Effects on Flavor

CONTENTS 7.1 Introduction ........................................................................................................................ 120 7.2 Flavor of Fruits and Vegetables....................................................................................... 120

7.2.1 Sensory Assessment................................................................................................ 121 7.2.2 Chemical Flavor Constituents............................................................................... 122 7.2.3 Linking Sensory and Chemical Analysis............................................................. 123

7.2.3.1 Gas Chromatography-Olfactometry ....................................................... 123 7.2.3.2 Statistical Analyses.................................................................................... 123

7.2.4 Prestorage Factors Affecting Flavor ..................................................................... 124 7.2.4.1 Genetics....................................................................................................... 124 7.2.4.2 Preharvest Environment........................................................................... 124 7.2.4.3 Maturity ...................................................................................................... 124 7.2.4.4 Postharvest Treatments ............................................................................ 125

7.3 Dynamics of Postharvest Flavor Change ....................................................................... 125 7.3.1 Metabolic Changes.................................................................................................. 125 7.3.2 Diffusional Changes ............................................................................................... 127

7.3.2.1 Flavor Loss ................................................................................................. 127 7.3.2.2 Natural Barriers ......................................................................................... 127 7.3.2.3 Artificial Barriers ....................................................................................... 128 7.3.2.4 Taints=Migration ....................................................................................... 128

7.4 Atmosphere Effects on Flavor.......................................................................................... 129 7.4.1 Oxygen ..................................................................................................................... 129 7.4.2 Carbon Dioxide ....................................................................................................... 131 7.4.3 Humidity.................................................................................................................. 132 7.4.4 Ethylene.................................................................................................................... 132 7.4.5 1-Methylcyclopropene............................................................................................ 134 7.4.6 Other Gases.............................................................................................................. 135

7.4.6.1 Argon .......................................................................................................... 135 7.4.6.2 Carbon Monoxide...................................................................................... 135 7.4.6.3 Nitrous Oxide............................................................................................. 136 7.4.6.4 Nitric Oxide................................................................................................ 136

7.4.7 Precursor Atmospheres.......................................................................................... 136 7.5 Packaging Effects ............................................................................................................... 137

7.5.1 Passive MAP............................................................................................................ 137 7.5.1.1 Effects on Flavor ........................................................................................ 137 7.5.1.2 Off-Flavor Development........................................................................... 138

and

7.5.2 Active MAP ............................................................................................................. 139 7.5.2.1 Interactive Features ................................................................................... 139 7.5.2.2 Gas Flushing............................................................................................... 140 7.5.2.3 Sachets......................................................................................................... 140

7.5.3 Interaction with Packaging Films......................................................................... 141 7.5.3.1 Scalping and Permeation.......................................................................... 141 7.5.3.2 Perforations ................................................................................................ 142

7.6 Interactions of Coatings .................................................................................................... 142 7.7 Future Research Needs ..................................................................................................... 144 7.8 Conclusions......................................................................................................................... 145 References.................................................................................................................................... 146

The flavor of fresh fruits and vegetables is an important factor in determining quality and consumer satisfaction. However, there is often dissatisfaction among consumers concerning the flavor of fruits and vegetables. First-time purchases are usually based on appearance and firmness, but repeat buys are dependent on internal quality traits such as texture and flavor (Baldwin, 2002). The loss or lack of flavor following postharvest handling, storage, and marketing of fresh fruits and vegetables often precedes the loss of visual quality, which has been reported for both whole and fresh-cut fruits and vegetables (Gorny, 2005). Ensuring good flavor is critical to encourage increased consumption, which is important for human health and well being as well as strengthening and expanding markets for the horticultural industry. Postharvest flavor change can be affected by many preharvest as well as postharvest factors. However, the impact of postharvest technologies on product flavor is not always appreciated nor are the biochemical and genetic mechanism regulating flavor understood. Atmosphere modification through traditional controlled atmosphere (CA) storage,

modified atmosphere packaging (MAP), or the application of edible coatings can impact the flavor of fresh produce in both positive and negative ways. Altered atmosphere composition can affect metabolic changes in flavor compounds in fresh produce during storage or marketing. In addition, packaging can affect diffusional loss of flavor compounds. In this chapter, we will first discuss what determines flavor of fresh fruits and vegetables and then how CA, MAP, and coating technologies influence postharvest flavor change.