Dr. Jeff Brecht, Director, Center for Food Distribution & Retailing, University of Florida, USA, (jkbrecht@ufl.edu), March 2009.
Is anyone truly satisfied with the taste of the fruits that we find in supermarkets today? Fruits that are destined to be stored for extended periods to regulate marketing, or to be shipped extended distances to reach far-flung markets, are too often harvested at an early stage of development that provides no chance that those fruit will ever develop excellent flavor and aroma.
If one examines international grade standards for fruit, the reason for this situation becomes clear. It is obvious that tolerances in grade standards are largely based on visual appearance factors, and are especially stringent for such defects as bruising and decay that disproportionately affect riper fruit. Has anyone ever heard of a load of fruit being rejected because the fruit were too firm? But woe to the shipper whose fruit arrive over ripe, soft, bruised, or worst of all, with decay!
Grower/shippers too often address the problem of how to avoid having their customer ever open the doors of a trailer or marine container and find over ripe, soft, bruised, or decayed fruit by always erring on the side of an earlier, rather than a later, harvest. So it is that hard, green fruit are so commonly shipped, and their counterpart, the tasteless, dry fruit, find their way onto market shelves.
One way to change this situation might involve removing from the equation the incentive to harvest fruit early. If this could be done, then a more physiologically advanced population of fruit could be harvested. What is needed is a technology that can assure the grower and the packer that the ‘problem’ fruit that are most likely to cause a rejected load can be removed. The ability to sort items online according to maturity and quality factors such as texture and composition could potentially transform fruit handling systems.
Nondestructive online testing includes several approaches that are fairly mature technologies for real time measurement of factors that relate to quality and maturity. Commercial equipment has already been available for several years. For example, acoustic online firmness sorters are used by the avocado industry to measure firmness according to the acoustic resonance of the fruit and sort them according to when they will be ready to eat. The acoustic response can also potentially be related to ripeness, juice content, and the internal structure (i.e., density) of other products. Near infrared (NIR) light penetrating beneath the skin of a fruit can be detected by a sensor and the light spectrum analyzed to determine the sugar content and other internal quality aspects such as dry matter and acidity as well as defects such as apple water core or mango jelly seed. Internal quality sorters for packinglines that use NIR transmission are sold by several companies and are being used for several tree fruits. For example, NIR sorting of peaches according to sugar levels is being used to allow the fruit to be harvested at a more advanced maturity stage.
Changes in the surface appearance of fruits can provide visual clues to maturity and ripeness. These changes can be accurately captured and quantified through the use of digital imaging software such as a noninvasive glossmeter developed recently by the Michigan State University.
It is my belief that the use of online nondestructive quality sorting will increase, and must increase, if fruit suppliers are to recapture consumers who are currently turned off by the quality of most fruit that is available in stores.