WSU Tree Fruit Research & Extension Center

Postharvest Information Network

Wednesday, June 28, 2017

WSU-TFREC/Postharvest Information Network/Delicious Harvest Maturity and Storage



Delicious Harvest Maturity and Storage


Factors to Consider in Making the Harvest Decision

The harvest decision is made by combining information collected in the orchard with warehouse data, Apple Maturity Program data and orchard history. Maturity testing begins two weeks or more before estimated time of harvest and continues each week until harvest. Firmness, soluble solids and starch content are the primary tests performed in the orchard. The number of days from full bloom, temperature patterns of the current and previous years, fruit size, taste, seed and skin color are also considered when making harvest decisions. Advancing maturity is indicated when values of each measurable parameter begin to increase and the rates of change increase from week to week.

The horticulturist makes harvest decisions based on fruit volume, maturity, color, size and orchard history and then communicates these decisions to the grower. Fruit segregation, storage and marketing decisions are most accurately made through frequent and detailed communications; between horticulturists, warehouse receiving personnel, storage and quality control personnel and marketing staff. Adjustments in harvest timing and the rate of progress might be necessary to meet storage and marketing goals. Apple quality and maturity must be monitored throughout the storage duration to assure that apples of the highest quality reach the marketplace.


Delicious Maturity and Marketing

One of the goals for any marketing plan is to provide the market with fruit of the highest quality and condition throughout the entire season. Apples must be held in storage for different lengths of time to facilitate an orderly marketing season. Therefore, marketing strategies must be in place before field personnel begin designating storage regimes for each block. The marketing period and outlook for every variety have a great impact on preharvest handling.

Fruit quality is assessed to determine which storage regime will be suitable for each block. A balance between color, size, firmness, and appearance is important in deciding how long the fruit will be stored and the type of marketing scheme it will require. Although it is not a reliable indicator of maturity, growers are rewarded for red color. This can pose problems for growers and warehouses during years when color development is slow, especially since they must comply with Washington's 12-lb firmness mandate. If fruit from a given block does not match expectations outlined in the storage and marketing plan, it should be used in an alternative plan and other blocks should be used to meet the original goal.

Harvest and storage plans can be tailored to fit marketing forecasts for each season based on historical data from each orchard. The history of each block is important for predicting storability and determining which storage regime to use. Stored apples from some blocks lose more firmness or develop more storage disorders than others. Fruit with a history of large firmness losses in storage might need to be sold earlier than fruit with a history of good firmness retention. Orchard histories also might indicate whether apples from different blocks and different maturities could be stored in the same room and still meet required post-storage conditions.


Factors Affecting Delicious Maturity

Differences in elevation, tree vigor, and rootstock affect apple maturity differently. Orchards located in higher elevations that are exposed to a cool climate generally produce Delicious with better storage life than those in a warmer climate. Temperature affects fruit bud differentiation, bloom, fruit size and fruit quality. If buds or wood are damaged by cold winter temperatures, fruit size, quality and maturity will be adversely affected for the next few years. Orchards located in areas with wide preharvest diurnal temperature fluctuations generally produce fruit that ripens more consistently, has less scald development and better red color than fruit grown in less fluctuating temperatures. Apples grown in high temperatures have greater sunburn and sunscald potential. Fruit within a single orchard can mature at different rates. Different microclimates within an orchard can cause temperature differences even if the trees are in close proximity. When several microclimates are present in a single orchard, several different stages of fruit maturity might exist at the same time, adding additional challenges to harvest management.

Excessive tree vigor can delay fruit maturation, while low vigor can accelerate it. Vigor is influenced mainly by tree nutrition, pruning and type of rootstock. If an orchard is heavily pruned and fertilized, or if it is grown on a vigorous rootstock, the trees will respond by growing shoots and leaves and only small amounts of fruit which usually are slow to mature. A combination of adequate but not excessive fertilizing and pruning will promote optimum fruit production, fruit size and maturation.


Grower and Warehouse Expertise

Experienced growers understand the importance of good organizational skills, flexibility in harvest plans, and having capable crews of adequate size. Confidently organizing activities before and during harvest, the ability to change harvest speed and timing, and hiring enough experienced pickers will increase a grower's chance of completing harvest when the fruit is at optimum maturity for the intended storage. If the harvested fruit is not at optimum maturity, then alternative storage and marketing plans will be needed. Excellent warehouses understand the value of excellent fruit quality. The expertise of a warehouse to properly handle the fruit and the ability of its sales staff to sell it translates into increased returns to the warehouse and grower. The sales season must begin with premium fruit on the market, since the first fruit will influence buyer expectation for the entire year. When fruit maturity is monitored before harvest and through the storage season, it allows the warehouse to maintain order in marketing and consistently provides both domestic and export markets with fruit of good quality.

Joyce Thompson, moderator
Panel discussion: Tom Butler, Brent Milne, Mike Saunders, and Don Van Wechel

15th Annual Postharvest Conference
March 9-10,  1999

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