Thermal Food Processing

Thermal Processing of Fishery Products 237
(16°F) and surimi-based products pasteurized at an internal temperature of 90°C
(194°F) for at least 10 min. The control of later refrigeration is critical for the
safety of these products.
Sous vide is a French term that means “under vacuum.” Sous vide involves the
cooking of fish inside a hermetically sealed vacuum package. Sous vide technology
or cooking under vacuum defines those foods that are cooked in stable containers
and stored in refrigeration. Because these products are processed at low temperatures
(65 to 95°C), the sensorial and nutritional characteristics are maximized in
comparison with the sterilized products. The final product is not sterile and its shelf
life depends on the applied thermal treatment and storage temperature. Because
the pasteurization does not produce the commercial sterility, the final fish product
requires refrigerated storage. There are not many studies on the effect of sous vide
pasteurization on the quality of seafood, and more research is necessary.
8.2.1 THERMAL PROCESSING FOR CANNED FISHERY PRODUCTS
The heat treatment applied in sterilization of canned fish manufacture is aimed
to eliminate pathogenic microorganisms, together with others that cause spoilage
during storage. The bacteria vary in their resistance to moist heat, and some can
form resistant spores. Among the spore-forming microorganisms, C. botulinum
types A and B is the most heat resistant, constituting a potential health hazard.
For low-acid products with pH values greater than 4.5, such as canned fish, the
anaerobic conditions are ideal for growth and toxin production by C. botulinum.
Therefore, its destruction is the critical parameter used in heat processing. It has
been established that the minimum thermal process sufficient for safety should
achieve 12 decimal reductions in the population of C. botulinum spores; this is
known as a 12-D process. For such heat processes, the probability of C. botulinum
spore survival is 10 −12 , or one in a million million. This probability of survival
is commercially acceptable and does not represent a significant health risk. When
the thermal process is sufficient to fulfill the criteria of safety and prevention of
nonpathogenic spoilage under normal conditions of storage, the product is “commercially
sterile.” Figure 8.1 and Figure 8.2 show the calculation of z values and
F for the canning of mussels performed at our pilot plant.
There are infinite numbers of time–temperature combinations that can produce
commercial sterility, but it is important to establish a combination that
provides a final product that retains quality attributes. For this reason, the optimization
of thermal processes for nutrition and quality retention is necessary. In
this chapter we have summarized the main aspects affecting seafood components
subjected to thermal stress.
8.3 PROXIMATE COMPOSITION OF FISH MUSCLE
The muscle of fish contains a series of chemical constituents as proteins, lipids,
minerals, and vitamins. Around 60 chemical elements are present in fish muscle:
75% is oxygen, 10% hydrogen, 9.5% carbon, 3% nitrogen, 1.5% calcium, and
other traces of elements.