White sapote (Casimiroa edulisLlave & Lex)E. M. Yahia and F. Gutierrez-Orozco, Autonomous University of Queretaro,Mexico

Abstract: White sapote is a climacteric fruit and only slightly susceptible to chillinginjury. The fruit is commercially produced and consumed in few countries. Limitedinformation is available on its postharvest physiology and handling, and thereforeresearch is needed on several physiological, biochemical, pathological, and entomologicalaspects related to this fruit. This chapter discusses some of the information available onthe handling of the fruit.

Key words: Casimiroa edulis, white sapote, postharvest, quality, nutrition, health,processing, insects.

Contrary to what is sometimes believed, white sapotes are not related to theSapotaceae family, but actually belong to the Rutaceae family. Although whitesapotes are not very popular among consumers they still have great potential forcommercialization as an exotic fruit. In addition, the white sapote tree has greatadaptability to arid regions which represents a sustainable option in these areaswhere other species do not grow. However, information on their postharvestbiology and technology to establish optimum storage and transport conditions isstill very limited.

24.1.1 Origin, botany, morphology and structureWhite sapote (Casimiroa edulis L1ave & Lex), also known as Mexican-apple,casimiroa, zapote blanco, chapote, matasano, cacchique, ceaxmisttea, cochitzapoti,is native to Mexico and Central America. It can be found in central and southernMexico as a cultivated and wild species and is also grown in Guatemala, EI

Salvador and Costa Rica. Commercially, it is grown in New Zealand and on asmall scale in South Africa. It is an evergreen tree that can grow up to 5-20 metersdepending on the cultivar and type of soil. It has a dense crown, with glossy andbright green leaves. White sapote flowers are small and green to yellow whichmake them very attractive to insects like bees or ants. Fruit of white sapote varyfrom 2 to 15cm in length with an apple-green color when young to orange-yellowcolor at maturity. Fruit (see Plate XLIJI(A-C) in the colour section betweenpages 238 and 239) are oval, symmetrical or irregularly shaped with a thin andsmooth skin that may be bitter. Its external appearance sometimes resembles thatof an apple. Flesh color depends on the variety. Fruit with green skin present whiteflesh, while fruit with yellow-colored skin present flesh of the same color. Theflesh is sweet and presents a gritty texture. Its flavor is similar to that of peach orbanana and it may be bitter sometimes. If the fruit is left to become overripe, theflesh becomes pungent and an unpleasant flavor develops (Morton, 1987).

24.1.2 Worldwide importanceWhite sapote adapts to subtropical weather, growing not only in Mexico and theUnited States, but also in temperate areas of New Zealand, Australia, and Israel.The fruit has recently been introduced in Japan, where it is little known as a freshcrop (Yamamoto et aI., 2007). White sapote is also cultivated in Egypt for its fruit(Romero et aI., 1983). Interest in commercialization of fresh white sapote in theUnited States and other countries has increased in recent years, as has interest inits medicinal properties (Campbell and Vallis, 1994).

24.1.3 Culinary uses, nutritional value and health benefitsFruit of white sapote are usually eaten alone or mixed in fruit salads, and can beserved with cream and sugar. The pulp can be added to ice cream, milkshakes ormade into jam.

The nutritional value of white sapote is presented in Table 24.1. White sapotefruit are rich in p-carotene and ascorbic acid. Reducing sugars contribute to 66.2%ofthe total sugars in pulp which presents about 14.7 °Brix (Osama Samaha, 2002).Antioxidant capacity of white sapote leaf-extracts has been evaluatedusing the ABTS+ (2,2'-azinobis(3-ethylbenzothiazolone-6-sulfonic acid) freeradical assay). Ethanol extracts presented the highest values of antioxidantcapacity followed by the ethyl acetate extracts (842 and 71211MTrolox equivalentsg-I dry weight, respectively). Phenolic compounds isolated from leaves extractsincluded quercetin and its 3-0-rutinoside, 6-hydroxy 5-methozyflavone, and5-methosyflavone 6-0-P-D-glucoside (Awaad et at., 2006).

It is generally believed that white sapote seeds are toxic to humans if eaten raw.Indeed, its common name 'matasano' in Spanish means 'killing healthy person'.InMexico and some other countries it is claimed that white sapote fruit helps torelieve pain caused by arthritis and rheumatism. Actually, the meaning of theNahuatl name for white sapote is 'sleepy sapote' or 'sleep-producing sapote'.

Water contentProteinFatFiberAshCalciumPhosphorusIronCaroteneThiaminRiboflavinNiacinAscorbic acid

78.3%0.143 g0.03 g0.9 g0.48g9.9mg

20.4 mg0.33 mg5.98 mg0.042 mg0.043 mg0.472 mg

37.75 mg

There have been reports about the sedative properties of seed, bark and leafextracts in Mexico where they have been used for a long time for these purposes.All these effects are thought to be due to the presence ofthe glucoside casimirosine,mainly in seeds but also in the bark and leaves.

The blood-pressure lowering properties of white sapote have been confirmed insome studies (Petit-Play et al., 1982) and extracts of the leaves, bark and seeds areused for this purpose. In Mexico, a decoction from the leaves and seeds is used totreat anxiety, insomnia and hypertension (Vidrio and Magos, 1991; Hernandez,1993; Garzon-de la Mora, 1999). Compounds with cardiovascular activity wereidentified as histamine derivatives like N,N-dimethylhistamine (Magos et at., 1999).One study performed in mice showed that extracts prepared from white sapoteleaves possessed sedative properties along with anxiolytic and anti-depressantactivities when given at 6.25, 12.5, and 50mgkg-1 (Mora et at., 2005). Leaves ofCaimiroa edulis showed anxyolitic effects in rats, causing side effect reactions likereduced mobility (Molina-Hernandez et al., 2004). In rats, aqueous extracts of whitesapote seed have been shown to present vaso-relaxing activity which was found tobe endothelium-dependent (Magos et al., 1995; Muccillo Baisch et at., 2004). Someother compounds such as coumarins, f1avonoids and limonoids, among others, havebeen found in white sapote (Dreyer and Bertelli, 1976; Murphy et al., 1968; Rizviet al., 1984; Sondheimer et at., 1959). Some of these compounds are known topresent diuretic or anti-inflammatory properties (Morton, 1987).

A polymethoxylated flavone called zapotin has been isolated from white sapotewhich induced cellular differentiation, cell death and cell cycle arrest inHL-60 promyelocytic cells (Mata-Greenwood et al., 2001). Zapotin has alsoshown chemopreventive activity by inhibiting cell growth of the colon cancer celllines HT-29, SW480, and SW620. In addition, it caused cell cycle arrest as well asan increase in cell apoptosis which may suggest that this compound could be usedas a therapeutic agent in colon carcinogenesis (Murillo et al., 2007). Extracts of

white sapote seeds also showed anti-mutagenic action and inhibited inducedpreneoplastic lesions in a mouse model (Ito et aI., 1998). Isolation ofphytochemicalcompounds in these extracts showed four furocoumarins: phellopterin,isopimpinell in, (R, S)-5-methoxy-8-[ (6,7 -dihydroxy-3, 7-dimethy 1-2-octeny 1)osy]psoralen, and (R, S)-8-[ (6,7 -d ihydroxy- 3,7-dimethy 1-2-octeny 1)oxy]psoralen; fouralkaloids: casimiroin, 4-methoxy-l-methyl-2(1 H)-quinolinone, 5-hydrxoxy-l-methyl-2-phenyl-4-quinolone, and y-fagarine; and two f1avonoids: zapotin and5,6,2'-trimethoxyflavone (lto et al., 1998). Lastly, leaf and stem extracts of whitesapote showed fungicidal actions against Rhizopus stolonifer of ciruela fruit(Spondias purpurea L.) during storage (Bautista-Banos et aI., 2000).

24.2.1 Fruit growth, development and maturationThe growth of white sapote fruit follows a single sigmoidal pattern (Yonemotoet aI., 2006) and maturity is reached 6-9 months after blooming.

24.2.2 Respiration, ethylene production and ripeningWhite sapote is a climacteric fruit (Yahia, 2004). Fruit kept at 21 DCand 82% RHhad a respiratory peak after 4-5 days (199 mL CO2 kg-I h-I, 651 ilL C2H4 kg-I h-I)(Lozano et aI., 2006). Respiration rate is reduced when fruit is stored at I DCandno ethylene production is observed during these conditions (Yonemoto et al.,2002). Total sugar content of harvested fruit kept at 21 DC and 82% relativehumidity (RH) did not change during ripening but the level of reducing sugarsincreased from 6.1 to 7.8%. The ratio DBrix/acidity increased during ripening (from28.4 to 34.1%) as a consequence of the increased reducing sugars content anddecreased acidity (Lozano et al., 2006).

24.3 Maturation and quality components and indicesWhite sapote fruit should be harvested before ripening (Morton, 1987). The daysafter pollination could be used as a maturity index: for white sapote cultivar'Cuccio', it takes 212 days after pollination to reach maturity. Another maturityindex could be percent dry matter, since this parameter is strongly correlated withtotal soluble solids. A more convenient and non-destructive maturity index is skincolor measured by a colorimeter. In that case, a* value is measured on the sun-exposed side while b* is evaluated on the shaded side. Seed color could also bemeasured to determine maturity (Yonemoto et aI., 2006).

Skin color and size are used as quality parameters and according to McGregor(1987), good quality fruit are yellow to yellowish-green and are 60-120mm indiameter. According to Morton (1987), skin color of fully ripe white sapote fruitisusually apple-green to orange-yellow. White sapote fruit (see Plate XLIII(A-C)

in the colour section) are easily bruised ifnot handled correctly which producesbitterness of the flesh. Overripe fruit are pungent and have an unpleasant flavor(Morton, 1987).

A value of 18% dry matter at maturity of cv. 'Cuccio' is reported. In anotherstudy, mature fruit were reported to present a pH of about 5.1, 0.34% acidity, totalsoluble solids content of about 19.9% and about 14.7°Brix (Osama Samaha,2002). Volatile compounds responsible for the aroma of white sapote fruitswere identified during fruit ripening. They corresponded to 4 esters, 6 alcohols,I ketones, 4 aldehydes, and 3 terpenes. The sweet and fruity aroma was found tobe originated from ethyl butanoate (EI-Mageed, 2007). Some other aromaticcompounds with properties to attract fruit flies have been identified in whitesapote: myrcene, styrene, 1,2,4-trimethylbenzene, 1,8-cineole, linalool, and~-trans-ocimene (Gonzalez et al., 2006).

24.4 Preharvest factors affecting fruit qualityTemperatures below 3°C will damage young fruit, affecting the quality of ripewhite sapotes (Yonemoto et al., 2004).

24.5.1 Temperature managementStudies on white sapote cv. 'Yellow' showed that the respiration peak is reachedat day four from harvest and when fruit are held at 35°C, and at day 6 at 15,20,25, and 30°C. When stored at 10°C a respiration peak was not evident. Respirationrate was slowed down at 1°C and there was no ethylene production. Temperatureshigher than 30°C induced skin browning, which was not observed at 10-25°C.Fruit surface softening was observed at 5°C. Fruit stored at I °C for 10 to 63 daysripened normally after transfer to 25°C. However, chilling injury was observed infruit stored for 63 days at 1°C (Yonemoto et aI., 2002).

24.5.2 Physical damageSpecial care must be taken not to harvest the fruit by pulling it manually since thestem will be severed completely producing fruit bruising and decay later on.Young fruits bruise very easily, developing flesh bitterness, and therefore theymust be handled with care (Morton, 1987). Fruit that has been physically damagedwill develop browning of the skin and pulp bitterness (Yahia, 2004).

24.6 Physiological disorders24.6.1 Chilling injuryNo production of white sapote is seen when ambient temperatures fall below-2.5°C and as already mentioned, young fruit are severely damaged at 3°C.

However, when mature white sapote fruit were exposed for five hours at -2°C forfive days, no damage was observed. Thus, the recommended temperature forcultivation is higher than -2 °C (Yonemoto et al., 2004). As mentionedabove, chilling injury was observed in fruits stored at I °C for 63 days (Yonemotoet aI., 2002).

24.6.2 Other physiological disordersQuarantine treatments have been tested on white sapote in order to kill Anastrephasuspense. Immersion of fruit in water at 43.3 °C for 90 or 120 minutes or at 46°Cfor 60 or 90 minutes produced pitting and decay and ripening was abnormal. Thelevel of decay also increased and ripening was affected when white sapote fruitwas treated with methyl bromide at 20 to 40 g m3. In addition this produced areddish hue on the fruit (Hallman, 1993).

24.7 Pathological disordersFruit of white sapote present resistance to Phytophthora and Armillaria(Morton, 1987). White sapote is a host of Puccinia thaliae (Sivanesan, 1970).Although not affected by it, white sapote tree is a carrier of psorosis virus disease(El-Tomi et aI., 1963).

24.8 Insect pests and their controlFew pests affect white sapote fruit, however, the fruit are highly infestedby Anastrepha ludens (Aluja et al., 1987). Some volatile compounds inwhite sapote have been found to attract A. ludens to baited traps (Gonzalez et aI.,2006). Although not a target of the African citru psylla, Trioza erytreae,white sapote has been reported as a host for this pest (Fernandes and FranquinhoAguiar, 2001).

24.9.1 Harvest operationsThe white sapote season starts in late May until August in the Bahamas whilein Mexico it goes from June to October (Morton, 1987). In Florida, fruitmatures in November or December (Schroeder, 1954). Fruit are harvestedby cutting the stem and leaving a small part of the peduncle, which falls oncethe fruit is fully ripe. When fruit are harvested just before full ripeness, theybecome soft soon after. Because of that, it is recommended to harvest whitesapotes some weeks before ripeness so fruit can develop complete flavor(Morton, 1987).

24.9.2 Packinghouse practicesSome common practices during white sapote packing include grading accordingto size and wrapping to delay ripening. Fruit are usually packed in wooden boxeswith some type of cushioning material to avoid physical damage during holdingand shipping (Morton, 1987).

24.9.3 Recommended storage and shipping conditionsMaintaining white sapote fruit at 19-21 °C and 85-90% RH prolongs theirshelf life for up to 2-3 weeks (McGregor, 1987). The fruit might benefit from anadequate modified atmosphere system (Yahia, 1998).

White sapote fruit can be used to make different products such as juice, jam, tart,biscuit, and sherbet (Osama Samaha, 2002).

White sapote is a climacteric fruit with potential for commercialization due to itsorganoleptic properties and the fact that it is considered an exotic fruit. However,limited information on the postharvest biochemistry, physiology and technologyis available and thus it is difficult to establish the optimum conditions that wouldpreserve quality during extended storage and shipping. White sapote fruit,although mainly consumed fresh, could be used to produce added-value productssuch as preserves and other products.

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