Thermal process evaluation of tuna chunks in a formulated sauce

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The effect of various factors on the thermal process parameters and quality attributes of a formulated low-acid canned food (tuna chunks in sauce) were evaluated during thermal processing in a still horizontal batch retort. Sauce was formulated with vegetables, tomato paste, water, oil, corn flour and spices. The sauce was hot-filled (80°C) unto tuna cut into regular shapes and weight, vacuum-sealed in 307x113 cans and subjected to thermal processing. Process variables monitored were retort temperature (115°C,121.l°C and 125°C), solid to liquid ratio (50/50, 60/40 and 70/30) and can headspace (5mm and 10mm) Thermal process parameters (heating rate index, fh, heating lag factor, Jch, cooling rate index, fc and cooling lag factor, Jcc) and the resulting process lethality, Fo and cook value, Co were obtained from time-temperature data during processing for nine consecutive runs. Ball process time (BB) and heating times (Ht) were calculated using the Formula method. Quality attributes (crude protein, crude fat, ash, viscosity, colour and pH) were experimentally evaluated both before and after each run. Can headspace did not have any significant effect (P>0.05) on any of the thermal process parameters. Whereas solid to liquid ratio had significant (P<0.05) influences on fh, Jch and Jcc temperature on the other hand showed significant effect (P<0.05) on Jcc, Fo and Co were both affected significantly (P<0.05) by all the process variables. Ball process time ranged from 55.5-92.1 minutes. Average crude protein, crude fat and ash content in the canned samples were significantly lower than in the raw samples Quality attributes were, however, not adversely altered. The product was stable, commercially sterile and compared favourably with other canned fish products on the market.
A thesis submitted to the Board of Postgraduate Studies, Kwame Nkrumah University of Science and Technology, Kumasi, in partial fulfilment of the requirement for the award of the Degree of Master of Science in Food Science and Technology, 1999