The Absorption of Sulfur Dioxide by Fruit Tissue

Abstract

SUMMARY The influence of many individual factors on the uptake of sulfur dioxide by apricot, peach, and pear tissue before drying was tested in equipment designed to permit accurate control over sulfuring conditions. Exploratory trials showed that estimates of sulfur dioxide uptake were unreliable unless standardized sampling methods were used. Absorption rate was affected appreciably by type of fruit, surface area as influenced by size, and the use of irrigation, and less so by variety and maturity. Sulfur dioxide uptake through the skin was slow. Combinations of gas concentration and exposure time were the most important processing variables affecting absorption. Variation in air speed and temperature had little influence upon absorption. Holding cut fruits for up to 10 hr before sulfuring did not cause a decrease in gas uptake. Excess water on the fruit surface from spraying tended to decrease absorption, while steam‐blanching retarded it appreciably. Any disorganization of tissue, whether from increasing maturation, storage, or processing, retarded sulfur dioxide uptake, probably through sealing, of penetration pathways. The ready desorption of sulfur dioxide from tissue removed from the sulfuring environment indicated low chemical fixation at that stage.

Air Drying Characteristics of Apricots

“…It appears that temperature in the range studied had only a minimum effect on browning and the hardness of dried apricot while sulfiting was the controlling factor. Most workers in fruit drying confirm the important role played by SOa in preventing browning (Joslyn and Braverman, 1954;Burton et al, 1963;McBean et al, 1964;Bolin and Staford, 1974). The extent of browning was negligible (O.D.…”

Recent Advances in Anthocyanin Analysis and Characterization

“…Relative to storage and preservation of the anthocyanins is the bleaching effect of sulfur dioxide on these compounds. While SO 2 is often added to fruits and vegetables as an inhibitor of microbial growth, it also acts as a nucleophile and attacks the flavylium ion of the anthocyanin, effectively bleaching the pigment as it progresses to the colorless hemiacetal form [59][60][61].…”

Absorption of Aqueous Bisulfite by Apricots

“…After sulfuring, the trays of apricots are placed in the sun to dry until the moisture level reaches approximately 18%. The sulfur dioxide level in dried apricots processed by the traditional method can vary from 1000 ppm to over 6000 ppm (McBean et al, 1964). This wide variation is caused by factors which affect the absorption and retention of sulfur dioxide, such as sulfur house design, sulfur dioxide exposure concentration and time, and desorption losses during drying which are greatly affected by weather conditions.…”