CHAPTER 10

COMPLEMENTARY PRODUCTS AND BY-PRODUCTS

10.1 Trends

A commendable trend in fruit processing has been the increased attention to waste reduction, resource conservation and by-product utilization. Driven by environmental regulations, economic incentives and the cost of energy and waste disposal, all food producers must now pay more attention to by-products. Moreover, many juicing operations evolved from the need to dispose of materials generated during fresh market and solid pack fruit processing accompanied by the realization that fruit residuals had juice potential.

In addition, the current emphasis on "natural" products is having a profound effect on the demand for fruit ingredients. Although often more costly, difficult to isolate and less functional (in stability, potency and activity), natural ingredients have a much greater market appeal than commonly used (functional and safe) synthetic analogs that are now considered "artificial" and "unnatural".

10.1.1 Pectin

Citrus, apple and a number of other fruits have sufficient pectin to merit recovery from the by-products of juicing operations. Section 11.3 and 12 deal with pectin recovery while Section 12.8 addresses pectin utilization. In view of the wide occurrence of pectin in fruits, it is unfortunate that small-scale, economically feasible means of extracting pectinaceous materials from local citrus and other crops have not been developed.

10.1.2 Essential oils and essences

The taste and aroma appeal of most fruits is readily obtained in concentrated form by various extraction and/or distillation techniques from peel, flesh, juice, concentrate or combinations. The classic example is citrus (Section 11.3).

10.1.3 Pigments

The natural pigments in fruits are also in demand and highly pigmented fruit cultivars are the focus of breeding efforts. Table 10.1 lists some of the more common pigments of fruits. Natural pigments are far less stable than synthetic colourants. Anthocyanin colour is highly pH-dependent as some range from bright red, pH less than 3.0 to green at pH greater than 5.0. Carotenoids are susceptible to oxidation, particularly in dry juice powders.

Table 10.1: Natural colours
Courtesy Overseal Colour Inc.

10.2 Phytochemicals

The last decade has seen an amazing paradigm shift during which the potential health value of food components, beyond common nutrients is emphasized (Section 3.2). These substances, termed nutraceuticals in plant foods and phytochemicals, are the focus of a whole new industry (Table 3.3). Fortuitously, fruits and fruit juices play a major role both as dietary sources and carriers of nutraceuticals. Actually, the field is in its infancy. Probably a number of hitherto unrecognized valuable substances could very well be discovered in juices and fruit extracts.

Without a doubt, the reverse applies for potentially dangerous substances, excess amounts of beneficial components or hazardous interactions are likewise possible, even probable. Nevertheless, increased research on the health value of juices promises to enhance the appeal and value of traditional and exotic juice products plus by-products.

Fruit by-products have long had economic value (Table 10.2). Improved recovery technology, recognition of valuable components combined with stringent disposal regulations (and cost) provides the economic incentive to make a valuable resource from waste. In this regard, comparatively unknown tropical plants have an intriguing future, hopefully exploited by and in the countries of origin.

Table 10.2: By-product utilization.