Food Structure
Volume 6 Number 1 Article 9
1987
The Influence of Ingredients and Processing Variables on the Quality and Microstructure of Hokkien, Cantonese and Instant Noodles
R. Moss
P. J. Gore
I. C. Murray
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Recommended Citation Moss, R.; Gore, P. J.; and Murray, I. C. (1987) "The Influence of Ingredients and Processing Variables on the Quality and Microstructure of Hokkien, Cantonese and Instant Noodles," Food Structure: Vol. 6 : No. 1 , Article 9. Available at: https://digitalcommons.usu.edu/foodmicrostructure/vol6/iss1/9
This Article is brought to you for free and open access by the Western Dairy Center at DigitalCommons@USU. It has been accepted for inclusion in Food Structure by an authorized administrator of DigitalCommons@USU. For more information, please contact [email protected]. FOOD MICRO STRUC T URE, Vol. 6 (1987) , pp. 63-74 0730-54 I 9/87$3. 00+. 00 Scanning Mic roscopy Internat ional , Chicago (A MF 0' Hare) , I L 60666 USA
THE INFLUENCE OF IN GREDIENTS AND PROCESSING VARIABLES ON THE QUALITY AND MICROSTRUCTURE OF HOKKIEN, CANTONESE AND INSTANT NOODLES
R. Moss~ P . J. Go r e and I. C. Murray
Br ead Resea r ch Institute o f Aust ra lia P 0 Box 7, North Ryde NSW 2113 Aust r alia
Introducti on
Light and scanning electron microscopy have Noodles f orm an important part of the diet in been used as a part of a research program designed many of the count r ies of South East Asia, China to study the influence o f flour quality and and Japan. Hence, much o f the wheat that i s processing variables on three of the noodle types produced in the major exporting countries -is used that are popular in South East Asia . The noodles t o produce f l our for noodle manufacture However, selected _ for study were Cantonese, Hokkien and there has been relati ve ly little published on the modern 1nstant. They represent the range o f factors influencing noodle qual i ty, and even less cook1ng and processing variables that are commonly published on the microstructure of noodles. The encountered in these products . Flour particle size situation is fu rther campi icated by the fact that and the choice of alkal i ne ingredients inf l uence there a ~ e a n~mb er o f diffe re~t kinds_of noodles, protein deve l opment du ring the s heeting p rocess . A each ~o~lth dlffe r ent product 1on r equHements and continuous protein mat ri x is required in t he raw quality attributes The three types of noodles noodle if it is to have good eat ing qua l ity ~o~ h en that are considered in th 1s paper are : Cantonese cook~d. The swel ling o f the sta rc h granules during noodles which a r e so l d uncooked; Hokkien noodles cook1ng disrupts the p r otein matrix and the extent ~o~h ich are sold part ially cooked; and modern of this disruption at the surface of the noodle · instant noodles whi ch are steamed and fried befo re related to surface stickiness and cooking loss. sale There are certain similarities between the microstructure of some noodles and pasta, due in part to the similarities of low dough moisture and cooking methods . Resmini and Pagani 1201 have published a detailed review of the microstructure of pasta which contains an extensive bibliography. Oh et al cIS - 191 have published several papers on Japanese noodles, some of which used scanning electron microscopy CSEMl techniques to elucidate Initial pa per received November 03, 1986 the nature of various pr ocessing changes. Dexter 1\'lanuscript r eceived J a nua ry 14, 1987 et al.C4l have also used SEM to study the Di rect inquiries t o R . Moss microstructu r e of J apa nese noodles made from soft Telephone number: 61 - 2 888 9600 and du rum wheat f lours . Endo et al . CSJ used SEM t o study the effect of maturation on Chinese noodle quality . There do not appear to be any papers pu b lished rela t ing mi cros truc ture to qua lit y aspec t s of modern instant nood l es. Microscopy has been used, together wit h other techniques, in t he noodle research program conducted at t he Bread Research Institute of Australia and th1s paper attempts to relate the microstructure of Cantone se, Hokkien and modern Key Words: Cantonese noodles, Hok.kien instant noodles to processing and quality noodles, Instant noodles Kan swi, alkaline l="arameters . ingredie~ts, no?dle f?roce~sing, flour quality, c~yosect1ons, hght m1croscopy, scanning electron Flours m1croscopy . --Thr ee strai gh t run flours C73-75t. extraction! of 9.07., 12.07. and 18 . 77. protein were prepared fo r this study using a Buhler experimental mi ll . A sam p le of bread wheat CT riti cum aestivuml semolina was milled on a Miag Varia-Roll mill and sieved to p r oduce four flours of different particle sizes
63 R. Moss, P. J. Gore and I. C. Murray
Table 1 Cantonese Noodles Tab 1 e 3 Noodle Processing Variables
Effect of flour particle s 1ze and starch damage Cantonese Hokkien Instant on eating quality Compression stage 3COJ:.: 3 .8CO l 410 l Flour Nood 1e 3C 1 l 3 . 8C 1 l 4( 1 l 3< 2) 3 .8< 2) t.l 2) Pa rti c 1 e Maltose Cooking Eati ng Coo king Time 310 l 3 .81 0 l 4 ( 0 l s i ze (/. mal tosel (m in l Quality LOSS( Z l Rest time 30 min 0 min 0 m1n <85 lJm 3 . 3 7 . 0 Good II .0 85-180 um 2.0 6. 5 Good II .0 Reduc ti on stage 2 . 2 3 .0 2 .0 265 -355 lJ m I .9 6 . 5 Inter. 12 . 3 I . 4 2 .0 1 . 2 >355 lJm 0 .8 7.0 Poor 12.6 0. 95 I .0 0 .8 High Sta rch Final dough Damage <85 lJ m 5 . 0 8 . 25 Very poor, 17.7 sheet th ickness 1.5 2 .0 1.0 gummy Cut noodle flable 11 The final fraction was then subdivided size Cmml 1.5 X 1.5 2.0 X 2 . 5 1.0 X 1_5 and a portion remilled to increase the level of starch damage as indicated by the high maltose x Roller gap in mm and numbers of folds 1n figure /Table 11. The protein contents of these arenthesis. five flours were simi lar Cl2 .2: 0 .11.1 and thus Noodle Cooking would not significantly influence noodle qual ity. AI~ noodles ~e re stored in plastic bags at 0 Two commercially milled flours 111 . 01. and 12.5z 22 C pr10r to cooklng. Cantonese noodles clOl were proteinl were also used for certain trials as co?ked on the day o f preparation by immersion in indicated in the tex t. Flours were analysed fo r bo1ling wat er until the uncooked core had just protein content and diastatic activity by standa r d disappeared !Table 41. methods c ll. Hokkien noodles ( 11 l were pre-cooked 1n boi 1 ing wate r f or 40 sec on the day of Noodle Prepa ration preparat1on They were t hen o i l ed and on t he T here are sl 1ght dif f erences in the f ollow1 ng day t hey ~o~ere fully cooked by bo i l ing formu l ation and processing techniques used to for 2 . 5 min . produce the threr: dif!erent kinds o f noodle s, and Instant noodles were steamed f o r 1 min at 35 the~e are summansed 1n Tables? and 3 . However, kilopascals followed by frying in palm oil at 150 bas1cal ly noodle doughs cons1sting of flour, 0 c for 45 sec . Instant noodles were sealed in alkal i ne salts Ckan swil or common salt and water a plastic bag and stored at 22°C for one month CTable 21 were mixed in a Hobart N50 mixer as before o rganoleptic evaluation. previously described C101 The crumbly mix was transferred to an Otake noodle machine and Table t. Cantonese Nood les compressed four times, with va r ious folds, into a coherent sheet fTable 31. The sheet was rested Effec t of flour protein content on o ptimum cooking and then reduced in th i ckness by passage three time and eating quality times between the rollers at successively decreasing clearance. The dough was then cut Optimum Cooking into st rips by passage between the cutting rolls. Flour Protein (Zl Time Noodle Evaluat i on Tab l e 2 Noodle Formulae Nood l e eatwg q ual i ty wa s dete rmi ned by the method of Miskelly and Moss (101. S tickiness Cantonese Hokkien Instan t ~ubjectiv ely assessed by a trained taste panel and lts presence was identified by the noodles Flour 100 100 100 100 100 sticking to the teeth during mastication o r by ( 13 . 5Z mbl stickiness during handling. Noodle pH was Water 32 32 32 31 31 determined by the method of Moss et al . c 12 l Kan swi Co?king loss was determined by evaporating an amount 0 .5 al1quot <70mll of cooklng water to dryness in a - type:.: A :B D: A :B A:B tared pyrex dish. The dish plus re sidue was then (9: 1 ) f 10:9:1) ( 3 : 21 weighed, the residue ashed at 600° C for 1 h and then we1ghed Cooking loss was the amount of o rganic material rem oved during ashing and was expr':ssed as mg dry matter per lOOg raw noodles . Cooklng water pH was measured on a separat e aliquot of cooking water. 64 Noodle quality and microstructure Microscopy Legend to Figures. The samples were prepared for 1 ight All light mic r ographs are transverse sections. In microscopy fLM1 as previously described fl31 and colour micrographs of sections s t ained with stained for protein (8, 14), starch (6), fat (7), periodic acid Schiff reagent (PAS)/Fast g r een the and bran C91 or germ C91 . In the case of cooked starch is stained magenta a nd the protein products, the samples were prepared for sectioning blue-green. by rapid ly freezing in iso-pentane, cooled by liquid nitrogen to just above the freezing point E - edge of noodle; of the i so-pentane. Some sect ions o f these F.P - endospe rm particle; samples were allowed to dry in the cryostat and GS- gross ~y swollen starch granules; examined, unstained and moun t ed in a synthetic M - prote~n mass; resin CEukitt, Ca rl Zeiss, West Germanyl using P - prote1n; either polarised 1 ight or phase-contrast S - s tar c h. microscopy . This wa s done to avoid any further swelling of the gelatinised or partially gelatinised starch granules due to contact with aqueous solutions. Samples for scanmng electron microscopy were rapidly frozen in a similar manner, freeze-dried and prepared for examination in a Cambridge S600 SEM as previously described ( 131. Results and Discussion Noodle Doughs The same general microstructural changes took place for all types of noodle doughs during processing, but the rate of development of the dough wa s influenced by such factors as flour Fig Light micrograph of a section of bread quality, othe r ingredients and the processing dough during the early stages of mix1ng. ~ote the variables selected for each product. isolated protein masses formed by the pul l 1ng away In all types o f noodle doughs there 1s very of the protei n from the f l our endosperm particles. little gluten deve l opment in the mixing stage, Stain Ponceau 2R Bar "' 70 \Jm. which is in contrast to bread dough . In the latter the protein is pulled away from the sta r ch granules in the ea r ly s tages of mixing to form a coarse, discontinuous network rFig. 1 l. Further mixing is then required to develop the desired fine continuous network. In noodle doughs the protein does not pull away from the starch granules during mixing and the microstructure resembles that of compacted flour, with many endosper m particles being cl ear ly discernible CFig. Zl. This is due to the low moisture content of noodle doughs !31-32%1 and is characteristic of such products as pasta, -in addition to noodles. I n noodle manufacture, the main aims of mix ing are, t herefore, to uniformly distribute Fig . 2. Light micrograph of a Hokkien noodle dough ingredients and to hydrate the f lou r particles. at the end of mixing . The prote1n has not pulled Dough development is car ried out by passage away from the starch 1n the endosperm masses through rollers. Stain Ponceau 2R. Bar "' 70 JJ m. After mixing, all noodle doughs are then compressed into a continuous sheet by repeated passage through pa ir s o f rolle r s. Examination of dough microstructure during t his process indicates that adjacent endosperm particles become 11 fused 11 t ogether so that the protein matrix within one endosperm particle becomes conti nuous with that of adjacent particles . There is much less protein o rientation in noodle doughs than in bread doughs that are passed through rollers . On ly a few, sub aleurone, protein masses show orientation in noodle doughs. At the end of the compression stage the visual appearance of the dough sheet looks quite uniform, but mic r o-structurally, fusion of endosper m particles is not complete . Fig. 3 . Light micrograph of a Hokki~n noodle dough The outline of partially fused endosperm partlcles at the end of the compression stage . Dough is still clearly recognisable CF ig. 31. development is not complete as the outline of some The reduction stage which f ollows furthe r of the endosperm part1cles is still clea r ly develops the gluten. To obtain the best quality recognisable . Stain Ponceau 2R . Bar"' 70l.Jm. 65 R. Moss, P. J. Go r e and I. C. Murray noodles, an extremely uniform protein matrix must appea rance of the starch from the edge to the be obtained, with no traces of endosperm particles centre of the noodle After 2.5 min final cooking being discernible. However, the upper and lower the r e were no birefringent starch g r anules in the surfaces of the noodle sheet have a slightly less centre of the noodle, but an increase in size of continuous protein matrlX than that seen in the the sta r ch granules was not apparent At the cent r e of the noodle . After the final reduction outer edge of the noodle, the surface stage the noodles are cut but this does not have any appreciable effect on the microstructure. ... Cooked Noodles Fig . L. a. L1ght micrograph of the cent r e of dO The cooking process var 1es cons1derably for uncooked Hokki e n noodle, taken with polarised the 3 types of nood l e un der co nside r ation I t i s light and a 114 wav e pla t e . Note the majority of therefore dif f icu lt to gene r al i se details of t he s tarch granules a r e strongly biref ringent . microstructura l ch anges and s pecific Stain Ponceau 2R . Bar "' 70 lJ m. information wi l l be given later. However, in boiled nood l es softness i s re lated eithe r to the Fig . 4b. Light micrograph of the centre of a 20 occur r ence of voids i n the noodle or the presence sec pre- cooked Hokkien noodle taken o.~ith of highly swollen sta r ch granules. It has been pola rised light and a l/4 wave plate. Note that reported CSl that in Chinese noodles a 24 h small voids have been f o rmed (arrows l and that all maturation per i od pr ior to cooking improves eating the starch granules have started to lose som e quality and produces voids in the noodle. biref ri ngence indicating that they are start1ng to However, the improvement may be due to the effect gelatinise. Stain Ponceau 2R. Bar= 70 IJI!l . of o the r factors that pl ay a r ole during the maturation, rather than the production of voids Fig . 5 . Li ght micrograph of the edge of a 20 per se. Surface s t ickiness is related to a sec pre-cooked Hokkien noodle, taken with breakdown of the protein matnx at the surface and polarised light and a l/4 wave plate. Note the to a wide outer core of grossly swollen starch non-birefringent , grossly swollen star ch granules granules. Cooking loss is also usually related to at the edge of the noodle and the d1 f fuse prote1n surface st i ckiness, as the disruption of the matrix . This zone is approximately 400 urn wide , protein matrix at the periphery of the noodle and the more central starch granules still show allows particles to become detached from the bulk some degree of birefringence. Stain Ponceau o f the nood l es due to t he vigo rous action of the 2R . Bar "' 70 lJm. bo i ling water. Fig . Light mi crograph of a Hokkien nood l e (40 Hokkien Noodles sec . pre-cookl cooked for 2 . 5 min Coptimuml Genera l Although t he swollen sta r c h granules in the outer - -A-11 Hokk1en noodles were prepared from the zo ne have pa rtially disrupted the protein matrix, commerc ia l \y milled flou r of 11.01. protein the outer edge of the section is smooth . Stain content. Some of the major changes that take place PAS/Fast green . Bar "' 60 urn. during cooking can be illustrated considering the case of Hokkien noodles. After only 20 sec Fig . 7 . Light micrograph of a Hokkien noodle C40 immersion in boi 1 ing water all the starch had pre-cook l cooked for 4.0 m1n Covercookedl . started to swell and lose some birefringence Note the e xtensive disruption of the noodle ccompare Figs . 4a, 4b, & 51. There was an outer surface due t o the vigor ous action of the boiling zone of total gelatinisation that was 400 u m wide. water and the excessive swelli ng of the starch The grossly swollen starch in this zone was held granules . Stain PAS/Fast green. Bar· "' 60lJm . in place by a diffuse protein matrix and also probably by sta rch molecules that had leached out Fig Light m1crograph of a Cantonese noodle of the gelatinised starch granules !Fig . 51 . The made from the high prote i n Cl8.7t.l flour. Note the starch in the central region o f the noodle had thicker, mo re intensely stained pr otein matri x and also started to swell and lose some birefringence the trapped air cells . Sta in PAS/Fast green. cFig.4bl. The prot ei n was sti ll quite compact and Bar =- 60 lJm . there were some very small voids C20-SO \Jm widel. Pre-cooking fo r an addit ional 20 o r 40 sec caused Fig 11 Ligh t microg r aph of a Ca n tonese noodle, o nly a s light i ncrease i n w1 dth of the outer zone a f ter the compression stage, made from the flou r !max. width 600 lJml but i nternally, with l onger of coarse pa rticle size 1265-335 JJml . Sta i n cook1ng, the starch granule s welling wa s more PAS/Fast Green . Ba r = 60 lJffi. apparent and the numbe r and size of the vo i ds increased (max . diameter 100 JJml . F1g 12 Light micrograph of a Cantonese noodle, In the final cooklng stage the pre-cooked after the comp r ess1on stage, made from the noodles were reheated in boiling water until there flou r of fine particle s i ze c <85 uml. Stain was no longer a white core in the centre of the PAS/Fast Green . Bar: 60 urn. noodle. In the case o f the 40 sec pre-cooked noodle this occurred after 2.5 min cooking. Flg 18 Light micrograph of an Instant noodl e , However, after 1 minute 1 s final cooking there was made from the 9.01. protein flour, after the frying only the slightest trace of birefringence in the process . The re is no layer of fat at the surf a ce cent re of the noodle . Yet , the noodle still of the noodle, and the fat is distributed looked opaque, presumably due to the llm1ted uniformly throughout in the fo r m of coarse swelling and water up-ta ke of the starch . There globul es which are stained red . Stain Sudan IV/Oil only a ve r y gradual transition in the Red 0 . Bar = 50 lJm. 66 Noodle Quallty and mlcrostructure 67 Noodle quality and mi crostructure relatively smooth and not showing any sign of shorter cooking time. However within this zone disruption CFig. 61. The swelling of the starch, there was conside rable surface dis r uption due t o however, had stretched and partially disrupted the the weaker protein network cFig . 91. The s tarch pro tein matrix in the outer zone. In t he centre granules in the central region of the noodle of the noodle the protein matrix was still displayed a greater overall degree of swelling continuous . After 4 min final cooking there was than was seen in the other two samples. The mo re extensive disruption of the noodle surface due to extensive swelling was confirmed by the extremely excessive swe lli ng of the starch granules CFig . pale colou r of the starch granules when stained 7l. using the PAS reaction. The medium and high Effect of cooking water pH protein samples had similar, s lightly wider oute r Transverse sect10ns of pre-cooked nood l es zones of gelatinization (400-500 1.1ml. The medium containing ei th er sodium hydroxide or kan s wi were protein samp le had a smooth outer su rface examined using phase contrast and polari sation indicating that the prote1n network was better microscopy . Cooking details and final pH o f the able to ho l d the structure together fFig . lOl . pre-cooking water are given in Table 5 . Table 5 Hokkien Noodles Effect of cooking water pH on cooking loss Cooking Loss Cg dry matter/ Pre-Cooking Water lOOg raw noodlesl Alkal1 Initial pH Final pH Initial Final I% NaOH 8.5 II . 0 2 . 67 3.00 lZ Kan swi 8.8 9 . 5 2.62 2 . 70 It was apparent that both the size and general appearance of the cent ral core was not influenced Fig Light micrograph of an opt imally cooked by the inc r ease in pH of the pre-cooking water. C4. 0 min. l Cantonese noodle made from the low However, the ove r all c ro ss-sectiona l area of the protein c9.0/.l f l our There ha s been considerable partly cooked noodles increased with alkali build surface disruption due to the weaker prote in up, being greatest in the case o f sodium network . Sta in Ponceau 2R. Bar= 70 \.lm. hydroxide, which was p robably due to the higher pH of the latter. Thus it is only the periphery of the noodles that is affected by the build-up of alkali in the pre- cooking water. The more extensive swelling in the outer region of the noodle is associated with increased cook i ng loss CTable 5 1 and stickiness of the partly cooked noodle. The latter can be a problem in high volume, automated noodle plants if the flow of fresh water into the cooking bath is not adequate. Cantonese Noodles Effect of flour protein content The three expenmenta lly milled flours, of protein content 9.0%, 12 . 0% and 18.7% were chosen Fig. 10 . Light microg raph of an opti mal ly cooked for th1s study. In all three samples the protein (4.25 min. l Cantonese noodle made from the medium network in the raw, cut nood le s t rings surrounded p r otein C12.0Zl f lou r. There ha s been relatively all the starc h. However, sections of the l ow little su rface disruption due to the stronger protein nood l es were mo re fragile than those from protein network. Stain Ponceau 2R . Bar = 70 IJffi. the other. two samples, indicating that the prote~n network 1n the former was weaker. The prote1n matrix in the 18.7% protein noodl es was noticeably However, the high protein sample showed sur f ace thicke: than that of the othe r two samples, and disruption equivalent to that of the l ow protein more a1r was trapped in the dough when compared to sample. This is partly due to the increased the other two samples cFig . 81. In transverse cooking time, but could also indicate some sections all doughs showed d isruption of the abnormality in the protein, since the protein starch-protein matrix at the edge of the section, content of the original wheat was abnormally high but the high protein sample showed the least cl9.6Zl. The eating quality of the noodles is contraction, suggesting that the protein matrix is showr in Table 4 and the differences in texture mo re r obust. would appear to be related more to the protein On cooking to optimum time CTable 41, the low network than the starch as the low pr otein sample protein sample had the smallest oute r zone of had a larger central zone of less s wollen starch gelatinization (300-400 ).lm widel due to the than the other tw o samples. Cook ing always 69 R. Moss, P . J. Gore and I C. Murray created voids in the central zone of the noodles, The protein structure in the high starch damage but for good, firm ea t ing quality, the voids sample is more uniform than t he two coarser shou ld be small (<50 lJffi diam1. The voids are samples, but less uniform than the two finer presumably crea t ed by forces i mparted by the samp 1 es. expanding, gelatiniz1ng starch partially These differences in gluten development are disrupting the structure. The more substantial reflected in terms of both eating quality and p rotein matrix of the high protein sample was cooking loss CTab l e 11. Oh et a l C181 reported respons1ble for the rubbery texture and s l owed that decreasing partic l e size did not increase the down water penetration to such an extent that firmness of cooked noodles, but they used pin sur f ace breakdown occurred it the centre of the mllled flour of tine particle size The very poor noodle was t o be adequa t ely cooked. eating quality and large cook i ng loss of the high When the three samples were cooked to the starch damage sample would be main l y due to the opt i mum t i me established for the high protein starch damage, rather than the slightly 1mpaired sample, the major d ifference was in t he appearance protein development It wou l d also appear that of the starch in the centre of the noodle. The the high starch damage had s l owed the rate of starch in the low protei n sample was more swollen water penetration into the nood l e, indlCated by and less intensely sta i ned by the PAS reaction the long cooking t ime than that 1n the other two samples, suggest1ng Effect of al kali that the prot ei n matrix in the low prote i n sample The ef f ect of alka l 1 on the quality of had allowed the water to penetrate into the noodle Cantonese noodles was examined using the rapidly and t hus a l lowed the starch to absorb commercially milled flour of 12 . 5/. protein. Al kali more water. In the centre of the other two samples (sodium hydroxide or kan swil is an essential the appearance of the starch was similar, being i ngredient in Cantonese noodles and the effect of intensely s t ained by the PAS reaction. alkali on gluten development and quality of This conflict in cooking requirements at t he noodles has been discussed elsewhere in relation high protein cont ent mean t that t he flou r was 11 out to Hokkien nOodles ell). Cantonese noodles showed of ba l ance 11 in terms of optimis1ng quality. The a similar trend in the dough stages. Sodium protein matrix should be such that i t allows the hydroxide slowed down the rate of gluten water to penetra t e into the noodle so that the deve l opment when compared to equivalent doughs central starch granules are optimally gelatinised containing either kan swi or sodium chloride. This before surface breakdown occurs Howeve r the effect was particularly noticeable at the upper matrix must be suf flcient l y strong to hold the and lower surfaces o f the dough sheet Even after noodle together. The best ubalancen was shown by the f inal reduction pass, the protein matrix in the medium prot ein noodle . the sodium hydroxide noodle was not uniform and Effect of f l our partic le size and starch damage traces of endosperm particles could be discerned. on nood 1 e qua l 1 t y However, the most obvious d~fferences be t ween the The m1crostructure of dough sheets made from three samples after the flna l reduct10n stage flours of different particle size and starch were; firstly, that t here were more voids in t he damage (Table 11 was examined a f ter the sodium hydroxide dough sheet, and secondly, that compression and reduction s t ages of processing. the discontinuity of the protein matrix at the After the compression stage it was apparent that upper and lower s u rfaces of the noodle sheet was the larger the particle size, the s l ower was the more apparent in the presence of sodium hydroxide. rate of gluten development and fus i on of endosperm The high pH of the sodium hydroxide noodl e CpH particles (compare Figs. 11 and 121. However, t he 11 . 51 did not a l ter the microscopic appearance of dough microstructu r e of the ex tremely fine, h1gh the majo r i t y of the starch granules, p robably starch damage sample was not as un i form as either because of t he 1 ow moisture content of noodle the ~85 lJm or t he 85 - 180 lJm sample. This doughs. suggests that the ex t ra milling had altered t he properties of the gluten as wel l as the starch Tabl e 6 Cantonese Noodles It was a l so interesting to note t hat the high starch damage samp l e did not requi r e any more Effect of alkal1 on optimum cooking time and water t han the other samples . This again cooking loss. emphas1ses the different nature of glut en Treatment development of noodles compared to bread doughs . However Oh et al C181 found that an increase i n 11. NaC l 1/. Kan swi 1/. NaOH s t arch damage did i ncrease water absorption of Japanese dned noodles. Th i s anomaly may be due Optimum cooki ng to d -i fferent -i ngred i ents or processing techniques . time (min) 4. 5 5 . 5 6 .0 Af te r the final reduc ti on pass the Cooki ng Loss m1crostructu r e of both the ~85lJm and the 85 -1 80 lJ m (g dry matter/ samp l es was ident ica l and tota l ly uniform . Th e 2 lOOg r a w p r odu ct 1 5 32 7 . 45 13.43 coarser samples ha d progressively uniform mi crostructures . Th i s indicat es that , noodl e Afte r cooking (Table 6l the voi ds were more doughs, fo r opt1mum gluten development the flou r plentiful in the sodium hydrox i de noodle, partly should be of relatively fine part icle si z e, b ut due to the l ack of continuity see n i n the doug h below 180 lJ m particle size is not critical. The sheet . However, the toughening of the gluten in rollers used in noodle process i ng are the refore the dough by the sod 1um hydroxide , may have not as effective as a pasta press in developing prevented t he gluten f r om expand1ng during the protein p resent in coa r se endosperm p a rticles . cooking, thus inc r easing the lack o f cont inu i ty. 70 Noodle quality and micros tructure The noodles co ntaining either kan swi o r sodium the starch granules. This gross swelling_had been chloride had a more delicate, continuous pro tein all owed to take place because o f the 1ncreased matrix, but that o f the latter was slightly _m o re protein contraction seen in this zone o f the raw disrupted. This could be related to the flrmer noodles. In the cooked rested noodle the o uter 11 biteu associated with the use of kan swi zone was narrower C200-300 ~ml and there was a After optimum cooking, the starch granules in more gradual transition from the _g~oss swell~ng the centre of the sodium hydroxide noodles were seen at the su rface to the more l1m1ted swell1ng more swollen than those in the other two samples. in the central reg10n. The improved eating The surface continuity o f the sodium hydroxide quality which res~lted from resting the noodles noodles was also less than that of the other two after the compress1on stage was thus due to the samples . The combination of more voids, greater presence of a more continuous protein matrix in swelling of the s tarch in the central zone, and the raw cu t noodle string Internally , the more surface disruption resul ted in the sodlUm changes 'in microstructure th~t occu rred due to hydroxide noodle having softer eating quality and cook ing obscu r e these subt le d1f!e~ences, but at surface stick iness . This cou ld be due in part to the oute r sur face t hey were magmfled. the longer cooking time required by t he sodium hydroxide noodles. Instant Noodles To gain a better understanding of the role of alkali during cooking, samples of sodium hydroxide Instant csteamed and friedl noodles were made and kan swi noodles were taken at intervals during from the three flours of differing protein content the cooking process. It was apparent that the c9.0Z 12 .oz and 18.7Zl and the structural voids present at the dough stage in the sodium diffe~ences at the dough stage were simila r to hydroxide noodle enlarged as the cooking those reported previously for Cantonese noodles. proceeded, but did not appear to increase in After steaming, all the starch granules we~e number during cooking . In the sodium hydroxide fully gelatinised, ?ut even the _9.0Z _prote1n noodles the size of the central core of less noodle had no apprec1able surface d1srupt1on and swollen starch granules was la rger than that of the- starch granules had not ruptured or fused the kan swi noodle at equivalent cooking times . together CFig . 151 This is in contrast to the This suggests that the water penetrates more cooking behaviour of the same flour when used for slow l y into the sodium hydro)(ide noodle, despite the production of Cantonese noodles. The lack o f the lack of continuity of the p r otein matri)(. surface disruption was presumably due to the The increase in cooking ti me r equ i red to r educed water uptake during the steami ng process eliminate the uncooked core in the centre o f the compa r ed to being p l aced in boiling water Cthe noodles meant that the oute r sur f ace of the noodle yield after s teaming was llOZ, compared to ove r wa s subjected to t he action of the boiling water 2001. for the corresponding Cantonese noodlesl. ! or t?O long and it failed to maintain its The surface continuity of th e 9 .0/. noodle was such 1ntegnty. that it was able to form large bubbles on the Effect of resting prior to reduction stage surface CFig . 161 . There were fewer such bubbles Tradlt1onally the noodle sheet 1s allowed to on the surface of the 12.0Z protein noodle and rest between the comp r ession and reduction stages. none on the surface of the 18.7z noodle. This produces a smoother dough sheet and results SEM examinat i on showed that during frying, in f-irmer eating noodles However, a la rge number large voids were created inside all the noodle~, of Cantonese noodles are now produced in a but the internal structure of the low prote1n continuous process with no provision for a rest noodle was mo r e unifor mly open CFig. 171. As the period. Hence it was decided to compare the protein content increased, the voids became l arger microstructure of noodles produced from both and the porosity less uniform. However, the use systems using the commercially milled 12. 5 1. of aqueous reagents that are es~ential to the ~r'l protein flour. tec hni que resulted in an expans1on of the m a~nx After the first reduc t1on pass, the sample and a mar ked reduction in the size of the vo1ds. that had been re sted had a more uniform prote1n The surface of the low protein noodle showed some matrix as the endosperm masses had started to fuse sl igh t disruption after frying but this disrupt i on together more effectively As a consequence, t he decreased as the protein content increased. The rested samp l e also had fewer air spaces. The shape of the starch granu les was st ill much mo re protein contraction at t he upper and lower c l early disce r nible t han in boiled noodles, _due to surfaces of the r ested noodle s heet was also less the low wate r content of t he steamed 1n stant t han that in the unrested sample Ccompare Figs. 13 noodles . & 141. All these observations 1nd1cate that the Fat up~ta k e during frying is an important prote l n becomes more extensible after r esting. factor, as high up~take increases the cost of the Further reduction passes lessened these finished produc t and may adversely affect shelf differences in microstructure, but they were still life. In the low pr otein noodle the fat was apparent in the cut noodle strings. distributed as coarse globules and had penetrated There was no di fference in cooking uniformly throughout the noodle CFig . 181. In the requirement between the two treatments, and after high protein noodle there was much less fat up~ cooking, the internal appearance of both noodles take some areas had virtually no fat and there was very similar. However there was a dif ference was iess fat in the centre of the noodle . Ho we ver in the wi dt h and appearance of upper and lower the intermediate protein noodle had a sim ilar fat outer zones of the noodles . In the non-rested up~take to the low- protein noodle. Thus protein sample the outer zone was wider CSOO vml and content is not the sole factor influencing fat up more clearly defined due to the gross swelling of take . It was also su rpr ising to observe that 71 R. Moss, P. J. Gore and I. C. Murray Fig. 13 Light micrograph o f a Cantonese nood le after the first reduction pass. Thi s sample has been rested f o r 30 mtn . after the compression Fig 16 SEM o f a fracture surface o f an Ins tant stage. There is very little contraction of the noodl e, made from the 9.0/. pr otein flour, af ter darkly stained protein netwo rk at the su rfa ce of the fry ing process. The large bl1ster on the the noodle sheet . Stain Ponceau 2R . Ba r = 70 um . surface was formed dur i ng steaming, and the internal voids we r e formed by steam generat1 on during frying. Bar" 400um Fig . 14 Light micrograph of a Cantonese noodle after the first reduction pass. This sample has not been rested for 30 min . after the comp r ession F1g. 17 SEM of a fracture surface o f an Instant stage. There is some contraction o f the prote in noodle, made from the 9.0/. pr otei n f lour , before network at the surface of the noodle sheet . fi nal cooking . Note the internal vo1ds formed Stain Ponceau 2R . Bar = 70 um. during fry ing. Ba r = 100 urn. Fig. 19 SE M of a fracture surface of an Instant noodle, made fr om the 9 .0/. pr otein f lour, a ft er Fig. 15. SE M of the surface of an Instant noodle, final cooking . The internal voids seen in the made from the 9 . 01. p r otein flour, after the sample examined after frying have disappeared due steaming process . The starch granules have not to swe l ling of the starch granules on boiling . Bar ruptured and fused together . Bar = 40 urn. = 100 urn . 72 Noodle quality and microstructure there was no localised concentration of fat at the 5. Endo S, Hara H, Sa to T, Nagao S, ( 19841 outer surface of the noodles. Effect of maturation on microstructure and When the noodles were r e-cooked there was an rheological properties of Chinese noodles . increase in the area of the sections !321.1 due to Nippon Shokuhin Kogyo Gakkaishi . l!_ (I l imbibition of ~o~ ater, but the most obvious change 10-13. was in the condition of the voids . The starch pr otein matrix had swollen to such an extent that 6. Flint F 0, Moss R, Wade P, (19701 the voids had virtually disappe ared wh en examined comparative study of t he microstructure of using SEM Ccompare Figs . 17 and 191 . However, differen t types of biscui ts and their doughs . Food 1 ight mi crog raph s indicated that the internal ce ll Trade Review~ !41 32-39. wa l ls that separated the vo ids had not fully fused t ogether a ft e r the fina l cook i ng. The lipi d in 7. Gu rr E ( 1958 1 Methods of ana l ytical the centra l r eg i on appeared to ha ve migrated fr om hist o l ogy and histochemistry. Leonard Hill, the bo dy o f t he starch-protein matrix t o 1 ine the London p 153 . wa lls of the former voids Hoooeve r, the amoun t of l1p1d 1n this region was sim i l ar to that seen Gu rr E, (1 9 581 Methods of analytical aft e r f rying, but the outer zone !250 1Jm wide1 was histol The authors wish to thank Miss S Stiles for 14 . Moss R, C 19731. Conditioning studies on assistance with the SEM, and the Fuel Geoscience Aust r al ian wheat II Morphology of wheat and its Unit of the Institute of Earth Resources, CSIRO, relationship to conditioning J . Sci. Fd. Agr i c . for the use of the SEM . ~ (91 1067-1076. 15 . Oh N H, Sei b P A, De yoe C W Ward A B C 19831 Re fe r ences Noodles I . Measuring the textural cha racter i st i cs o f cooked noodles . Cereal Chern. £2. (61 433-438 . Cereal Labo ra to ry Met hods, 7 th edn. ( 19781 American Association of Ce rea l Che mists, St . Pau l , 16 . Oh N H, Seib P A, Dey oe C W, Wa rd A 8 (19851. Minn esota. Nood l es II . The surface firmne ss o f cooked nood l es from soft and hard wheat fl ou r s . Ce r ea l DIEgidio M G, De Stefanis E, Fort~n a S, Chern . g f6 1 431 - 436 Gal t e ri o G, Nardi S Sgrulet ta D Bozz1n1, A (19821 Standardization of cook ing quality 17 . Oh NH, SeibPA,ChungDSCl985l No odles analysis in macaroni and past a products. Cereal III . Effec ts of processing variab l e s on qual1ty Foods World , :!]_ (8) : 367-368 . c haracteristics of dry noodles. Ce real Chern . 62 (61 437-440 . - 3 . Dexter J E, Kilborn R H, Morgan B C, Matsuo R , 119831 . Laboratory compression tester . 18 . Oh N H, Seib P A, Ward A B, Deyoe C W, C19851 . Ins t r umenta 1 measurement of cooked spaghetti Noodles IV . Infl uence of flour pr otei n, stick1ness . Cereal Chern . , £Q : 139- 142 . extract i on rate, particle size and starch damage on the qual i ty characteristics of dry noodles Ce real Chern . g C6l 44 1-446. 19. Oh N H, Seib P A, Ward A B, Deyoe C W (19851 . 73 R. Moss, P. J. Gore and I. C. Murray Noodles VI. Functional pr operties of wheat flour be strong, medium or weak in terms of Farinograph components in oriental dried noodles. Cereal characteristics? Foods World~ 121 176- 178 . Author s: The th r ee Buhler milled flours of 9.0 ~nd 18.7Y. pr otein were milled from the hard 20 Resmini P, Pagani M A il983J. Ultrastructure grained, medium strength, Australian wheat variety studies of pasta . A review . Food Microstruc. Osprey However , as descriptive interpretations of ~ . 1 -12 and 98 . ~ tr ength c an be misleading , the authors have 1nc l uded Fa r inograph and Extensograph data for t he Discussions wi t h Reviewe r s th r ee flou r s (Table 7l . D. D. Chr i st i a nson : Cou l d t he aut ho r s elabo r ate on t he produc t1 on o f t he vo i d spac e s i n noodles? Do t he gli adin and gluteni n contents influence void fo rmat ion? Authors. The gliadin and glutenin contents of the Flour Pr Farinograph Ex tensograph flours used in these tr ials were not measured and ( Y. 1 Water Abs Dev T1me Max Resi Ext although this f actor is known to influence ( Y. l ( minl 1 BU 1 ( cml extensibility in bread doughs it is not certain 9.0 63.0 3 . 1 250 20 . 4 whether it plays the same role in noodle doughs 12 . 0 63.6 4.5 259 25.2 where the moisture content is much lower. The 18.7 70.1 8.4 330 27 .9 prote i n does not necessar i ly have to be extensible to fo r m a continuous ma t r i x i n noodle doughs as the matrix is formed by the fusion of the matrices al r eady exist i ng i n the flour particles. However, on cooking, the expansion of the starch granules R.R. Matsuo : It is surprising that stickiness is as they gelatinise puts a stra i n on the protein noted 1n Hokkien noodles where the surface is network . Voids are c r e a ted when the protein coated ..,; th oi 1 Do the authors have a method for netwo r k i s to rn apa r t at 1ts weakest points by assessi ng sur f ace stickiness? t hese forces . Au tho r s : As the r eviewer has indicated, sticki ne ss D. D. Chr is t ianson: Does some chemica l ~ov e r c ome i n Hok kien noodle manufact u re by gelat l n1Sa t 10n of the sta r c h take place in the the add i tion of oi l. The stickiness refe r red to by a l kaline media? Barr iers that reduce water the aut hors was observed in the un-oiled noodles. penet r ation in NaOH nood l es could be solubilized Ho wever applica t ion of extra oil to overcome starch and/or degraded p r otein. excess st i ckiness 1mposes a cost penalty on the manufactu r er . Author s: .In isola~ed cases, some sections taken The authors are currently evaluating two objective from sod1Um hydrox1de doughs in the early stages methods of measuring stickiness 12,3l but our of sheeting did occas i onally contain streaks estimates of stickiness in this work were where the starch granules appeared to have subjective, belng either stickiness as observed suffered some chemical gelatinisation. However during mastication or handling. this fact was not emphasised in the text as it was not always observed . It would seem most likely R.R. Matsuo: The autho;s state that the less that any chemically gelatinised starch would have umform m1crostructure of the high starch damage arisen from the initial contact of the starch with sample nsuggests that the extra milling had t~e. h ighly alkaline water at the start of the altered the properties of the gluten as well as m1x 1ng . the sta r ch1• . Is it not ;JOssible that differences no t ed may be due to the preferential water uptake P . A. Seib · In t he Chi nese style noodles how does by dam ~ g ed s t a r ch rather than a c ha nge in gluten one dete r mi ne the op ti mu m mo i s tu re and' alkaline prope r t 1es? agen ts to use? Aut hors : The autho r s wished to emphasise t hat bo t h Authors : For most t rials wa ter addit i on was not factors are i mportant and did not -i ntend to imply 110pt1m1sed11 but rat her added at a standard level tha t s t arch damage was not an important factor . determined thr ough sur veys carried out Ho¥Jever the gluten damage which can occur as a by t he Br ead Research Instit ute of noodle consequence of the deliberate creation of st a rch manufactur ers and flour mill ers in the da~age i n r oller m~lling is often overlooke<:J, and southeas~ Asian r egion . The type and amount of th1s can also 1nfluence dough propernes as nkan SW1 11 was also dete rmined 1n this manner. discussed elsewhere R. R. Matsuo : Could the authors indicate whether the flou r s used fo r t he t rials we r e considered to 74