Fruit quality impact

Exaggerated chemical application rates may also adversely affect the crop quality. If the exaggerated rate causes the crop to be abnormal in some way at maturity, the processing applied to the crop may not result in typical fraction samples. The adverse impact may be obvious, such as slowed maturation of the crop, or the impact may be less obvious, such as a change to the internal structure of the individual fruits and vegetables, grains, nuts or roots. 

Table 10.2 presents a summary of odour qualities, odour thresholds in water, and concentrations of some selected volatile compounds, which are characteristic flavour impact compounds, owing to their typical flavour quality and their rather low odour thresholds. These compounds are not formed during fermentation but originate from the raw material and contribute significantly to the typical flavour of a fruit. The components summarised in Table 10.2 are important compounds in wine and different fruits and are discussed later. 

In spite of the progress which has already been made, there still exist, in citrus fruit and products, numerous qualitative aspects which are either very difficult to measure or whose contribution to quality is a function of the organoleptic sensitivities of the consumer. For the purpose of this paper we would like to concentrate on two groups of naturally occurring compounds which have a major impact on the taste of citrus fruit and their products. 

If a spatial olfactory code underlies a subsequent identification of an odor, then we would expect concentration-dependent variations of odor maps to have an impact on the perceived odor quality. Stimulus concentration can indeed influence perception of odor quality and behavior of insects. For example, olfactory responses of the fruit fly, Drosophia melanogaster, shifted from attraction to repulsion as the concentration increased (Siddiqi, 1983 Stensmyr et al., 2003). Future studies should thus involve correlations of behavior with glomerular activity at different concentrations. 

Vltlcultural aspects. Vitlcultural research would benefit from detailed investigations concerning influences of major preharvest variables on monoterpene composition of fruit. Different pruning techniques, trellis designs, soil characteristics and climatic variables have yet to be assessed for their impact on grape flavorants. Research has been carried out on some of these factors in relation to wine quality (92,93) and now their effect on fruit... 

The agricultural production of flavor and fragrance materials has several disadvantages, including variation in consistency and quality, and dependency on climatic, seasonal, geographic, and even political factors. The microbial production of flavor and fragrance materials may compliment or offer an alternative to traditional sources of these materials. Fermentation may be particularly suited to the production of unique, highly intense character impact components, i.e., substances that can potentiate the aroma and flavor of fruits, dairy and other flavors at low levels ( 100 ppm in the finished flavor). 

While the permeation process may have a negative impact on product quality, there are instances where permeation is required to maintain product quality. For example, in modified atmosphere packaging of fresh fruits and vegetables, the package is designed so that O2 and COj will permeate through the package at a desired rate, which depends on the product characteristics. 

Physical, biochemical, and physiological changes which occur during fruit development imply that intracellular variations play an important role in the distribution of different metabolites in the cells [11], For years food analysts and plant physiologists have been interested in the effects of maturation on the chemical components in the industrial parts of fruits because of their impact in the market quality of some industrial products made with petroselinic acid derivatives. 

Significant aliphatic sulfur compounds are methional, 3-methyl-but-2-ene-1-thiol, 3-mercapto-3-methylbutan-l-ol (8-124), its ester 3-mercapto-3-methylbutyl formate, methanethiol and dimethyltrisulfide. 3-Mercapto-3-methyl-l-ol also occurs in passion fruit and blackcurrant, and as a putative cat pheromone in cat urine, where it is formed as a degradation product of amino acid L-felinine (see Section 2.2.1.2.2). Of more than 70 known pyrazines, the most important compounds in roasted coffee are isopropylpyrazine, 2-isobutyl-3-methoxypyrazine, 2-ethyl-3,5-dimethylpyrazine, 2,3-diethyl-5-methylpyrazine, 2,6-dimethyl-3-vinylpyrazine and 2-ethyl-6-methyl-3-vinylpyrazine. Pyridine and its alkyl derivatives and bicyclic pyridines have a negative impact on the quality of coffee aroma. Important aromatic... 

The aroma substances that comprise flavors are found in nature as complex mixtures of volatile compounds. A vast majority of volatile chemicals that have been isolated from natural flavor extracts do not provide aroma contributions that are reminiscent of the flavor substance. For instance, n-hexanal is a component of natural apple flavor (1) however, when smelled in isolation, its odor is reminiscent of green, painty, rancid oil. Similarly, ethyl butyrate has a nondescript fruity aroma although it is found in strawberries, raspberries, and pears, it does not uniquely describe the aroma quality of any of these individual fruits. It has long been the goal of flavor chemists to elucidate the identity of pure aroma chemicals that have the distinct character impact of the natural fruit, vegetable, meat, cheese, or spice that they were derived from. Often, these are referred to as character impact compounds (2). 

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