Microbiological Surveillance Sampling: FY21-22 Sample Collection and Analysis of Domestic Refrigerated RTE Dips and Spreads
Microbiological Surveillance Sampling Main Page
In 2021, the U.S. Food and Drug Administration (FDA) conducted a routine assignment to collect domestic multi-commodity ready-to-eat (RTE) refrigerated dips and spreads to test for Listeria monocytogenes and Salmonella spp. The agency’s goal in conducting this assignment was to determine the presence of these pathogens in RTE dips and spreads and remove adulterated product from the market, when possible. This sampling assignment started in early March 2021 and sample collection and analysis completed in January 2022.
This assignment is part of the FDA’s risk-based approach to food safety, as outlined in the FDA Food Safety Modernization Act (FSMA). The agency is reviewing this assignment’s findings to identify common factors or patterns (e.g., origin, variety, manufacturing practices) related to the contamination of RTE dips and spreads, when possible. This data will help FDA develop guidance and update program priorities, including sampling assignments and the prioritization of surveillance inspections.
Background
Refrigerated dips and spreads is a broad and growing category of food that encompasses a diverse range of products including hummus, tahini, pimento cheese, and yogurt-based products. A “dip” is thinner in consistency and another piece of food (e.g., chip, vegetable) is submerged into it, such as salsa. A “spread” is food that is spreadable, usually with a knife, onto other foods (e.g., bread, crackers), such as pimento cheese.
Many Americans purchase refrigerated RTE dips and spreads for quick and nutritious snacks. In response to consumers’ lifestyles and preferences, dips and spreads manufacturers have created on-the-go and portion control packaging.[1] In 2020, 191.14 million Americans used dips as snacks.[2] As the popularity of plant-based diets continues to grow, so does the consumer demand for RTE dips and spreads. U.S. refrigerated plant-based dip annual sales increased from about three million dollars in April 2016 to about 11 million dollars in April 2019.[3]
RTE foods can become contaminated through environmental pathogens (i.e., harborage and cross-contamination within the food manufacturing environment/process) or contaminated ingredients (i.e., during or after processing). Dips and spreads may have pH and water activity that make it easy for bacteria to survive and grow, if present. Consumers typically eat these dips and spreads without a ‘kill step,’[4] such as cooking, to reduce or eliminate any pathogenic bacteria that may be present. As such, dips and spreads contaminated with L. monocytogenes or Salmonella can present a significant public health risk and have been associated with multiple recalls over the past few years. This assignment was established due to the five recalls of hummus products and six recalls of multi-commodity dips due to contamination with L. monocytogenes or Salmonella from FY2017 through FY2020.
The agency planned to collect and test 750 domestic samples of multi-commodity, refrigerated RTE dips and spreads that contain ingredients such as sesame, vegetables, cheese, and seafood for this assignment. Since the agency conducted a large-scale sampling assignment on processed avocado and guacamole from FY17-19, this assignment did not include the collection of guacamole. Due to the foreign inspection limitations of COVID at the time of this assignment, imported multi-commodity RTE dips and spreads were excluded from this assignment and collected using our regular import sampling procedures.
The FDA collected and tested 747 samples for L. monocytogenes and Salmonella. Of these samples, the agency collected 743 domestic samples. The assignment did not include the collection of import or domestic/import samples, however there were also 4 domestic/import samples collected (products originated in Canada (2), Jordan (1), and Mexico (1)). The agency collected samples from as many different brands and manufacturers as possible, depending on inventory available at the time of sampling. Samples were collected nationwide from manufacturers/processors (9.9%), distributors/warehouses (16.5%), and retail operations (73.6%) (i.e., grocery stores).
A minimum of 10 and a maximum of 30 subsamples were collected per sample. Each subsample included one container weighing at least 8 ounces. Subsamples were collected from the same lot. The agency collected a total of approximately 11,400 subsamples. This approach – the collection and testing of samples composed of multiple subsamples – increases the probability of detecting pathogens when their presence is low and/or not uniformly distributed.
RTE Refrigerated Dips and Spreads Samples (747 Total Samples)
| Type | Amount | Type | Amount |
|---|---|---|---|
| Cheese | 82 | Dairy & Vegetable | 46 |
| Cheese & Fruit | 6 | Dairy, Pepper, & Vegetable | 1 |
| Cheese & Meat | 3 | Fruit | 1 |
| Cheese & Pepper | 54 | Hummus | 336 |
| Cheese & Seafood | 13 | Macaroni Salad | 1 |
| Cheese & Vegetable | 65 | Meat & Vegetable | 1 |
| Cheese, Fruit, & Pepper | 1 | Nut Based | 7 |
| Cheese, Meat, & Pepper | 1 | Pepper | 1 |
| Cheese, Seafood, & Vegetable | 1 | Salsa | 37 |
| Dairy | 63 | Seafood | 1 |
| Dairy & Seafood | 5 | Vegetable | 21 |
Agency field staff collected unopened samples in accordance with the FDA’s Investigation Operations Manual (IOM).
Taking into consideration the COVID-19 pandemic, the agency took additional precautions to ensure the integrity of sample collection and the safety of FDA investigators, firm or company employees, and any other parties present at the companies visited. Agency field staff completed COVID training, were provided personal protective equipment, and followed state, local, and applicable CDC guidance. The agency offered FDA investigators the COVID-19 vaccination and provided access to testing.
Out of the 747 samples tested in this assignment, four were detected to have a human pathogen. The FDA shared these findings with the responsible firms and determined appropriate follow up as described below.
Pathogen Findings: Salmonella
The agency detected Salmonella spp. in one hummus sample collected from a retail establishment in Kingsburg, CA. The FDA detected the serovar Salmonella Havana in one of the two composites. Upon detecting Salmonella spp., the FDA performed Whole Genome Sequencing (WGS) analysis on the organism and determined that it did not match any known human illnesses and was not linked to any other product or environmental samples.
Pathogen Findings: Listeria monocytogenes
The FDA detected Listeria monocytogenes in three dips and spreads samples – two cheese samples, one cheese and pepper sample – collected from a retail establishment in Colorado Springs, CO. All three of the samples contaminated with L. monocytogenes were produced by the same manufacturer. After detecting L. monocytogenes, the agency conducted WGS analysis on the organisms and determined they did not match any known human illnesses and were not linked to any other product or environmental samples.
During the assignment, the agency also detected two subspecies (i.e., Listeria welshimeri, Listeria innocua) of non-pathogenic Listeria spp. in three samples – two samples collected from retail establishments and one sample collected from the manufacturer/processor. Since these samples were non-pathogenic, they were not analyzed by WGS.
The agency submitted the WGS results for the Salmonella spp. and L. monocytogenes pathogenic findings to the national GenomeTrakr database.
Upon detecting four positive findings, the agency assessed that further follow-up actions were needed to identify potential routes and sources of contamination and protect the public health.
Follow-Up Actions: Salmonella
Upon identifying Salmonella spp. in a sample of hummus from a retail establishment in California, the FDA notified the firm about the positive sample. The firm initiated a recall of the product associated with the positive finding. Upon learning about the positive findings, the firm identified areas for correction and started to institute some of these corrections prior to the agency’s follow-up actions.
The FDA conducted a follow-up inspection at the manufacturer identified as the producer of the contaminated product to evaluate the firm’s manufacturing operations and collect environmental samples. The environmental samples collected at the follow-up inspection did not yield any positive pathogens and FDA shared the results with the firm. After taking corrective actions the firm was unable to identify a root cause for the Salmonella Havana contamination in the hummus.
The follow-up inspection covered the firm’s written food safety plan and its implementation, including hazard analysis, preventive controls and their management components (i.e., monitoring, verification including validation), records, and current good manufacturing practices (e.g., training, manufacturing operations and equipment, plant and grounds, and pest control). The FDA found that the firm did not establish and implement adequate written procedures for monitoring sanitation control procedures (i.e., cleanliness of food-contact surfaces) and the firm initiated voluntary corrections. The agency issued the firm a warning letter after the follow-up inspection.
Follow-Up Actions: L. monocytogenes
Once the FDA identified L. monocytogenes in three samples from a retail establishment in Colorado, the agency notified the firm where the positive samples were manufactured. All three of the samples contaminated with L. monocytogenes were produced by the same manufacturer. Upon notification of the contaminated samples, the firm recalled and destroyed the products associated with the positive findings. The agency issued a Consumer Advisory in conjunction with the firm’s recall.
The agency conducted a follow-up inspection at the manufacturer of the three contaminated products. The follow-up inspection sought to evaluate the firm’s manufacturing operations and collect environmental samples to determine potential sources and routes of contamination. The FDA found L. monocytogenes in 23 swabs collected within the production environment, including samples collected from food contact surfaces. WGS analysis was conducted on the L. monocytogenes isolates[5] obtained from both the retail product samples and the inspection environmental samples. The isolates were a genomic match to each other, representing a single strain of L. monocytogenes. No additional isolates were determined to match this strain of L. monocytogenes.
The FDA’s follow-up inspection determined the firm’s employees were not trained on safety or hygiene and found multiple instances of deficient sanitation practices related to equipment, utensils, employees. The agency determined that the firm did not respond appropriately to the positive samples at issue in this report and had not addressed the objectionable conditions that were observed by the FDA during a previous 2020 inspection. At the end of June 2021, the firm went out of business and no longer produces any products. The agency issued the firm a post inspection letter.
Over the past few years, there have been a few outbreaks and many recalls of dips and spreads. In FY2019, there were two outbreaks of Salmonella linked to Tahini (12 confirmed cases, 1 hospitalizations). In FY2017, there were two outbreaks of L. monocytogenes linked tohummus (31 confirmed cases, 26 hospitalizations, 3 fetal losses); one of the outbreaks may have contributed to 3 deaths. These past outbreaks and recalls are what prompted FDA to initiate this surveillance sampling assignment to survey the industry, perform follow-up inspections to positive samples to identify potential routes and sources of contamination, when possible, and ensure potentially contaminated product was removed from the retail market to protect public health.
In the absence of good manufacturing practices and implementation of preventive controls, pathogens can become resident strains which put a firm’s food products at increased risk of contamination from the manufacturing environment. The findings of this assignment suggest that Salmonella spp. and L. monocytogenes were not widespread in the multi-commodity RTE dips and spreads collected nationwide. Since the three L. monocytogenes positives were from the same manufacturer and collected on the same day and retail establishment, these are not representative of the entire population of cheese dips and spreads.
The FDA cautions against making inferences more broadly about the contamination or potential for contamination of RTE dips and spreads based solely on this assignment’s findings. However, the presence of contamination in the samples suggests the risk of contamination still exists. For example, from FY2017 through FY2022, there were a total of 22 recalls of dips and spreads due to potential Salmonella or L. monocytogenes contamination; of these hummus and cheese dips and spreads make up 64% of the recalls (10 hummus recalls, 4 cheese dips and spread recalls).
As stated in the “Findings” section, the FDA detected Salmonella spp. in one sample and L. monocytogenes in three samples out of the 747 collected and tested samples. All four of the positive samples were collected from retail establishments. None of the positive findings were linked to any known human illness, though, based on the agency’s WGS analysis.
The agency’s finding of three positive product samples and over 23 positive environmental samples all from one firm indicates that the controls that firm established were not effective at significantly minimizing or preventing L. monocytogenes from contaminating their RTE finished products. The large number of positive environmental samples found in the follow-up inspection indicates the firm had not implemented effective sanitation controls. The agency followed up to ensure the business implemented corrective actions to the previously identified deficiencies and no contaminated or potentially contaminated products entered commerce. The firm ultimately made the decision to discontinue their manufacturing operations.
As noted in the “Background” section, RTE dips and spreads can be contaminated with pathogenic bacteria and can support their survival and/or growth. Since refrigerated RTE dips and spreads do not undergo a ‘kill step’ prior to consumption, consumers should immediately refrigerate or freeze this commodity to reduce the potential for pathogen growth. Once a frozen RTE dip or spread is thawed for use, do not refreeze it. To reduce the risk of foodborne illness, consumers should read and follow the package instructions for use and storage on RTE dips and spreads. When serving RTE dips and spreads on a buffet, make sure to keep cold foods cold (at or below 40 °F) – by placing shallow food containers inside a pan filled with ice – and hot foods hot (at or above 140 °F) – by using chafing dishes, warming trays, or slow cookers.
[1] U.S. Refrigerated Spreads and Dips - Statistics & Facts | Statista
[2] U.S.: usage of dips for snacks and vegetables 2020 | Statista
[3] Plant-based dips retail sales U.S. 2019 | Statista
[4] The step where pathogens (e.g., Salmonella) are reduced or removed from a food product, usually by killing the pathogen. Executing a ‘kill step’ (e.g., cooking, frying, pasteurization) drastically reduces pathogens in food.
[5] A culture of microorganisms isolated for study