Stone Fruit: Developing Flavor

Recently, a longtime peach and apple grower faced a dilemma. After losing his entire peach crop to frost this season – the first time in his eight decades of growing fruit trees on the same land where his father started the orchard – Bob Best Sr. was debating whether or not to purchase peaches from other growers in order to satisfy his customers’ desire for peaches. The Bests sell their peaches at their farm market, and also sell peaches to select other local farmers.

Throughout the years, they’ve carefully selected peach cultivars and rootstocks and found winning combinations to support a peach season that runs from late June to mid-September. Bob Best has passed on the bulk of the growing to his son (also Bob Best), the only one that harvests the peaches – unlike the apples, where a small crew brings in each harvest. The peach harvest is too delicate to leave to less experienced hands.

The dilemma – whether to offer peaches that weren’t going to be the same as the ones his customers expect, and risk disappointment, or to not sell peaches at all and risk disappointment – wasn’t about economics, but about taste. Best was concerned that no other grower’s peaches would taste the same as his. The perception of his longtime customers that his peaches had specific flavor qualities that set them apart from other peaches was an important consideration for him.

So why might Best’s Fruit Farm peaches – or any farmer’s peaches – have a different flavor profile than others, even those grown nearby?

Quality of Stone Fruit

Macarena Farcuh, Ph.D., assistant professor of horticulture at the University of Maryland, has spent her career studying the development of fruit quality. She presented a workshop, “Development of Stone Fruit Flavor,” at the Bay Area Fruit School earlier this year.

Farcuh explained that the three attributes which stone fruit quality is dependent upon are texture, color and flavor. Color refers to both the degradation of chlorophyll as well as the accumulation of non-photosynthetic pigments such as carotenoids and anthocyanins. Texture is the softening of the fruit, which changes during different stages of maturity due to cell wall structure, turgor pressure and cuticle composition of the fruit, and which is impacted by handling and post-harvest storage.

Flavor development is not simple – and it is not simply taste. Taste refers to the sweetness in the fruit, which is dependent upon the quantity of sugars, along with the composition of sugars and acids, and the balance between them. But other factors come into play when discussing fruit flavor.

“It’s really a complex trait,” Farcuh said. “Flavor is not just taste. There are a series of volatile compounds that are being produced all the time by the fruit, and it’s going to affect how we perceive that fruit that we are eating.” Aroma compounds, plus the consumer’s own perception, influence overall fruit flavor.

The peach industry has seen a decrease in the consumption of fresh peaches, and the primary reason for that decline is disappointed consumers. “There is a big inconsistency in what consumers are looking for in a fruit, and what the whole overall food supply chain is providing them,” she said. “Fruit flavor presents a major opportunity to grow markets.”

Development of Flavor

Genetics determines flesh color, acidity, shape, texture and whether the peach is a free or cling stone. Consumers prefer free stone peaches with a melting texture, primarily due to their flavor profile. These peaches happen to be the hardest to handle for growers, however. But growing flavorful peaches is the key to consumer demand.

Flavor is influenced by several factors: genetics, environment, orchard management, maturity at harvest and harvest practices and post-harvest storage. Each of these factors is complex, and combined they determine the final flavor of the fruit. It’s important for growers to realize that fruit which has not been bred to develop flavor is not going to do so, no matter what other factors they hope to use to influence that.

“If genetic material has not been bred for flavor-related traits, those will never be developed in the field,” Farcuh emphasized.

The cultivar and the rootstock, plus the interaction between the two, influence the performance of flavor. The genetics impact many factors, such as vigor, bloom, ripening time and harvest maturity, all of which also impact flavor.

“It’s so important to consider cultivar/rootstock interactions,” she said, encouraging growers to do small trial runs on their own land to determine how flavor is impacted by their farm environment.

That’s because the rest of the factors influencing flavor are farm-dependent. The environment (temperature, sunlight, photoperiod) are all specific to the microclimate where the tree, and even the specific peach, is growing. The environment, in conjunction with the cultivar/rootstock genetics and interactions, is a primary factor in flavor development.

Orchard management practices, including canopy management, irrigation and fertilization, crop load, light manipulation, use of plant growth regulators and planting density, also interact with the genetics and environment to further shape flavor.

Key points in development of maximum flavor involve optimizing the crop load and avoiding excess nitrogen and water. When growing to optimize yield, flavor is sacrificed. Instead, a balanced approach to the orchard provides enhanced flavor, she said.

Maturity at harvest, along with harvest practices, also plays a role in determining final fruit flavor. Harvest before full maturity – the time of the typical commercial harvest – and the full flavor will not develop, although the fruit will store better. Harvest too late, and the fruit will have a fermented quality and decay faster.

“We know that when the fruit is fully ripe is when it is going to have its richest flavor and components,” Farcuh said. “Once you harvest fruit, that is the maximum quality that your are going to reach of the fruit.”

Post-harvest storage and its impact on fruit flavor are dependent upon both time and temperature. Chilling injury occurs between 36º and 42º F. A primary symptom of chilling injury is a decrease in flavor, which is combined with flesh browning and mealiness.

Cold storage must be maintained consistently along the supply chain, and humidity needs to be regulated at 90% – 95%. Pre-conditioning fruit is a technique used to maintain flavor, and is accomplished by holding fruit at 68º for 24 – 48 hours prior to cold storage. While this will decrease the risk of chilling injury, there will be fruit softening and weight loss.

It isn’t surprising that Best is correct in his assessment that his peaches aren’t the same – and don’t have the same flavor – as those of other farmers, even if they are growing the same variety, on the same rootstock, in proximity to his orchard. Flavor is complex, and the many factors that contribute to its development are hard to replicate from farm to farm.

2020-11-23T15:06:24-05:00November 23, 2020|Grower, Grower East, Grower Midwest, Grower West|0 Comments

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