Extended Field Storage In Processing Tomatoes: Does It Fit In CA Production?

Average annual production of processing tomatoes in California is about 12 million tons per year, accounting for more than 90% of the U.S. crop and about 40% of worldwide production.  Since the 1960’s harvesting has been by machine where all fruit from an entire field is collected in a single pass, resulting in a mix of fruit with a range of maturities.  After sorting to remove unripe green fruit, tomatoes are transported by truck to processing plants where they are converted into a variety of products, including whole peeled tomatoes, diced tomatoes, and tomato paste.  A major challenge in this production system is coordination of harvests with available processing plant capacity.  Often it is necessary to delay harvesting until sufficient processing capacity becomes available.  This “field storage” affects the average maturity of the fruit being processed.  Certain processing tomato cultivars have been bred for high production during hot temperatures and Extended Field Storage (EFS).  Seven field trials from 2005 through 2009 in the San Joaquin Valley evaluated a cultivar’s potential for EFS by harvesting at maturity and then delaying harvest up to four weeks. In some trials planting dates were arranged so that the second harvest coincided with the first harvest of a successive planting. This planting and harvest arrangement supplied information on variety performance over a range of time and temperature. Yield, harvest quality (maturity, color, soluble solids, pH, etc.), and product quality (pH, titratable acidity, sugars, lycopene, etc.) were measured. We determined the magnitude of maturity effects in several California processing tomato cultivars.  Overall average yield decreased by more than 5 tons/acre with each successive planting date. Average yield decreased with each successive harvest, but not all varieties had a similar response.  There was a benefit of planting earlier to maximize fruit set during favorable temperatures and holding fruit in the field rather than planting later. Allowing tomatoes to remain on the vine for up to 4 weeks after ripening resulted in an increase in fruit pH of between 0.01 and 0.02 unit per day for the cultivars examined.  As pH increased, titratable acidity decreased, due to a loss of citric acid.  Glucose and fructose concentrations declined with increasing maturity after ripening.  Other quality parameters (color, lycopene, total pectin, pectin solubility, and Bostwick consistency) showed little change.