Raspberry ketone is an important compound for the flavour industry. It is frequently used in products such as soft drinks, sweets, puddings and ice creams. The compound can be produced by organic synthesis. Demand for "natural" raspberry ketone is growing considerably. However, this product is extremely expensive. Consequently, there is a remaining desire to better understand how raspberry ketone is synthesized in vivo, and which genes and enzymes are involved. With this information we will then be in a better position to design alternative production strategies such as microbial fermentation. This article focuses on the identification and application of genes potentially linked to raspberry ketone synthesis. We have isolated candidate genes from both raspberry and other plants, and these have been introduced into bacterial and yeast expression systems. Conditions have been determined that result in significant levels of raspberry ketone, up to 5 mg/L. These results therefore lay a strong foundation for a potentially renewable source of "natural" flavour compounds making use of plant genes.

Model samples containing soy, casein, or fish protein were analyzed by gas chromatography and mass spectrometry. The headspace of samples, unheated and heated and with or without fat and starch added, was investigated. Over 150 compounds were identified representing aliphatic hydrocarbons, alcohols, aldehydes, ketones and furan derivatives, and sulfur-containing compounds. The absolute concentrations in the headspace gas were determined for about 80 com-pounds judged to be of at least potential interest from the aroma point of view. On heating, the concentrations of volatiles generally increase and new compounds are detected. Of particular importance for the aroma of all heated samples is the presence of branched chain aldehydes and sulfur compounds. Moreover, straight chain aldehydes and furans are important in the soy protein samples and hydrogen sulfide in the fish protein sample.For economical and nutritional reasons it is sometimes desirable to replace a conventional protein such as meat with less expensive but still nutritious unconventional protein materials, such as soy, rapeseed, fish, and single cell proteins. In processed protein foods the protein part acts as one of several precursors for compounds responsible for different sensory properties, such as color, taste, and aroma.Thus a change of the protein part is likely to cause changes in one or more of the sensory properties. There is very little to be found in the literature concerning aroma properties of protein concentrates or isolates from various sources.However, the sources themselves and products made using these raw materials are more often treated in the literature. This is particularly true with soybeans and food products made from soybean, such as soy sauce, miso, etc.

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