Effects of Sulfur Dioxide on Food Quality - Food Shelf Life Stability: Chemical, Biochemical, and Microbiological Changes - page 270

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FIGURE 8.7 Calculated concentrations of free acetaldehyde as a function of total S(IV)
concentration in mixtures containing various total concentrations of acetaldehyde. Data were
obtained using a dissociation constant of acetaldehyde hydroxysulfonate of 2 × 10 -6 mol l -1 .
Total acetaldehyde concentrations were 20 ppm (——), 50 ppm (------), 100 ppm ( ...... ).
flavor stability of such a food may be degraded. It is well known that the S(IV)-
content of most sulfited foods decreases with time, particularly when beverages are
exposed to air repeatedly. Since hydroxysulfonate formation is reversible, free ace-
taldehyde is released as the concentration of free S(IV) falls.
In the U.K., S(IV) may be added as an antimicrobial agent to certain meat
products, e.g., to preserve and impart a unique characteristic to pork sausage. The
additive is effective 41 against Salmonellae even at the relatively high pH of this meat
product, and any spoilage is restricted initially to Gram-positive microflora consist-
ing of Lactobacilli and Microbacterium thermosphactum . Thus, the spoilage of
sulfited meat tends to be associated with a sour odor, unlike the spoilage of untreated
meat which leads to a “putrid” smell. The important microbial contaminants iden-
tified in sausages which are sensitive to S(IV) include Brochothrix thermosphacta ,
Enterococcus spp., Lactobacillus spp., Pseudomonas spp., Enterobacteriacea, and
Salmonella spp.; the concentrations of S(IV) (pH 7 in batch culture medium) to
inhibit growth decrease in the above order of microbial contaminant. On the other
hand, yeasts are not inhibited significantly at concentrations of S(IV) found in
sausages. The total S(IV)-content of sulfited pork sausage falls with time during
storage, e.g., a sample to which 450 ppm SO 2 had been added could lose 70 to
80 ppm SO 2 after 8 d at 4°C, but the level of free S(IV) falls to 100 ppm SO 2 or
less under the same conditions. The principal S(IV)-binding compound is, again,
acetaldehyde of microbial origin, and is an important reason for the reduced storage
life of this product.