ABSTRACT
References ............................................................................................................... 54 1.3.2 Determination of Optical Properties in Turbid Media:
Time-Resolved Approach.................................................................. 55 1.3.2.1 Light Propagation in Diffusive Media: Photon Migration..... 55 1.3.2.2 Mathematics for Photon Migration...................................... 60 1.3.2.3 Time-Resolved Instrumentation for Photon Migration ....... 67 1.3.2.4 Applications of Time-Resolved Reflectance
Spectroscopy to Fresh Fruit and Vegetable......................... 73 References ............................................................................................................... 78
Consumer demand for high-quality fresh fruit and vegetable has increased in the past decades, and is still increasing. Theword quality has many ramifications and canmean
many things to different groups in the supply chain from the farmer to the consumer. For the farmer it generally means high yield of a product with few blemishes or decay problems. For the supplier and marketer it can mean a firm product that has good shelf life and which does not decay before being sold. For the consumer it can mean good external appearance and good taste. It has been shown repeatedly (Kader 2002) that a commodity can still appear acceptable when its taste has already been lost (Figure 1.1.1). Therefore, the appearance of a commodity is not sufficient when we speak about quality. Many consumers complain that the taste of fruits and vegetables that they remember from the past has been lost in the commodities being sold in the global marketplace. There is some truth in this, since breeding for longer shelf life generally (not always) is at the expense of some flavor. In addition, fruits and vegetables used to be seasonal and so were consumed only for that part of the year. These products were produced locally, had a short marketing chain, and so could be harvested at an advanced stage of development or ripening. With the increase in global marketing many local varieties have beenmarginalized and denied shelf space in the supermarket chain. The fruit and vegetable marketing chain in a developed country is shown in Figure 1.1.2. Produce has a number of way stations to go past before reaching the consumer. At each of these points the produce may be loaded, unloaded, cooled= warmed, or sorted=unsorted, on its way to the final destination. The shortest route is the local farmers’ market, which accounts for only a small portion of the total market. A positive aspect of global marketing is the marketing of products that have been bred for enhanced nutritional and health-promoting aspects. These include fruits and vegetables with high pigmentation, and increased antioxidant and vitamin content. Hence, it is important to define what is meant by quality. I have divided this parameter into four aspects: visual, organoleptic, nutritional, and hygienic.
