Pertanika 13(2), 211-215 (1990)

COMMUNICATION II

Microflora of Ciku (Achras sapota L.) of Variety Jantung

ABSTRAK

Keselwuhan kiraau mikrob pada ciku adalah rendah dan dikuasai oleh )Iis. yang didapati paling Linggifmda hari he/iga selepas tuai. Pembasuhan mengurangkan hiraan mihmb pada. buah dengan 11lenurunkanpopulasi yis sebanyak 89% dan bahter'ia seban)'ak 75 %. Setnasa hecederaan, flora dominan ialah bakteriadan kemudiannya dolam masa pensloran ia diambil alih olek kulat. Flara '1nikrob nonnal pada ciku terdi'lida'lipada bahteria. yis dan kulapuk. Kerosakan semasa penstomn suInt Tendah dihaithan dengan strain­slmin bam yis daa kulapuk. S,,,,;las; dan peagendalian lepas Itlai yang baik pealing bagi mengawalhe111,gian dm'i segi llerosakan buah-lJuahan yang disebabkan oleh mikroorganisma.

ABSTRACT

The overall 11licrobial connt of ciku is law and predominantly )'east. which peaks at day three after hamest.Washing reduced Ihe microbial counls of the fruils, 1darding the yeast population by 89% and bacteria by75 %. During injury, the dominant flora is bacteria which is replaced later by fungi as the storage timeprogeressed. Nomral microbialflora ofaim consists ofbacteria, )'easl and moulds. Spoilage during cold storageis associated with new st'l'ains of,'east and moulds. Proper sanitation and post haroest handling t'l'eatmentsare imf)01tant in controlling fruit losses associated with microorganisms.

INTRODUCTION

Ciku (Manil/wra Achras L.; Achms Sapota L.)originated from u'opical Americas probablyfrom South Mexico. It belongs to the familySapotaceae. Besides the name ciku, it is alsoknown as sapota, sapotilla, chiko, bully andnaseberry (Mustard, 1982). There are fourvarieties of ciku grown commercially inMalaysia, namely jantung, betawi. pasir andsubang. Fruits are produced throughout the yearbut production is not consistenL Unless optimalmeasures are taken during storage, many fruitsmay be spoilt. Wastage of fruits bymicroorganisms during movement from harvestto consumption can be rapid and severeparticularly in tropical areas where hightemperatures and high humidity favour rapidmicrobial growth. TvIany bacteria and fungicause postharvest decay of fruits mostly in theform of weak pathogens, in that they can onlyinvade damaged produce where therelationship between the host (fruits) and themicrobes is reasonably specific (Wills et aLI

1981). This study aims at identifying themicroflora of ciku during ambient and lowtemperature storage as well as the effect ofwashing and injury on the microbial profiles.As there is very little published informationavailable regarding the microbiology of thefruit, this will provide baseline information qnthe change in microbial growth patterns duringstorage.

MATERIALS AND METHODS

FruitsMature (7-month-old) ciku fruits of cv. janlungwere mechanically halV'ested using a cikuharvester (Abdul Karim, 1988) from theSerdang Experimental Farm, UniversitiPertanian Malaysia (UPM). They were thenseparated into two portions, with one beingleft unwashed and the otller washed withrunning tap water. Some of the un,.".ashed fruitswere .artificially injured by dropping the fruitson to sterilized floor from a uniform height offive feet. They were then placed inside sterile

FATll\lAH ABU-BAKAR AND M.L .B. ABDUL-KARIM

glass incubators and stored at roomtemperature. Low tempel-aturc storage studieswere conducted on washed fruits kept at IOoeand 15°C. Aseptic procedures were usedwherever posibble.

Microbial Enumemtion and Isolation Procedu11!sThe enumeration procedure was carried outover a period of six days after harvest. Surfacesample measuring ten square cm. was swabbedwith sterile cotton buds and rinsed with steriledistilled water. Four fruits were used at eachsampling time and immediately discarded afterswabbing. The number of bacteria and fungiwas counted using the poured plate and spreadplate methods, respectively. Plate count agar(PCA) (Oxoid) was used for the estimation oftotal aerobic bacteria whilst potato dextroseagar (PDA) (Oxoid) was used for theenumeration of moulds and yeasts. PCA plateswere incubated at 35°C for 24 hours while PDAplates were incubated for two to five days at30°C.

The composition of the microbial flora wasdetermined by isolating and identifying dif­ferent colonies chosen randomly from the totalcount plates according to Gill and Newton(1980). The different isolates were maintainedat 4°C on nutrient agar (NA) (Oxoid) and PDAslopes for bacteria and fungi respectively.Subculture was performed once a month foridentification procedures.

Composition oaf Microbial FloraIdentification of bacteria was done accordingto Buchanan and Gibbons (1974). Moulds wereidentified from their cultural characteristics andmicroscopical appearance according to Samsonet aL, (1984). Identification of yeasts was accor­ding to methods described by Deak and Beu­chat (1987) and the use of API 20°C Identi­fication System (API International S.A., France).

RESULTS AND DISCUSSION

The normal microflora of ciku consisted ofbacteria, moulds and yeasts (Table I). Bacteriawere found to belong to the genera Bacillus,El1l1inia and Micrococcus. Moulds were identifiedas those of strains of Aspergillus nige1~ Geotrichumspp., and Mucor spp., whilst yeasts belonged to

TABLE 1Microbial flora of ciku during one week stordge

3l room lemperature (28°C ± 2)

Bacteria Yea'\ts Moulds

BaciUus spp. Pichia Aspergultusanomala niger

Envinia spp RJuxlotorula Geotrichum spp.acheniorum

lW"icrocOSSIlS spp. Brellanomyces Mucorspp.CIlslersii

the species RJlOdotorula acheniol1l,m, Brettanomycescustersii and Pichia anornala. Studies on the yeastflora of citrus fruit (Recca and Mrak, 1952),apples (Marshall and Walkley, 1952), andgrapes (Mrak and McClung, 1940) alsoindicated that the population of yeasts wasabout evenly divided bel'll/een ascosporogenousand imperfect stages. Examples of the lesscommon ascosporogenous genera wereSaccha1YJmyces, Pichia and Hanseniaspora andthose of the more common ascosporogenousspecies we~e Candida and Rhodatamla. Thepredominants moulds genera were Aspergillus,Muc01~ Alternaria and Botrytis.

Some of the washed ciku stored at low tem­peratures (lOOC and 15°C), after sixteen daysor more were found to be infected around thecalyx portion of the fruits. The bacteria wereidentified to be identical to that of the normalflora (Table 2). Strains of yeasts, however, hadchanged with the addition of Candida bacarium,Candida silvicultrix, Klyveromyces manxianus inplace of Rhodotorula acheniorum and Brella­nomuces clls(ersii. In the case of moulds, Fusmiumspp. replaced Mucor spp. It is known thatEnuinia cause bacterial soft rot in many fruitsand vegetables (Ryall and Lipton, 1979;Tugwell, 1989). Geotrichum had been reportedto cause sour rot, whilst Fusarium could causeFusarium rot in fruits (Ryall and Lipton, 1979).

The microbial profile of ciku is shown inFig. 1. In general, the overall microbial countof ciku was rather low. The peak for totalnumber of yeasts was achieved at day three,decreasing thereafter. The bacteria and mouldcounts increased throughout the enumeration

212 PERTAN[J(A VOL. 13 NO.2, [990

MICROFLORA OF CIRU (ACHMS SAPOTA L) OF VARlETYJA 'TUNG

/:/g. I: ,\III fohial/no}il" oj ('ikll dlllillK 011I' 1!'1'('k oj slumg'pat room temperature

period. According to Beuchat (1978), althoughthe surfaces of fresh fruits harbour largenumber of molds and yeasts, the latter generallylack the mechanisms to invade and infect planttissue. Therefore, they are secondary ratherthan primary agents of spoilage.

The proliferation of yeasts was obviouslyreduced by washing (Fig. 2). The bacterial countwas also reduced for the first four days afterwashing, bUl the number started to increase by

TABLE 2Microbial flora of ciku spoiled after 16 days or

more at low temperature storage of 10° and 15°C.

Baleria Yeast Moulds

BaciUus spp. Pichia anomala AJpe'?flluJniger

bwinia spp. Candida Geotrichumbacru1um spp.

Micrococcus spp. Candida Fusm7umsilvicullrix spp.

Kiyveromcesmmu:ianlls

,

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" Yeasl-"",

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u

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06

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Fig. 2: l:.ffect oJ washing on thp microbial profile of eikltduring one week ofstorage at room temperature

the fourth day and decreased thereafter.Moulds kept an almost constant profilethroughout the enumeration period. Washingreduced the number of microorganismsattached to the liuit detaching some of themicroorganisms found on the fruits. Accordingto Beuchat (1978) washing, usually one of thefirst steps in fruits processing, would removemuch of the original microflora. Our results(Figs. ] and 2) showed that washing reducedthe yeasts count by about 89%; the bacterialcount by about 75% and the mould counts byonly about I %. Murdock and Brokaw (1958)reported that a brush wash followed by a rinsewith chlorinated water reduced the microbialpopulation on the surface of oranges by 95%,'\vhile a reduction in viable count ;over 99.9%was observed when apples were washed inrunning water (Marshall and Wakley, 1951).

Fig. 3 showed the effect of i~ury on themicrobial profile of ciku. As can he seen, thebacterial and mould COUlllS increased duringstorage. The bacterial count dropped graduallyafter the fourth day. The yeast populationincreased, peaking at day five, with a slight fallat three days of storage. The results indicated

PERTANIKA VOL. 13 NO.2, 1990 213

MICROFLORA OF CIKU (ACHRAS SAPOTA L.) OF VARIETYJANTUNG

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(Received 3 February, 1990).

PERTANlKA VOL. 13 NO.2, 1990 215