Investigating the Potential of Sulfur Dioxide (SO₂) Applications for Decay Control of Brown and Yellow Color Figs

 

 

Carlos H. Crisosto, David Garner, Vanessa Bremer, Ed Stover, and Louise Ferguson

Objective

Evaluate decay incidence and phytotoxicity of different SO₂ concentration time (CT) applications on dark and yellow color figs.

Materials and Methods

Individual trays of 'Brown Turkey' (dark skinned) and 'Kadota' (yellow skinned) figs were sealed in plastic fumigation container systems inside an environmental room at 68°F as described by Palou et al. (2002).  Sulfur dioxide was applied for different periods of time calculated to result in treatments of 0, 25, 50 and 100 CT (ppm-hr).  Actual CT was verified with passive dosimeters tubes placed in the boxes during the fumigation.  The three SO₂ fumigation treatments and control were applied to 444 'Brown Turkey' and 520 'Kadota' (one quarter of the total number of fruit per cultivar were used for each treatment).  After fumigation, figs were stored at 32°F for 13 days.

Fruit quality evaluations and firmness measurements were done after 6 and 13 days at 32°F and during shelf life up to 4 days at 68°F.  Firmness was measured with a Fruit Texture Analyzer (FTA) (Güss, GS.14, Strand, South Africa) with a flat tip and expressed in pounds-force (lbf).  Firmness was measured on 15 fruit per cultivar after 13 days at 32°F and on 5 fruit per evaluation for shelf life.  Fruit quality parameters measured were percent of sound fruit (commercial fruit), percent of fruit with decay, percent of fruit with "off color" (color not typical for the cultivar), percent of fruit with growth cracks, percent of fruit with splits, and percent of fruit with other blemishes.  The percent of bleaching per fruit on 'Brown Turkey' was measured after 6 days.

Conclusions

·       The SO₂ treatments increased the percent of bleaching on the fruit (Table 1).

·       After cold storage and during shelf life, the 25 ppm-hr treatment produced the highest percent of sound fruit in 'Brown Turkey' and 'Kadota' fig (Table 2, 3).

·       In general, firmness was not affected by SO₂ fumigation in 'Brown Turkey' or 'Kadota' (Table 4, 5).

References:

Palou, L., C.H. Crisosto, D. Garner, L.M. Basinal, J.L. Smilanick, and J.P. Zoffoli.  2002.  Minimum constant sulfur dioxide emission rates to control gray mold of cold-stored table grapes.  American Journal Enology and Viticulture 53(2):110-115.