For centuries, farmers decided their fruit was ready to pick by plucking one from a tree and taking a bite. Agricultural scientists now know that shipping and storage affect fruit flavor, and that standardized, scientific tasting produces more reliable results.
Nearly a decade ago, University of California agricultural scientists began systematic taste testing at the UC Kearney Research and Extension Center near Parlier. At the 330-acre research center -- a hub for valley research in irrigation techniques, pest management, variety testing and pruning systems -- groups of taste testers began sampling research fruit.
Early taste testing results have been so promising in predicting consumer satisfaction, scientists sought to expand their work. Produce industry groups, farmers and the UC Division of Agriculture and Natural Resources collaborated to build a new laboratory for sensory testing at Kearney, which was completed last month. The 1,100-square-foot laboratory features neutral white paint and broad-spectrum lighting. The ventilation system will minimize distracting odors and six tasting booths are set apart with dividers.
"The human factor sets sensory testing apart from the other agricultural sciences," said Susan Collin, a staff research associate at Kearney. "As human beings, we are very complex and tend to blend taste with vision, hearing, smell and texture when we make judgments. Here, we have tried to minimize those distractions."
Sensory testing research has been underway for 10 years
Even though previous sensory testing at Kearney was conducted in a less perfect environment, they have yielded helpful results for the industry. Under the direction of UC subtropical horticulturist Mary Lu Arpaia, research at Kearney has supported the avocado industry's efforts to provide good-tasting fruit to consumers, which has an enormous impact on future purchases.
"We know that if someone buys an avocado they don't like, it may be six weeks before they will purchase one again," Collin said.
When UC researchers released a new avocado variety -- Lamb Hass -- growers needed an objective measure of maturity that would ensure the fruit would ripen properly and taste good when it reached consumers' tables. Scientists harvested avocados at various levels of maturity, extracted a core of flesh from the middle of each one and replaced the core with a plastic rod that doesn't interfere with the fruit's ripening process. The unripe core samples were analyzed for dry matter. Later, after the fruit ripened, it was subjected to sensory testing.
"The Avocado Inspection Committee wanted to know the earliest level of maturity Lamb Hass could be picked and still be perceived by tasters as likable," Arpaia said. "We figured out a way to measure the dry matter of fruit and learned that those that had at least 22.8 percent dry matter when picked will ripen into an acceptable fruit."
Navel oranges have been the subject of sensory testing at Kearney
Similar studies have been done with navel oranges. The top and bottom of the orange are sliced off and discarded. Previous studies have shown that the bottom is the sweetest part of the orange and the top the least sweet. The center portion is divided in half, with one part going to the tasters and the other to the lab for scientific analysis.
"We determined each fruit's sugar-to-acid ratio," Arpaia said. "Human tasters judged how much they liked the fruit. We were able to establish a correlation between the sugar-to-acid ratio and acceptability for navel oranges for the beginning of the harvest season."
The research established a correlation, but there was still significant variability. Arpaia suspects that some of the orange variability may be due to volatiles -- the delicious scent that wafts from cut fruit. She and Collin are planning another study designed to make a connection between scientifically measured volatiles and people's preferences. The work will be done with plant physiologist David Oberland of the USDA San Joaquin Agricultural Sciences Research Center, located across the street from Kearney.