MARDIRes. J. 19(l) (1991):i,29-135 Chemical,microbiological and sensoryquality changesof semi- cooked"roti canai" during low temperaturestorage @erubahankimia, mikrobiologidan nilai rasaroti canaisemasa penyimpanan pada suhurendah) H. A. Hasimah*,M. S. Faridah*and M. Y. RafiahHasanah* Key words:"roti canai",quality changes,low temperaturestorage Abstrak Roti canai yang separuhmasak dan dibungkus dengan beg polietilena keturnpatan tinggi telah disimpanpada suhu-10 hingga -12,24 dan 9-1 I t untuk 90 hari. Perubahankimia, mikrobiologi dan nilai rasa telah dikaji pada hari penyimpanan yang ke-5, ke-14, ke-18, ke-23, ke-28, ke-36, ke-60 dan ke-90. Kajian mikrobiolo gi menrmjukkan bahawa keti ga-tiga suhu penyimpanan kurang memberi kesan terhadap perubahan bilangan mikroorganisma di dalam roti canai. Ujian nilai rasa dari segi warna, teksmr, rasa dan penerimaankeseluruhan tidak menunjukkan perbezaanyang nyata antara roti canai yang disimpan pada suhu -10 t hingga -12 qC selama90 hari dan roti canai yang baru dibuat. Abstract Semi-cooked "roti canai" packed in high density polyethylene bags were stored at temperature ranges of -10 w -12,24 and 9-l I qC for 90 days. Chemical, microbiological and sensory qualiry changesin the samples were studied on the 5th, l4th, 18th, 23rd, 28th, 36tl', 600r and 90th day of storage. Microbiological analysis indicated that the three storage temperanlresdid not have much effect on the microbial count in the product. Sensory evaluation tests indicated that roti canai storedat -10 to -12 "C for 90 days were not significantly different from freshly prepared roti canai in terms of colour, texture, taste and overall acceptabiliry. Introduction canailocally and abroad in suitableunit "Roti canai",a type of unleavenedflat bread packs.Stored roti canaishould have the of Indianorigin, is a popularfood in the characteristicsof freshlyprepared roti canai. Indianand Malay community in Malaysia.It Similarly,any mechanizationprocess should is usuallysold by food outletsin a ready-to- resultin a productsimilar to thosemade by eat form. I"ately,various outlets have been traditionalmethods. sellingchilled and frozenroti canaias well Very little informationon roti canaiis as roti canaidough. availablein literature.Capati, another type In view of the increasingdemand for of unleavenedflat bread,is the nearest, chilled, frozen and convenientfood equivalent to roti canai. However, it differs products,there is potentialfor the large- from roti canaiin termsof formulationand scalemanufacture and marketing of roti preparation. rFood TechnologyDvision, MARDI, P.O.Box 12301,50774 Kuala Lumpur, Malaysia Authon' full names:Hasimah Hafiz Ahmad,Faridah Motrd. Som andRafiah Hasanah Mohd. Yusof @MalaysianAgricultural Research and Development lnstitute l99l r29 Quality changes of stored rotr canar KameshwaraRao et al. (1964)reported Storage ttr,atcapati packed in foil-polyethylene Batches of 30 roti canai pieces were slored laminate(0.025 mm) couldbe keptfor over at temperaturesof -10 lD -12,24 and l0 dayswithout becoming mouldy at -5 "C 9-ll 'C for 90 days. to -10 € andrelative humidity of 70-90Vo. However,capati could only be kept for 5 A naly sis and evaluations daysat 16 {. VenkateswaraRao et al. Samples were taken from each storage (1986)found mould growth on capati temperatureon the 5th, l4th, l8th, 23rd, packedin polyethylenepouch after 3 days 28th, 36th, 60th and 90th day of storage for of storageat atmosphericconditions of chemical,microbiological and sensory temperature(25-27 .C) and humidity evaluaLion.hoximate analvsiswas done on (6O45Vo).However, for capatipacked in the fresh sample. waxedpaper, the onsetof mould growth wasdelayed by 12 h probablydue to the Chemicalanalysis Peroxidevalue of the lossof aboutTVomoisture. Spoilage of storedsamples (in duplicate)was capatiwas due to attackof mouldsthat need determined according to the method of moisturefor growthand germination of A.O.C.S.(1975) while proximateanalysis spores. on the fresh sample(in duplicate)was dorle This studywas undertakento assessthe according to Pearson(1976). Moisture chemical,microbiological and sensory content.was determined throushout.fie quality changesduring low temperature storageperiod. stomgeof semi-cookedroti canaiover 90 days.The storagetemperatures used were Microbiological analysis A piece of roti -10 to -12,24 and9-l I .C as usually canai was taken from each storage found in domesticrefrigerators. The effecs temperatureon each sampling day and left of consumerstorage in domestic to thaw for 3 h at4 'C. A l0 g samplewas refrigeratorson roti canaiquality can thus then weighed and homogenizedwith 90 mL be evaluatedsince in thehome, chilled and Ringen solution using a stomacher.Serial frozenproducts are moresusceptible to dilutions were made and I mL volumes of consumerabuse unlike in the manufacturing appropriatedecimal dilutions were pour- sectorwhere strict temperaturecontrol and plated using total plate count agar CIPCA) storageare carried out. and potato dextrose agar (PDA) to determinetotal viable count, and yeastand Materialsand methods mould count respcctively.Microbial colony Preparationand packaging was countedafter 48 h of incubationat Roti canaiwas prepared using a standard 37'C for TPCA and 5 days at 25 "C for formulationconsisting of ingredientssuch as PDA (modification of ICMSF 1978).Water wheatflour, condensed milk, sugar,eggs, activity was determinedat 23-25'C with a salt,.cookingoil, ghee,margarine and water. Rolronic Hygroskop DT meter model CH- The ingredientswere mixed, shaped into 8M0 Zurich. roundpieces and heatedfor I min on each sidewith a mixtureof 4 partsof oil to I part Sensory evaluation The storedroti canai of ghee.After cooling for I h at room were evaluatedorganoleptically using temperature(27 "C), eachpiece of roti canai freshly preparedsamples as control. Each waspacked in 255 mm x 170mm high stored sample was thawed for 2 h ^t 26 'C densitypolyethylene bags of 0.04mm and heated for 5 min on a heated metal plate thicknessand heatsealed. with 1.5 mL of oil-ghee mixtue (ratio of 4:l). The quality attributesassessed by l0 taste paneliss were colour, texture, taste and 130 ll. A. Ilasimah. M. S. Faridahand M. Y. Rafiah Hasanah overallacceptability. Sensory evaluation the 23rd and 28th day (Figure /). The PV scoreswere described by usinga nine-point were10.61 and 11.25 medkg respectively. hedonicrating scaleranging from I (dislike Freshoils usuallyhave PV well below l0 extremely)to 9 (like extremely)(Larmond meq/kg(Egan et d. l98l). Accordingo 1977). Augustineand Chong (1986), a PV greater than l0 meqftg indicatesthat the fat has Statisticalanalysis The meanscore of undergonea substantialdegree of oxidation. eachquality attributewas usedas a measure The PV of samplestored at 9-l I "C of productacceptance. A two-wayanalysis indicatedthat the fat hasundergone of variance(ANOVA) wasconducted for all substantialoxidation and this may suggest quality attributesof the four samplesstored that the storagetemperature is not very for 90 daysto determinethe significant suitable.However. the usefulness of thePV differencebetween the treatments.The is limitedo the initial 5tagesof oxidation sourcesof variationshown to be significant and the interpretationof resultshas to be by ANOVA werefurther tested using l€ast donein relationto organolepticassessment SignificantDifference test to estimatewhich for ranciditywhich is discussedin thenext meanswere statistically different (tarmond scction. t977). In theearly stages of lipid oxidation, hydroperoxideformation has taken place in Resultsand discussion the productdue to the oxidationof fatty Chemicalchanges acids.This can be seenfrom the sharprise Peroxidevalue This valueis usuallyused in PV by the 28th day of storageat all three to assessthe rate of lipid oxidation. storagetemperatures. As lipid oxidation Peroxidevalue @V) is thereactive oxygen progressed,PV decreasedafter the 28th day contentexpressed in milliequivalensof free probablydue to decompositionand reaction iodineper kilogramof fat. The PV is of the unstablehydroperoxides with other determinedby titratingthe liberatediodine materialssuch as proteinand enzymesin the from potassiumiodide with thiosulphate. semi-cookedroti canai. It is likely thatthe Mostof the samplesstored at -10 to -12, enzymesin the flour havenot denaturedas 24 and9-ll "C hadPV bclow l0 meq/kg the roti canaiwas only semi-cooked.After exceptfor samplesat 9-l I 'C analysedon the 60th day,PV increasedagain probably Peroxidevalue (meq/kg) O-a _10ro _12oC o---o 24.9 a-J 9_l I .C Storagerinre (days) Figure I. Peroxide value ofroti carni during low temperature storage r3l Qudity changes of sored rotr canar due to furtheroxidation of fatty acidsin Moisturecontent Resultsobtained from :rnotherpart of the chaintaking place. the two storagestudies (average) showed ttr,atthe moisturecontent of samplesstored Proximate analysis Resultsshowed that at the thee temperatureswas in the rangeof the freshlyprepared roti canaihad values 30.39-32.96Vothroughout the storageperiod (Table1) fakly similar to thosecompiled by (Figure2). This is becausepolyethylene is a Tee et al. (1988).Fresh roti canaihad a fat good moisturebarrier and resistant !o contentof 8.967oderived from the temperaturesas low as -20lC (Flatman ingredientssuch as condensedmilk, eggs, 1977;Oswin 1977). oil, gheeand margarine. M icrobiological change s Table 1. Proximate analysis of freshly prepared Resultsof the microbiologicalanalysis roti canai showedthat tlre storagetemperatures did not havemuch effect