Extraction and Characterisation of Pectin from VariousTropical Agrowastes

Suhaila Mohamed and Zahariah Hasan

ABSTRACT canned fruit processing industry has increased tobecome one of the 10 most 'factory processed' fruits

The extraction of pectin from kalamanzi, pineapple waste of Malaysia (FAMA, 1988) and the disposal of wasteand cocoa pods using ethanol, metallic salt and acetone (skin and seed) has become a problem. Utili sing theprecipitalion were compared and evaluated in terms of yield, skin as a source of pectin is a possibility. Althoughcolour and gelling characteristics. Acetone precipitation was duku is a seasonal fruit it has a very thick skin whichthe best method so was used to extract pectin from other can be used as a pectin source, complimentary to theagrowastes. The yields, jelly grades and chemical non seasonal sources available. Rambutan and dukucharacteristics of pectins (moisture, ash, total uronic acid, have the added advantage of being very prolific fruitacidic and methylated uranic acids, jelly grade, setting time, producing crops and the skins have a low watergel unit and colour) from the different sources were content which could reduce the cost of transportationcompared. The overall pectin producing potential in order and drying. Recent interest in processing musk melonaf merit were kalamanzi (musk lime), jackfruit waste, cocoa into juice and other products will result in localisedpod husk, durian skin, banana skin, reject immature waste (skin) which may be a viable pectin source.starfruit, melon skin, rambutan pod, pineapple skin and Cashew apple is often discarded due to its ratherduku skin. Cashew apple gave a very high yield of pectin unacceptable astringent taste. Malaysia's sandy groundbut the pectin mass was gummy and could not be ground covers a vast area of 365,000 acres, giving the cashewto a powder. nut fruit industry good potential. Jackfruit 'wastes'

(rind, core and undeveloped perianth), form 59.1 % ofthe fruit (Bhattia, Sidappa and Lal, 1955) while in the

INTRODUCTION canning of jackfruit, the rejected part is 80-85% of thetotal fruit (Muhammad, 1972), which may be utilised

The Statistical Department of Malaysia reports that in as a source of pectin. Durian is one of the ten most1989 Malaysia imported about 60 tonnes of pectin 'factory processed' local fruits (FAMA, 1988) and hasworth almost RM one million (US5250,000). There is very thick, flexible but tough skin. Since duriana vast resource of agricultural products and agro\vastes consumption results in a lot of waste, it 'would be anwhich can be used to produce pectin. A banana advantage if the waste could be processed into usefulprocessing factory alone produced 1,381 metric tonnes products.of banana peel waste in 1984. Kalamanzi lime (Limaukasturi), is non seasonal, cheap and a prolific Francis and Bell (1975) reviewed theproducing crop which is underutilised and would be commercialisation of pectin from breadfruit, jackfruit,a good source for pectin production. Cocoa pod husk papaya, coconut, taro, yam, water hyacinth,has long been a disposal and pollution problem to kangkong, sweet potato, cassava, banana, guava,the cocoa industry and could be a cheap source of sugarcane, tamarind and cocoa pod. A more recentpectin if it can be processed immediately and the review on pectin from some tropical fruits were madeprocessing modified to suit the nature of raw material by Hodgson and Kerr (1991).(eg: high pigmentation). During pineapple canning,45% of the total weight of the fruit is wasted and The objectives of this study were: (1) to investigatecan be used to extract pectin, while pectin can also indigenous plant materials and agrowaste as potentialbe obtained from the leaves and stems of the sources for pectin; (2) to characterise the pectinpineapple plant. In order to get carambola of good extracted from the various sources; and (3) to assesssize, farmers have to limit the numbers of fruits per the potential of the sources as a raw material for pectintree, plucking away large quantit'ies of immature fruits manufacture.and discarding them. The use of rambutan in the

The plant materials and agrowastes investigated were:Kalamanzi or Musk lime (Citrus microcarpa),pineapple(Ananas comosus) skin, cocoa pod (Theobroma cacao)

Based Oll a paper presented at the 'Symposium Sumber Alam husk immature starfruit (Averrhoa carambola) rarnbutanTropika' Kuchim:, Sarawak, Malaysia, organised by Universiti ( hI. . .I

.

M I . 5Ck UNIMAS (6 9 0 1993) Nep e/lllln lappaceum) skm, duku (Lansilim domestlCllm)aaYSla arawa - ec . . .

skin, jackfruit (Artacarpus heterophylllls) waste,Theauthorsarefrom the Facultyof FoodScienceand Bioteknologi, n:usk:nelon .(Cuclimis mela LJ ski~11durian (DurioUniversiti Pertanian Malaysia, 43400 Serdang, Selal1gorDaml zlbethmus) skm, banana (Musa acuml1lata)and cashewEhsan, Malaysia. (Anacardillm occidelltale) apple.

ASEA~ Food Journal Vol. 10, 0Jo. 2, 1995 43

MATERIALS AND METHODS about 15 seconds whereupon a pectin aluminium-copper complex separated throughout the liquor as

Samples of citrus peel, pineapple skin, cocoa pod husk, an extremely finely divided continous gel whichimmature starfruit (reject), duku skin, durian skin, immediately coagulated into curds and rose to occupycashew apple, jackfruit 'waste' and rambutan skin about a quarter of the liquor volume, the finalwere obtained locally. optimum pH of the mother liquor being 3.9 to 4.2 at

25C. The solution was centrifuged at 3500 G for 10The agrowastes were washed then immersed in 95% mins to separate the coagulated gel from the motherboiling methanol for 15 mins followed by washings. liquor of sulphuric acid and methanol (10.8% andThe peel was then dried at 80'C for 2 days. 70.4% respectively). The gel was then rinsed in ethanol,

drained, and fresh 75% alcohol added to make a fluidThree methods of extraction were initially compared mixture and enough alkali buffer (ammoniumto find the best method for obtaining good yield and hydroxide, sodium carbonate or a mixture of the hvo),quality pectins. Duplicate extractions were carried out added to adjust the pH. After about 30 minutes, thefrom each source. pH of the suspension was about 5.5 :t 0.3 and the

pectin upon drying and preparation into a 1% sol

Extraction using ethanol-HCl yielded a pH of 3.9 :t 0.3. They were then dried at60'C and ground.One hundred grams of ground and dried peel wereweighed into a tared 2000 mL beaker containing 500 Extraction of pectin using acetonemL distilled water. Twelve grams of freshly groundsodium hexametaphosphate (BDH) were then added 1 kg of the macerated sample was heated at 75C inand the initial pH adjusted with 3 :\ HCl to 2.2:t a vessel containing 4 L water and 12 g of freshly0.1, heated with constant stirring at 80 :t 5C for 1 ground sodium hexametaphosphate. The pH washour and the pH checked at intervals of 15 mins. adjusted to 4.0 :t 0.5 when necessary using citric acid\-Vater loss was replaced at intervals except in the last or sodium hydroxide. Water lost by evaporation \\'3S20 minute of extraction. replaced at intervals except in the last 20 min of

extraction. The extract \vas filtered using a centrifugalThe extract was filtered through muslin cloth and the separator / filter, lined with cheesecloth. The collectedresidue washed with 200 mL of warm water. The filtrate was concentrated to 1/3 of the original volume.'washings were added to the filtrate, which wasconcentrated by evaporation on a hot plate to The cooled filtrate \vas poured into 2 volumes ofapproximately one fifth of its initial volume. The acetone containing 0.5 M HCl (pH of the slurry atconcentrated pectin solution was cooled to 50'C and about 1) and stirred for 30 min. The precipitate waspoured into a volume of ethanol in a ratio of 1:3, the separated on coarse mesh nylon or muslin cloth andethanol contained 0.5 M HCl. The mixture was stirred washed at the same pH to remove all but traces offor 0.5 hour and allowed to stand for one hour. The ash. The precipitate was washed repeatedly in 500 mLprecipitate was centrifuged at 3500 G for 15 mins, portions of 70% acetone until it was essentiallywashed at the same pH with more ethanol-HCl chloride ion-free or the pH was above 4.0, dehydratedsolution and centrifuged at the same speed for 15 further in 500 mL of acetone and dried overnight atmins. Finally the precipitate \vas washed with acetone 45C. The precipitate \vas weighed to determine theto remove all traces of HCl and ethanol which could yield and this pectin was used for further analysis.interfere with the methoxvl determination. Theprecipitate was dried at 60C to constant weight. The dried pectin ,vas tested for ammonia which would

interfere with many of the proposed analytical

Extraction of pectin using metallic salts (Wiles and methods. This was done by adding 1 mL of 0.1 NSmit, 1971) NaOH to a small amount of dried sample. On heating,

the presence of ammonia could be detected bySamples were treated as above except that they were moistened litmus paper. Ammonium ion, if presentalternatively treated with 1% sodium bisulphite instead was washed out with acidified 60% alcohol, followedof sodium hexametaphosphate, and heated at 70-75'C by neutral alcohol to remove the acid and dried. Thisfor 1 hour with constant stirring. The extract ,vas pectin was used for further analysis.filtered through muslin cloth and the residue washed\vith 100 mL of ,varm \vater. The washings were Characterisation of pectinadded to the filtrate which was then cooled to 50'Cand 1.75'70(v/v) of the metal salt precipitating solution Moisture was determined according to AOAC (1980),was added (540 g aluminium sulphate and 45.9 g with 1 g of ground sample weighed and dried atcopper sulphate/LJ over about 1 minute. Immediately 105'C for 4 hours to constant weight. For Ash, 1 gthereafter 1.05% v /v of the soda ash solution (169.6 of pectin (ground to pass 80 mesh) was weighed ing sodium carbonate/ L) was added and stirred for a tared crucible and ignited slowJy, then heated for

44 ASEAN Food JournalVol. 10, :'-Jo.2, 1995

about 4 hours at 600'C to constant weight (Owens, Jelly grade (the quality of pectin) was estimated by1952). Equivalent Weights were done by weighing measuring the jelly firmness of a standard 65% sugar0.5 g pectin (ammonia and moisture free) in a 250 jelly, pH 3.0 :!: 0.5 on a finger pressure test.mL conical flask, moistened with 5 mL ethanol. 1 gof sodium chloride were added to sharpen the end "Grade" of pectin means the weight of sugar withpoint. 100 mL of carbon dioxide free distilled water which one part by weight of pectin will, under suitableand 6 drops of phenol red indicator were added. The conditions at ambient temperatures, form a satisfactorypectic substances were stirred rapidly to dissolve, then jelly. Test jellies were made and compared with a jellytitrated slowly with 0.1 N NaOH until the colour of made under similar conditions with a standard 100-the indicator changed (pH 7.5) and persisted for at grade pectin sample after an 18-hour time lapse. Aleast 30 seconds. The neutralised solution was used piece of jelly was cut and squeezed between the thumbfor methoxyl determination. Methoxyl contents were and forefinger until the jelly breaks and compareddetermined by adding 25 mL of 0.25 N NaOH to the with the standard jelly. Differences of up to 5% couldneutral solution, mixing thoroughly, and allowing to be detected by an experienced operator. If the jellystand for 30 minutes at room temperature in a did not have the strength of a standard one, a jellystoppered flask. 25 mL of 0.25 N HCl was then added was prepared by increasing the amount of pectin andand titrated with 0.1 N NaOH to the same end point compared with the standard jelly.as before.

Pectin Equivalents based on Jelly gradeMethoxyl = mL of alkali X N of alkali X 3.1 X 100content (%)

.

. ht f 1 Wt x Grade of pectmwelg a samp eb . dW f . . d emg uset a pectm req Ulre =

0/. R COOH (A'd' . 'd) Grade of pectin to0 - Cl IC uronlC aClbe used

% R-COOH used for calculating the anhydrouronic.

acid content was determined by titration with sodium Rate of Settmg (Kertesz, 1951)hydroxide. to pH 7.5 using phenol red indicator.

If h . 11 . 10 t 2"

.

th ". .-

t e Je y set In O:J mIn, e pectin \vasMolecular weIght of AUA (1 umt) - 176 g. .d d ' .d., d "f h . . d fconSI ere rap! settmg an 1 t e hme reqUIre or

T t I h d . .d (ADA) ( b . I the setting of jelly was more than 25 min, it was0 a an y fourontc aCI S ara 1l10se, ga actose ,d . ., I 1

.,

d th ) me !Um settmg to s ow settmg .an 0 er sugars.% AUA

=% R-COOH + % R-COOCH,

J II U . . 1 . f . II h . 1 b= 176 x O.lz x 100 + 176 x O.lv x 100

e y mt IS t1e quantIty a Je y w IC1 can e, produced from a gIven weIght of raw matenal (FrancIs

w x 1000 w x 1000 and Bell, 1975). This unit indicated the economich potential of the pectin sources under study. (Jelly Unitwere

"

. ld " II d)z = mL (titre) of NaOH from % R-COOH = pectm Yle x Je Y gra e.

determination.y = mL (titre) of NaOH from % R-OCH Determination of acid insoluble ash (silicous

determination.3

contaminants)w = weight of sample. ..

The ash was weIghed and treated wIth 0.5 M HCl.Evaluating gel properties: the pectins used were of two The colloidal solution formed was filtered to obtaintypes: (1) with pH adjustment in the final extraction the insoluble material, ignited and weighed (Gee, etprocedure. (2) without pH adjustment in the final al., 1958).extraction procedure. The experiment was carried outwith the assumption that they are high-ester pectins.The standard formulation for the preparation of jelly RESULTS AND DISCUSSIONwithout pH adjustment (Table 1 and 2) was 105.0 mLwater, 2.5 g pectin and 54.0 g sugar. Three methods of extraction were initially compared

to determine the yield and characteristics of pectinThe amount of pectin that sedimented after forming the produced from three different sources i.e kalamanzi,gel was measured for solubility of the pectin. The pineapple and cocoa pod. Table 1 shows that themethoxyl content or degree of esterification is an important pectin from Kalamanzi peel (Limau kasturi) wasfactor controlling the setting time of pectins, the sensitivity higher than from pineapple skin and cocoa pods. Thisto polyvalent cations and their usefulness in low solids, yield value of Kalamanzi was comparable to the yieldgels films and fibres and was detennined by saponification of lime peel Citrus auranUfolia S. (32.25%) obtainedof the pectin and titration of the liberated carboxyl group by Rouse and Crandall (1978) using nitric acid. The(Gee, McComb and McCready, 1958). extraction of pectin from cocoa using acetone with

ASEAN Food Journal VoL 10, No.2, 1995 45

sodium hexametaphosphate gave the best yield (9.6%) extraction gave a slightly lower yield value of 5.3%together with the most desirable colour. For but produced the best colour (pale yellow). Acetonepineapple skin, the pectin extracted using alcohol extraction using sodium hexametaphosphate was thegave the highest yield (6.7%) although the colour of best extraction method in terms of yield, colour andpectin was very undesirable i.e. black. Acetone cost.

Table 2 indicates that there was only a slight variation.in the solubility of the pectin between Kalamanzi peel,pineapple skin and cocoa pods and that pH affectsthe strength of the gel. Owens (1952) showed tha t fora lo\v-rnethoxyl pectin, used \"it11 a constantcalcium:pectin ratio of 40:1, a maximum gel strengthwere obtained, with values decreasing on either sideof the optimum pH. However, since the formulationfor gel preparation was done on the assumption ofhigh-ester pectins, only extraction methods werevaried. The extraction method, which did not employfinal adjustment of pH, resulted in firmer gels andthe pectin had a pH range of 1.9 :t 0.5.

Gels from Kalamanzi pectin and pineapple pectinresulted in favourable pale colour and that from cocoawas very dark in colour. Decolourising techniquesneed be incorporated for the extraction of pectin fromcocoa.

Moisture values for the pectin from Kalamanzi peelwere 3.9 :t 1.3% on drying for two days at 105'C.For pineapple skin pectin it was 11.3 :t 2.7% and forcocoa pods 12.7 :t 7% when dried overnight at 105'C.If the pectin from Kalamanzi peel was not dried for2 days the moisture content remained too high for itto be ground or reduced in size. Overall, metallic saltextraction produced a higher ash content than acetoneextraction. The optimum aqueous extract:acetone ratiowas 1:1.5 (Table 3) which was used in all followinginvestigations.

Yield

Table 4 shows that the highest yield was from cashewapple (38.7% dwb), followed by jackfruit pericarp(22.5% dwb) and musk lime (19.8% dwb). Melon skinpericarp-mesocarp (12.5% dwb) and banana skin(11.9% dwb) gave intermediate yields, while cocoapods (9.7% dwb), young immature starlruit (8.3%dwb), rambutan skin (7.1% dwb) and durian skin(6.2% dwb), gave fairly low yields. Pineapple skin andduku skin both had very low yields (dwb) of 3.7%and 2.7% respectively. A source with a yield of above

ASEAN Food Journal Vol. 10, No.2, 1995

10%, coupled with good jelly grade, is usuallyconsidered commercially viable.

Although cashew apple gave the highest yield, thepectin precipitate was gumlike and ungroundable. Thisunexpected texture could indicate either high moisturecontent or the presence of acetone insoluble substancesother than pectin occluded in the precipitate.

Moisture

All the sources except cashew apple, produced pectinhaving moisture contents from 9% to 14% (Table 4).Commercially, this would be considered a normalmoisture content. The moisture content of cashewapple pectin was not measured.

Ash

The inorganic impurities in commercial pectin areindicated by the ash content. Table 2 shows that thepectins extracted using sodium hexametaphosphatehad high ash content and could be as high as 45.9%(pineapple). All the pectins extracted (Table 4) usedsodium hexametaphosphate and had quite high ashcontent indicating high inorganic impurities. Howeverrepeated washing with acid only reduced the ashcontent very slightly and was suspected to be silicousmaterial as the ash behaved and looked like a typicalsilicous ash. To confirm this, "acid insolubledetermination" was carried out on the extractedpectins and sodium hexametaphosphate (the possiblesource of the contaminant). Table ,5 shows sodiumhexametaphosphate contained a considerable amountof acid insoluble ash (9.8%). Rambutan pod pectinextracted using sodium hexametaphosphate alsocontained a considerable amount of acid insoluble ash(4.9%). The % ash increases as the pectin yielddecreases, indicating that the contaminant did notoriginate from the raw material, but from somethingthat has been added to the raw material in consistentproportion, i.e sodium hexametaphosphate. Upontreatment with hydrochloric acid, material like CaCO,or NazCO, would have dissolved out leaving behindacid insoluble ash, e.g: silica, alumina, various silicatesor alumina silicate. However it is beyond the scopeof this work to determine the exact silicous material.This "Nork can only caution against using sodiumhexametaphosphate having no detailed specificationon the labelling. 1% sodium bisulphite can be usedinstead.

%AUA

The %AVA indicates the purity of pectin against otherorganic material i.e neutral polysaccharides such asarabinose, galactose and other sugars which can becalculated by the expression 100% - AVA %. Table 4shows that the sources investigated produced pectincontaining quite good %AUA in the range of 70% to

47

90%, except for jackfruit skin (pericarp) whichcontained about 52.8% AVA. Despite the low %AUA,jackfruit skin pectin still showed very good pectinpotential. Durian skin had the highest %AUA of 90.1%.

Methoxyl content is an important factor in controllingthe setting time of pectins, their combining power withmetallic ions and the ability of the pectin to form gels.All the sources produce pectins with quite highmethoxyl content (9-13%) (Table 4) suggesting that theyarc all high methoxyl pectin (HMP). They would beexpected to exhibit the typical HMP characteristics suchas having a rapid /medium gel-setting period, requiring

48

sugar and acid for gel formation and the ability todisperse more easily than do pectins of less than 7%methoxyl content (Low methoxyl pectin/LMP).

Jelly grade (JG) is defined as the parts by weight of colours of pectins from durian skin (almost colourless),sugar with which one part by weight of pectin, under jackfruit waste (nearly colourless), musk lime (offstandard conditions, will form a jelly of satisfactory white), melon waste (off white), pineapple (off white)properties. The higher the grade, the less pectin 1s and immature starfruit (off white) were the lightestrequired, but this is not the only criterion for selecting followed by pectins from cocoa pod husk (clear lighta specific grade. It is apparent (Table 4) that the brown gel), duku skin (clear light brown gel), bananapectins from musk lime (JG > 100), durian skin ()G skin (clear light brown gel) and rambutan pod (rather90-100) and jackfruit pericarp (JG 90) had the highest cloudy light brown gel).JG, followed by pectins from immature starfruit (JG80), cocoa pod husk ()G 70-80) and rambutan pod ()G Adomoko (1972) obtained a 25-29% dwb yield of crude70-80), and then banana skin (JG 70), melon peri carp pectin from the immature husk (ash content 7.9-8.8%)and mesocarp (JG 60) and duku skin ()G 60), whilst and 8-11 % yield from the ripe cocoa pod husk (ashpineapple skin pectin had the lowest JG (40-60). content 8.9-9.8%) using mild acid extraction. The pectinComparisons of JG are only valid when the extraction on precipitation was described as a white gelatinousmethod employed is the same, as JG is much affected precipitate, unlike that obtained by Blakemore, Dewarby the method of extraction. and Hodge, (1966) on a sun-dried material which has

undergone a lot of enzymic browning. Sun-dryingSetting time (Approximate) altered the proto-pectin nature resulting in a reduction

in yield and potential gelling power of the isolatedCommercially marketable pectin product should be pectin (Francis 1965, unpublished). Because pecticable to set satisfactorily \vithin a given time according substances play an important role during theto the requirement of the product manufacturing development of the cell-wall in immature cocoa fruit,procedure. In the manufacture of jam, quick-setting the pectic substances form a higher proportion of thetimes of a few minutes at 90-95C are desirable so husk than in the ripe pod husk. The ripe pods havethat the fruit particles become embedded throughout about 9 times more dry husk material per pod thanthe pectin gel and do not float to the top of the do the cherelles (immature pod) of the size used, thuscontainer. Slow-set pectins take approximately one the total yield of pectin from the husk of one ripehour at 50-60C and are used for jellies which must pod is estimated to be 3 times more than can bebe filled and cased before setting starts. obtained from the husk of one immature fruit

(Adomoko, 1972). Adomoko also found that extractionTable 4 shows that, as expected of high methoxyl with 0.05 N or 0.1 N HCI at 70-80C was too drasticpectin, all the sources gave pectins having rather as judged by loss of solubility and the ability to imbiberapid gel-setting periods ranging from 5 to 35 water.minutes, with banana skin and jackfruit pericarphaving a remarkably rapid gel-setting period of about The pectins from some of the sources investigated5 minutes. were quite highly coloured, probably due to the

presence of polyphenols or other V'later solubleJelly unit (JU) pigments trapped inside the pectin during

precipitation. Better filtration techniques using a filterTable 4 indicates that the pectin from jackfruit pericarp aid, activated carbon, diatomaceous earth, etc may(JU 2007-2034) and musk lime (> 1980) had the highest remove these pigments to improve the colour of pectinjelly unit followed by pectin from banana skin ()U extracted.819-847), melon pericarp and mesocarp (JU 732-768),cocoa pod husk (JU 560-770), immature starfruit (JU656-664), durian skin ()U 562-620), rambutan skin (JU CONCLUSIONS364-455), pineapple skin (JU 174-180) and duku skin(JU 162). This unit is useful in assessing the production The pectin producing potential in order of merit waspotential of pectin raw material. It represents the musk lime, jackfruit \vaste, cocoa pod husk, durianquantity of jelly which can be produced from a given skin, banana skin, reject immature starfruit, melonweight of raw material. This unit would be useful skin, rambutan pod, pineapple skin and duku skin.in ranking the economic potential of agrowastesources.

REFERENCESColour

AOAC Association of Official Analytical Chemists.Colour of pectin is important as it affects the Official methods of analysis, 13th Edition.appearance of the gel produced. The lighter colours Washington D.C; 1980.having little effect on the final appearance of a foodproduct would be preferred. Table 4 indicates that the Adomoko, D. Cocoa Pod Husk Pectin. Phytochemistry.colours of pectins vary according to the source. The 11: 1145-1148; 1972.

ASEAN Food Journal Vol. 10, No.2, lYYS 49

Bhattia, BS., Sidappa, GS., and Lal, G. Composition Kertesz, 2.1. The Pectic Substances. lnterscienceand Nutritive Values of )ackfruit. Indian). Agric. Publishers Inc., New York. p. 485; 1951.Sci. 25(4): 6303-6306; 1955.

Muhammad, Y. Some Major Factors WorthBlakemore, W.R., Dewar E.T. and Hodge R.A. Consideration in Manning for a Diversified Fruit

Polysaccharides of the cocoa pod husk. ). Sci. Processing Plant, Ministry of Agriculture andFood Agric. 17:558-560; 1966. Fisheries, K.L., Malaysia; 1972.

FAMA, 1988. Malaysia Federal Agricultural Marketing Owens, H.S. Methods used at Western RegionalAuthority Kuala Lumpur: Marketing Research Research Laboratory for Extraction of PecticDepartment; 1988. Materials, AIC-340, Western Regional Research

Laboratory, Albany, California; 1952.Francis, B.)., and Bell) .K. Commercial Pectin: a

Review. Trop. Sci. 17 (1). p. 25;1975. Wiles KK and Smit C).B. US. Patent 3,622559. Nov23. Sunkist Growers Inc; 1971.

Gee, M., McComb, A and McCready KM. Food Res.,23, 72; 1958. Rouse AH. and Crandal P.G. Pectin content of lime

and lemon peel as extracted by nitric acid. ). FoodHodgson AS. and Kerr L.H. Tropical fruit Products. Sci. 43: 72-73; 1978.

In The Chemistry and Technology of Pectin.Walter KH. ed. Academic Press, San Diego 67-86; 1991.

50 ASEANFood Journal Vol. 10, No.2, 1995

page 1TitlesABSTRACT canned fruit processing industry has increased to I. . . I . UNIMAS (6 1993) ASEA~ Food Journal Vol. 10, 0Jo. 2, 1995 43

page 2TitlesMATERIALS AND METHODS about 15 seconds whereupon a pectin aluminium- One hundred grams of ground and dried peel were Smit, 1971) NaOH to a small amount of dried sample. On heating, 44 ASEAN Food Journal Vol. 10, :'-Jo. 2, 1995

page 3Titles. ht . . emg use 0/. R COOH (A'd' . 'd) Grade of pectin to If 11 10 " . th " Molecular weIght of AUA (1 umt) - 176 g. . ' . ., . . conSI ere rap! settmg an 1 t e hme reqUIre or . . (ADA) . ., I ., th II . . II = 176 x O.lz x 100 + 176 x O.lv x 100 e y mt IS t1e quantIty a Je y w IC1 can e w x 1000 w x 1000 and Bell, 1975). This unit indicated the economic ld II d) w = weight of sample. .. ASEAN Food Journal VoL 10, No.2, 1995 45

page 4ImagesImage 1

page 5ImagesImage 1

TitlesYield ASEAN Food Journal Vol. 10, No.2, 1995 Moisture Ash %AUA

page 6ImagesImage 1Image 2

Titles48

page 7TitlesASEAN Food Journal Vol. 10, No.2, lYYS 49

page 8TitlesFAMA, 1988. Malaysia Federal Agricultural Marketing Owens, H.S. Methods used at Western Regional 50 ASEAN Food Journal Vol. 10, No.2, 1995