Time, Temperature, Travel -----a quality balancing act

Transcription

1 Time, Temperature, Travel -----a quality balancing act Steve Otwell from the University of Florida s Aquatic Foods Product Laboratory, analyses the effect of time and temperature on fish during international transportation, and reports on new technological methods designed to monitor both A key challenge in refrigerated seafood processing and distribution is the accurate monitoring of the combined effects of time and temperature on product quality and safety, From the moment of harvest and death, fish quality continues to decrease at rates dependent on exposure, time and temperature. For chilled fish the deterioration rate, or typical pattern of spoilage, is rapid relative to other meats. Refrigerated fish are more susceptible to spoilage due to the naturally higher proportion of non-protein nitrogen components in the flesh that promote bacterial growth. In general, a properly refrigerated fish held at constant temperatures below 1 deg C (33.8 deg. F) will display top quality attributes for 6-8 days, and will remain 'acceptable' with secondary, grade 'B' quality attributes for days. Any increases in storage temperature will decrease this average shelf life. Fluctuating and prolonged exposure at elevated temperatures stimulates chemical reactions (autolysis) that reduce product flavors, color and texture while allowing further bacterial growth. Advanced bacterial growth can include potential pathogenic varieties, or production of natural toxins that can result in food poisoning. For example, one of the more common seafood poisonings around the world is due to time and temperature abuse in handling that is associated with certain bacterial production of histamines in the edible meat of some oily fish species such as tuna and mahi mahi. S-228 Page 1

2 Sensitech temperature monitor, Template Mindful of these concerns, commercial interests and regulatory authorities are increasing their scrutiny for time and temperature controls, This trend was most significantly demonstrated by the recent mandate for HACCP (Hazard Analysis and Critical Control Point) inspection programs for domestic seafood processors and foreign processors exporting to the USA. The new HACCP regulations administered by the U.S. Food and Drug Administration (FDA) become effective on December 18. Specific HACCP time and temperature concerns for various products and processes are outlined in the FDA Fish and Fisheries Product Hazards and Controls Guide This requirement calls for monitoring and record keeping to ensure compliance with established critical limits for food safety that also influence product quality during harvest and distribution. These limits and accompanying good manufacturing practices include specific storage and handling temperatures. A similar scenario has been issued by a Technical Advisory Group for the US Department of Agriculture (USDA) on product 'transportation' relative to HACCP concepts. The USDA report advocates temperature controls during transport of seafoods and similar items. The Aquatic Food Products Program at the University of Florida teamed up with the Chilean Salmon Association to utilise innovative time temperature monitoring devices to accompany shipments of farmed Atlantic salmon from Puerto Montt, Chile, through retail commerce in Florida. The intent was to demonstrate the utility of simple, inexpensive monitoring devices for refrigerated fish shelf life during ground and air transport, and S-228 Page 2

3 subsequent handling, storage and display. VITSAB's TTI (ampoule tabs) as packaged with a salmon shipment from Chile Atlantic salmon (Salmo salar) cultured at Puerto Montt was chosen for initial trials due to its quality reputation through controlled production and harvest, and its evident growth in worldwide fresh exports. Salmon fillet imports to the USA in 1995 were valued at $51 million, compared with less than $1 million in 1994 Chile accounted for more than 85 per cent of the imported fillets. This trend was predicted to continue through 1996 and The cultured salmon were harvested and processed in June during the winter in Chile and the warmer seasonal temperatures (28-34 deg C) in Florida. Fresh, skin-on fillets were packaged and shipped by traditional methods and routes. The chosen pack was a polystyrene box (inside dimensions: 80cm x 20cm x 16.5cm with 2cm wall thickness for box and lid). Each box contained six skin-on, 7-6 lb fillets. The fillets were individually wrapped in plastic, then layered in the box over a double film of frozen gel packs lining the bottom of the box. The lid was sealed tight with tape. The sealed boxes were then crosschecked in layers on a pallet with three boxes per layer. Time from harvest to sealed boxes was less than 24 hours Twelve of the boxes from one pallet were equipped with the VITSAB's visual time temperature integrators (TTIs) provided by VITSAB. Sweden. The TTIs were placed about S-228 Page 3

4 the inside perimeter of the boxes. These integrators were thin plastic ampoules, approximately 2mm thick, with a diameter of 12mm and with an adhesive mount to secure them to the polystyrene surface. The ampoules contain the components for an enzyme lipid reaction that causes a ph change in the solution evidenced as a color change. The chemistry of the color change depends on the enzyme concentration, the nature of the enzyme substrate and the combination of time temperature exposure. Increases in exposure accelerate the color changes. The enzyme solution and substrate suspension in the TTIs are separated by a barrier which can be broken by slight surface pressure. This step is carried out during the packaging process. The end-point of the indicator, which was custom-formulated to signal progressive losses of acceptable fish quality, is a green to yellow color change. VITSAB time temperature indicators are currently available with activation energies (Ea) in the range of 12 to 30 kcal/mol. This Ea factor relates to the ram of color changes during different temperature exposures. Three different VITSABs were used in this study to mimic progressive quality changes in the salmon fillets through distribution, storage and retail display (see table). The listed days indicate the time of color change from green to yellow at the respective, constant temperatures. S-228 Page 4

5 Map depicting salmon source and route Although the need for temperature controls for seafood Quality Is not a new concern, there is emerging interest in better and mandated controls. The cost effective criteria for these controls include simplicity, accuracy and immediate response in daily commercial practice. Emphasis is on prevention of problems rather than explanations after the problem is discovered. New time temperature integration and recording devices are available to suit this situation. VITSAB no 0 deg C 5 deg C (32 deg F) (41 deg F) days 4.9 days days 6.6 days days 9.6 days Note: The TTI could be made as single ampoules, or multiple ampoules on one tab. In keeping with commercial practices, the boxes were transported by truck to Santiago, Chile, for air transport to Miami where they were intercepted by the investigators for ground transport to Gainesville, Florida, and subsequent storage in a variety of refrigeration schemes. A portion of the fillets was also stored in Winn-Dixie supermarket display ease6 for daily observation. The thermal history of the boxes was recorded by TempTale data loggers, which are continuous temperature and time recorders based on a precision resistance thermistor with self-calibrating circuits. They are calibrated to +/- 0.2 deg C between O deg C and 70 deg C. The recordings are downioaded to a computer in Windows format for actual readings and graphs. TempTales were placed inside all boxes positioned at the top and middle of the layers of fillets. Six boxes were nine equipped with TempTales fastened to the outside end of the boxes to monitor temperature changes in the environments surrounding the boxes. S-228 Page 5

6 The time temperature patterns recorded by the TempTale data loggers showed that the internal box temperatures warmed from approximately 2 des C (35 deg F) in Chile to approximately 7 deg C (45 deg F) before arrival in Gainesville. The packaging and refrigerant (gel packs) provided for these flesh fillets appeared sufficient to reach Santiago, but began to lose cooling capacity during transport to and beyond Miami. Despite the slight temperature Increase during transport, there were no discernible differences in the sensory attributes among the boxes of the raw fillets when they arrived in Gainesville. All fillets appeared in excellent condition and all TTIs were 'green'. The internal meat temperatures as measured by a hand held probe thermometer indicated that the fillet temperatures on arrival in Gainesville ranged from 1 deg C (33 deg F) to 9 deg C (48 deg F) depending on the location of the fillets in the boxes. Fillet temperature was colder towards the bottom of the box where the layer of frozen gel packs was partially thawed. This pattern of temperatures was consistent for all boxes as evidenced by comparison of the TempTale data loggers plaid in the top and middle of the boned fillets. The elevated external box temperatures recorded in Santiago and Miami air freight had contributed to a thermal gradient, yet consequences in terms of product quality were not evident in the initial sensory evaluations. Following initial product examinations, fillets samples were placed in four separate storage schemes: 2 deg C (35 deg F), constant 7 deg C (45 deg F), constant 2 deg C for 24 hours, then 13 deg C (55 deg F) for 24 hours before returning to 2 deg G, constant 2 deg C for 48 hours, then 13 deg C for 24 hours before returning to 2 deg C, constant S-228 Page 6

7 a: Time-temperature profile provided by Sensitech s TempTales during salmon shipment from Chile b-e: Sensory ratings and TTI color changes for cultured Salmon fillets from ChiIe S-228 Page 7

8 The first storage scheme was considered ideal, the second storage scheme was abusive, and the third and fourth storage schemes tried to simulate possible abuses during further handling or transport. All fillets were stored in covered, plastic totes. The original TTIs activated during packaging in Chile were relocated in the totes to accompany the fillets during this simulated retail storage. This storage method was more abusive than typical retail displays that would use ice. Product consequences were monitored daily relative to color changes in the TTIs. Monitoring involved sensory assessments, aerobic bacteria counts, and objective measures for changes in product moisture, water activity and color. All monitoring was based on a series of preliminary trials with earlier purchases of similar fresh cultured salmon stored at the same ideal and abusive temperatures. This sensory development work incorporated quality assessment guidelines outlined by the Fisheries Council of British Columbia, the US National Marine Fisheries Services grading standards for salmon the FAO Codex Alimentares Commission's standard for quick frozen gutted Pacific salmon, and the trade standards used lot product in Chile. The resulting sensory scale was referenced by 4-6 graders who pooled their ratings-per-day-per-storage scheme. 'The judges monitored changes in general appearance (Gen), and muscle color (Me), gaping (Gap), Texture (Tex) and odor. Ratings from 14 would be con-sidereal most desirable or the so-called grade 'h' product. Ratings from 4-6, grade '13' product, would be acceptable, but lee4 desirable. Ratings greater than 6 were objectionable and approached rejection. Sensory ratings for general appearance, meat color and odor were the most telling for storage consequences. Naturally, a longer shelf life was scored for fillets stored at 2 deg C (35 deg F). These fillets remained in the grade 'A' category for at least 5 days' storage and remained acceptable, or grade 'B' for at least 7 to 8 days. In contrast, the fillets constantly stored at 7 deg C (45 deg F) exceeded the acceptable grade 'B' quality after 4 and 2 days storage, respectively. During the constant temperature storage, the color changes in the three customformulated TTIs simulated the sensory ratings. For example, the color change for 2004 tabs was evident after 4-5 days' storage at 2 deg C, when sensory ratings increased to the end of product grade 'A'. S-228 Page 8

9 Similarly, the 2007 and 2010 tabs displayed color change on days 6 and 9-10, respectively, which corresponded with the sensory judgments for product grades 'B' to rejection. The 2004 and 2007 tabs Indicated thermal abuse at 7 deg C and unacceptable product by day 4-5 as denoted by the accompanying 2010 tab. Similarly, the TTls simulated the product consequences caused by temperature variations during storage. Changes in the formulated tab colors accounted for the initial storage time at 2 deg C. In the simulated abusive storage, the tabs changed color after the product wm exposed to 13 deg C. Although the spoilage patterns differed depending on when the fillets were exposed to 13 deg C, the TTIs mimicked the resulting quality changes per day. Similar observations were noted in the supermarket displays. Seafood managers with a simple introduction to the interpretation of the TII color changes were better able to judge remaining shelf life. These judgments would allow for market decisions to retain or adjust pricing to move product, and to segregate product according to quality. The VIISAB time temperature integrators effectively monitored the shelf life consequences for fresh, cultured salmon fillets during transport and refrigerated storage. The TTI color changes simulated sensory judge-meats and objective measurements for product quality as influenced by constant and variable changes in product temperature. Use of a series of TTI formulations to provided variable response times per storage temperature simulated the progressive loss of product quality during storage and would assist market decisions. Likewise, the use of the Sesitech TempTale data loggers during transport of the fresh fillets provided a complete thermal history of the product from initial packaging through all routes and means of transport. Thermal histories recorded during transport of the fillets from Chile to Florida in June indicated current packaging and transport conditions provided adequate refrigeration below 5 deg. C until the fillets arrived in Miami, but additional refrigeration or repackaging would be advisable to assure adequate refrigeration after arrival in Miami, and during subsequent transport and storage. This Information is essential to assuring seafood product quality and safety. Following completion of the salmon shipments, additional trials were conducted for flesh Mississippi cultured catfish and mahi mahi harvested in Costa Rica. Again, the VIISAB time temperature integrators mimicked shelf life consequences through shipments and retail storage. S-228 Page 9

10 The TTI technology has proven useful in buyer-supplier plans to assure product quality and safety through time temperature controls. S-228 Page 10