Citrus Flavour

About two thirds of the citrus produced worldwide is consumed as fresh fruit. Unfortunately, citrus utilised as fresh fruit cannot constitute a source of commercial flavours. However, in certain high-production countries such as the USA (Florida) and Brazil, the majority of the citrus crop is processed. In Florida over 90% of the orange crop is processed and is a major source for citrus flavouring material. Citrus fruits are processed primarily into juice, but oil from the outer layer of the peel, flavedo, and the condensate from making concentrated juice are also major sources of flavour products from citrus fruit. 

Citrus-flavoured drinks, notably lemon drinks, are frequently susceptible to oxidation and so antioxidants may feature in their formulation. 

Analysis of the volatile compounds of tamarind revealed the presence of more than 80 compounds. Aromatic and furan derivatives were dominant. The major constituents were 2-phenyl acetaldehyde (25.4% of total volatiles), which has a fruity and honey-like odour, 2-furfural (20.7%), having a caramel-like flavour, followed by hexadecanoic acid (18.1%) and limonene, which has a citrus flavour. A list of the volatile compounds detected in tamarind is given in Table 20.5. 

Citrus essential oils are widely used as a raw material of flavour in food and perfumery industries. They are also called "cold-pressed oils" and contain more than 200 compounds which can be grouped in three fractions the hydrocarbon terpenes (unsaturated compounds) that constitute the major amount (from 60 to 98% by weight) but have undesirable off-flavours characteristics the oxygenated compounds (flavour fraction) that are directly responsible for the characteristic citrus flavour and the non-volatile residues. 

R. Rouseff P. R. Perez-Cacho, Citrus Flavour. In Flavours and Fragrances Chemistry, Bioprocessing and Sustainability ... 

The carrier material may also protect the active ingredient against external influences. Flavourings which tend to oxidize, e.g. citrus oils, require encapsulation in order to prevent contact with atmospheric oxygen. These encapsulated citrus flavourings, mainly consisting of essential oils, may be stabilised further by removing the residual... 

The preservation effect for flavours, however, proceeds oppositely. Kopelman, Mey-dav and Wilmersdorf [45] have demonstrated with freeze-dried citrus flavourings that the flavour preservation increases with rising DE-value. For practical applications, analysis of the raw material and pre-trials with various carrier matrixes have, therefore, to be employed to find the optimum. The groups of Thijssen as well as Flink and Karel [45-56] hme performed exhaustive basic studies on this problem. 

The flavour properties of the citrus oils are based on compounds like aldehydes, esters and alcohols. Aldehydes play the most important role in citrus flavours. Mainly the saturated C-8, C-10 and C-12 long-chain constituents as well as the terpenoid aldehydes citral (a mixture of neral and geranial) and citronellal form the basic notes of the fresh and pleasant citms flavour. Also sesquiterpene aldehydes and ketones, such as sinensal or nootkatone, are significant for citms flavours. The aldehyde content, therefore, is frequently used as a quality criterion for citms oils. Important citms alcohols are linalool, octanol, a-terpineol (especially in distilled lime oil) and ter-pinen-4-ol. Furthermore, esters contribute to the flavour properties of citms oils. Especially the acetates of geraniol and nerol and, to a lesser extent, citronellol are... 

Enhanced stability and improved solubility are features of concentrated citrus oil products as a result of their reduced amounts of terpenes. These properties are of particular importance for flavouring soft drinks, the most important field of application for citrus flavourings in the food sector. 

Breweries have implemented innovations such as citrus-flavoured beer, slightly sweetened and acidified to offer trendy and fashionable new products for the younger generation of consumers as well as attract female customers. 

The most widely used soft drink flavouring ingredients are citrus oils which have a high content of terpenes that inhibit the solubility of the citrus flavour components in water. Of the commercial deterpenation methods [27], it has been shown that it is technically possible to dissolve the terpenes from citrus oils with CO2 [28] by countercurrent flow. However, the capital costs of the countercurrent extraction equipment is about ten times that of conventional deterpenation equipment. On the basis of capital cost, this author thinks that it is unlikely that liquid CO2 will be used commercially for citrus deterpenation in the beverage industry, and that conventional countercurrent technology will prevail [29]. 

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