TIME AND TEMPERATURE ANALYSIS OF A SCHOOL LUNCH MEAL PREPARED IN A COMMISSARY WITH

CONVENTIONAL VERSUS COOK-CHILL SYSTEMS’

TAEHEE KIM. PhD

Director of Business Planning Team Contract Foodservice Division

LG Mart Co., Ltd. 10 Mullae-dong-6-ga, Youngdungpo-gu

Seoul, Korea

AND

CAROL W. SHANKLIN, PhD, RD2

Professor h Graduate Program Director Department of Hotel, Restaurant, Institution Management and Dieietics

Kansas State University I03 Justin Hall

Manhattan, KS 66506-1404

Received for Review November 9, 1998 Accepted for Publication October 6, 1999

ABSTRACT

This study was conducted at three elementary schools in a Midwestern school district, which was converting its food production system from a centralized conventional to a centralized cook-chill system. Time and temperature histories of a selected menu item prepared by two different food production systems were monitored throughout the food product flow for three days. No consistent reheating method for chilled products was observed among schools in the cook- chill system. Hot holding time of chilled products was extended because of time and equipment constraints. Wide variations in time and temperature histories during hot holding and reheating processes were found among sclrools in both

‘This project was partially funded by the American School Food Service Foundation. The authors gratefully acknowledge Donna Keyser, MS, RD, the Foodservice Director in the USD 383, for her support and assistance on this project and KSU graduate students for their assistance with data collection. Contribution # 98-209-5 from the Kansas Agricultural Experiment Station.

’Send correspondence to Dr. Shanklin at the above address. Phone: (785)532-2206, Fax: (785)532- 5522, E-mail: shanklin@humec.ksu.edu

Foodservice Research International 11 (1999) 237-249. All Rights Reserved. ‘“Copyright 1999 by Food & Nutrition Press, Inc.. Trumbull, Connecticut. 237

238 T. KIM and C.W. SHANKLIN

systems. Results may have been influenced by variability observed in temperatures of hot holding carts and steam tables among the schools. Inconsistencies in food quality and potential food safety problems associated with time and temperature abuse were observed morefiequently in the cook-chill system than the conventional system. The results indicate that stringent operating procedures for holding and reheating foods should be developed for both systems to assist school foodservice personnel in maintaining quality and safety of the products. Continuous in-service training and supervision are very important for foodservice personnel in a cook- chill system. Availability of equipment, labor, and time at a unit kitchen should be considered when menus are planned to eliminate an extended hot holding time. Both management and foodservice personnel are responsible for maintaining high quality of foods by the implementation of controls throughout the system.

INTRODUCTION

Commissary food production has been considered the most cost-effective system for school and hospital foodservice operations because of the potential benefits of reduced food costs and increased control through centralization of receiving, storage, and inventory (Bender 1991; Schuster 1997). In recent years, school foodservices have been implementing centralized cook-chill systems to achieve cost savings in labor and increase control of food quality (Bond 1997; Friedland 1992; King 1992; Updating school kitchens 1997; Wolson 1993, 1996). Cook-chill systems are used worldwide; however, not all users have experienced the same benefits (Pizzuto and Winslow 1989). Research does not support the cost savings of a cook-chdl system identified in a trade publication (Carroll and Montag 1979; Franzese 1984; Greathouse et a!. 1989).

Financial concern is one of the most important reasons for changing the type of food production system (Nettles et al. 1997; Updating school kitchens 1997; Wolson 1993, 1996). Even though cost-related issues are important, school foodservice directors should not overlook other issues related to child nutrition programs. All systems in school foodservices should support the objective of the National School Lunch Program and provide high quality food to students. Quality food means a food that is acceptable to consumers (Brown et al. 1995; Miller 1997). If food is not acceptable to students, the food production system fails to achieve a goal of the school lunch program. When evaluating school lunch programs, school-aged children perceive that taste and temperature of food are directly related to food quality (Brown et al. 1997).

Conditions and operating procedures in food production and handling are very critical to maintaining proper food temperature. Brown et al. (1 982) examined operating procedures and practices that might affect quality and safety of food in a school foodservice operation that had a centralized, conventional, food-

TT ANALYSIS IN TWO FOOD PRODUCTICN SYSTEMS 239

production system. Time and temperature histories of selected entrees and employee hygiene and food handling practices were studied. To date, 110 study has compared time and temperature histories of a conventional system and a cook-chill system in a school foodservice operation.

Microbiological safety, sensory quality, and nutrient retention have been investigated in over 100 previous research studies of time and temperature effects on food quality in different food production systems (Klein et al. 1984). Little research has been conducted that analyzes time and temperature histories from operational perspectives. Even though operational research in an actual setting presents challenges associated with not being able to control all variables, it provides data that is useful for establishing standards for operations. Results of such a study would assist directors in identifying critical issues required to manage food quality in a cook-chill production system. The purposes of this study were to compare time and temperature histories of a selected menu item prepared by two different production systems and to ascertain important operational practices affecting food quality and safety in a school foodservice operation.

METHODOLOGY

Research Design

A school district in the Midwest converted its food production system from centralized conventional (Pretest) to centralized cook-chill (Posttest). A pretest- posttest research design was employed to compare time and temperature histories of a selected menu item prepared by the two systems. Data were collected in three elementary schools. Research assistants monitored time and temperature histories of the selected menu item for three days during each test period.

Training Session and Pilot Test

Research assistants were trained in data collection procedures including how to use a thermometer, read temperatures, and record data. Following the training sessions, a pilot test was conducted at an elementary school other than three participating in this study to determine whether any modifications were needed in the data collection procedure. Data from the pilot test were not included in data analysis.

Test Menu Item

Spaghetti with meat sauce was selected as a test menu item. The same food production personnel using the same recipe in both pre- and posttest periods prepared the products. During the pretest period, the selected menu items were

240 T. KIM and C.W. SHANKLIN

prepared on the day of service between 5:30 am and 7:30 am. The products were shipped in hot holding carts to satellites between 9:OO and 1O:OO am. In the cook- chill system, spaghetti and meat sauce were cooked separately, chilled, and stored for two days at the central kitchen. The chilled products were transported to schools on the day before service and reheated at the satellite schools on the day of service.

Data Collection Form

A data collection form was developed to record time and temperature data. Temperatures of spaghetti (SP) and meat sauce (MS) in a hot holding cart (HC) and on a steam table (ST) during service hours were monitored and recorded separately at various points throughout the product flow. Temperature readings were taken at the end of batch cooking at the central kitchen, right before shipment to satellites, and at 30-min intervals during service hours from 10:30 a.m. to 12:OO noon. Research assistants documented reheating time and methods and equipment used at each school also.

Procedures

Temperature readings were taken by inserting a thermometer (Oakton, TempTestr", Model No. 35628-00) into three locations near the center of a full pan. If the test menu item was in the plastic bag, the bag was wrapped around the stem of the thermometer to obtain a reading. During service hours, research assistants measured temperature of the test menu items left in a serving pan on a steam table and in a hot holding cart. On the test days five lunch trays were selected randomly from the serving line at each school to measure the temperature of the spaghetti with meat sauce at point of consumption.

Statistical Analysis

Data were analyzed by SAS (version 6.12, Cary, NC). A mixed model was used to analyze temperature history data and the serving temperature of the selected menu item.

RESULTS AND DISCUSSION

Reheating Equipment and Methods

A steamer and a convection oven were used most often to reheat chilled SP and MS. School 1 used running hot water to reheat chilled SP and a steamer for the MS. A steamer or convection oven, depending on availability, was used to reheat both SP and MS in Schools 2 and 3. The plastic bags sometimes were opened during the

TT ANALYSIS IN TWO FOOD PRODUCTION SYSTEMS 24 1

reheating process and sometimes not. No consistent reheating method was observed among the three schools.

Because of time constraint or use of cooking equipment to heat other menu items, some foodservice managers in the cook-chill system began reheating chilled products at 7:OO a.m. Products then were held in a ST or a hot HC until they were served at 11:OO a.m. There was little difference between the two systems. The reheating step is critical to maintaining food quality in a cook-chill production system. A chilled product should be reheated right before service to maintain the same quality as when the food was cooked. From the operational standpoint, however, batch reheating was not possible in a unit kitchen because of a shortage in labor and time. As a result, the extended holding time (chilling period + hot holding) in the cook-chill system could result in poor food quality. Since quality of the pasta was difficult to maintain using the current procedure, other preparation methods should be considered. Schools that have steam equipment (could prepare the pasta on the day of service. The district should evaluate the feasibility of preparing and delivering the pasta on the day of service. Management may want to evaluate the method used by the Wichita School District. Hot water is pumped into casings containing measured amounts of pasta. The casings are placed in hot holding carts and transported to the serving sites. This procedure has resulted in acceptable pasta products (S. Carlson, personal communication, May 20, 1999).

Time and Temperature Analysis in Conventional System

Figure 1 illustrates the mean temperature of the SP in the hot HCs and on the STs at the three schools. The temperature of SP-HC at one school was significantly higher (ps . O l ) than at the other two schools. School 2 maintained the highest holding temperature of SP in the HCs and on the ST. Thermostats on the ST did not appear to be working properly at the other two schools.

Significant differences were found in the temperature histories of SP-HC and SP-ST among schools (ps.01) and for various time periods (ps.0001) in the conventional system. Figure 2 illustrates the mean temperatures of the SP-HCs at various time points. Temperature of SP-HC significantly decreaslcd during the various process stages (ps .0001), indicating that temperature of the hot HC was not maintained properly in the conventional system. No significant differences were found among schools.

Significant interactions were observed in the mean temperatures of MS-HC in the conventional system among various time periods and schools '(ps.05). The mean temperature of MS-HC dropped continuously during service hours at most schools (Fig. 3). The temperature of MS-HC at school 2 increased approximately 5F during service hours. This increase might have resulted from recording temperatures from different serving pans left in an HC.

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F"

140

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190 -

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170 -

160 -

150 -

140 -

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; T. KIM and C.W. SHANKLIN

162 160

1

144

1 Hot Holding Cart Steam Table

(n=54) (n=45)

FIG. 1. MEAN TEMPERATURE OF SPAGHETTI IN HOT HOLDING CARTS AND ON STEAM TABLES BY SCHOOLS IN CONVENTIONAL FOOD PRODUCTION SYSTEM

Minimum Holding Temperature (14OOF)

130 ! 1

Cooking Shipped to 10:30am 1l:OOam 11:30am Noon Satellite

FIG. 2. MEAN TEMPERATURE OF SPAGHETTI IN HOT HOLDING CARTS IN CONVENTIONAL FOOD PRODUCTION SYSTEM (n=27)

TT ANALYSIS IN TWO FOOD PRODUCTION SYSTEMS

190 -

180 -

170 -

160 -

150 -

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140 ! ,I

Cooking Shipped to 10:30am 11 :OOam 11 :30am Noon Satellites

FIG. 3. MEAN TEMPERATURES OF MEAT SAUCE IN HOLD HOLDING CARTS IN CONVENTIONAL FOOD PRODUCTIONS SYSTEM (n=9)

Time and Temperature Analysis in Cook-Chill System

In the cook-chill system, significant interactions were found in the mean temperatures of SP-HC and MS-HC among various time periods and. schools (p s .01) (Fig. 4 and 5) . Some schools failed to maintain hot food:s above the minimum holding temperature of 140F. The SP in school 2 remaiined in the temperature danger zone for at least 2 h before being reheated (Fig. 4). This could result in food safety problem because cooked pasta is considered as SL potentially hazardous food. All chilled products must be stored in a refrigerator until being reheated.

Compared to the previous system, the new system added one more task (reheating) to the responsibilities of the satellite kitchen managers. Because of time constraint or cooking equipment being used to reheat multiple products, the actual holding time of chilled products was longer than expected for a cook-chill system.

Comparison of Time and Temperature Histories in the Two Systems

Figures 6 and 7 illustrate the comparison of mean temperatures of SP-HC and MS-HC by schools and systems and at various time points. The chilling stage of the cook-chill system was not included for comparison. Comparison of the

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50

0

200 -

180 -

160 -

140 - 120 - 100 -

80 - 60 -

40 -

20 -

T. KIM and C.W. SHANKLIN

+School 2 +School 3 -Min. Holding Temp.

Cooking Chilling (Storage) 1O:tOam 1l:OOam 11:30am Noon I I I I

2-3 days prior to service On the day of service

FIG. 4. MEAN TEMPERATURE OF SPAGHETTI IN HOLT HOLDING CARTS IN COOK- CHILL SYSTEM (N=9)

+School 2 +School 3 -Min. Holding Temp.

0 1 I

Cooking Chilling (Storage) 10:30am 11:OOam ll:30am Noon

I I I I

2-3 days prior to service On the day of service

FIG. 5. MEAN TEMPERATURE OF MEAT SAUCE IN HOT HOLDING CARTS IN COOK- CHILL SYSTEMS (n=9)

190 - 170 - 150 - 130 -

110 -

90 - 70 -

TT ANALYSIS IN TWO FOOD PRODUCTION SYSTEMS

200 -

190 - 180 ~

170 - 160 -

150 -

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50 I

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+CVSCHl +CVSCHZ b - C V S C H J ' . 0. . CCSCHl . - El-. CCSCHZ . - O - - CCSCH3 -Min. Holding

Temp. (140'F

Cooking (Chilling 10:30arn 1l:OOarn 11:JOam Noon

I I

6 Storage)'

2-3 days prior to service'

On the day of service

FIG. 6. COMPARISON OF MEAN TEMPERATURE OF SPAGHETTI IN HOT HOLDING CART IN CONVENTIONAL VERSUS COOK-CHILL SYSTEMS (n=9)

CV= conventional system, CC=cook-chill system, SCH=school, MHT=minimuin holding temperature, *For a cook-chill system only.

- 4+-CVSCHI 4c CVSCH2 -+I-CVSCH~ -4-CCSCHl -€CCCSCHZ ~ - C C S C H S -- Min. Holding

Temp.(140°F] -

120 4 3

Cooking (Chilllng b 10:30arn l1:Wam 11:30arn Noon

- L I

Storage)'

2-3 days prior to *Nice*

On the day of service

FIG. 7. COMPARISON OF MEAN TEMPERATURE OF MEAT SAUCE IN HOLDING CARTS IN CONVENTIONAL VERSUS COOK-CHILL SYSTEMS (n=9)

CV= conventional system, CC=cook-chill system, SCH=school, MHT=minimum holding temperature, *For a cookthill system only.

246 T. KIM and C.W. SHANKLIN

conventional system with the cook-chill system showed significant interactions in the time-temperature histories of SP-HC (p' ,0001) and MS-HC (p' .05) between the systems and schools. These interactions might have resulted from inconsistent reheating methods and holding times in the cook-chill system among schools. The minimum holding temperature of 140F was not always maintained during the holding stage. This could not only affect the quality of the menu item produced in the foodservice system, but also provide many opportunities for mishandling of products and food safety problems.

Comparison of Actual Serving Temperature of Menu Item in the Two Systems

Figure 8 illustrates the means of actual serving temperatures of SP with MS by schools and systems. The average temperatures of the SP with MS that students were eating for lunch ranged from 1 18F to 143F. Once food leaves a serving line, temperature cannot be controlled. However, holding hot foods at the minimum of 140F during service should increase the chances that food will still be hot when eaten.

130

120

115

110

105

0 Conventional (n=45)

HCook-Chill (n=45)

143 138

r-- 1

School 1 School 2 School 3

FIG. 8. COMAPRISON OF TEMPERATURE AT POINT OF CONSUMPTION OF SPAGHETTI WITH MEAT SAUCE IN CONVENTIONAL VERSUS COOK-CHILL SYSTEMS

TT ANALYSIS IN TWO FOOD PRODUCTION SYSTEMS 241

APPLICATIONS

Standard operating procedures for holding and reheating processes must be identified to improve temperature control at all stages of food flow in both systems. In a cook-chill system, reheating method and time must be standardized for each chilled food. Procedures should describe the reheating process and equipment needed to safely reheat food to the proper serving temperature, while maintaining its color, texture, flavor, and nutritional content. Furthermore, school foodservice operations should determine which reheating method is best for each specific product. The decision may depend on production and packaging methods used. Foods packaged in a plastic bag should remain in the bag and be rehleated as close to service time as possible to minimize holding time and optimize food quality.

Food quality and safety issues must be emphasized continuously .when training is provided to foodservice managers and employees in both systems. Continuous in-service training is particularly important for school foodservice personnel in a cook-chll system, because they are handling chdled products that must be reheated properly. School foodservice operations must develop and maintain stringent procedures to control food temperature in both systems. Foodservice managers in a unit kitchen should have primary responsibility for monitoring anld maintaining proper temperatures of foods when they are shipped to unit kitchens. In a cook- chi11 system, all chilled foods must be kept in a refrigerator until being reheated. Foodservice managers need to make sure that STs and hot HCs maintain proper holding temperatures during service. If equipment fails to meet standards, corrective actions must be taken to avoid potential food safety risks.

Production scheduling should be considered when menus are planned in a cook- chill system. Equipment, labor, and time at a unit kitchen should be utilized effectively and efficiently to serve quality food. Minimizing hot holding time between production and service and maintaining proper temperature during holding are essential to maintaining the quality of food items regardless of thle type of food production system.

School foodservice operations should not rely just on a food production system. Good management and ability of foodservice personnel to perform standard operating procedures are as important to successful cook-chill operations as are financial considerations and acceptance of food.

A cook-chill system may fail because a foodservice director simply is not committed to the system. Management and foodservice personnel all should have responsibility to meet the requirements of the cook-chill system. Carefid planning, continuous training, and good management and operating practices are fundamental for effective and quality foodservice systems.

This study identified the following procedures and practices that might impact on food quality and safety in a school foodservice operation witlh a cook-chill production system:

248 T. KIM and C.W. SHANKLIN

K

K

( 1) standardized reheating procedures for chilled products, (2) continuous in-service training on taking temperature during service, (3) continuous supervision to assure that procedures are being followed, (4) limited holding time of foods after being reheated, ( 5 ) menu consideration, (6) production scheduling: availability of equipment and labor at a unit

(7) commitment of foodservice managers to successful implementation of kitchen for reheating chilled products close to service and

a cook-chill operation.

REFERENCES

BENDER, B. 1991. The central commissary: reduce and control food service costs. School Business Affairs 57(1 l), 16-19.

BOND, M. 1997. As possibility of double sessions loom: Nevada schools seeking new ways to feed students. Foodservice Director 20(5), 52.

BROWN, N.E., DANA, J.T., GILMORE, S.A. and BROOKS, A.D. 1995. Food qualityevaluation and assurance manual for school foodservice. Publication No. NFSMI-R15-95. National Food Service Management Inst., Hattiesburg, MS.

BROWN, N.E., GILMORE, S.A. and DANA, J.T. 1997. Perceptions of food quality and dining environment in schools. School Food Service Res. Rev.

BROWN, N.E., MCKINLEY, M.M., ARYAN, K.L. and HOTZLER, B.L. 1982. Conditions, procedures, and practices affecting safety and food in 10 school foodservice systems with satellites. School Food Service Res. Rev. 6( l), 36-4 1.

CARROLL, G.H. and MONTAG, G.M. 1979. Labor time comparison of a cook- freeze and cook-serve system of food production. J. Canadian Diet. Assoc.

FRANZESE, R.A. 1984. Foodservice survey shows delivery shift. Hospitals 58(16), 61.

FRIEDLAND, A. 1992. Modesto reorganizes a hodgepodge foodservice. Food Management 27(11), 58,63.

GREATHOUSE, K.R., GREGOIRE, M.B., SPEARS, M.C. and NASSAR, R.F. 1 989. Comparison of conventional, cook-chill, and cook-freeze foodservice systems. J. Am. Diet. Assoc. 89(11), 1601-1611. NG, P. 1992. Central production scores in America’s heartland. Food Management 27(9), 58, 63. ,Em, B.P., MATTHEWS, M.E. and SETSER, C.S. 1984. Foodservice systems: time and temperature effects on food quality. North Central Regional Research Publication No. 293, Illinois bulletin 779, University of Illinois at Urbana- Champaign Agricultural Experiment Station, Urbana-Champaign, IL.

21(1), 38-45.

40( l), 39-49.

TT ANALYSIS IN TWO FOOD PRODUCTION SYSTEMS 249

MILLER, D.C. 1997. 12 steps to better food quality. Foodservice Director 10(5), 208.

NETTLES, M.F., GREGOIRE, M.B. and CANTER, D.D. 1997. Analysis of the decision to select a conventional or cook-chill system for hospital1 foodservice. J. Am. Diet. Assoc. 97(6), 626-63 1.

PIZZUTO, R. and WINSLOW, E. 1989. Why cookkhill systems don’t work - when they really should. The Consultant 22( l), 32-34.

SCHUSTER, K. 1997. Healthcare re-visits the commissary concept. Food Management 32(6), 42-47.

Updating School Kitchens 1997. July. Satelliting/Central kitchens. Workshop Presented by National Food Service Management Institute at the 5 1 st Annual Conference of American School Food Service Association, Orlando, FL.

WOLSON, S. 1993. Cuts labor, expands market potential: The cook-chill “fit”. Foodservice Director 6(6), 138.

WOLSON, S. 1996. Growing in prisons, schools, hospitals: Cook-chill. Foodservice Director 9(8), 146.