Performing Department
(N/A)
Non Technical Summary
Certain fruits do not change color as they ripen and hence it may be difficult for consumers to select fruit that is ready to eat. Melons and winter pears are examples of fruit that is difficult to select. Most fruit is now individually labeled and this project will develop a label that will change color as the fruit approaches ripeness. This colorimetric label will provide the consumer with an immediate visual clue that will allow them to select fruit that is approaching ripeness, or is ripe. The label will be inherently safe, in case of accidental ingestion and the incremental cost of the label over the current labels will be small.
Animal Health Component
(N/A)
Research Effort Categories
Basic
(N/A)
Applied
100%
Developmental
(N/A)
Goals / Objectives
The skin color of some fruits does not change color as the fruit ripens. Examples of these fruits include winter pears, melons and kiwi fruit. This makes it difficult for unsophisticated consumers to select fruit, with the result that they may have an unsatisfactory experience with the fruit and will, therefore be reluctant to repeat it. The objective of this project will be to develop a colorimetric label that will respond to the ripening process of fruit. The label will be designed to respond to the increasing flux of ethylene as the fruit approached optimal ripeness. The color change will provide the consumer with an immediate visual clue that will allow them to select fruit that is in an ideal condition for eating, either immediately or later. If the consumers have a positive experience when they eat fruit in optimal condition they will be more inclined to repeat it, thus leading to an increasing demand for the fruit and higher prices to the growers. The
principal objectives will be to develop a label that will be sufficiently sensitive to show an incremental color change over a period of several days, as the fruit ripens. Because of the risks of accidental ingestion, the reagents must be inherently safe and must be present in quantities that do not offer any risk to the consumer. The labels will be designed to be compatible with current labeling machinery and the incremental cost must be low to achieve acceptance from the growers.
Project Methods
Ripening of fruit involves a number of changes. In fleshy fruit, the chlorophyll is degraded, and other pigments may form, changing the fruit color. Simultaneously, the fleshy part of the fruit softens, due to the enzymatic digestion of pectin, the principal component of the middle lamellae. As the middle lamellae are weakened, cells are able to slip past each other. During the same period, starches and organic acids, or, in the case of avocados, oils, are metabolized into sugars. During the time of ripening of certain fruits such as pears, melons and some tropical fruits, there is a large increase in cellular respiration, evidenced by increased uptake of oxygen and the evolution of ethylene. This phase is known as the climacteric. After the climacteric, senescence sets in and the fruit becomes susceptible to fungi and other microorganisms. Ethylene production actually begins before the climacteric but reaches a maximum at the climacteric. Once the climacteric
has passed the production of ethylene falls precipitously. Climacteric fruit include winter pears, avocados, kiwi fruit, melons and certain tropical fruits. Citrus fruit and apples do not pass through a climacteric phase. There have been a number of test methods developed to determine the ripeness of fruit. Test methods have included spectrometric measurements of fruit colors (tomatoes, apples, peaches, apricots), optical density (pears), nuclear magnetic resonance (nectarines, oranges, cherries), reflectance (bananas, apples), gas-sensing and odor (apples, bananas, papaya, melons), and impact (avocados, melons). Many of these techniques were intended to assist in assessing the harvest maturity and/or sorting in the packing house and are not for use by the consumers at the point of purchase. Most produce is now labeled. The labels carry the Price Look-Up number to identify the variety and other information such as the producer or packer. This project will exploit the production
of ethylene as an indicator of fruit ripeness by developing a modification to existing labels that will respond to the cumulative evolution of ethylene by a colorimetric reaction with the reagents in the label. The color of the label will provide immediate feedback to consumers, allowing them to select fruit that is unripe, close to ripeness, or ready to eat. The label will be compatible with current labeling machinery and materials and will safe for consumers. The label design will include multiple layers to isolate the colorimetric reagents from the skin of the fruit and to contain all of the ethylene within the reactive layer. The label will be designed to be compatible with current labeling machinery and materials and costs will be of the order of 0.1c per label for pears.