Evaluation of a sub-micron slurry ice system compared to chilled seawater to improve seafood safety and quality
Seafood perishability can be dramatically impacted by handling methods and chilling rates, which vary with the type of chilling method. The objective of this study was to evaluate chilling rates and cooling curves of sub-micron ice (NanoICE, Inc, Seattle, WA) compared to Chilled Sea Water (CSW). Comparisons included: cooling rates as impacted by ratio of sub-micron ice to fish (1:1, 1.5:1, 2:1); handling techniques of 2:1 sub-micron ice drained vs not drained; and handling techniques of 2:1 sub-micron ice (drained or not drained) vs 2:1 CSW (not drained).
Temperature was monitored by inserting thermocouple wires into the geometric center of whole fish and recording data every 15 seconds until product temperature increased above 4°C. There were no significant differences in time from the initial, equilibrated fish temperature of 18°C to 0°C between different ratios or between different handling techniques. The 2:1 ice:fish ratio of sub-micron ice kept the fish below 0°C and below 4°C significantly longer than 1:1 or 1.5:1 (p < 0.05). Non-drained sub-micron ice significantly chilled the product below 0°C and below 4°C than drained sub-micron ice or CSW (p < 0.05). Both drained and non-drained sub-micron ice kept fish below 0°C and below 1°C significantly longer than CSW (p < 0.05).
Results indicate that a 2:1 ice:fish ratio is more desirable than 1.5:1 and 1:1 ratios when cooling seafood products. Seafood products are also cooled to lower temperatures for a longer amount of time in sub-micron ice than CSW. Subsequent studies currently being conducted are comparing the shelf-life of Arrowtooth flounder (Atheresthes stomias) after 2 days storage in sub-micron ice or CSW. This study will mimic maximum holding times of fish at a processing plant in a chilling medium after off-load from the boat, but prior to processing.