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FRUITS OF TEMPERATE CLIMATES | Fruits of the Ericacae
2762 FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae
Fruits of the Ericacae J F Hancock and R M Beaudry, Michigan State University, East Lansing, MI, USA J J Luby, University of Minnesota, St. Paul, MN, USA Copyright 2003, Elsevier Science Ltd. All Rights Reserved.
Global Distribution 0001
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The family Ericaceae is perhaps best known around the world for its showy garden members such as rhododendrons and heathers. However, some 13 genera contain species with fleshy berries, which are consumed locally in many parts of the world (Table 1). The fruits of these species are commonly eaten fresh or sometimes dried. Many are processed into preserves, juice, or wine. Vaccinium is the most important genus in terms of fruit production. The majority of species inhabit open mountain slopes in the tropics, with the balance being distributed in subtropical, temperate, and boreal regions of the northern hemisphere. Plants of Vaccinium vary in form from epiphytes to trailing vines to trees, with the majority being terrestrial shrubs. Some form crowns, whereas others produce new aerial shoots from rhizomes. Flowers may be solitary or in racemes or clusters.
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Commercial fruit production is mainly from species of section Cyanococcus (cluster-fruited blueberries), including cultivars of V. corymbosum L. (highbush blueberry) and V. ashei Reade (rabbiteye blueberry) and native stands of V. angustifolium Ait. and V. myrtilloides Michx. (lowbush blueberries). Vaccinium macrocarpon Ait. (large cranberry), a member of section Oxycoccus, is also an important domesticated fruit, although most of the cultivars were selected from the wild. Vaccinium myrtillus L. (bilberry, whortleberry), in section Myrtillus, is collected exclusively from the wild. Vaccinium vitis-idaea L. (lingonberry, mountain cranberry or cowberry), in section Vitis-idaea, is also collected predominantly from the wild, although it has recently been domesticated. The highbush blueberry is by far the most important commercial crop, producing over 95 000 t of fruit annually on over 20 000 ha. Highbush production occurs in 36 states in the USA, in six Canadian provinces, and in Europe, Australia, and New Zealand. Highbush plants have recently been established in South American countries, especially Chile. The largest acreages are in Michigan, New Jersey, and North Carolina in the USA, and British Columbia in
Canada. Interest is growing in California. Half-high types (V. corymbosum V. angustifolium) have made an impact in Minnesota and regions too cold to successfully grow pure highbush. The commercial production of rabbiteye blueberries is largely confined to southeastern USA, centered in Georgia, and extending from North Carolina to Texas. The estimated area in production in the USA is over 3000 ha with approximately half of this in Georgia. The total annual production is over 5500 t. There is also interest in growing rabbiteye blueberries in warm temperate and subtropical regions of the world, such as southern African and South American countries. The commercial production of lowbush blueberries is largely confined to approximately 50 000 ha in Maine (USA) and Quebec and the Maritime Provinces of Canada. Maine has only 43% of the hectarage, but generates over half of the production. Annual production now exceeds 55 000 t. Cranberry production is over 200 000 t annually from over 15 000 ha, primarily in Wisconsin, Massachusetts, New Jersey, Washington, Oregon, and Nova Scotia. A major planting of cranberries was also recently made in Chile, along with modest plantings in Ireland, the UK, and northern Europe. Lingonberries are commonly harvested in Scandinavia, the former USSR, Poland and several other European countries, and in eastern Canada, whereas bilberries are gathered and consumed primarily throughout northern Europe, Siberia, and northeastern China.
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Varieties Highbush blueberry breeding was begun by Dr. Fredrick Coville of the US Department of Agriculture in 1908. Over 70 cultivars are now available, although only two, Bluecrop and Jersey, constitute more than half the hectarage. Bluecrop is the most dominant cultivar, owing to its high yields and long storage life, and now encompasses about a third of the total hectareage. It is the leading cultivar in nearly all production regions, and its acreage is still increasing. Most of the Jersey acreage is located in Michigan, and it is no longer being actively planted. Among the newer releases, Elliott and Duke are the most popular. Other important cultivars include Croatan, Blueray, Bluetta, Weymouth, Berkeley, Patriot, Bluejay, and Rubel. Beginning in the 1970s, the introduction of highbush cultivars with a low chilling requirement for budbreak (so called ‘low-chill’ or ‘southern’ highbush) heralded the extension of ‘highbush type’ blueberry culture into more southern latitudes in the USA and Australia. Sharpblue is now the most widely
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FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae tbl0001
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Table 1 Species of the family Ericaceae with edible fruits Genus and species
Geographic range
Usesa
Vaccinium angustifolium Ait. V. andringtrense Perr. V. arbuscula (A. Gray) Mart. V. arctostaphylos L. V. ashei Reade V. berberifolium (A. Gray) Skotts V. boreale Hall & Ald. V. caespitosum Michx. V. confertum Kunth V. consanguineum Klotzch V. corymbosum L. V. cylindraceum Sm. V. darrowi Camp V. deliciosum Piper V. dentatum J. Sm. V. erythrocarpum Michx. V. floribundum H.B.K. V. hirsutum Buckl. V. leucanthum Schlect. V. littoreum Miq. V. macrocarpon Ait. V. membranaceum Dougl. ex Hook. V. meridionale Sw. V. mortinia Benth. V. myrsinites Lamarck V. myrtillus L. V. myrtillodes Michx. V. myrtoides (Blume) Miq. V. oldhamii Miq. V. oxycoccus L. V. ovalifolium Smith V. padifolium Sm. V. pallidum Ait. V. praestans Pamb. V. stamineum L. V. tenellum Ait. V. uliginosum L. V. vitis-idaea L. Arbutus unedo L. Arctostaphylos arguta Zucc. A. manzanita Parry A. pungens H.B.K. A. tomentosa Pursh A. uva-ursi (L.) Spreng. Gaultheria antipoda Forster G. hispida R.Br. G. hispidula (L.) Torr. & Gray G. myrsinites Hook. G. procumbens L. G. shallon Pursh. Gaylussacia baccata (Wang.) Koch G. brachycera (Michx.) Gray G. dumosa (And.) T. G. frondosa Torr. & Gray G. ursina Curtis Macleania ecuadoriensis Horold M. popenoei Blake Menziesia feriuginea Sm. Chiogenes hispidula (L.) Hitchc. Disterigma margaricoccum Blake D. popenoei Blake
Eastern N. America Madagascar Western N. America Southern Europe Southeastern USA Hawaii Eastern N. America N. America Mexico Mexico, C. America Eastern N. America Azores Eastern N. America Western N. America Hawaii Eastern N. America Andean S. America Eastern N. America Mexico Malaysia Eastern N. America Western N. America Jamaica Andean S. America Southeastern USA Europe, Asia, N. America N. America Philippines Eastern Asia Europe, Asia, N. America Western N. America Madeira Eastern N. America Eastern Asia Eastern N. America Eastern N. America Europe, Asia, N. America Europe, Asia, N. America Mediterranean Mexico Southwestern USA Mexico, Southwestern USA Western N. America Europe, Asia, N. America Tasmania, New Zealand Australia Eastern N. America Western N. America Eastern N. America Western N. America Eastern N. America Eastern N. America Eastern N. America Eastern N. America Eastern N. America Ecuador Ecuador Western N. America N. America Ecuador Ecuador
D, F, P, J D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P A, D, J, F, P D, F, P D, F, P D, F, P F, P D, F, P D, F, P D, F, P D, F, P D, J, P A, D, F, J, P D, F, P D, F, P D, F, P A, D, F, J, P D, F, P F, P D, F, P D, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, P A, D, F, P M A, P D, F, P A, D, F, P D, F, P F F P P D F, P F, P F, P F, P F, P F F D, F F, P F F
a Uses of fruits: A, fermented for alcoholic beverage; D, dried; F, eaten fresh; J, juice; M, medicinal; P, cooked preserves, jelly, or jam. From Uphof JCT (1986) Dictionary of Economic Plants. Leure, Germany: Cramer J; Usher G (1974) A Dictionary of Plants used by Man. London: Constable.
2764 FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae
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planted southern highbush blueberry. Other important low-chill cultivars are Reveille, O’Neal, Star, Misty, Gulfcoast, and Floridablue. Of the half-high types released for northern cold regions, Northblue and Northland are the most popular. Over 25 cultivars of rabbiteye blueberries have been released since their breeding began in the 1930s. Tifblue and Climax form the foundation for the present industry, and Brightwell Premier and Powderblue are also being actively planted. In addition, the very-low-chilling cultivars Beckyblue and Bonita are gaining in importance in Florida. Although lowbush breeding programs existed in Maine, Michigan, West Virginia, Wisconsin, Minnesota, and Nova Scotia at various times, the industry is still based on native selections. Only seven cranberry cultivars account for about 90% of the crop, and all these varieties were selected from the wild in the nineteenth century. Early Black, Stevens, and Searles represent at least half of the area, with most of the remainder being Ben Lear, Pilgrim, Howes, and McFarlin. Most of the new hectareage is Stevens, Ben Lear, and Pilgrim because of their high color. Selection and breeding of lingonberries was initiated in the late 1960s in Sweden, and the crop is now being domesticated at several locations across Europe, Scandinavia, and, most recently, the USA. At least 12 cultivars have been released: Sussi and Sanna in Sweden, Koralle, Ammerland, and Red Pearl in The Netherlands, Erntekrone, Erntedank, and Erntesegen in Germany, Masovia in Poland, and Splendor and Regal in the USA.
Blueberry fruit enlarge following pollination, according to a double sigmoidal growth curve, and they go through several phases of color development: (1) immature green, (2) translucent greenish white, (3) greenish pink, (4) blue–red, and (5) completely blue. Up to 50% of the increase in berry volume occurs during the shift from greenish pink to blue. Flowering occurs in early spring, and the fruits are ripe in 40–60 days, depending on the variety and environmental conditions. (See Ripening of Fruit.) Cranberries also go through several stages of color development, including green, white, and red. However, the size development of the fruit is more linear than blueberry. Once berry growth begins, it continues at a relatively constant rate for 4–6 weeks. Cranberry fruit matures between 60 and 120 days after blossom. The anthocyanin pigments that give the fruits their characteristic colors are in the cells of a surrounding endocarp layer. A layer of wax often covers the surface of the berry. The light blue color of many blueberry cultivars results from the combination of dark blue pigments overlaid by the translucent wax. Temperature plays an important role in the development of color, as picked fruit will develop a normal color at 16–27 C whether they are shaded or not, whereas lower temperatures stop normal development. The blueberry and cranberry are mildly climacteric, with only modest elevations in respiration and ethylene production associated with fruit ripening. (See Colorants (Colourants): Properties and Determination of Natural Pigments.)
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Chemical and Nutritional Composition Morphology and Anatomy of the Fruits 0012
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The fruits of all flesh-fruited ericaceous species are berries containing many seeds. A waxy cuticle covers the epidermis of the fruit. In blueberries, the fruit are held on corymbs or racemes. Pure inflorescence buds are formed in the late summer and autumn on shoots of the current season. In cranberries, the fruits are borne singly at nodes 3 to 5 on upright shoots that develop from mixed buds on the trailing vines. Fruit of lingonberries are held in drooping racemes on terminal inflorescences. Bilberries are borne singly in the axils of the lowermost leaves of the vegetative shoot. The Vaccinium berry contains one to 50 seeds surrounded by a fleshy and, usually, colorless mesocarp. In most genotypes, seeds are necessary for normal fruit development, although varying levels of parthenocarpy exist. The ultimate size of fruits is strongly correlated with the number of seeds per fruit.
An average blueberry fruit is composed of approximately 83% water, 0.7% protein, 0.5% fat, 1.5% fiber, and 15.3% carbohydrate (Table 2). Cranberries contain 88% moisture, 0.2% protein, 0.4% fat, 1.6% fiber, and 7.8% carbohydrate. Blueberries are 3.5% cellulose and 0.7% soluble pectin, and cranberries contain 1.2% pectin. The total sugars of blueberries amount to more than 10% of the fresh weight, bilberries average 14%, and cranberries contain 4%. The predominant reducing sugars in blueberries are glucose and fructose, which represent 2.4%. The edible portion of the cranberry is composed of 2.66% glucose, 0.74% fructose, and 0.14% sucrose. Its pulp contains measurable amounts of lignin, glucose, arabinose and xylose. Refer to individual nutrients. The overall acid content of Vaccinium fruit is relatively high. Ripe cranberries range from 2 to 3%, whereas blueberries fall in the range of 1–2%. The primary organic acid in blueberries is citric acid
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FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae tbl0002
Table 2 Composition of 100 g of fresh Vaccinium species Constituent Energy value Food energy (kJ) Chemical composition (%) Moisture Reducing sugars Nonreducing sugars Acids (as citric) Pectin Fat (ether extract) Protein Ash Fibre Mineral content (mg) Potassium Sodium Calcium Phosphorus Magnesium Iron Vitamin content Vitamin A (IU) Vitamin C (mg) Thiamin (B1) Riboflavin (B2) Nicotinic acid (mg) Pantothenic acid (mg) Pyridoxine (B6) (mg) Biotin Niacin (mg)
Blueberry
Cranberry
260.4
109.2
83.20 12.75 1.46 1.15 0.66 2.60 0.70 0.30 1.50
88.00 4.20 0.11 2.40 1.20 0.40 0.20 0.25 1.60
81.0 1.0 15.0 13.0 5.3 1.0
53.0 2.0 13.0 8.0 5.5 0.4
100.0 22.5 0.03 mg 0.06 mg na na na na 0.50
40 7.5–10.5 13.5 mg 3.0 mg 33.0 25.0 10.0 Trace na
na, not applicable. From Eck P (1988) Blueberry Science. New Brunswick: Rutgers University Press; Eck P (1990) The American Cranberry. New Brunswick: Rutgers University Press.
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(1.2%). They also contain significant amounts of ellagic acid, a compound thought to reduce the risk of cancer. The cranberry contains high levels of several organic acids, including quinic (1.3%), citric (1.1%), malic (0.9%), and benzoic (0.6%); lingonberries also have very high levels of benzoic acid. Ingestion of cranberries or lingonberries leads to increased acidity of the urine through conversion of its high quinic and benzoic acid contents to hippuric acid by the body. The high acidity and possible antibacterial effects of hippuric acid may relieve urinary tract infections and reduce some types of kidney stones. (See Acids: Natural Acids and Acidulants.) Compared with other fruits and vegetables, blueberries and cranberries have intermediate to low levels of vitamins, amino acids and minerals (Table 2). Blueberries contain 22.1 mg of vitamin C per 100 g of fresh weight, and cranberries contain 7.5–10.5 mg. Bilberries contain 5 mg of N per 100 g of alcohol-soluble nitrogen, whereas blueberries contain 15–60 mg of N per 100 g. Blueberries are unusual in that arginine is their most prominent
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amino acid. Glutamic acid and valine predominate in bilberries, and lingonberries contain high levels of serine and aminobutyric acid. Lingonberries also possess appreciable levels of the unusual amino acids 1-aminocyclopane-1-carboxylic acid and 5-hydroxypipecolic acid. In general, blueberries and bilberries are two of the richest sources of antioxidant phytonutrients among the fresh fruits, with total antioxidant capacity ranging from 13.9 to 45.9 mmol of Trolox equivalents per gram of fresh berry. Berries from the various Vaccinium species contain relatively high levels of polyphenolic compounds, with chlorogenic acid predominating. Total anthocyanins in blueberry fruit range from 85 to 270 mg per 100 g, and species in the subgenus Cyanococcus carry the same predominant anthocyanins, aglycones and aglycone sugars, although the relative proportions vary. The predominant anthocyanins are delphinidin monogalactoside, cyanidin monogalactoside, petunidin monogalactoside, malvidin monogalactoside, and malvidin monoarabinoside. Among the other Vaccinium spp., cranberries have total anthocyanins varying from 25 to 100 mg per 100 g fruit, with the most important anthocyanins being cyanidin-3-monogalactoside, peonidin-3monogalactoside, cyanidin-3-monoarabinoxide, and peonidin-3-monoarabinoside. Cowberries contain high quantities of cyanidin-3-galactosides. Bilberries contain high quantities of hydroxycinnamic acid and possess very high levels of quercitin-3-glucoside, rhamnoside, and arabinoside. The various Ericaceae species also contain appreciable amounts of several carotenoids. The major volatiles contributing to the characteristic aroma of blueberry fruit are trans-2-hexanol, trans-2-hexanal, and linalool. The predominant volatiles in the bilberry are trans-2-hexanal, ethyl3-methyl butyrate, and ethyl-2-methyl butyrate. In the cranberry, 2-methyl butyrate is rare, but a-terpineol predominates. Benzaldehyde also contributes to the aroma of the cranberry. (See Sensory Evaluation: Aroma.)
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Handling and Storage Most fresh-marketed fruits of Vaccinium are harvested by hand, although lowbush blueberries are commonly removed from the bush with hand-held rakes. Highbush and rabbiteye berries are mechanically harvested for the processed market with overthe-row machines that shake or beat the fruit on to catching pans or conveyors. Fruits are mechanically harvested as a clean-up operation after several handpickings, or when 60–70% of the fruit on a bush are
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Processed berries are generally frozen. Most cranberries are stored in bulk, but some berries are prepackaged in perforated 0.45-kg cellophane bags or unsealed cardboard boxes. Storage life can be extended up to 12 weeks if berries are kept cool in bulk and packaged just before harvest. Controlledatmosphere storage does not appear to have significant benefits, except that treatment with ethylene gas after harvest may increase the anthocyanin content of the fruit. (See Controlled-atmosphere Storage: Applications for Bulk Storage of Foodstuffs; Storage Stability: Mechanisms of Degradation; Parameters Affecting Storage Stability.) Blueberry fruit are generally packaged in plastic pint or quart ‘clam shell’ containers, or open containers that are covered loosely with cellophane or shrinkwrapped. Shelf-life can be greatly extended by lowering fruit temperatures to 0 C (Figure 1). Decreasing the storage temperature slows respiration and other metabolic processes, but even more importantly, it greatly reduces the activity of decay organisms (Figure 2). In addition, spore germination of Alternaria and Botrytis occurs only very slowly at 0 C, whereas germination of Glomerella spores is stopped altogether. During long-term storage (3 weeks or more) at 0 C, senescent breakdown can occur in the berry flesh, leading to the formation of watersoaked areas and the bleeding of blue skin pigments into the normally colorless mesocarp. However, few precautions other than modest chilling
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120 Low O2 Optimal O2 High O2 Air Shelf life (days)
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blue. A limited amount of fruit is mechanically harvested for the fresh market, but only with careful sorting to remove defective fruit. Cranberries are mechanically harvested either dry or wet. Dry harvested fruit are generally stripped from the vines with a picking machine that combs or scoops fruit off the plant. To wet harvest fruit, the bogs are flooded to lift the vines, and the floating fruit are raked or beaten off the surface of the water. Wet harvesting recovers a higher percentage of the fruit, but water-raked berries deteriorate more rapidly. A typical grading line for fresh-marketed blueberries consists of a ‘blower’ to remove leaf material and small green berries, a ‘tilt belt’ to separate soft from firm fruit, and a sorting line, where four to eight people visually scan the fruit for defects. Grading lines for processing berries are usually composed, in order, of a blower, tilt belt, a water tank, where ripe berries sink, a fruit destemmer, and a sorting line. Processed berries are generally frozen either in bulk or individually quick-frozen. The color of blueberries is well preserved by freezing, although they form exudates and redden upon thawing. Dry-harvested cranberry fruit are generally sorted by bouncing them over a barrier board. Sound berries bounce and travel forward on a conveyor belt, and soft berries are collected below. Small and large berries are then separated over a wire screen and carried along moving belts for further sorting. Water-harvested berries are first dumped on a long, inclined mesh belt that passes through a dryer to prepare them for sorting. Flotation tanks are also used in some instances to sort both wet- and dryharvested fruit. Suggested quality standards for sorted blueberry fruit are as follows: (1) pH at 2.25–4.25; (2) citric acid at 0.3–1.3%; (3) soluble solids, greater than 10%; (4) ratio of soluble solids to acid, 10–33%; (5) firmness, greater than 7 g of force for 0.01 cm of deformation on the Instron testing machine; (6) diameter, greater than 10 mm; (7) color, blue with less than 0.5% of the surface having a pink coloration. Cranberry quality is largely determined by its color, particularly in juice products. Other important quality traits are sweeter, darker, uniform-colored fruit for fresh marketing, increased aromas, firmness, uniform size and shape, organic acids, and glossiness. Methods have been devised for sorting Vaccinium fruit by firmness and optical density, and these are growing in popularity. Cranberry fruit can be successfully stored for several months without any significant losses in quality. Fruit were once stored for the fresh market in large ventilated rooms at ambient temperatures, but now refrigerated storage is recommended at 2–4 C.
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0 0
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10 15 Temperature (⬚C)
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Figure 1 Effect of storage temperature and atmosphere composition on the visual shelf-life (days in marketable condition) of Bluecrop blueberry fruit sealed in low-density polyethylene packages. For the various oxygen (O2) treatments, the approximate O2 and carbon dioxide (CO2) concentrations were, respectively, as follows: low O2, 0.8% and 12%; optimal O2, 2% and 7%; high O2, 7% and 3%; air, 21% and 0%.
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Lesion diameter (mm)
25 1.2 20 15
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10 15 20 Temperature (⬚C)
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Figure 2 Effect of temperature on (s——s) the development of decay lesions (generalized curve redrawn from Kader AA, Kasmire RF, Mitchell FG, et al. (1985) Postharvest Technology of Horticultural Crops. Extension Bulletin 311. University of California at Davis.) and (.——.) respiratory metabolism of Bluecrop fruit at ambient oxygen levels. Adapted from Beaudry RM, Cameron AC, Shirazi A and Dostal DL (1992) Modified atmosphere packaging of blueberry fruit: effect of temperature on package oxygen and carbon dioxide. Journal of the American Society of Horticultural Science 117: 436–441, with permission.
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Off-flavour rating
1.6
Respiratory quotient
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Oxygen uptake (mmol O2 per kg per h)
FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae
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0 0
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8 12 Steady-state O2 (kPa)
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Figure 3 Effect of oxygen (O2) concentration on (s) the respiratory quotient (RQ) and (.) off-flavor development of Bluecrop blueberry fruit at 20 C. The increase in the RQ as O2 levels decline below 2 kPa is indicative of fermentation.
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Effect of Modified-atmosphere Packaging on Food Quality; Fungicides.)
Industrial Uses
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are generally taken to attain a storage life of 7–10 days. Once the fruit have been cooled below approximately 10 C, they must be kept chilled to avoid condensation (‘sweat’) upon returning the fruit to warm conditions. Modified atmospheres (elevated CO2 and low O2 conditions) can enhance the visual shelf life of blueberry fruit (Figure 1), although temperature management plays the most important role in maintaining fruit quality. Lowering O2 to 2% does not have a significant benefit by itself, but combinations of low O2 and high CO2 can improve storability. CO2 levels of 8–10% or greater can significantly reduce decay development of blueberry fruit, but may not slow the decline in internal condition that normally occurs during storage. Packaging systems presently under development rely on the fruit, the packaging film, and temperature control to generate and maintain optimal O2 and CO2 levels. Packages must be designed to avoid excessively low O2 levels, or fermentation and off-flavors will result (Figure 3; note that O2 partial pressures are in kPa, which can be read as %). Packaging systems that boost package CO2 levels and/or provide some level of humidity control have been developed for other products and may have considerable potential for packaged blueberry fruit. Chlorine and fungicide dips can also reduce postharvest decay. (See Chilled Storage: Use of Modified-atmosphere Packaging; Chill Foods:
Blueberries and bilberries are eaten both as dessert fruits and in processed forms. About 46% of the rabbiteye crop and 50% of the highbush crop are marketed fresh, and the remainder are processed. Nearly all commercially harvested lowbush blueberries, cranberries, and lingonberries are processed. The first widespread use of cranberries was to make sauce as a speciality item served at Christmas and the American holiday, Thanksgiving. During the 1960s, juice products made their appearance in the USA and now dominate the market. Cranberry ‘cocktail’ is drunk alone or mixed with other juice products. Cranberries are also made into a syrup, a dried raisin-like product, and a natural red food coloring, which has been used successfully to enhance the color of cherry pie filling. Blueberries are used primarily in pie fillings, yogurts, icecream, and prepared muffin and pancake mixes. Blueberries are sometimes added to dried products after dehydration using an explosionpuffing process. Syrups, jams, and preserves are also produced, but in limited quantities. The juice of blueberries is rarely consumed directly as it has a very strong flavor and dark color. Lingonberries are quite tart, but quite edible when cooked and are commonly used for juice, pie fillings, and jam. Bilberries are used fresh or in juice, preserves, or wine. Fruit extracts are also used in pharmaceutical preparations for the treatment of microcirculatory diseases.
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2768 FRUITS OF TEMPERATE CLIMATES/Factors Affecting Quality See also: Acids: Natural Acids and Acidulants; Chilled Storage: Use of Modified-atmosphere Packaging; Chill Foods: Effect of Modified-atmosphere Packaging on Food Quality; Colorants (Colourants): Properties and Determination of Natural Pigments; Controlledatmosphere Storage: Applications for Bulk Storage of Foodstuffs; Fungicides; Ripening of Fruit; Sensory Evaluation: Aroma; Storage Stability: Mechanisms of Degradation; Parameters Affecting Storage Stability
Factors Affecting Quality W S Conway and M Faust, Beltsville Agricultural Research Center, Beltsville, USA C E Sams, University of Tennessee, Knoxville, USA This article is reproduced from Encyclopaedia of Food Science, Food Technology and Nutrition, Copyright 1993, Academic Press.
Introduction Further Reading Ballington JR, Kirkman WB, Ballinger WE and Maness EP (1988) Anthocyanin, algycone, and aglycone-sugar content in the fruits of temperate North American species of four sections in Vaccinium. Journal of the American Society of Horticultural Science 113: 746–749. Beaudry RM, Cameron AC, Shirazi A and Dostal DL (1992) Modified atmosphere packaging of blueberry fruit: effect of temperature on package oxygen and carbon dioxide. Journal of the American Society of Horticultural Science 117: 436–441. Beaudry RM, Moggia CE, Retamales JB and Hancock JF (1998) Quality of ‘Ivanhoe’ and ‘Bluecrop’ blueberry fruit transported by air and sea from Chile to North America. HortScience 33: 313–317. Eck P (1988) Blueberry Science. New Brunswick: Rutgers University Press. Eck P (1990) The American Cranberry. New Brunswick: Rutgers University Press. Hancock JF and Draper AD (1989) Blueberry culture in North America. HortScience 24: 551–556. Hulme AC (ed.) (1970) The Biochemistry of Fruits and their Products. London: Academic Press. Kader AA, Kasmire RF, Mitchell FG et al. (1985) Postharvest Technology of Horticultural Crops. Extension Bulletin 3311. University of California at Davis. Kalt, W, Forney CF, Martin A and Prior RL (1999) Antioxidant capacity, vitamin C, phenolics and anthocyanins after fresh storage of small fruits. Journal of Agriculture Food Chemistry 47: 4638–4644. Luby JJ, Ballington JR, Draper AD, Pliszka K and Austin ME (1990) Blueberries and cranberries (Vaccinium). In: Moore JN and Ballington JR (eds) Genetic Resources of Temperate Fruit and Nut Crops. Wageningen, The Netherlands: International Society for Horticultural Science. Maas JL, Galletta GJ and Stoner GD (1991) Ellagic acid, an anticarcinogen in fruits, especially in strawberries: a review. Horticultural Science 26: 10–14. Uphof JCT (1986) Dictionary of Economic Plants. Lehre, Germany: J Cramer. Usher G (1974) A Dictionary of Plants used by Man. London: Constable. Vander Kloet SP (1988) The Genus Vaccinium in North America. Agriculture Canada Publication 1828. Ottawa: Agriculture Canada. Yarborough DE and Smagula JM (eds) (1996) Proceedings of the sixth international symposium on Vaccinium culture. Acta Horticulturae 446.
The primary goal of the fruit grower is to produce a product of such quality that it is attractive to the potential consumer in both appearance and taste. In order for quality fruit to reach the consumer, it must be properly grown in the orchard, harvested at the time of proper maturity, and stored in such a manner that the quality is maintained. Economic losses occurring in postharvest channels are greater than often realized, and the avoidable loss of quality ‘between the farm gate and the consumer’ is the cause for real concern. Fresh fruit increases several-fold in unit value while moving from the field to the consumer, because of the added cost of careful harvesting and handling. Factors that affect fruit quality can be classified into three groups: (1) nutritional factors during growth; (2) factors associated with the time of harvest; and (3) factors associated with storage. These factors, as they relate to the quality of the major temperate fruits, including apples, apricots, cherries, peaches, pears, and plums, will be discussed.
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Tree Nutrition In order for the fruit tree to produce quality fruit, it must be supplied with the proper mineral nutrients and photosynthates. Orchard trees grow and produce fruit in the same place for 15–50 years. By the time these trees are mature enough to produce a crop, they have developed extensive root and branch systems and are able to acquire nutrients from the soil, intercept light, and produce photosynthates. The perennial nature of the tree and the necessity of producing large crops of fruit regularly imposes demands for nutrition not found in herbaceous plants or forest trees. The tree has changing nutrient needs during the year, particularly when it sets and raises its fruit. These occasional high mineral nutrient needs may not be met by uptake through the roots and must be supplied by foliar application. Fruit nutrition must often be concerned with the nutrition of not only the whole tree but also individual organs. For example, fruit should have a certain nutrient content for maximum storability. This requires techniques other than nutrition for maintaining the tree. First, nutrients must be applied and the translocation and
0002
Fruits of the Ericacae J F Hancock and R M Beaudry, Michigan State University, East Lansing, MI, USA J J Luby, University of Minnesota, St. Paul, MN, USA Copyright 2003, Elsevier Science Ltd. All Rights Reserved.
Global Distribution 0001
0002
The family Ericaceae is perhaps best known around the world for its showy garden members such as rhododendrons and heathers. However, some 13 genera contain species with fleshy berries, which are consumed locally in many parts of the world (Table 1). The fruits of these species are commonly eaten fresh or sometimes dried. Many are processed into preserves, juice, or wine. Vaccinium is the most important genus in terms of fruit production. The majority of species inhabit open mountain slopes in the tropics, with the balance being distributed in subtropical, temperate, and boreal regions of the northern hemisphere. Plants of Vaccinium vary in form from epiphytes to trailing vines to trees, with the majority being terrestrial shrubs. Some form crowns, whereas others produce new aerial shoots from rhizomes. Flowers may be solitary or in racemes or clusters.
Commercial Importance 0003
0004
Commercial fruit production is mainly from species of section Cyanococcus (cluster-fruited blueberries), including cultivars of V. corymbosum L. (highbush blueberry) and V. ashei Reade (rabbiteye blueberry) and native stands of V. angustifolium Ait. and V. myrtilloides Michx. (lowbush blueberries). Vaccinium macrocarpon Ait. (large cranberry), a member of section Oxycoccus, is also an important domesticated fruit, although most of the cultivars were selected from the wild. Vaccinium myrtillus L. (bilberry, whortleberry), in section Myrtillus, is collected exclusively from the wild. Vaccinium vitis-idaea L. (lingonberry, mountain cranberry or cowberry), in section Vitis-idaea, is also collected predominantly from the wild, although it has recently been domesticated. The highbush blueberry is by far the most important commercial crop, producing over 95 000 t of fruit annually on over 20 000 ha. Highbush production occurs in 36 states in the USA, in six Canadian provinces, and in Europe, Australia, and New Zealand. Highbush plants have recently been established in South American countries, especially Chile. The largest acreages are in Michigan, New Jersey, and North Carolina in the USA, and British Columbia in
Canada. Interest is growing in California. Half-high types (V. corymbosum V. angustifolium) have made an impact in Minnesota and regions too cold to successfully grow pure highbush. The commercial production of rabbiteye blueberries is largely confined to southeastern USA, centered in Georgia, and extending from North Carolina to Texas. The estimated area in production in the USA is over 3000 ha with approximately half of this in Georgia. The total annual production is over 5500 t. There is also interest in growing rabbiteye blueberries in warm temperate and subtropical regions of the world, such as southern African and South American countries. The commercial production of lowbush blueberries is largely confined to approximately 50 000 ha in Maine (USA) and Quebec and the Maritime Provinces of Canada. Maine has only 43% of the hectarage, but generates over half of the production. Annual production now exceeds 55 000 t. Cranberry production is over 200 000 t annually from over 15 000 ha, primarily in Wisconsin, Massachusetts, New Jersey, Washington, Oregon, and Nova Scotia. A major planting of cranberries was also recently made in Chile, along with modest plantings in Ireland, the UK, and northern Europe. Lingonberries are commonly harvested in Scandinavia, the former USSR, Poland and several other European countries, and in eastern Canada, whereas bilberries are gathered and consumed primarily throughout northern Europe, Siberia, and northeastern China.
0005
0006
Varieties Highbush blueberry breeding was begun by Dr. Fredrick Coville of the US Department of Agriculture in 1908. Over 70 cultivars are now available, although only two, Bluecrop and Jersey, constitute more than half the hectarage. Bluecrop is the most dominant cultivar, owing to its high yields and long storage life, and now encompasses about a third of the total hectareage. It is the leading cultivar in nearly all production regions, and its acreage is still increasing. Most of the Jersey acreage is located in Michigan, and it is no longer being actively planted. Among the newer releases, Elliott and Duke are the most popular. Other important cultivars include Croatan, Blueray, Bluetta, Weymouth, Berkeley, Patriot, Bluejay, and Rubel. Beginning in the 1970s, the introduction of highbush cultivars with a low chilling requirement for budbreak (so called ‘low-chill’ or ‘southern’ highbush) heralded the extension of ‘highbush type’ blueberry culture into more southern latitudes in the USA and Australia. Sharpblue is now the most widely
0007
0008
FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae tbl0001
2763
Table 1 Species of the family Ericaceae with edible fruits Genus and species
Geographic range
Usesa
Vaccinium angustifolium Ait. V. andringtrense Perr. V. arbuscula (A. Gray) Mart. V. arctostaphylos L. V. ashei Reade V. berberifolium (A. Gray) Skotts V. boreale Hall & Ald. V. caespitosum Michx. V. confertum Kunth V. consanguineum Klotzch V. corymbosum L. V. cylindraceum Sm. V. darrowi Camp V. deliciosum Piper V. dentatum J. Sm. V. erythrocarpum Michx. V. floribundum H.B.K. V. hirsutum Buckl. V. leucanthum Schlect. V. littoreum Miq. V. macrocarpon Ait. V. membranaceum Dougl. ex Hook. V. meridionale Sw. V. mortinia Benth. V. myrsinites Lamarck V. myrtillus L. V. myrtillodes Michx. V. myrtoides (Blume) Miq. V. oldhamii Miq. V. oxycoccus L. V. ovalifolium Smith V. padifolium Sm. V. pallidum Ait. V. praestans Pamb. V. stamineum L. V. tenellum Ait. V. uliginosum L. V. vitis-idaea L. Arbutus unedo L. Arctostaphylos arguta Zucc. A. manzanita Parry A. pungens H.B.K. A. tomentosa Pursh A. uva-ursi (L.) Spreng. Gaultheria antipoda Forster G. hispida R.Br. G. hispidula (L.) Torr. & Gray G. myrsinites Hook. G. procumbens L. G. shallon Pursh. Gaylussacia baccata (Wang.) Koch G. brachycera (Michx.) Gray G. dumosa (And.) T. G. frondosa Torr. & Gray G. ursina Curtis Macleania ecuadoriensis Horold M. popenoei Blake Menziesia feriuginea Sm. Chiogenes hispidula (L.) Hitchc. Disterigma margaricoccum Blake D. popenoei Blake
Eastern N. America Madagascar Western N. America Southern Europe Southeastern USA Hawaii Eastern N. America N. America Mexico Mexico, C. America Eastern N. America Azores Eastern N. America Western N. America Hawaii Eastern N. America Andean S. America Eastern N. America Mexico Malaysia Eastern N. America Western N. America Jamaica Andean S. America Southeastern USA Europe, Asia, N. America N. America Philippines Eastern Asia Europe, Asia, N. America Western N. America Madeira Eastern N. America Eastern Asia Eastern N. America Eastern N. America Europe, Asia, N. America Europe, Asia, N. America Mediterranean Mexico Southwestern USA Mexico, Southwestern USA Western N. America Europe, Asia, N. America Tasmania, New Zealand Australia Eastern N. America Western N. America Eastern N. America Western N. America Eastern N. America Eastern N. America Eastern N. America Eastern N. America Eastern N. America Ecuador Ecuador Western N. America N. America Ecuador Ecuador
D, F, P, J D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P A, D, J, F, P D, F, P D, F, P D, F, P F, P D, F, P D, F, P D, F, P D, F, P D, J, P A, D, F, J, P D, F, P D, F, P D, F, P A, D, F, J, P D, F, P F, P D, F, P D, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, F, P D, P A, D, F, P M A, P D, F, P A, D, F, P D, F, P F F P P D F, P F, P F, P F, P F, P F F D, F F, P F F
a Uses of fruits: A, fermented for alcoholic beverage; D, dried; F, eaten fresh; J, juice; M, medicinal; P, cooked preserves, jelly, or jam. From Uphof JCT (1986) Dictionary of Economic Plants. Leure, Germany: Cramer J; Usher G (1974) A Dictionary of Plants used by Man. London: Constable.
2764 FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae
0009
0010
0011
planted southern highbush blueberry. Other important low-chill cultivars are Reveille, O’Neal, Star, Misty, Gulfcoast, and Floridablue. Of the half-high types released for northern cold regions, Northblue and Northland are the most popular. Over 25 cultivars of rabbiteye blueberries have been released since their breeding began in the 1930s. Tifblue and Climax form the foundation for the present industry, and Brightwell Premier and Powderblue are also being actively planted. In addition, the very-low-chilling cultivars Beckyblue and Bonita are gaining in importance in Florida. Although lowbush breeding programs existed in Maine, Michigan, West Virginia, Wisconsin, Minnesota, and Nova Scotia at various times, the industry is still based on native selections. Only seven cranberry cultivars account for about 90% of the crop, and all these varieties were selected from the wild in the nineteenth century. Early Black, Stevens, and Searles represent at least half of the area, with most of the remainder being Ben Lear, Pilgrim, Howes, and McFarlin. Most of the new hectareage is Stevens, Ben Lear, and Pilgrim because of their high color. Selection and breeding of lingonberries was initiated in the late 1960s in Sweden, and the crop is now being domesticated at several locations across Europe, Scandinavia, and, most recently, the USA. At least 12 cultivars have been released: Sussi and Sanna in Sweden, Koralle, Ammerland, and Red Pearl in The Netherlands, Erntekrone, Erntedank, and Erntesegen in Germany, Masovia in Poland, and Splendor and Regal in the USA.
Blueberry fruit enlarge following pollination, according to a double sigmoidal growth curve, and they go through several phases of color development: (1) immature green, (2) translucent greenish white, (3) greenish pink, (4) blue–red, and (5) completely blue. Up to 50% of the increase in berry volume occurs during the shift from greenish pink to blue. Flowering occurs in early spring, and the fruits are ripe in 40–60 days, depending on the variety and environmental conditions. (See Ripening of Fruit.) Cranberries also go through several stages of color development, including green, white, and red. However, the size development of the fruit is more linear than blueberry. Once berry growth begins, it continues at a relatively constant rate for 4–6 weeks. Cranberry fruit matures between 60 and 120 days after blossom. The anthocyanin pigments that give the fruits their characteristic colors are in the cells of a surrounding endocarp layer. A layer of wax often covers the surface of the berry. The light blue color of many blueberry cultivars results from the combination of dark blue pigments overlaid by the translucent wax. Temperature plays an important role in the development of color, as picked fruit will develop a normal color at 16–27 C whether they are shaded or not, whereas lower temperatures stop normal development. The blueberry and cranberry are mildly climacteric, with only modest elevations in respiration and ethylene production associated with fruit ripening. (See Colorants (Colourants): Properties and Determination of Natural Pigments.)
0014
0015
0016
Chemical and Nutritional Composition Morphology and Anatomy of the Fruits 0012
0013
The fruits of all flesh-fruited ericaceous species are berries containing many seeds. A waxy cuticle covers the epidermis of the fruit. In blueberries, the fruit are held on corymbs or racemes. Pure inflorescence buds are formed in the late summer and autumn on shoots of the current season. In cranberries, the fruits are borne singly at nodes 3 to 5 on upright shoots that develop from mixed buds on the trailing vines. Fruit of lingonberries are held in drooping racemes on terminal inflorescences. Bilberries are borne singly in the axils of the lowermost leaves of the vegetative shoot. The Vaccinium berry contains one to 50 seeds surrounded by a fleshy and, usually, colorless mesocarp. In most genotypes, seeds are necessary for normal fruit development, although varying levels of parthenocarpy exist. The ultimate size of fruits is strongly correlated with the number of seeds per fruit.
An average blueberry fruit is composed of approximately 83% water, 0.7% protein, 0.5% fat, 1.5% fiber, and 15.3% carbohydrate (Table 2). Cranberries contain 88% moisture, 0.2% protein, 0.4% fat, 1.6% fiber, and 7.8% carbohydrate. Blueberries are 3.5% cellulose and 0.7% soluble pectin, and cranberries contain 1.2% pectin. The total sugars of blueberries amount to more than 10% of the fresh weight, bilberries average 14%, and cranberries contain 4%. The predominant reducing sugars in blueberries are glucose and fructose, which represent 2.4%. The edible portion of the cranberry is composed of 2.66% glucose, 0.74% fructose, and 0.14% sucrose. Its pulp contains measurable amounts of lignin, glucose, arabinose and xylose. Refer to individual nutrients. The overall acid content of Vaccinium fruit is relatively high. Ripe cranberries range from 2 to 3%, whereas blueberries fall in the range of 1–2%. The primary organic acid in blueberries is citric acid
0017
0018
FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae tbl0002
Table 2 Composition of 100 g of fresh Vaccinium species Constituent Energy value Food energy (kJ) Chemical composition (%) Moisture Reducing sugars Nonreducing sugars Acids (as citric) Pectin Fat (ether extract) Protein Ash Fibre Mineral content (mg) Potassium Sodium Calcium Phosphorus Magnesium Iron Vitamin content Vitamin A (IU) Vitamin C (mg) Thiamin (B1) Riboflavin (B2) Nicotinic acid (mg) Pantothenic acid (mg) Pyridoxine (B6) (mg) Biotin Niacin (mg)
Blueberry
Cranberry
260.4
109.2
83.20 12.75 1.46 1.15 0.66 2.60 0.70 0.30 1.50
88.00 4.20 0.11 2.40 1.20 0.40 0.20 0.25 1.60
81.0 1.0 15.0 13.0 5.3 1.0
53.0 2.0 13.0 8.0 5.5 0.4
100.0 22.5 0.03 mg 0.06 mg na na na na 0.50
40 7.5–10.5 13.5 mg 3.0 mg 33.0 25.0 10.0 Trace na
na, not applicable. From Eck P (1988) Blueberry Science. New Brunswick: Rutgers University Press; Eck P (1990) The American Cranberry. New Brunswick: Rutgers University Press.
0019
(1.2%). They also contain significant amounts of ellagic acid, a compound thought to reduce the risk of cancer. The cranberry contains high levels of several organic acids, including quinic (1.3%), citric (1.1%), malic (0.9%), and benzoic (0.6%); lingonberries also have very high levels of benzoic acid. Ingestion of cranberries or lingonberries leads to increased acidity of the urine through conversion of its high quinic and benzoic acid contents to hippuric acid by the body. The high acidity and possible antibacterial effects of hippuric acid may relieve urinary tract infections and reduce some types of kidney stones. (See Acids: Natural Acids and Acidulants.) Compared with other fruits and vegetables, blueberries and cranberries have intermediate to low levels of vitamins, amino acids and minerals (Table 2). Blueberries contain 22.1 mg of vitamin C per 100 g of fresh weight, and cranberries contain 7.5–10.5 mg. Bilberries contain 5 mg of N per 100 g of alcohol-soluble nitrogen, whereas blueberries contain 15–60 mg of N per 100 g. Blueberries are unusual in that arginine is their most prominent
2765
amino acid. Glutamic acid and valine predominate in bilberries, and lingonberries contain high levels of serine and aminobutyric acid. Lingonberries also possess appreciable levels of the unusual amino acids 1-aminocyclopane-1-carboxylic acid and 5-hydroxypipecolic acid. In general, blueberries and bilberries are two of the richest sources of antioxidant phytonutrients among the fresh fruits, with total antioxidant capacity ranging from 13.9 to 45.9 mmol of Trolox equivalents per gram of fresh berry. Berries from the various Vaccinium species contain relatively high levels of polyphenolic compounds, with chlorogenic acid predominating. Total anthocyanins in blueberry fruit range from 85 to 270 mg per 100 g, and species in the subgenus Cyanococcus carry the same predominant anthocyanins, aglycones and aglycone sugars, although the relative proportions vary. The predominant anthocyanins are delphinidin monogalactoside, cyanidin monogalactoside, petunidin monogalactoside, malvidin monogalactoside, and malvidin monoarabinoside. Among the other Vaccinium spp., cranberries have total anthocyanins varying from 25 to 100 mg per 100 g fruit, with the most important anthocyanins being cyanidin-3-monogalactoside, peonidin-3monogalactoside, cyanidin-3-monoarabinoxide, and peonidin-3-monoarabinoside. Cowberries contain high quantities of cyanidin-3-galactosides. Bilberries contain high quantities of hydroxycinnamic acid and possess very high levels of quercitin-3-glucoside, rhamnoside, and arabinoside. The various Ericaceae species also contain appreciable amounts of several carotenoids. The major volatiles contributing to the characteristic aroma of blueberry fruit are trans-2-hexanol, trans-2-hexanal, and linalool. The predominant volatiles in the bilberry are trans-2-hexanal, ethyl3-methyl butyrate, and ethyl-2-methyl butyrate. In the cranberry, 2-methyl butyrate is rare, but a-terpineol predominates. Benzaldehyde also contributes to the aroma of the cranberry. (See Sensory Evaluation: Aroma.)
0020
0021
0022
Handling and Storage Most fresh-marketed fruits of Vaccinium are harvested by hand, although lowbush blueberries are commonly removed from the bush with hand-held rakes. Highbush and rabbiteye berries are mechanically harvested for the processed market with overthe-row machines that shake or beat the fruit on to catching pans or conveyors. Fruits are mechanically harvested as a clean-up operation after several handpickings, or when 60–70% of the fruit on a bush are
0023
2766 FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae
0025
0026
0027
0028
Processed berries are generally frozen. Most cranberries are stored in bulk, but some berries are prepackaged in perforated 0.45-kg cellophane bags or unsealed cardboard boxes. Storage life can be extended up to 12 weeks if berries are kept cool in bulk and packaged just before harvest. Controlledatmosphere storage does not appear to have significant benefits, except that treatment with ethylene gas after harvest may increase the anthocyanin content of the fruit. (See Controlled-atmosphere Storage: Applications for Bulk Storage of Foodstuffs; Storage Stability: Mechanisms of Degradation; Parameters Affecting Storage Stability.) Blueberry fruit are generally packaged in plastic pint or quart ‘clam shell’ containers, or open containers that are covered loosely with cellophane or shrinkwrapped. Shelf-life can be greatly extended by lowering fruit temperatures to 0 C (Figure 1). Decreasing the storage temperature slows respiration and other metabolic processes, but even more importantly, it greatly reduces the activity of decay organisms (Figure 2). In addition, spore germination of Alternaria and Botrytis occurs only very slowly at 0 C, whereas germination of Glomerella spores is stopped altogether. During long-term storage (3 weeks or more) at 0 C, senescent breakdown can occur in the berry flesh, leading to the formation of watersoaked areas and the bleeding of blue skin pigments into the normally colorless mesocarp. However, few precautions other than modest chilling
0029
120 Low O2 Optimal O2 High O2 Air Shelf life (days)
0024
blue. A limited amount of fruit is mechanically harvested for the fresh market, but only with careful sorting to remove defective fruit. Cranberries are mechanically harvested either dry or wet. Dry harvested fruit are generally stripped from the vines with a picking machine that combs or scoops fruit off the plant. To wet harvest fruit, the bogs are flooded to lift the vines, and the floating fruit are raked or beaten off the surface of the water. Wet harvesting recovers a higher percentage of the fruit, but water-raked berries deteriorate more rapidly. A typical grading line for fresh-marketed blueberries consists of a ‘blower’ to remove leaf material and small green berries, a ‘tilt belt’ to separate soft from firm fruit, and a sorting line, where four to eight people visually scan the fruit for defects. Grading lines for processing berries are usually composed, in order, of a blower, tilt belt, a water tank, where ripe berries sink, a fruit destemmer, and a sorting line. Processed berries are generally frozen either in bulk or individually quick-frozen. The color of blueberries is well preserved by freezing, although they form exudates and redden upon thawing. Dry-harvested cranberry fruit are generally sorted by bouncing them over a barrier board. Sound berries bounce and travel forward on a conveyor belt, and soft berries are collected below. Small and large berries are then separated over a wire screen and carried along moving belts for further sorting. Water-harvested berries are first dumped on a long, inclined mesh belt that passes through a dryer to prepare them for sorting. Flotation tanks are also used in some instances to sort both wet- and dryharvested fruit. Suggested quality standards for sorted blueberry fruit are as follows: (1) pH at 2.25–4.25; (2) citric acid at 0.3–1.3%; (3) soluble solids, greater than 10%; (4) ratio of soluble solids to acid, 10–33%; (5) firmness, greater than 7 g of force for 0.01 cm of deformation on the Instron testing machine; (6) diameter, greater than 10 mm; (7) color, blue with less than 0.5% of the surface having a pink coloration. Cranberry quality is largely determined by its color, particularly in juice products. Other important quality traits are sweeter, darker, uniform-colored fruit for fresh marketing, increased aromas, firmness, uniform size and shape, organic acids, and glossiness. Methods have been devised for sorting Vaccinium fruit by firmness and optical density, and these are growing in popularity. Cranberry fruit can be successfully stored for several months without any significant losses in quality. Fruit were once stored for the fresh market in large ventilated rooms at ambient temperatures, but now refrigerated storage is recommended at 2–4 C.
80
40
0 0
5
10 15 Temperature (⬚C)
20
Figure 1 Effect of storage temperature and atmosphere composition on the visual shelf-life (days in marketable condition) of Bluecrop blueberry fruit sealed in low-density polyethylene packages. For the various oxygen (O2) treatments, the approximate O2 and carbon dioxide (CO2) concentrations were, respectively, as follows: low O2, 0.8% and 12%; optimal O2, 2% and 7%; high O2, 7% and 3%; air, 21% and 0%.
fig0001
Lesion diameter (mm)
25 1.2 20 15
0.8
10 0.4 5 0.0
0 0
fig0002
5
10 15 20 Temperature (⬚C)
25
30
Figure 2 Effect of temperature on (s——s) the development of decay lesions (generalized curve redrawn from Kader AA, Kasmire RF, Mitchell FG, et al. (1985) Postharvest Technology of Horticultural Crops. Extension Bulletin 311. University of California at Davis.) and (.——.) respiratory metabolism of Bluecrop fruit at ambient oxygen levels. Adapted from Beaudry RM, Cameron AC, Shirazi A and Dostal DL (1992) Modified atmosphere packaging of blueberry fruit: effect of temperature on package oxygen and carbon dioxide. Journal of the American Society of Horticultural Science 117: 436–441, with permission.
2767
5
5
4
4
3
3
2
2
1
1
Off-flavour rating
1.6
Respiratory quotient
30
Oxygen uptake (mmol O2 per kg per h)
FRUITS OF TEMPERATE CLIMATES/Fruits of the Ericacae
0
0 0
4
8 12 Steady-state O2 (kPa)
16
Figure 3 Effect of oxygen (O2) concentration on (s) the respiratory quotient (RQ) and (.) off-flavor development of Bluecrop blueberry fruit at 20 C. The increase in the RQ as O2 levels decline below 2 kPa is indicative of fermentation.
fig0003
Effect of Modified-atmosphere Packaging on Food Quality; Fungicides.)
Industrial Uses
0030
are generally taken to attain a storage life of 7–10 days. Once the fruit have been cooled below approximately 10 C, they must be kept chilled to avoid condensation (‘sweat’) upon returning the fruit to warm conditions. Modified atmospheres (elevated CO2 and low O2 conditions) can enhance the visual shelf life of blueberry fruit (Figure 1), although temperature management plays the most important role in maintaining fruit quality. Lowering O2 to 2% does not have a significant benefit by itself, but combinations of low O2 and high CO2 can improve storability. CO2 levels of 8–10% or greater can significantly reduce decay development of blueberry fruit, but may not slow the decline in internal condition that normally occurs during storage. Packaging systems presently under development rely on the fruit, the packaging film, and temperature control to generate and maintain optimal O2 and CO2 levels. Packages must be designed to avoid excessively low O2 levels, or fermentation and off-flavors will result (Figure 3; note that O2 partial pressures are in kPa, which can be read as %). Packaging systems that boost package CO2 levels and/or provide some level of humidity control have been developed for other products and may have considerable potential for packaged blueberry fruit. Chlorine and fungicide dips can also reduce postharvest decay. (See Chilled Storage: Use of Modified-atmosphere Packaging; Chill Foods:
Blueberries and bilberries are eaten both as dessert fruits and in processed forms. About 46% of the rabbiteye crop and 50% of the highbush crop are marketed fresh, and the remainder are processed. Nearly all commercially harvested lowbush blueberries, cranberries, and lingonberries are processed. The first widespread use of cranberries was to make sauce as a speciality item served at Christmas and the American holiday, Thanksgiving. During the 1960s, juice products made their appearance in the USA and now dominate the market. Cranberry ‘cocktail’ is drunk alone or mixed with other juice products. Cranberries are also made into a syrup, a dried raisin-like product, and a natural red food coloring, which has been used successfully to enhance the color of cherry pie filling. Blueberries are used primarily in pie fillings, yogurts, icecream, and prepared muffin and pancake mixes. Blueberries are sometimes added to dried products after dehydration using an explosionpuffing process. Syrups, jams, and preserves are also produced, but in limited quantities. The juice of blueberries is rarely consumed directly as it has a very strong flavor and dark color. Lingonberries are quite tart, but quite edible when cooked and are commonly used for juice, pie fillings, and jam. Bilberries are used fresh or in juice, preserves, or wine. Fruit extracts are also used in pharmaceutical preparations for the treatment of microcirculatory diseases.
0031
0032
0033
0034
2768 FRUITS OF TEMPERATE CLIMATES/Factors Affecting Quality See also: Acids: Natural Acids and Acidulants; Chilled Storage: Use of Modified-atmosphere Packaging; Chill Foods: Effect of Modified-atmosphere Packaging on Food Quality; Colorants (Colourants): Properties and Determination of Natural Pigments; Controlledatmosphere Storage: Applications for Bulk Storage of Foodstuffs; Fungicides; Ripening of Fruit; Sensory Evaluation: Aroma; Storage Stability: Mechanisms of Degradation; Parameters Affecting Storage Stability
Factors Affecting Quality W S Conway and M Faust, Beltsville Agricultural Research Center, Beltsville, USA C E Sams, University of Tennessee, Knoxville, USA This article is reproduced from Encyclopaedia of Food Science, Food Technology and Nutrition, Copyright 1993, Academic Press.
Introduction Further Reading Ballington JR, Kirkman WB, Ballinger WE and Maness EP (1988) Anthocyanin, algycone, and aglycone-sugar content in the fruits of temperate North American species of four sections in Vaccinium. Journal of the American Society of Horticultural Science 113: 746–749. Beaudry RM, Cameron AC, Shirazi A and Dostal DL (1992) Modified atmosphere packaging of blueberry fruit: effect of temperature on package oxygen and carbon dioxide. Journal of the American Society of Horticultural Science 117: 436–441. Beaudry RM, Moggia CE, Retamales JB and Hancock JF (1998) Quality of ‘Ivanhoe’ and ‘Bluecrop’ blueberry fruit transported by air and sea from Chile to North America. HortScience 33: 313–317. Eck P (1988) Blueberry Science. New Brunswick: Rutgers University Press. Eck P (1990) The American Cranberry. New Brunswick: Rutgers University Press. Hancock JF and Draper AD (1989) Blueberry culture in North America. HortScience 24: 551–556. Hulme AC (ed.) (1970) The Biochemistry of Fruits and their Products. London: Academic Press. Kader AA, Kasmire RF, Mitchell FG et al. (1985) Postharvest Technology of Horticultural Crops. Extension Bulletin 3311. University of California at Davis. Kalt, W, Forney CF, Martin A and Prior RL (1999) Antioxidant capacity, vitamin C, phenolics and anthocyanins after fresh storage of small fruits. Journal of Agriculture Food Chemistry 47: 4638–4644. Luby JJ, Ballington JR, Draper AD, Pliszka K and Austin ME (1990) Blueberries and cranberries (Vaccinium). In: Moore JN and Ballington JR (eds) Genetic Resources of Temperate Fruit and Nut Crops. Wageningen, The Netherlands: International Society for Horticultural Science. Maas JL, Galletta GJ and Stoner GD (1991) Ellagic acid, an anticarcinogen in fruits, especially in strawberries: a review. Horticultural Science 26: 10–14. Uphof JCT (1986) Dictionary of Economic Plants. Lehre, Germany: J Cramer. Usher G (1974) A Dictionary of Plants used by Man. London: Constable. Vander Kloet SP (1988) The Genus Vaccinium in North America. Agriculture Canada Publication 1828. Ottawa: Agriculture Canada. Yarborough DE and Smagula JM (eds) (1996) Proceedings of the sixth international symposium on Vaccinium culture. Acta Horticulturae 446.
The primary goal of the fruit grower is to produce a product of such quality that it is attractive to the potential consumer in both appearance and taste. In order for quality fruit to reach the consumer, it must be properly grown in the orchard, harvested at the time of proper maturity, and stored in such a manner that the quality is maintained. Economic losses occurring in postharvest channels are greater than often realized, and the avoidable loss of quality ‘between the farm gate and the consumer’ is the cause for real concern. Fresh fruit increases several-fold in unit value while moving from the field to the consumer, because of the added cost of careful harvesting and handling. Factors that affect fruit quality can be classified into three groups: (1) nutritional factors during growth; (2) factors associated with the time of harvest; and (3) factors associated with storage. These factors, as they relate to the quality of the major temperate fruits, including apples, apricots, cherries, peaches, pears, and plums, will be discussed.
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Tree Nutrition In order for the fruit tree to produce quality fruit, it must be supplied with the proper mineral nutrients and photosynthates. Orchard trees grow and produce fruit in the same place for 15–50 years. By the time these trees are mature enough to produce a crop, they have developed extensive root and branch systems and are able to acquire nutrients from the soil, intercept light, and produce photosynthates. The perennial nature of the tree and the necessity of producing large crops of fruit regularly imposes demands for nutrition not found in herbaceous plants or forest trees. The tree has changing nutrient needs during the year, particularly when it sets and raises its fruit. These occasional high mineral nutrient needs may not be met by uptake through the roots and must be supplied by foliar application. Fruit nutrition must often be concerned with the nutrition of not only the whole tree but also individual organs. For example, fruit should have a certain nutrient content for maximum storability. This requires techniques other than nutrition for maintaining the tree. First, nutrients must be applied and the translocation and
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