrigerators the warmest place was in the top and in 45. 1% the coolest place was in the middle(Table 12. 4). However, the top of the refrigerato for was not always the warmest and the bottom was not always the coldest place(Table 12.5, Fig. 12.8) The mean temperature range within a refrigerator was found to vary between refrigerator types. Ice box refrigerators had the smallest range

(80.3%) was spent between 3 and 8.9 °C. Only small amounts of time were spent above 9 °C (Fig. 12.7). However, only 4 refrigerators (1.6%) in the whole survey operated below 5 °C during all the monitoring period and 33.3% of refrigerators spent all their time above 5 °C. A further analysis showed that in 69.9% of refrigerators the warmest place was in the top and in 45.1% the coolest place was in the middle (Table 12.4). However, the top of the refrigerator was not always the warmest and the bottom was not always the coldest place (Table 12.5, Fig. 12.8). The mean temperature range within a refrigerator was found to vary between refrigerator types. Ice box refrigerators had the smallest range Consumer handling 259 14–14.9°C 13–13.9°C 12–12.9°C 11–11.9°C 10–10.9°C 9–9.9°C 8–8.9°C 7–7.9°C 6–6.9°C 5–5.9°C 4–4.9°C 3–3.9°C 2–2.9°C 1–1.9°C 0–0.9°C –1 to –0.1°C –2 to –1.1°C –3 to –2.1°C –4 to –3.1°C –5 to –4.1°C 0 5 10 15 20 25 Percentage Fig. 12.6 Overall mean temperatures for all refrigerators in survey (source: Evans et al., 1991). Table 12.4 Position of highest temperature within refrigerators investigated Position % of refrigerators Highest mean Lowest mean temperature temperature (°C) (°C) Top 69.9 20.3 Middle 8.1 45.1 Bottom 22.0 34.6 Source: Evans et al., 1991

260 Meat refrigeration 15-16.9°c 13-149°c 11-129°C 7-8.9C 5-6.9C 3-49°C 1-29°c 3to-0.9°C 5to-29°C 05101520253035 Fig 12.7 Frequency distribution of temperatures in all refrigerators(source: Evans eta.,1991). Table 12.5 Positions of lowest and highest mean temperatures in refrigerators nvestigated Refrigerator of lowest mean %o of highest mear Middle Bottom Middle Bottom Ice box 41.6 104 28.6 117 597 Fridge-freezer 10.6 Larder 50.0 0.0 100.0 0.0 Source: Evans et al. 1991 (average 1.8C), whereas the range in temperature in fridge-freezers and larder refrigerators was nearly twice as great(average of 3. 4C in fridge freezers and 3.7C in larder refrigerators)(Table 12.6, Fig. 12.9). A survey carried out in China found higher ranges in temperature within domestic refrigerators with only 2.3% of the refrigerators surveyed operating with a emperature range of less than 6C: 34.1% had differences of 8-12C, 34.1% in the range of 12-14C and 29. 5% differences greater than 14C (Shixiong and Jing, 1990) The time for storage of frozen foods in the UK is based on the star-rating system(Table 12.7). This was introduced in the early 1960s relating equip ment capability with frozen food keeping quality(Ware, 1974; Sanderson Walker, 1979)

(average 1.8 °C), whereas the range in temperature in fridge-freezers and larder refrigerators was nearly twice as great (average of 3.4 °C in fridge￾freezers and 3.7 °C in larder refrigerators) (Table 12.6, Fig. 12.9). A survey carried out in China found higher ranges in temperature within domestic refrigerators with only 2.3% of the refrigerators surveyed operating with a temperature range of less than 6°C: 34.1% had differences of 8–12 °C, 34.1% in the range of 12–14 °C and 29.5% differences greater than 14 °C (Shixiong and Jing, 1990). The time for storage of frozen foods in the UK is based on the star-rating system (Table 12.7). This was introduced in the early 1960s relating equip￾ment capability with frozen food keeping quality (Ware, 1974; Sanderson￾Walker, 1979). 260 Meat refrigeration 0 5 10 15 20 25 30 35 40 15–16.9°C 13–14.9°C 11–12.9°C 9–10.9°C 7–8.9°C 5–6.9°C 3–4.9°C –1 – 0.9°C 1–2.9°C –3 to – 0.9°C –5 to –2.9°C Percentage Fig. 12.7 Frequency distribution of temperatures in all refrigerators (source: Evans et al., 1991). Table 12.5 Positions of lowest and highest mean temperatures in refrigerators investigated Refrigerator % of lowest mean % of highest mean type temperatures in: temperatures in: Top Middle Bottom Top Middle Bottom Ice box 48.1 41.6 10.4 28.6 11.7 59.7 Fridge-freezer 10.6 45.5 43.9 84.6 8.9 6.5 Larder 0.0 50.0 50.0 100.0 0.0 0.0 Source: Evans et al., 1991