Tucker - Hygiene Issues
Hygiene Issues

Hygiene Issues Posed by Pathogenic and Indicator Bacteria Associated With Foodservice Potholders and Oven Mitts

Barry Michaels,* Troy Ayers1 and Wafa Birbari1 *Georgia-Pacific Corporation, Technology Center, PO Box 919 (190 CR 216), Palatka, Florida 32178, USA. 1ABC Research, 3437 S.W. 24th Avenue, Gainesville, Florida 32607, USA.

Foodservice kitchen oven mitts and potholders are indispensable forms of personal protective equipment (PPE). Because mitts and potholders are often contaminated with both raw and cooked food soils that support microbial survival and growth, it has been suggested that they possibly present a risk to food safety. To ascertain the extent to which these items might contribute to crosscontamination, 10 dirty oven mitts and 3 dirty potholders obtained from a variety of establishments in the US were surveyed for microbial populations. Aerobic Plate counts (APC) as high as 7 x 106 colony forming units (CFU) were found on outer surfaces. Potholders taken from a hospital kitchen were found to have approximately 106 CFU coliforms and B. cereus. Overall, samples examined were seen to have high coliform, B. cereus, and Pseudomonas spp. counts with occasional C. perfringens found. Interior surfaces of mitts, while lower than exterior (geometric mean APC 1.2 x 105 vs. 6.0 x 104), were also found to be contaminated with S. aureus. While no E. coli, Listeria spp. or Salmonella spp. were found, indications are that foodservice PPE offering thermal protection can become contaminated and may, in turn, contaminate hands and food, unless frequently cleaned or sanitized.

Protective gloves or mitts are forms of personal protective equipment (PPE) commonly used in many occupations for one, or both, of two reasons: worker safety, and/or patient/customer protection from infectious hazards. Gloves used in the health care field by nurses or hospital personnel have, in a few instances, been found as the source of cross-contamination between patients. For example, Hepatitis C and Malaria were actually passed from patient to patient via gloves (Okuda et al. 1995; Piro et al. 2001). In the food processing environment, protective steel mesh gloves have been difficult to sanitize and considered as a source of cross-contamination, sometimes being colonized by potential food pathogens or indicator species (Gill et al. 1999; Hedman et al. 1990). In New Zealand, despite advantages to food workers for obvious safety reasons, protective gloves are not allowed in pre-inspection areas because they are considered by food safety managers to be a hazard for that same reason (crosscontamination) (Legg et al. 1999). In the United States, it is reported by the Centers for Disease Control and Prevention (CDC) that there are over 14,000 burn cases each year in the foodservice industry (CDC 1999). As a means of reducing the risk of burn injuries, foodservice directors provide various types of PPE, such as oven mitts and potholder pads. These are necessary forms of protection and, unfortunately, are sometimes used for long periods of time without washing and sanitizer treatment. Since most mitts are made of quilted cotton with no liquid-vapor barrier, they cannot be used wet, without the risk of steam burns. Thus, foodworkers would not consider rinsing freshly soiled mitts as should occur, for fear of causing a burn to themselves at some point later. Observations are that few such products will withstand frequent laundering, or are even cleanable once heavily soiled.

While working with raw food, protective mitts may be donned without washing hands, possibly causing PPE to become a cross-contamination hazard. As observed by the present authors, these implements (PPEs) are also accidentally soaked, splattered or dipped into food by cooks or chefs at all levels of foodservice. In the typical foodservice kitchen, large pots of hot food require transport to chillers. Liquid food soils, such as soups, sauces and bases, frequently wet protective gloves, endangering food workers and possibly the food. Because mitts and potholders become soiled during use with materials such as fats, oil, proteins and carbohydrates from raw and cooked foods, they can also become contaminated with microorganisms found in the foodservice environment. Organic soils and contaminating microorganisms can theoretically penetrate the covering, contaminating what is usually a quilted-cotton insulation and inner liner. It has been suggested that hot potholder pads and oven mitts may become reservoirs of pathogenic bacteria capable of causing foodborne illness (Weklinski 2001). As a result of this concern, a survey of potholder pads and oven mitts obtained from various foodservice locations around the US was initiated.

Materials and Methods
Oven mitts and pot holders: Overall, twenty (20) items considered to be food worker thermal protective apparel was collected from sixteen (16) commercial foodservice locations in Indiana, Florida and Colorado. Of these, ten (10) oven mitts and three (3) potholders were surveyed for microbial populations. These items were obtained through an exchange program (used oven mitt or potholder for a new one) offered to study participants. All items tested were in active foodservice usage. The samples obtained in the state of Indiana came from a silver service restaurant, school cafeteria and hospital food preparation area located in the city of Terre Haute. Two (2) of the three (3) potholder pads came from a hospital kitchen in that location. The Florida samples came from a barbeque restaurant and diner outside of Jacksonville, while the Colorado samples came from 6 different restaurants in and around Colorado Springs, also providing the third potholder pad.

Physical Appearance and Description: As the test method chosen called for destruction of the test sample, pictures of the oven mitts and potholder pads in this study were taken as a record prior to testing. Their appearance was considered similar to many such items used in foodservice establishments around the world. In addition to various types of heavy food, burn and scorch marks, several objects had strong food or rancid oil odors. In several cases, upon handling the mitt or potholder pad, fibers or dried food debris was visibly shed from these objects, falling onto surfaces below.

Testing: In most cases oven mitts and potholder pads were tested within a day of being collected. Upon receipt, they were typically placed in an ice chest with freezer packs for shipping to the laboratory for testing. Samples collected were tested for potential food pathogens and indicator organisms at ABC Research Laboratory in Gainesville, Florida. Survey testing included total aerobic plate counts, anaerobic bacterial plate counts and total coliform counts, as well as E. coli, Clostridium perfringens, Bacillus cereus, Pseudomonas spp., Salmonella spp., Listeria spp., and Staphylococcus aureus counts. Where positive, the most probable number (MPN) of microorganisms was determined for the oven mitts and potholders. The insides (I) and outsides (O) of the mitts were tested independently. Two potholder pads were tested in their entirety, (E) while the third was tested on its outer surface (O) and inner padding (I). Where microorganisms were found above detection limits, counts are expressed as colony forming units (CFU) per item.

Several methods for sampling microbial populations from the protective mitts and potholders were trialed. Methods employing the use of a Waring Blender with Butterfields Phosphate Buffer containing 1.0% Triton worked best. In method I, mitts and potholder pads were cut up into 1 inch squares in an aseptic manner using sterile scissors and scalpels, then placed in sterilized Waring Blenders with 600 ml of sterile Butterfield’s Phosphate Buffer (BPB) with 1% Triton and blended for 1 minute. Method II proceeded as above, followed by incubation at 7°C overnight. After overnight storage, samples were stomachered for one minute prior to testing. It was believed this would aid soil dissolution and microbial desegregation. A comparison test was carried out to compare the different methods where a glove was cut into pieces, and evenly parceled out. The results showed little difference in microbial counts recovered using either test procedure. Standard US FDA Bacteriological Analytical Manual (BAM) procedures were used for plating and microbial counts. Table 1 shows selective media types used for enumeration, as well as incubation times, temperatures and detection limits for microorganisms surveyed.

Table 2 shows all results from this study with all samples coded per location, device type and surfaces being tested. Both foodservice oven mitts and potholder pads were sometimes heavily contaminated with microorganisms. The tested potholders were consistently more contaminated with indicator bacteria, with Geometric mean aerobic plate counts being 2 x 106 CFU. Geometric mean aerobic plate counts for the inside surfaces of foodservice oven mitts were 6 x 104 CFU while outside surfaces were more contaminated, having geometric mean counts of around 1.2 x 105 CFU. The highest aerobic and anaerobic plate counts for all the items tested were 7.2 x 106 CFU and 1.3 x 106 CFU, respectively, these being for inside surfaces of mitts. The highest total coliform count was 9.6 x 105 on a potholder derived from a hospital kitchen, with 1.2 x 106 Bacillus cereus CFU on another potholder from the same kitchen. The highest outside surface APC revealed 7.2 x 105 CFU for an oven mitt. No Salmonella spp., Listeria spp., or E. coli were found on or in any of the objects tested. While these may have been present in low numbers, detection limits were sometimes high due to the amount of blender fluid utilized. Pseudomonas spp. was found in several mitts and potholders from the Colorado Springs, Colorado area, with counts as high as 3 x 105 CFU.

Oven mitts and potholder pads are an important tool for burn prevention, but oftentimes are not of requisite quality for frequent laundering or sanitizer treatment. The failure to use oven mitts capable of functioning while wet, which would require a liquid-vapor barrier, effectively prevents timely rinsing and cleaning. The result is that many oven mitts and potholder pads go for long periods of time without cleaning or laundering. Oven mitts and potholder pads surveyed were often found to be cracked and “dripping” of food soils and fiber material when handled. The dirty outer fabric of these protective gloves can be a potential source of cross-contamination. Oven mitts and potholder pads are used to protect workers when handling hot pots and pans or cooking utensils. The handling of hot equipment may occur between periods of handling or cutting raw food (meats such as poultry, beef, seafood, etc.), where workers do not perform hand washing before putting hands in mitts. In this case, the inside of the mitt can also become contaminated with raw food on hands. Similarly, hands are not usually washed after removing mitts, which could cause ready-to-eat (RTE) food to be contaminated. Bacterial counts as high as 7.2 x 106 CFU were found on the outsides of dirty foodservice oven mitts, and counts as high as 3.5 x 106 were found on potholders. Most food safety experts and regulators require food contact surfaces to have very low microbial profiles, and even non-food contact surfaces are to be “…free of an accum ulation of dust, dirt, food residue and other debris” (FDA 2001A). In fact, a strong argument could be made that oven mitts are food-contact surfaces being “a surface of equipment or a utensil from which food may drain, drip or splash (i) into a food or (ii) onto a surface normally in contact with food” (FDA 2001B). It appears that oven mitts and potholders may be frequently overlooked as a potential food safety issue. The cross-contamination potential for the insides of gloves is brought out by the fact that geometric mean counts were 6 x 105 CFU, with the presence of up to 1.2 x 104 CFU S. aureus on the inside of one mitt.

There are numerous performance requirements that could be placed on protective apparel such as oven mitts or potholders, designed to protect the worker. In addition to having an effective liquid and vapor barrier, they must be able to withstand oven-range temperatures, and an open flame without breaking down or falling apart. They must be washable and cleanable allowing them to be constantly maintained in a sanitary condition. The microbial results presented here of foodservice protective apparel found in the US, are believed to be in no way unique with respect to contamination and soils found on these implements. Oven mitts of similar appearance have been seen by the current authors in foodservice locations in the UK and around the world. As an aid to foodservice management, several recognized third-party certifying agencies are now setting specification for implements of this type providing assurance of function and durability to foodservice managers. One such certification (NSF 1996) specifies cleanability requirements under test conditions, such that, 99% of marker bacteria (E. coli and S. aureus) are removed in a single machine washing.

Numerous examples of potholders and oven mitts having high microbial counts were found in this survey. Microbial counts on some objects tested were such that they could be seen to represent a sanitary hazard. Protective oven mitts and potholder pads should be cleaned and sanitized inside and out (or replaced) when they become soiled. Hands should be washed prior to using mitts or potholder pads if handling raw food, and it is advisable to wash hands after using soiled mitts or potholders prior to handling RTE foods to prevent crosscontamination. To reduce the risk of cross-contamination, oven mitts and potholders should be clean, in good repair, and of sufficient quality to withstand frequent and thorough laundering. This is especially true for health care or extended care facilities. Potholders used in one hospital kitchen were seen to be extremely contaminated. These objects may have been overlooked as possible sources of gram negative bacterial contamination in health care settings. Protective apparel that can effectively withstand frequent laundering without loss of protective barrier properties can mitigate risk of food product contamination events, as long as frequent laundering is carried out.

The authors wish to acknowledge the help provided by Cheryll Keller in preparing this report, and by Vincent Tucker of Tucker Industries who, in addition to providing some of the test funding, supervised the collection of oven mitts and potholders, as well as providing replacement mitts to survey participants. Funding for this project was provided in large part by a grant from the Georgia-Pacific Health Smart™ Institute.

Detection Limit/Item Species Identity Media
3 x 102 - 6 x 102 Aerobic Plate Count Standard Method Agar- SMA (TGY –
Tryptone Glucose Yeast Extract Agar)
3 x 102 - 6 x 102 Anaerobic Plate Count SMA with LVA Overlay – (Liver Veal
3 x 103 - 3 x 104 Bacillus cereus MYP – Mannitol Egg Yolk Polymixon
3 x 101 - 3 x 102 Clostridium perfringens SFP – Shahidi Ferguson Perfringens
9 x 101 - 9 x 102 Staphylococcus spp.
Coagulase –
BP – Baird-Parker
3 x 102 Pseudomonas spp. Pseudomonas Isolation Agar
3 x 102 - 3 x 103 E. coli / Coliform Bacteria E. coli Petrifilm™
2.5 x 101 – 5.0 x
101 CFUcfu
Salmonella spp. TECRA® Diagnostics – AOAC (Elisa)
(Method 989.14 & 998.09)
2.5 x 101 – 5.0 x
101 CFU
E. coli O157:H7 Bio Control Assurance EIA AOAC
(Method 996.10)
2.5 x 101 – 5.0 x
101 CFU
Listeria spp. TECRA® Diagnostics – AOAC (Elisa)
(Method 995.22)

Table 2 Microbiological Survey Results of Oven Mitts and Pot Holders from foodservice Locations Around the United States (Counts expressed as CFU per unit tested)

Foodservice Oven Mitts

ID Mitt/Pot
e (O)
35° C
35° C
1 | Silver Service
(Terre Haute,
ND ND ND ND 6000 ND ND |
  O   18,60 ND ND ND 12000 ND ND |
2 | School
(Terre Haute,
6600 ND ND ND 18000 ND ND |
  O   18600 ND ND ND 6000 ND ND |
3 | Hosptial
(Terre Haute,
7200000 12000 ND ND ND ND 1800 ||
  O   408000 ND ND ND ND ND ND ||
4 | Barbecue
Restaurant #1
780000 156000 18000 ND ND ND ND ||
  O   162000 24000 ND 2400 ND ND ND ||
5 | Diner
24000 12000 ND 600 ND ND ND ||
  O   144000 180000 18000 72000 ND ND ND ||
6 | (Bon Jon)
Springs, CO)
306000 30000 ND ND ND 12000 12000 ||
  O   222000 240000 ND ND ND 6000 ND ||
7 | Family
Springs, CO)
1188000 1260000 ND ND ND 300000 5460 ||
  O   570000 780000 ND ND ND 84000 ND ||
8 | Barbecue
Restaurant #2
Springs, CO)
720000 216000 ND 600 ND 6000 ND ||
  O   720000 252000 ND 600 ND ND ND ||
9 | European
Style Café
Springs, CO)
48000 ND 6000 ND ND 6000 ND ||
  O   24000 468000 ND ND ND ND ND ||
10 | Delicatessen
Springs, CO)
60000 ND ND ND ND ND ND ||
  O   78000 ND ND ND ND ND ND ||
Foodservice Pot Holders
1 E Hospital
(Terre Haute,
2460000 780000 960000 ND 48000 ND ND |
2 E Hospital
(Terre Haute,
3540000 ND ND ND 1200000 ND ND |
3 | Mexican Style
Springs, CO)
720000 ND ND ND ND 48000 ND ||
  O   174000 24000 ND ND ND 72000 ND ||

ND* - See Table 1 for non-detect limits of each microorganism investigated in this survey.

Reference List

Center for Disease Control (1999). National Institute for Occupational Safety and
Health. 1999. Most Teen Worker Injuries in Restaurants Occur in Fast Food.
NIOSH Publications, Updated 4 -7-2000. www.cdc.gov/nisoh/teenfast.html.

Gill CO, Baker LP, Jones T. (1999). Identification of Inadequately Cleaned Equipment
Used in a Sheep Carcass-Breaking Process. J Food Prot 62(6):637-643.

Hedman P, Ringertz O, Eriksson B, Kvarnfors P, Andersson M, Bengtsson L. (1990).
Staphylococcus saprophyticus Found to be a Common Contaminant of Food. J
Infect 21(1):11-19.

Legg SJ, Khela N, Madie P, Fenwick SG, Quynh V, Hedderley DI. (1999). A
Comparison of Bacterial Adherence to Bare Hands and Gloves Following
Simulated Contamination From a Beef Carcass. Int J Food Microbiol 53(1):69-74.

NSF. (1996). Oven Mitts Used in Commercial Foodservice. National Sanitation
Foundation Protocol. Protocol No. P149.

Okuda K, Hayashi H, Kobayashi S, IrieY. (1995). Mode of Hepatitis C Infection not
Associated with Blood Transfusion Among Chronic Hemodialysis Patients. J
Hepatol 23:28-31.

Piro S, Sammud M, Badi S, Al Ssabi L. (2001). Hospital-Acquired Malaria Transmitted
by Contaminated Gloves. J Hosp Infect 47(2):156-158.

FDA (2001A). Food and Drug Administration of the United States - Food Code.
Cleaning of Equipment and Utensils, Equipment, Food-contact Surfaces, Non
Food-contact Surfaces, and Utensils. Chapter 4, subpart 4-601.11.

FDA (2001B). Food and Drug Administration of the United States - Food Code. Definitions, Applicability of Terms Defined, Statemetn of Application and Listing of Terms. Chapter 1, subpart 1 -201.10 (34) (b).

Weklinski P. (2001) Oven Mitts as a Vehicle for Cross-Contamination in Commercial Foodservice Establishments. Environmental Health 64(1):27-28.


You Should Know
1 Why are BurnGuard Oven Mitts Better than Quilted Cotton Oven Mitts?
2 The increased compliance of effective protective apparel directly reduces operational costs.
3 63.8% of restaurant workers report that they have worked while sick - Serving While Sick ROC
4 45.8% of all restaurant workers surveyed had been burned on the job and 49% reported being cut - Serving While Sick ROC
5 BurnGuard Oven Mitts last 10 times longer than Quilted Cotton and COST LESS!
6 There is an NSF Certification for Oven Mitts used in commercial foodservice.
Testimonies - Read what our customers are sayingNSF - Tucker Safety Products is the first Manufacturer to receive a NSF Protocol Certification

Legal Information Site Map Rep Login Catalog