A preliminary investigation report of iced tea contamination.

Introduction

Taxonomy

Common tea is obtained from the leaves of an evergreen plant Camellia sinensis (L.) O. Kuntze of family Theaceae. In Species Plantarum published in 1753, Linnaeus assigned the name Thea sinensis to the tea plant. In some older literature the tea plant is also referred to as Thea chinensis (1). A native of Asia, tea is grown extensively in a wide range of latitude and cultivated principally in China, India, Japan, Ceylon, Java, Sumatra, Uganda, Kenya, Malawi, and Mozambique. Commercially-grown tea plants are pruned to keep a height between 3 and 4 ft, but an unpruned plant could reach up to 30 ft in height.

All commercial tea comes from the same plant. The difference in variety and tea quality depends upon the position of the harvested leaf on the stalk and the curing method employed after plucking. Curing methods vary with the country in which the plant is cultivated. Tea flavor is affected by the age of the leaf when picked, the climate, altitude and soil conditions. The leaves are picked from three to seven times each year and assorted by size. Older leaves give poorer flavor and are less expensive.

Tea Manufacturing

After hand picking, the tea leaves are spread on large trays or mats made of jute fibers and left for withering and polyphenol oxidation for 12 to 20 hours. The fermentation process starts as soon as the leaves get bruised during picking - sometimes in the plucker's hand or in the baskets used for transportation.

The next step involves the rolling of the leaves. The basic principle behind this process is to compress and twist the leaves in a continuous motion, resulting in twisting and breaking of the leaf leading to expression of juices without actual rupture of cells. Once oozed outside the cells, the catechin phenol reaction begins.

Rolled leaves are cooled, aerated, and finally separated by passing them through various grades of sieves. This process is done either mechanically or manually by spreading and covering the rolled leaves with a wet cloth until the fermentation is completed, accompanied by change to a bright copper color. Next, the fermented leaves are subjected to a firing, or drying, process to get rid of excess moisture (up to about 50% by weight). This is accomplished by forcing a blast of hot air through fermented leaves sitting on perforated trays. The drying process also inactivates the enzyme responsible for fermentation. At this stage, tea leaves look twisted and appear black due to dried coating of condensed and oxidized catechins on leaf surfaces.

The tea is now ready for grading and quality control. Commercially, teas from different gardens and different countries are blended to retain the quality standard of the brands. The blended product is carefully checked against the manufacturer's set standard by professional tea tasters (2).

Public Health Concerns

Food service rules and regulations are intended to control foodborne illnesses which may result from improperly processed, handled, or transported food. Food service operations should be concerned with the sources of food they use (Ohio Administrative Code [OAC] 3701-21-04) (3). Accordingly, the provisions of this Section are intended to ensure that, in general, food must be obtained from sources considered satisfactory by the regulatory authority. Along with the wholesomeness of food, food service regulations also regulate the personal hygiene of workers involved in food preparation (OAC 3701-21-06) (3). Ohio Administrative Code 3701-21-08 safeguards against waterborne contamination in food service operations and, therefore, requires the use of safe and sanitary water (3). To guarantee the delivery of uncontaminated food to the public, all states in the United States have adopted similar regulations and empower their sanitarians and environmental inspectors to investigate, and make recommendations to control, foodborne illnesses and problems.

Table 1

Results of bacterial colony counts isolated from the complainant's
sample, bought from a restaurant (Restaurant A) and another chain
restaurant (Restaurant B) - Ohio Department of Agriculture (ODA)
guidelines are included for comparison

Sample                   Standard Plate Count    Coliform Count/mL
                         (Organisms/mL)

Complainant's Sample     9,000,000               2,200,000
Restaurant A             [less than]1            No Test
Restaurant B             60,000                  No Test
(*)ODA Guidelines        200-500                 Not Available

* See discussion for ODA Guidelines

Investigation and Methodology

The Food Protection Unit of the Cincinnati Health Department's Environmental Health Program received a citizen complaint through the central lab, alleging that a tainted product, iced-tea, was purchased at a local fast food restaurant. The complainant claimed that the sample gave a rancid odor, smelled like sewage, and tasted offensive and unwholesome. According to the complainant, the sample of purchased tea was frozen at his home before he delivered it to the health department lab. The sanitarian in charge of the area visited the location (Restaurant B) and discussed the matter with the manager in charge, who acknowledged receiving a complaint of such nature. She also mentioned, however, that another restaurant (Restaurant A) of the chain was mentioned to her by the complainant as the site where the tea was purchased. During this visit to Restaurant B, the sanitarian inspected the tea brewer, checked the water on the premises for odor and color and checked the tea for odor. The tea maker was found to be clean, and the tea inside did not give any unusual odor. The water on the premises was found to be normal, without any offensive sewage odor. At the conclusion of the inspection, sample containers of iced-tea, ice cubes, and water were taken from the location to the Cincinnati Health Department laboratory for bacterial analysis. A sanitarian then contacted the management of Restaurant A, informed them of the complaint received, and proceeded to inspect the premises.

The test results from Restaurants A and B prompted us to investigate twenty more restaurants in Cincinnati, Ohio for tea contamination (as indicated by standard plate count, total coilforms and fecal coilform). The Food Protection Unit prepared a survey questionnaire to obtain the following information regarding tea preparation and storage:

1) How clean are the utensils used for brewing and holding tea?

2) Are there any plumbing problems?

3) What brand of tea is used and what is the method used for brewing it?

4) Is the tea served hot or cold?

5) What is the source of the purchased tea?

6) Are there signs of rodent activity in the tea storage area or signs of any other potential sources of contamination?

7) What is the status of employee health?

8) How available are hand washing facilities and how well are they functioning?

9) How are products handled overall?

10) What type and specific brand of tea is served (i.e., name brand) and does the tea served come from bags, instant granule, or bulk for use in a commercial tea brewer?

11) What is the holding time and temperature for the finished tea?

12) What methods are used to clean brewing equipment?

The questionnaire was used to survey only the first ten restaurants. The remaining restaurants were not surveyed. All the facilities inspected generally demonstrated adherence to normal hygienic practices. The utensils were found to be clean, and water collected from the tap was found to be free of any unusual or offensive odors. However, the brewing method was found to be questionable. It was observed that hot tap water was used for brewing the tea, that it was often held at room temperature for up to 12 hours without additional heating, and that warm or room temperature tea was poured into ice-filled glasses immediately before being served.

Sample Collection

A sanitarian, certified and registered by the State of Ohio, collected two samples of iced-tea (approximately seven to eight ounces each) in a restaurant cup without any ice, directly from the counter dispenser. The samples were covered immediately with plastic lids and transported in an ice chest to the Cincinnati Health Department's central laboratory, where they were stored in a refrigerator. These samples were used to perform standard plate count, total coliform, and fecal coliform tests (4,5). Brewing and holding temperatures were also measured by the sanitarian, using a dial thermometer at the time of sample collection.

Biological Media

Growth media were prepared in-house in one-liter batches, using the manufacturer's (DIFCO) instructions for Plate Count Agar for standard plate count (SPC), m-Endo Agar for total coliform, and MFC media for fecal coliform. The specific recommendations for the preparation, inoculation and incubation of these media are found in Standard Methods for the Examination of Water and Wastewater, and Compendium of Methods for the Microbiological Examination of Food (4,5).

Sample Dilution

Samples for total coliform and fecal coliform tests were prepared in dilution blanks at 1:100 and 1:1000. One mL of these dilutions was filtered through a membrane filter held on a sterile funnel, followed by a 99 mL water rinse. The membrane filters were removed with flame sterilized forceps onto the MFC and m-Endo plates. After incubation, bacterial colonies were counted using an overhead binocular microscope.

Samples for SPC were diluted as described above. A one-mL inoculum was placed into a sterile petri-dish before the addition of liquefied agar. The pour plate method as described in Standard Methods for the Examination of Water and Wastewater was followed (4). After incubation, SPC plates were counted on a "Quebec Colony Counter."

Results

The health department sanitarians conducted a survey of ten restaurants to determine adherence to food service regulations after receiving a complaint of iced-tea contamination. In general, all restaurants met the current regulatory requirements. The utensils were found to be clean, and tap water was found to be free of any unusual or offensive odors. The brewing method in some restaurants, however, was found to be questionable, as they used hot tap water for brewing the tea. Table 1 shows the results of bacterial colony counts found in the complainant's sample and in samples from Restaurant A and Restaurant B. The complainant's sample showed exceedingly high counts of SPC as well as total coliforms. Restaurant B was found to have an SPC of 60,000 organisms per mL - which exceeded by more than 100-fold the Ohio Department of Agriculture guidelines for bottled water. Samples of ice cubes collected from these restaurants were found to be negative for bacterial presence.

[TABULAR DATA FOR TABLE 2 OMITTED]

Out of the initial ten restaurants surveyed, we found that only 40% of the establishments were brewing tea in the range of 175-212 [degrees] F. It was also determined that 40% of restaurants were brewing at 165 [degrees] F and that 20% were brewing at 90 [degrees] F (Table 2). A holding temperature of 80 [+ or -]5 [degrees] F was the most commonly observed (70%) temperature. The holding time for brewed tea ranged between 2.3 and 12 hrs, which is within the recommended range specified by commercial brewers (Table 2).

Of the initial ten restaurants surveyed, six restaurants used a wash-rinse-sanitize sequence for cleaning and sanitizing their equipment. Two used quaternary ammonia, and one used bleach as a sanitizing agent. Other restaurants soaked brewers in bleach solution followed by washing with water. Bacteriological analyses performed on all twenty samples of tea are reported in Table 2. Significant coliform counts were found in 16 of the 20 samples including high counts of fecal coliforms in 14 samples. Our survey indicated that various brands of tea were served by the restaurants. The brands were: Lipton, Luzianne, Southern Style Orange Pekoe, Shoney's Incorporated, Nestea, Worldwide Coffee (iced-tea), Maxwell, Willingford Orange Pekoe, and McDonald teas. Due to the wide variety of tea brands used at the twenty sites, we found no correlation between brands used and the level of bacteria found in the finished tea.

In our survey of restaurants, we found that four restaurants used a Bunn-O-Matic brewer, two used a Standard Coffee Service brewer, and the remaining restaurants used Automatic Mark Industries, Bloomfield/Satellite, Coffee Inn, and New Co. brewers.

Discussion

Leaf tea is almost exclusively produced and processed in third-world countries. The leaves could be exposed to bacterial contamination at any step between harvesting (picking) and serving. Leaf tea, therefore, should not be considered free from bacteria. It is our understanding that normally, the product is not tested for coliform bacteria. Its suppliers recommend brewing it at 175-212 [degrees] F for 5 to 10 minutes.

Due to the absence of clear-cut guidelines from the Ohio Department of Agriculture (ODA) for any leaf-tea contamination standard, the Food Protection Unit employed ODA's standards for drinking water and carbonated juice to provide a comfortable range of "acceptable" bacterial counts in tea. Duane Murray, R.S., Coordinator of Guidelines for Food Inspection Programs at ODA, indicated guidelines for bacterial contamination of drinking and bottled water (2.2/100 mL coliforms and 500/mL SPC) and carbonated soft drinks and juices or pasteurized cider (200/mL SPC) (6). In Table 1, a range of 200-500 SPC colonies for leaf tea as an arbitrary acceptable level was considered. It is anticipated that the data could be used to develop a basic framework for ODA guidelines for leaf-tea contamination.

The basic reason for testing the complainant's tea sample for the presence of coliform was dictated by the medical condition (multiple sclerosis) of the complainant. Due to the involvement of weakened immune systems among multiple sclerosis patients, our laboratory ran bacteriological tests beyond standard plate counts.

Samples of tea were collected from the two restaurants, from one of which the complainant had purchased the original iced-tea that was submitted to the laboratory. The results in Table 1 indicate that the tea from Restaurant B was found to have high bacterial counts consistent with the complainant's sample, whereas that for Restaurant A was below detectable limits. The Food Protection Unit found from twenty other random sites a contamination rate of 80% for coliform and 90% for SPC in excess of our own "established standard." It should be noted that samples #4, #7, and #17 had colony counts below the ideal countable range, which may raise the question of reproducibility of results.

Brewing-temperature surveys (Table 2) indicated that only 40% of restaurants were adhering to suppliers' recommendation of brewing leaf tea between temperatures of 175-212 [degrees] F. Wide variations noted in bacterial counts (Table 2) could be attributed to many unknown factors involved in bacterial growth and multiplication, for example, initial counts on tea leaves, grab sampling, storage conditions, etc. Samples were collected at any time between the first brew to the time of restaurant closing. We suspect that the time lapse would have a direct effect on the bacterial count. Our results represent the bacterial count at the time of sample collection only. Comparing the site-survey to laboratory-analysis holding temperature for the range stated and holding time did not indicate any direct relationship to bacterial counts. It may be argued that brewing temperature plays an important role in determining how many bacterial cells would be killed by the process, whereas storing brewed tea at room temperature provides acceptable conditions for the growth of surviving bacteria. It may be further argued that restaurant holding time for finished tea should have more of an impact on bacterial growth than was seen. We have no way of determining the validity of holding time as stated by restaurant management. All temperature measurements were conducted by the inspecting sanitarian using a calibrated dial thermometer. We intend to expand our studies to include a larger number of restaurants in order to understand the time/temperature relationship with respect to bacterial growth in iced-tea. The manufacturers of tea believe that tea steeping temperature within the range of 100-140 [degrees] F is not a satisfactory practice for two reasons: Any potentially harmful microorganisms present on the tea leaves will not be destroyed by relatively low temperatures of hot tap water; and, brew quality will suffer and the tea will likely be too weak.

Due to the sheer number of variables in our observations, the authors cannot conclusively make a statement as to the definitive cause of the high bacteria counts in the finished tea. It could be any single factor or any combination of factors which occur from the plucking of tea leaves until it is served on the table.

It is, therefore, suggested that restaurants and the public follow the Tea Council of the USA, Inc.'s recommendations for "beverage protection and sanitation practices for fresh-brewed iced-tea equipment." (7) Their guidelines include:

1) Tea should be steeped in potable water at a minimum temperature of 175 [degrees] F for 5 to 10 minutes for complete destruction of harmful bacteria on the tea. Proper maintenance and sanitizing of equipment used for tea preparation and storage is recommended.

2) Never hold iced-tea at room temperature for more than 8 hours. IF HELD OVERNIGHT, BREWED TEA MUST BE KEPT REFRIGERATED AT OR BELOW 40 [degrees] F. (PREFERABLY 36-38 [degrees] F) for no more than 72 hours.

3) To protect tea flavor and to avoid bacterial contamination and growth, CLEAN AND SANITIZE tea brewing and storage equipment at least ONCE A DAY as follows:

a) Dismantle dispensing spigots, hoses, storage reservoirs (removing gaskets, "O" rings, etc.) and rinse in warm water along with other brewing and storage utensils (e.g., pitchers, spoons, etc.).

b) Wash equipment, using a good dish detergent, in hot water at 100-120 [degrees] F. Be sure to remove any encrusted soil deposits with a brush or cleaning pad, if needed.

c) Rinse thoroughly with clear warm water.

d) Sanitize by immersing for at least one minute in hot water at 170 [degrees] F or by immersing for at least five minutes in a clean chlorine solution (e.g., made by mixing 1/4 cup of Clorox, or other "household bleach," with every one gallon of warm water used). [NOTE: The authors recommend a concentration of one-tenth this strength to restaurants to avoid pitting and damaging utensils.!

e) Replace any worn gaskets, "O" rings, or any other badly scratched or damaged parts before reassembling.

Due to the responsibility placed on public health agencies to ensure the safety and wholesomeness of food products, it is imperative that we ensure full compliance with current regulations, and do not discount or ignore the slightest level of product contamination. In Cincinnati, Ohio, we are not aware of foodborne illness attributable to iced-tea. Our reported level of bacterial counts from iced-tea, if found in products like drinking water, juices, or carbonated drinks, would definitely not meet public health standards and could have serious health consequences for consumers. As the health department of a large metropolitan area, we felt obligated to study the problem of tea contamination and report our findings to the public and to health professionals.

Addendum

The information presented here was released to the public and the media as a news release on August 15, 1995. Subsequently, we have received numerous inquiries, concerns, and informational calls confirming our findings. Northern Kentucky Health Department verified our findings by testing their own samples and reporting the results in the Cincinnati Enquirer Newspaper dated September 6, 1995. The Department of Health Services, Commonwealth of Kentucky, Frankfort, Kentucky, collected samples from restaurants and reported their iced-tea survey on August 28, 1995. They reported variable levels of total and fecal coliform contamination.

In 1987, the FDA had communicated internally the isolation of Klebsiella and other coliform bacteria from iced-tea samples. This report was generated after foodborne illness reports in Dallas and Lubbock, Texas implicated the consumption of iced-tea. San Diego County verified the reporting of small numbers of food illness cases due to iced-tea consumption (8). Verification of our findings by other health departments across the country implies the soundness of our methodology and validity of reported data. At this time, the authors are aware of several public health agencies that are interested in researching this subject and that intend to collect information beyond our reported data.

In a memorandum to the Ohio State Health Department dated January 10, 1996, the Centers for Disease Control and Prevention (CDC) affirmed the information and recommendations in our advisory. The only difference between the CDC information and our advisory is an increase in the recommended brewing temperature from 175 [degrees] F to 195 [degrees] F, consistent with the change in the recommendation from the Tea Association dated August, 1994 to their current advisory dated December 29, 1995.

The Cincinnati Health Department staff is working with the Ohio Department of Health, the CDC, and the Food and Drug Administration to help develop standardized laboratory procedures for future investigations. In the meantime, the Tea Association of the U.S. has issued a national tea advisory recommending precautions similar to ours in the preparation of safe and wholesome tea.

Corresponding Author: Mohammad I. Alam, Director, Environmental Health Services, The Cincinnati Health Department, 3101 Burnet & King, Cincinnati, Ohio 45229.

Acknowledgements

We wish to express our appreciation and thanks to Ms. Kimith A. Bush and Ms. Kathy Howard for typing and proofreading the manuscript. Thanks are also due to Malcolm P. Adcock, Ph.D., Health Commissioner and Food Microbiologist, who critically reviewed the manuscript, made valuable comments, and helped in the interpretation of various data; and to Walter S. Handy, Ph.D., Assistant Health Commissioner, for his constant support, encouragement, and philosophy of sharing information with sanitarians and laboratory personnel.

The authors also acknowledge gratefully the valuable suggestions and discussions with the officials of the Product Technology Section of Nestle's Brand Food Service Corporation; and Mr. Logan Daugherty and Steve Kohrman, both of Cincinnati Health Dept., for experimental design and review of the manuscript.

REFERENCES

1. McCormick's Teas (1926), Tea - Its Culture, Manufacture and Packing, 1st edition, McCormick and Company, Baltimore, Md.

2. Eden, T. (1976), "Tea," in Tropical Agriculture Series of Longman Group Limited, Ed., Rhind, D., Lowe and Brydone Ltd., Thetford, Norfolk, Great Britain.

3. Ohio Department of Health (1992), Ohio Administrative Codes, OAC 3701-21-04; 3701-21-06; and 3701-21-08; Columbus, Oh.

4. American Public Health Association (1989), Standard Methods for the Examination of Water and Wastewater, 17th edition, Ed., Clesceri, L., A. Greenberg, and R. Trussel, Part 9000:9.1-9.104, Washington, D.C.

5. Compendium of Methods for the Microbiological Examination of Food (1992), Ed., Vanderzant, Carl and Don F. Splittstoesser, 3rd edition, Chapter 4:75-95, American Public Health Association, Washington, D.C.

6. Murray, Duane, R.S., Coordinator of Guidelines for Food Inspection Programs (August 8, 1991), personal communication, Ohio Dept. of Agriculture, Oh.

7. Tea Council of the U.S.A., Food Service Committee (1994), Fact sheet: "Beverage Protection and Sanitation Practices for Fresh-Brewed Iced Tea Equipment," NY.

8. Tanner, Paula, Epidemiologist (August 25, 1995), personal communication, San Diego County Dept. of Environmental Health, Ca.