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3.1 Distinctions

Botanically, fruit is the structure resulting from the growth of a flowering plant. The fleshy component, which is normally the portion eaten, serves to protect and eventually nourish the seed(s) as part of the natural development of the original plant's progeny. The morphology of fruits varies substantially as does the plant tissue consumed (Figure 3.1.).

Figure 3.1: Plant tissue consumed as fruit.
(Coombe, 1976; Kays, 1991)

Fruit types dictate the mechanics and ease of juice extraction (Arthey and Ashurst, 1996). There are about nine categories of fruit/vegetable types (Kader, 1992; Kader and Barrett, Somogyi, et al., 1996a):

There are fruits that do not fit clearly into these definitions, or differ so much according to cultivar and maturity state that they are intermediate. For example, a soft mature mangosteen falls apart upon peeling, whereas a less ripe, firmer one can be peeled and eaten out of the hand.

As with juice definitions, there is some disagreement over what constitutes a fruit. Custom dictates the distinction that a tomato is a fruit, but it is normally regarded and consumed as a vegetable. Similarly, peppers and cucumbers are vegetables; yet watermelon, a member of the cucurbitaceae family along with cucumber, is a vegetable but used as a fruit. Pepper juice is viewed as a strange concoction, although perhaps with some merit (Chapter 16). In contrast, the plant stalk or petiole portion of the rhubarb is consumed as a fruit while the swollen inflorescence of broccoli is the epitome of a vegetable.

A rough, arbitrary, but recognizable distinction is if the juice is sweet and somewhat acid or sweetened with or without added acid for consumption, it is a fruit. If salt and/or spices enhance the juice flavour, it is a vegetable.

For the purpose of this text, most major and some minor horticultural crops capable of yielding a sweet (usually acidic) juice or puree from any portion of the plant customarily consumed and considered a fruit will be covered, along with some major vegetables. Leaf, stem and root extracts are presently gaining greater attention as "teas", herbal medicines or phytochemicals and have relevance in the context of juice by-products and nutraceuticals (Section 3.3)

3.2 Fruit/juice general composition

The structure and functional aspects of fruits dictate their composition. Table 3.1 shows some typical constituents of fruit (and subsequently juices) and the range of values dependent upon fruit, cultivar, cultivation, maturity and other factors to be presented later.

Table 3.1: Fruit edible portion composition ranges* (Fresh weight basis).


Range (%)



97 - 70

Influenced by cultivation and post-harvest conditions


25 - 3

Sugars and polymers - pectin, hemicellulose, cellulose


5 - trace

More in oily fruit and seeds


25 - trace

Traces in cell membrane, in seeds, high in avocado


3 - trace

Citric, tartaric, malic, lactic, acetic, ascorbic + minor


0.5 - trace

Tannins and complex phenols


0.2 - trace

Water soluble > fat soluble


0.2 - trace

Soil and species dependent

Dietary fibre

<1 to >15

Peel and core dependent


0.1 - trace

Carotenoids, anthocyanins, chlorophyll

*For more specific generalized values see USDA, 2000a.

Despite the small amounts of some compounds, they can influence dramatically the appeal, stability, or health value of the fruit. Many intrinsic (fruit-specific) and extrinsic (extraction-dependent) factors influence juice composition, as will be emphasized. Food composition tables provide a reasonable first approximation to fruit and juice make up (USDA, 2000a). Nevertheless, there can be substantial differences in the same species and analytical experience with a given cultivar under controlled production and processing conditions is very important.

3.3 Phytochemicals

This category of compounds, also known as nutraceuticals and functional foods, is increasing in importance and merits special attention. Phytochemicals are defined as:

Fruits and their juices are an especially good source of phytochemicals (Table 3.2). Close to one thousand different phytochemicals have been found in plants and the
identification and promotion of hitherto unrecognized compounds with real or
imputed health value continues unabated. In fact, the science is in its infancy and additional
phytochemicals, mechanism of action and beneficial effects (toxic properties also), will
become apparent and attributed to traditional and exotic juices.

Given the propensity of some consumers to place the therapeutic value of medicines over foods, one company even incorporates the active ingredients from 17 different fruits, vegetables, grains, fibres and probiotics, into capsules and chewable pills. Their trademark, "Juice PLUS+" acknowledges the phytochemical value of juices. Of course, juices and blends are a less costly and more appetizing alternative, albeit requiring more attention and awareness on the consumer's part.

One unique and fascinating class of phytochemicals is phytoalexins. These compounds are synthesized in plant parts, including fruit, as a response to external stress, i.e. drought, sunburn, temperature extremes, insect damage, pathogen infection, etc. Resveratrol, a
stilbene type compound has been studied extensively as a stress mediated substance with likely chemopreventive effects against cardiovascular disease and cancer. Red grapes, juice and wines have significant amounts of such compounds, believed to be in part responsible for the health benefits of red wine and attributed to their antioxidant properties (Adrian, et al., 2000).

Needless to say, the total composition of fruits and the expressed juice provide a range of pleasing sensory and health attributes that can be optimized by the juice processor, even to the extent of improving upon the raw material.

Table 3.2: Some phytochemicals in fruit and vegetable processing protective properties against cancer and cardiovascular disease*.



Antioxidant Vitamins

Many fruits and vegetables



Acid (Vitamin C)


Tocopherols (Vitamin E)


Selenium (a soil mineral)

Incorporated from soil


Most yellow/red/orange fruits and vegetables, dark green leafy vegetables

 (Some haveCarotenes provitamin A Lycopene activity)






Dietary Fibre

Ubiquitous cell wall constituents (lower in juice)










Most fruits and vegetables Can be highly pigmented or colourless, highly astringent or flavourless












Flavones/Isoflavones Apigenin

Some vegetables - celery, olives (others in soybean)




Cruciferous vegetables possessing pungent flavour -


Brussels sprouts, cabbage, broccoli, cauliflower, etc.





Phenols and Phenolic Acids

Most fruits and vegetables, some very highly flavoured, astringent or bitter; teas and herbals

Capsaicin, Carnisol, Gingerol,


Piperine, p-cresol, Caffeic,


Ellagic, Gallic, Chlorogenic,


Ferulic, Vanillic, p-coumaric


Phytosterols and Stanols


Sulphur (Allylics)

Allium Vegetables possessing pungent flavour -onion, garlic, chive, shallot, etc.








Some fruits and vegetables, especially red grapes

Resveratrol, Stilbenes



Potato, beans, legumes


Citrus, cherries, ginger, liquorice

Mycrene, d-Limonine, Carvone,


Carnosol, Glycyrrhizin,




* Adapted from Broihier, (1999); Guhr and LaChance, (1997) and expanded.

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