Sous Vide Salmon Temperature Rebecca Cong Li1, Helen Heacock2, Lorraine McIntyre3 1 Lead Author, School of Health Sciences, British Columbia Institute of Technology, Burnaby, BC 2 Supervisor, School of Health Sciences , British Columbia Institute of Technology, Burnaby, BC 3 Contributor, British Columbia Centre of Disease Control, 655 West 12th Ave, Vancouver, BC

ABSTRACT Objectives: foods to a specific temperature and temperature control are often very difficult due to the frequent fluctuation of heat during the traditional dry heat (oven) cooking process. “” cooking of vacuum-packaged foods immersed in water provides constant and controllable time and temperature measurements throughout the process. Some sous vide style foods are cooked at temperatures that are lower than 60oC for short periods of time. This presents a recognizable concern including the survival of harmful as well as conditions that do not achieve pathogen during either the sous vide cooking or finishing () process. This research project investigated the time and temperature relationship for sous vide salmon in order to examine if pasteurization temperature was achieved if an additional searing step was performed. Methods: Temperature values were measured using data-loggers (SmartButton) for 30 samples of vacuum- packed salmon and cooked sous vide inside a circulating water bath at 50oC for 20 minutes. A one sample one tailed t-test was conducted to assess whether the internal temperature of salmon reached instantaneous pasteurization temperature of 70oC after a final searing step was performed at 220oC for 45 seconds. Results: Five out of the 30 (16.7%) salmon samples achieved 70oC after the final searing step. Statistical analyses were statistically significant, and the null hypothesis (Ho: measured internal temperature of salmon ≥ target temperature) was rejected with 100% power and a p-value of 0.00. Conclusion: These results indicate that salmon cooked sous vide style under 50oC for 20 minutes with a final searing step of 220oC for 45 seconds will likely not achieve pasteurization providing adequate pathogen reduction according to guidelines set out by BCCDC. For sous vide style cooked salmon cooked at lower temperatures for short periods, freezing for control of parasite hazards is recommended. Key words: Sous vide, salmon, temperature, SmartButton, public health

INTRODUCTION LITERATURE REVIEW For hundreds of years, chefs and food critics History of Sous vide around the world have been in search of Sous vide is defined as the “raw materials or better ways of preparing, cooking, serving raw materials with intermediate foods that are and preserving food. In order to create the cooked under controlled conditions of perfect food item, precise control of time and temperature and time inside heat-stable temperature is often required. Traditional vacuumed pouches”. Vacuum style of ways of cooking often involve high and cooking was first developed in 1969 in fluctuating temperatures, with little tolerance Europe. In the early 1970s, a French chef of error. Constant temperature control is named George Pralus discovered that the often very difficult due to the frequent vacuum style of cooking is able to better fluctuation of heat during the cooking preserve food’s texture and taste process. “Sous vide” cooking evolved as an (Schellekens, 1996). It has since been further attempt to provide constant and controllable developed through experimentations in order time and temperature measurements to determine the appropriate cooking time throughout the process. This research topic and temperature for various food items. was brought forward by Lorraine McIntyre at Sous vide is a new way of cooking that has the British Columbia Centre for Disease only been actively studied and used since the Control (BCCDC) as a continuation project 1990s in North America (Meyer, 2008). from a previous student project on sous vide Some researchers and food scientists have cooking that investigated whether safety analyzed the safety of sous vide cooking objectives were achieved during the sous vide through various temperature monitoring and cook step. microbiological analyses. The results of these studies vary depending on the food item and extracellular matrix and in connective temperature which foods are cooked under. It tissue”, shrinks at 60oC to 70oC and is is important to note that in the 1990s, sous converted to its denatured form, gelatin, at vide techniques were used primarily as a 80oC in meat (Lodish, Berk, Zipursky et al. means of preserving food in order to extend 2000). Research has shown that tenderness of shelf life. However, in the past 20 years, sous cooked meat products is directly related to vide has evolved as a cooking style to make heating to temperatures that disrupts dishes that are served immediately at collagen. This disruption, along with restaurants, catering events or homes moisture loss and myofibrillar hardening, are (Stringer, Fernandes & Metris, 2012). In the major contributors in decreased order to determine the safety of cooking sous tenderness of meat products (Turner & vide style, it is important to examine its Larick, 1996). As a result, sous vide cooking techniques, advantages, microbiological and is being adopted by chefs to produce temperature concerns, relevant legislation desirable tender food items through and public health significances. minimum disruption of collagen at low heat and preservation of moisture with vacuum Techniques of Sous Vide Cooking packaging. Sous vide, literally meaning “under vacuum” in French, involves slow cooking food items Temperature Control. In addition, sous vide in vacuum packages, submerged in hot water cooking guarantees the control of baths, with the purpose of preserving the temperature throughout the whole cooking food’s taste, texture and tenderness. The raw process through the use of reliable immersion food is first put into food grade plastic circulator in hot water baths. Immersion pouches, then vacuum-sealed. The vacuum- circulators are usually equipped with sealing step is important as removing air precious time and temperature controls that prevent the pouches from floating in the can achieve desired final cooking water bath, providing an even distribution of temperature, therefore chefs do not have to heat across the food item while cooked in the worry about overcooking the food item even circulating water bath under low heat. It also if it is left in the water bath for extended eliminates risks of recontamination during periods of time. A circulating water bath can storage and therefore increases the food’s also increase cooking contact surfaces so that shelf life (Baldwin, 2011). In addition, the heat can evenly distribute through oddly juice and seasonings are guaranteed to stay in shaped or very thick food items (Baldwin, the bag while the food is being cooked to 2014). Through the use of immersion preserve flavor. In food establishments, sous circulators, temperature swings of the vide foods are generally cooked in water circulating water baths are usually less than baths with immersion circulators or a 0.1oC, which contributes to precise combination of steam or forced convection temperature measurements and control oven in order to precisely control temperature (Baldwin, 2011). of the water bath (NSW Government Food Authority, 2012). There are several ways Economic Advantages. In addition to sous vide food items can be prepared. Details providing tenderness in food and precious on the steps involved can be found in later time and temperature control, sous vide sections of this paper. cooking also presents with noticeable economic advances. Due to the nature of sous Advantages of Sous Vide vide cooking, it can provide “better use of Tenderness. In order to assess the necessity labor and equipment through centralized of putting foods at more risk by cooking sous production” (Schellekens, 1996). It also vide style, it is important to note the requires less kitchen space for food advantages of this technique. Collagen, the production and adds variety and “major insoluble fibrous protein in the diversification to the restaurant (Meyer,

2 2008). If an establishment has well trained botulinum bacteria, is known to block nerve staff with good knowledge of sous vide functions and lead to respiratory and cooking and adequate equipment, savings can muscular paralysis. Foodborne be observed in labor cost of staff needed for resulting from contaminated and improperly food preparation. processed food can cause fatal conditions if not diagnosed immediately (WHO, 2013). As Sous vide products cost slightly more to a result, bacterial hazards are assumed to be prepare than food items that are prepared present in any of the sous vide cooking steps, using traditional methods. However, savings and critical control points must be in place to in labor and overhead can counterbalance this reduce and eliminate pathogens as well as increased cost. When sous vide products are possibilities of recontamination. used in restaurants and banquets, because employees do not need as much culinary Time and Temperature. Due to the nature skills, resources can be allocated to providing of sous vide cooking, food is usually cooked better service instead of production (Meyer, at lower temperatures in order to preserve and 2008). As a result, higher standards of enhance its quality. However, this practice services can help achieve increase in revenue raises food safety concern as it puts food at and popularity among other establishments. more risk while in the “danger zone”. Danger zone, described as the temperatures between Risks and Concerns 4oC and 60oC (40F to 140F), is when bacteria Microbiological. Similar to traditional can grow and multiply rapidly if left in that cooking methods, bacterial hazards can be range for prolonged periods of time (PHAC, introduced through raw material, improper 2012). In addition, temperature control or poor food handling can grow and proliferate even at 4oC practices. Examples of common bacteria (BCCDC 2014). Therefore, it is important involved are Staphylococcus aureus, E. coli, that sous vide food is kept either below 3oC and Salmonella spps (Foodsafety.gov, 2014). or above 60oC before and after cooking to Bacteria can multiply exponentially under the prevent bacteria growth. In order to reduce right conditions, which usually require warm pathogenic organisms in food, a safe internal temperature, moisture, and nutrients from the temperature must be achieved. For example, food. For food items that are cooked sous , veal and lamb are required to cook to at vide style, chilled, and reheated before least 63oC in order to consider it to be safe for service, pathogens such as Clostridium human consumption (PHAC). Pork and botulinum, Bacillus cereus and Clostridium poultry requires a slightly higher minimum perfingens are of most concern in sous vide internal temperature. In the case of sous vide, food items due to its ability to form spores food is usually cooked at temperatures that (Gilani & Media, 2014). Spore forming are lower than 70oC. As a result, the heating bacteria have the capability of surviving step, referred to as ”mild heat pasteurization”, under hostile environmental conditions, such requires enough time held at sufficient as heat and freezing, so harmful bacteria will temperatures in order to achieve continue to proliferate inside food items even pasteurization and kill all vegetative bacteria. after the initial cooking process. Therefore, time and temperature control is extremely important in the process of sous Cooking foods under vacuum provides the vide pasteurization. perfect environment for anaerobic bacteria to grow and thrive. Clostridium botulinum is of Seafood. Due to the delicacy of seafood, it is particular concern due to the anaerobic one of the most easily overcooked food items environment of vacuum packaged food and with traditional cooking techniques. its dangerous neurotoxicity in human when Therefore, sous vide styled seafood has consumed (Hyytia-Trees et al, 2000). gained wide popularity in recent years as it Botulism, the condition caused by the C. better preserves moisture, flavor and color of

3 the seafood, especially fish. However, due to then recombined with the sugars present to vulnerability of most fish items, restaurant produce color change and a “meaty” flavor chefs recommend cooking at temperatures of (Exploratorium, n.d.). Many chefs will using around 40-50oC in order to obtain optimal this method to achieve rare, or medium-rare texture and flavor of the fish (Picouet et al., , as this process was thought to kill 2010). This temperature will not achieve pathogenic organisms which only resided on sufficient pasteurization, as pathogens such the outside of the meat. However, due to the as Salmonella spp. will not be destroyed in process of meat tenderization, this step is no the process. Clostridium botulinum is also a longer effective in destroying surface concern as it is a naturally occurring marine pathogens that are traditionally the only organism. As stated previously, C. botulinum concern in solid cuts of beef. can grow and proliferate anaerobically even in low temperatures, therefore poses a great Legislations & Guidelines risk to sous vide seafood items if proper There is currently no legislation regulating temperature control is not in place. In sous vide cooking in BC or Canada. addition to bacterial concerns, certain fish However, the BC Centre for Disease Control species are also at risk for parasites from their Environmental Health Services and the BC natural environment. Parasites are heat Sous Vide Working Group developed the sensitive organisms; however, as sous vide “Guidelines for Restaurant Sous Vide fish does not usually achieve temperatures Cooking Safety in British Columbia” in 2014 required to inactivate parasites, additional in order to provide restaurant operators and freezing controls are generally required chefs guidance on safe sous vide cooking. (BCCDC, 2014). The guideline is based on recommendations and is not enforceable. However, under the Special Concerns Traditionally, solid cuts of Public Health Act, it specifies that “a person meats such as beef, are considered to be safe must not willingly cause a health hazard, or on the “inside” because microorganisms only act in a manner that the person knows, or reside on the outside of the meat slice and will ought to know, will cause a health hazard” be destroyed during the cooking or searing (2008). As a result, the guideline provides process. However, new techniques such as chefs and operators safe procedures on sous mechanically tenderizing meat have recently vide cooking that could prevent causing harm been introduced. This technique uses to the public. machines or tools specifically designed to pierce meat and break connective tissues in Guidelines for Restaurant Sous Vide order to improve the tenderness of meat when Cooking Safety in British Columbia. Due to it is cooked (Government of New Brunswick, the nature of the sous vide technique, 2013). However, this practice allows surface operators proposing to serve sous vide food contamination to enter the inside of the meat. in their establishments are required to ensure Due to increased risks of contamination for that processes meet public health mechanically tenderized meat, Health requirements. The facility needs to be Canada and Public Health Agency of Canada properly equipped to handle and monitor the recommends cooking temperature of steps and processes involved in preparation, minimum 71oC for mechanically tenderized cooking, chilling and serving of sous vide meat (2014). Sous vide cooking style rarely food. Equipment onsite may include achieves a high enough temperature to kill immersion circulators, water tanks, the pathogens as per recommendations. In appropriate thermometers, sous vide vacuum addition, is a well-known packaging bags, and vacuum packaging process used to produce flavor in cooked machines. Operators must consult with their meats and seafood. This involves cooking Environmental Health Officer before offering meat at around 150oC or higher to denature any food items cooked sous vide style proteins on the surface of the meat, which is (BCCDC, 2014).

4 Time and Temperature Relationship. According to the guideline, the minimum Equilibrium cooking is the point at which acceptable sous vide cooking temperature is “the internal temperature of sous vide food in 55oC for all meats, with the exception of 60oC an immersion circulator is at the same for all poultry, held at an established amount temperature as the water in the immersion of time. As with other food establishments, circulator”. Equilibrium cooking can also be the food service intending to serve sous vide referred to as the Come Up Time (CUT), style food must have a food safety plan which is the “period of time it will take for outlining the following criteria: food to reach a specific internal core • Time & temperature settings of the temperature” (BCCDC, 2014). After the immersion circulator internal temperature of the food reaches • Internal temperature of food for the sous vide CUT, it then needs to be held for a specified cook step and duration of hold time during period of time long enough to reach log pasteurization reductions of bacteria to achieve • Description of sous vide process in a food pasteurization. This is referred to as the flow chart “pasteurization time”. It is important to • Temperature and time combinations must record both CUT and pasteurization time as provide a 6.5log10 reduction for bacteria for this will determine if pasteurization was all sous vide pasteurized foods (poultry achieved after the food reached equilibrium requires 7log10 reduction) cooking. In addition, temperature must be measured after food is removed from pouches and During the cooking process, sous vide food before being served to customers to account items immersed in water baths undergo for any temperature changes (BCCDC, gradual increase in temperature until they 2014). achieve the same temperature as the water bath. For example, the temperature profile of Minimum Log Reduction. For all meats chicken breasts cooked sous vide style for 23 o cooked sous vide style, a recommended minutes at 66 C, shows a mathematical minimum of 6.5log10 reduction is required relationship between time and temperature. (minimum 7log10 for poultry) (BCCDC, The most rapid changes in temperature 2014). This means that the number of usually occur in the middle of the curve. The microorganisms needs to be reduced by internal temperature rises steadily once the approximately 3,200,000 to 10,000,000 in food is warmed up in the water bath, then order to be safe for consumption (Cleaning plateaus and slows down as food approaches Industry Research Institute, n.d.). For this to the target temperature in the immersion happen, food must be cooked to a certain circulator (BCCDC, 2014). When low temperature for a set period of time. For temperature sous vide food is cooked for a example, beef cooked sous vide style in the short time, it sometimes does not reach the water bath at 60oC will need to first reach the target temperature due to plateauing of temperature of the water bath, then be held at temperature at the end. Therefore, it is that temperature for at least 12 minutes to essential for temperature to be monitored achieve full sous vide pasteurization. Similar throughout the cooking process to ensure standards apply to seafood such as fish. food has time to reach the target Furthermore, fish that does not meet the pasteurization temperature before it is 6.5log10 reduction requirement during removed from the heat. heating will require additional freezing controls before cooking in order to be control Pathways and Critical Control Points. Sous for parasite hazards (BCCDC). vide cooking require precisely controlled procedures and monitoring of Critical Control Points (CCPs) throughout the process. Critical control points are the “steps

5 in food preparation processes where a hazard associated (2012). In BC, the guideline states can be controlled” (BCCDC, 2009). The that customer should be able to obtain common CCP among all pathways is to chill disclosure in the form of menu warnings, the food after vacuum packaging (prior to label statements, table tents and verbal cooking in circulating water bath). When all instruction by staff or the chef (BCCDC, of the CCPs are met and controlled 2014). Restaurants should take initiative in throughout cooking steps, the chance of sous providing disclosure to its patrons in order to vide preparation procedure causing protect public health and avoid possible foodborne illnesses is greatly minimized. liability issues.

Additional Requirements for Seafood. The Roles and Responsibilities. In terms of food BCCDC Sous Vide Working Group safety, both EHOs and restaurant staffs are recommends all sous vide style seafood to be responsible for keeping food safe for the cooked to full pasteurization to meet a public because inspection alone will not 6.5log10 reduction of bacteria. However, most eliminate risks and hazards from facilities. A seafood will not stand up well to higher written food safety plan is required for sous temperatures, so chefs will choose to cook vide products in order to aid EHOs and seafood in lower temperatures. In this case, restaurant staff in understanding the two additional controls are required to be in procedures and precautions of food place: processing in sous vide cooking. Proper food 1. Fish, with the exception of certain species safety precautions should be taken at every of tuna and farmed fish, must be pre- step along with regular monitoring of time frozen for parasite reduction. (BCCDC, and temperature during preparation in order 2010). to minimize any risks associated with sous 2. Consumer disclosures are recommended vide cooking. Restaurants serving sous vide via menu warnings, posted signs, and food should also offer frequent training to all verbal disclosure by staff or the chef employees who come in contact with sous (BCCDC, 2014). vide food to ensure that all staff are aware of the steps of the food safety plan and critical Public Health Significance control points are being met. Informed Customers. Sous vide style cooking done incorrectly poses a food safety PURPOSE OF STUDY issue because (1) foods cooked at lower A previous experiment was conducted in temperatures for extended periods of time 2013 by formal BCIT student using chicken (LTLT) potentially leads to growth of breast to examine if temperature reached microbial pathogens, and (2), foods cooked at pasteurization after cooking sous vide style. lower temperatures for shorter periods of Results showed that the chicken breasts time (LTST), may not achieve pathogen required an additional searing step in order to reduction requirements. Individuals at achieve the target pasteurization temperature increasing risk of food-borne illnesses should (Do, 2013). However, seafood is usually be informed of food cooked sous vide style cooked at lower temperatures and shorter when dining to avoid developing serious cooking time than other types of meat. complications. These individuals include: Therefore, the purpose of this research young children, the elderly, pregnant women project was to monitor the internal and any individual with lowered immunities temperature of a type of seafood (salmon) (Ministry of Primary Industries, n.d.). The cooked from raw using the sous vide NSW Food Authority’s Sous Vide Guideline technique in order to examine if combined states that patrons can only request to have effects of sous vide cook step will achieve the their food cooked essentially raw using the desired temperature for sufficient sous vide method if they are informed, healthy adults willing to accept the risks

6 pasteurization if a finishing (searing) step was performed.

METHODS Vacuum Packaging. Salmon portions were put into specific food grade plastic bags and Methods placed into the Komet Plusvac 20 for vacuum ACR SmartButtons. In order to setup packaging. The vacuum setting was set to Smartbutton for this experiment, maximum suction, as enough air must be TrendReader® for SmartButton software was evacuated to prevent air bubbles from installed on a PC computer. Following the developing during the heating process, which TrendReader® for SmartBotton Software will cause the package to float in water bath. Reference Guide, SmartButton set up was as Sealed salmon packages were labeled and follows: stored in the ice water bath until needed Data collection interval: 1 minute (MacDonald, personal communication, Memory usage: Stop when full 2014). Start time: For the purpose of this project,

start time was set to 30 minutes prior to start Immersion Circulator. Calibration of process. immersion circulator was carried out before initiating the cooking process using a probing Fish Preparation. Large packages of whole thermometer as the control. After calibration salmon were taken out of the cooler, de- was completed, the immersion circulator was skinned, cut into portion sizes, scaled, placed clamped onto the short side of the water tank in plastic bags and put into an ice bath until filled with water. Temperature was set to used. A small incision (approximately ½ 50.8oC as calibration showed that the inch) was made on each salmon portion and immersion circulator was 0.8 degrees off SmartButton was inserted into the thickest from the control thermometer. Fish packages part of the fish. Time of insertion was were not placed inside the tank until display recorded in the notebook. on immersion circulator showed a

temperature of 50.8oC.

Experiment Procedure. Vacuum packaged salmon packages were removed from ice and put directly into the hot water tank after immersion circulator displayed the target temperature of 50.8oC (Figure 1). Throughout the cooking process, the water bath was monitored to make sure that the packages were circulating in the water bath in order to achieve consistent cooking temperature. After the timer went off, salmon packages were removed from the tank and time of removal was recorded on the notebook. Time was recorded again as packages were opened and the fish samples were transferred to a pan for the searing step (Figure 2). Each sample of salmon was seared o in the pan 220 C for 45 seconds. Fish samples Figure 1: Immersion circulator with vacuum were then transferred to a plate and allowed packaged salmon in circulating water bath to sit for another 3 minutes before SmartButtons were removed. At the end of

7 the experiment, SmartButtons were Figure 2: Searing step setup with searing pan, connected to the computer via USB interface gas stove, salmon, and infrared thermometer cable for data retrieval.

RESULTS AND STATISTICAL ANALYSES Data collected throughout this experiment were temperature values and were therefore continuous numerical data. All samples reached an internal temperature equivalent to the water bath (50oC) within 20 minutes. However, only five out the 30 samples reached the target temperature of 70oC after the final searing step. Figure 3 illustrates the temperature of the SmartButton as it a) drops when the fish is put into a ice bucket, b) rises as the salmon is cooked in the circulating water bath (at 50oC), c) peaks and holds at the temperature of the water bath, d) rises abruptly when the fish is put into a pan for searing (at 220oC), e) falls abruptly when fish is removed from the pan and set aside to cool to room temperature.

Figure 3: Temperature data graph extracted from SmartButton (Small 30g serving size)

Descriptive Statistics Below are descriptive statistic values:

Descriptive Statistics Values Mean 61.7 oC Median 61.25oC Standard Deviation 5.90oC Mode N/A

Inferential Statistics 70oC) after final searing step to achieve Null and alternate hypotheses of this instantaneous pasteurization. o experiment were as follows: Ha: Salmon cooked sous vide at 50 C for 20 o o o Ho: Salmon cooked sous vide at 50 C for 20 minutes will not reach 70 C (< 70 C) after minutes will reach greater or equal to 70oC (≥ final searing step to achieve instantaneous pasteurization.

8 bacteria (2011). Another study by Gonzalez- All 30 temperature data points were Fandos, E., et al noted that Staphylococcus compared to a standard temperature as aureus, Bacillus cereus, Clostridium specified in the sous vide guideline to see if perfringens and Listeria monocytogenes were adequate temperature was reached. not found in any samples of salmon cooked Therefore, a one-sample one-tailed t-test sous vide at 90oC for 15 minutes and stored was used to determine if null hypothesis can at 2oC for 45 days. However, the sensory be rejected (NCSS, 2012). A one tailed t-test characteristics and quality of the salmon were was used because the temperature values greatly diminished (2005). Seafood, among collected were not expected to exceed the all other food items, is of special concern as target value. The p-value was set at 0.05. Data it is often cooked at lower temperature for collected was normal (cannot reject shorter time in order to preserve its quality. normality) for all three tests of assumption During an interview with a chef who is based on a sample size of 30. familiar with the procedures of sous vide, it was noted that even at the specific time and Interpretations of Data. One-sample T-test temperature of this experiment (50oC for 20 report was generated from NCSS for peak minutes), the salmon was considered to be temperatures AFTER final searing step. Test “overcooked” and not aesthetically appealing of assumptions showed that data was for service to customers (MacDonald, normally distributed under all assumption personal communication, January 2015). tests. Therefore, the One Sample T-Test was According to the Restaurant Sous Vide read (Heacock, 2014). The probability level Guideline by BCCDC, the minimum (p-value) of median <70oC was 0.00 with temperature requirement for sous vide is power of 1.00, which suggest that the results 55oC (2014), but chefs may be putting food were statistically significant (null hypothesis items at risk by cooking at much lower was rejected). Therefore, it can be concluded temperatures in attempt to achieve aesthetic that salmon cooked sous vide style at 50oC appealing appearances. for 20 minutes was not sufficient to achieve instantaneous pasteurization of 70oC with an In relevancy to the results of this experiment, additional searing step for 45 seconds. sous vide fish failing to achieve pasteurization temperature during cooking is required to comply with BCCDC’s seafood DISCUSSION controls. Although these standards have been Sous vide and Foodborne Illnesses (FBI). proven to destroy parasites in fish for the Based on the results of this study, salmon service of sushi and sashimi products, it does cooked at the specific conditions of this not account for bacteria and other pathogens experiment did not achieve pasteurization that may contaminate the fish during temperature even with a finishing (searing) preparation (BCCDC 2014). Vikraman’s step. Although the author did not find any study of sous vide salmon cooked under documented outbreaks related to sous vide similar conditions observed bacteria numbers salmon, there are outbreaks associated with reducing from four million (4,677,351) to restaurant sous vide food currently under only two million (2,187,761) after cooking investigation. Concerns regarding these (2011). If pathogenic bacteria were among outbreaks mostly revolve around time and the two million bacteria left on the salmon temperature abuse of sous vide prepared after cooking, it is likely that this will cause foods (McIntyre, L., personal foodborne illnesses in patrons consuming this communication, Feb 12, 2015). According to fish. Contrasting to sushi and sashimi a previous study by Vipin Vikraman, salmon products, sous vide fish usually does not cooked at 53oC for 20 minutes only achieved appear to be raw or undercooked. This may approximately 1.0log reduction in inoculated mislead consumers in thinking that the food they consume is fully cooked.

9

Fluctuation of Water Bath Temperatures. Research on Restaurant Sous Vide. In Vikraman’s study, it was noted that the Although sous vide has risen in popularity water bath temperature fluctuated as much as around the world, it has yet to become a 8-10oC in 15-20 minutes interval while food customary cooking style for most restaurants. was cooked in the circulating water bath. This However, it is predicted that with increasing was mainly due to adding large amount of numbers of establishments adding sous vide refrigerated foods during the process of food items to their menus, risks of foodborne cooking items already in the water bath illness outbreaks are also on the rise (2011). Similar effects were noted during the (McIntyre, personal communication, Feb 12, process of this experiment, although 2015). As more and more restaurants are temperature fluctuations were only between adopting sous vide style recipes for their 0.5-1.5oC, as this experiment was done under menus, the demand for knowledge on the a controlled environment to minimum risks and safe handling procedures of sous fluctuation of temperature. However, during vide cooking is also increasingly high. rush hours at busy establishments, chefs may Currently, many of the restaurants serving be unintentionally lowering the temperature sous vide food items are higher quality, fine- of the water bath by cooking too many dining establishments. Whether these refrigerated items at once in the circulating establishments have better food safety water bath. standards in cooking sous vide is yet to be determined. Many of the past research studies The immersion circulator used for this on sous vide were microbiological ones based experiment was widely used by professional on cook-chill-store pathway after cooking chefs and some food processing food at high heat. There is very limited establishments. However, other equipment research available on the effects of sous vide frequently used for sous vide cooking may cooking in the context of restaurant served also play a role in the fluctuation of water foods. Do’s research on sous vide chicken bath temperature, as steamer ovens have breast showed that chicken breast cooked shown to provide relatively less even heat sous vide at 66oC for 23 minutes only distribution compared to immersion achieved pasteurization temperature after a circulators (Sherd & Rodger, 1995). As searing step (2013). However, the results of mentioned in the literature review, one of the the current experiment indicated that salmon main advantages of the sous vide process is cooked at 50oC for 20 minutes with an that the food item can be cooked at a specific additional searing step was not able to lower temperature to achieve pasteurization achieve pasteurization. It is evident that more as well as tenderization (BCCDC, 2014). research is required to determine the specific Variation in equipment and adding of time and temperature relationship and risks refrigerated samples may result in failure to associated with each food item in order to achieve pasteurization as restaurants may not remediate for possible food safety concerns. be measuring temperature constantly, or at all, while more frozen food items are added LIMITATIONS in an effort to speed up the production Salmon Portions. Due to budget and time process. Therefore, it is important that constraints, this experiment was done with restaurant operators and chefs maintain salmon portions of approximately 30 grams constant temperature in the circulating water each, which were relatively smaller than bath in order to achieve appropriate come-up normal serving sizes. As such, smaller pieces and pasteurization time for the food items. It of salmon may have heated up faster in the is important to note that both come-up time water bath, reaching Come-Up Time faster and pasteurization time must be satisfied in than larger pieces. However, smaller portions order to consider the food to be fully of salmon still resulted in under-cooked (not pasteurized. fully pasteurized) salmon after the searing

10 step, which suggests that bigger pieces of onto the frying pan for the final searing step, salmon under the same conditions will also the temperature dropped slightly (b), and the not reach the target pasteurization subsequent searing step (c) was not long temperature. The researcher was able to test enough for the temperature to rise to higher two samples of salmon weighting 120 grams than around 46oC. This suggested that the each as an additional experiment. Figure 4 larger portions of salmon would need to be in shows a data collection graph for a larger the water bath for longer than 20 minutes in portion salmon cooked under the same order to reach the target temperature of the condition of the smaller pieces. The graph water bath. Also, further testing is required in indicates that the maximum temperature only order to examine if the searing step will make reached 48oC after being in the water bath for a statistically significant difference in 20 minutes (a), comparing to the target pasteurization temperature for larger portions temperature of 50oC. In addition, while the of salmon. salmon piece was prepared to be transferred

Figure 3: Temperature data graph extracted from SmartButton (Regular 120g serving size)

Minimum Data Collection Interval of This was done to minimize inconsistencies in SmartButtons. SmartButtons were chosen temperature recording, as temperature will for their compact size and accurate continue to rise for a few seconds after each temperature measurements. However, the sample is removed from the heat. shortest interval of data collection that can be set-up on the TrendReader® program was in Final Searing Step. The final searing step 1-minute intervals. Because the searing step was completed on a small pan on a portable was only performed for 45 seconds, there gas stove. As such, there may have been may have been discrepancies during peak temperature fluctuations during this step. temperature recording. For example, if the Although an inferred thermometer was used salmon was put into the searing pan at 21:50, to ensure that the pan was at 220oC prior to and taken out of the pan at 22:35 (after 45 placing each sample onto the pan, the seconds of searing), the SmartButton would position of where the sample was placed have measured the temperature of the salmon could have made a difference in transfer of only after 10 seconds of searing heat. The researcher attempted to minimize (SmartButtons takes the reading at 22:00 for temperature differences by placing samples 1-minute intervals). This could have been as closely to the center of the pan as possible, avoided if the searing time was increased to however, limitations in equipment and one minute instead of only 45 seconds, but personnel could have caused unintentional this may result in overcooking of the salmon. temperature fluctuations during the As an attempt to minimize this limitation, experimental process. each piece of salmon was seared for 45 seconds, and then taken out of the pan and set RECOMMENDATIONS aside for at least 3 minutes before the Based on this study, salmon cooked at the SmartButton was removed from the salmon. specific conditions did not achieve

11 pasteurization with an additional searing step. responsibility of informing its customers they Therefore, it is recommended that restaurant may be consuming undercooked or serving sous vide items take measures to essentially raw foods. This is of utmost prevent foodborne illness from occurring in importance for the “at risk” group, which their establishments. As such, Environmental includes young children, the elderly, Health Officers have the duty of helping pregnant women and people who are operators throughout this process so that immune-compromised, as they are at more public health can be protected. risk of developing adverse health effects resulting from foodborne illnesses. Public Health Significance. In recent years, Advisories can be communicated through efforts were put into encouraging disclosures verbal communication, menu labels or table when consuming undercooked or essentially tents. It was also noted that some restaurants raw food items and the potential for increased serving sous vide food items do not label food risk of foodborne illnesses. An example of a item as “sous vide” on their menus (Heacock, successful initiative is the customer personal communication, Feb 5, 2015). The disclosure program for raw or undercooked researcher noted a restaurant in Vancouver oysters implemented within the Vancouver serving sous vide sablefish only labeled the Coastal Health Authority region since 2007 menu as “Smoked Sablefish”. This may be (VCH, 2007). However, the effort was not misleading to customers as they are not aware successful for sous vide items, as restaurants that the fish was prepared sous vide. Having are generally reluctant in putting disclosures customers informed will not only give on their menus (McIntyre, L., Personal customer information regarding the risks they communication, Feb 12, 2015). As such, are taking with the food they consume, it can Environmental Health Officers (EHO) should also help the restaurant to avoid legal issues work with restaurant operators and educate regarding foodborne illnesses caused by them in the specific risks associated with sous potentially under-cooked foods. vide food items. Each category of food item prepared using sous vide (ie. meat, poultry, It was noted throughout the study that seafood, eggs) should have a food safety plan restaurants are often not up-to-date on their dedicated to the specific procedure of that equipment calibrations. The immersion item. The critical control points (CCPs) circulator used in this experiment was never which contain specific time and temperature calibrated, nor did the chef know the combinations that are required for achieving procedures of calibration. As sous vide adequate pasteurization should be clearly cooking requires strict time and temperature identified and adhered to by the chef or other control in order to ensure food safety parties responsible. For cook-chill-reheat throughout the process, chefs and restaurant sous vide foods, the reheat temperature and owners are strongly encouraged to obtain and duration should also be recorded, as it may be use accurate temperature measurement the sole pasteurization step. EHOs should devices throughout the cooking process. also familiar themselves with the Restaurant Written procedures should be available for all Sous Vide Cooking Safety Guideline staff as references when it comes to produced by BCCDC in order to better serve pasteurization temperatures for different food the restaurant operators throughout this items. Good resources may include the process. Internal Temperature Holding Times for Meats and Poultry chart produced by If food items do not achieve pasteurization BCCDC and other food safety plans throughout the sous vide cook step, in produced for specific food items. In addition, addition to ensuring that the fish comes from it is important that chefs are constantly approved sources that meet the monitoring internal temperature of foods to corresponding seafood control requirements, ensure adequate pasteurization was achieved. restaurant operators should also take the

12 Lastly, the most effective approach to As technology advances, better temperature minimizing foodborne illness in restaurants monitoring equipment may be available. and other establishments is adequate Future research can be conducted to compare cleaning, sanitation, and safe food handling the efficiency and appropriateness of practices. Even when food is cooked at different temperature monitoring devices to adequate temperature for sufficient amount better obtain accurate internal temperature of of time, it is still prone to cross- sous vide food. contamination from multiple handling procedures. Most of the time, foodborne CONCLUSION illnesses are not caused by one inadequate According to the results of this study, salmon cooking step, but rather a combination of cooked at 50oC inside a circulating water bath poor cleaning and sanitation, as well as a lack for 20 minutes with an additional searing step of knowledge or awareness on safe food at 220oC for 45 seconds did not achieve handling. Therefore, it is important that appropriate target pasteurization temperature restaurant owners and operators work (70oC). Therefore, salmon served under this together with the local health authority to condition must undergo adequate freezing actively prevent causing harm to the public control for parasite reduction (-35oC for 15 by complying with food safety procedures hours or -20oC for 7 days) (BCCDC, 2014). and adapting relevant food safety Safe food handling procedures should be recommendations. emphasized to minimize cross contamination of the fish as the condition of the sous vide FUTURE RESEARCH SUGGESTIONS process favors microbial survival and Due to time and resource constrains, this multiplication. Also, restaurants serving sous experiment was conducted on smaller pieces vide food items are encouraged to inform of salmon (30g) compared to regular serving their customers, especially the “at risk” sizes (approximately 120g). Further research group, about the risks associated with can be performed on larger sizes of salmon to consuming undercooked or essentially raw examine the come-up time and pasteurization food. time and temperatures in order to confirm the results of this study. ACKNOWLEDGEMENTS The author would like to thank Helen As this study examined the time and Heacock from BCIT for providing ongoing temperature relationship of sous vide salmon, support, advice, and guidance throughout the other types of meat or vegetable can be course of this study; Lorraine McIntyre from examined to see if the results of this study is BCCDC for providing resources, support and transferrable for other food items cooked guidance throughout this project; Also Chef sous vide under similar conditions. Tobias MacDonald from Vancouver Community Collage for providing the Sous vide usually involve vacuum packaging kitchen space, personnel and necessary the food item of interest and cooking in hot resources and equipment for this project. water bath. There are concern regarding the plastics that are used and whether it poses a COMPETING INTEREST chemical risk to the food if cooked in the The authors declare that there are no water bath for long periods of time. Future competing interests. research can be conducted to examine alternative methods of sous vide, for example, examining heat transfer for fish REFERENCES cooked in a sealed jar compared to vacuum- ACR Systems Inc. TrendReader for sealed bags. SmartButton: Software reference

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