Osmotic syrups can be reconcentrated and reused for osmotic water removal through at least five complete cycles without adversely affecting the fruit being concentrated, even though the properties of the osmotic medium do change. Syrup penetration rate into a fruit piece was faster with high fructose corn syrup (HFCS) than sucrose. Taste panel evaluation indicated that overall, sucrose was preferred as an osmotic medium over HFCS.
— Apple slices of two varieties were dipped in solutions at various pH values with and without sulfite and with and without calcium. After dipping, the apples were packed in plastic bags and stored at 34°F. At weekly intervals shear strength was measured and related to pH of the dipping bath for the following treatments: 1) unsulfited, 2) sulfited, 3) calcium treated, unsulfited and 4) calcium treated, sulfited. An alkaline sulfite dip resulted in firmer apple slices than an acidic sulfite dip. Addition of calcium to an alkaline sulfite dip resulted in a further increase in firmness, but addition of calcium to an acidic sulfite dip did not. Sulfite was necessary to preserve the light color of apple slices during storage of refrigerated apple slices for several weeks.
The interrelated factors that influence the effectiveness of SO2 as a preservative against yeast were studied and the correct quantitative relationships of SO2 molecular species determined. Widely differing pK values for SO2 were found in the literature, compared with experimental data, and one set of values was selected. Undissociated H2SO3 is the only effective form of SO2 against yeast and can be calculated from measurement of free SO2 and pH, and the correct dissociation constants. Duration of contact, pH, concentration of SO2 and yeast, and binding of SO2 all influence the preservative action of SO2. Lower total SO2 concentrations can be used for food preservation by optimum control of these factors.
The effect of sulfuring on bisulfite binding in apricots and apples was determined. Sulfuring methods had no effect on binding. Dehydration resulted in less conversion of the sulfur dioxide to the sulfate. An oxygen scavenger added to the packaged dried apricots reduced both the rate of sulfur dioxide conversion to sulfate and the total sulfur dioxide loss, resulting in the product remaining lighter in color for a longer time. In resulfuring, a progressively larger percentage of the added sulfur dioxide was bound as the storage time before resulfuring increased. The pH effect on sulfur dioxide binding was different in model solutions than in particulate fruit. In the former, there appeared to be a direct relationship to bisulfite dissociation but not in the latter.
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