ABSTRACT.doc

ABSTRACTThe physicochemical properties of purple sweet potato our (PSPF)-wheat our blendsandtheireffectsonsaltednoodle-makingqualitywereinvestigated.PSPFwas substituted at levels of 5, 10, 15, 20, 25 and 30% for wheat our. Addition of PSPF increased the gelatinization peak temperatures from 66.45 to 67.73C,but decreased paste viscosities at all substitution levels. Texture analysis showed that hardness of our gels decreased as the amount of PSPF increased,while springiness reached the maximum value with 10% PSPF substitution. Farinographic tests indicated that doughstabilitydecreasedfrom18.0to7.8 minwiththeincreasinglevelsof PSPFup to 30%. PSPF had a weakening inuence on cooking and texture properties of noodles, but could be added to wheat our under the level of 15% without drasti- cally affecting salted noodle-making quality.PRACTICAL APPLICATIONSPurple sweet potato our (PSPF) could be served as a substitute for cereal ours, which enhanced products through color and nutrient.Salted noodles made by par- tially replacing wheat our with 15% PSPF appeared the attractive color of pink redness and favorable cooking properties, which provided a basis to develop novel colored foods with good antioxidant capacity.紫薯粉和面粉混合形成的理化性质以及对含盐面条制作的影响作者 魏鹏，回民州 刊名 食品加工与保藏 出版日期2013 卷号vol37 期号No5江苏省江南大学 食品科学与工程学院 国家重点实验室摘要本实验研究的是紫薯粉（PSPF)和面粉的混合粉具有的理化性质对含盐面条制作的影响。此实验在面粉中加入含量分别为5%，10%，15%，20%，25%和30%的紫薯粉。紫薯粉的添加使最高的凝胶温度由66.45摄氏度提高到了67.73摄氏度，但是在任何水平的添加量上都会降低面团的粘性。对面团的结构分析表明面粉凝胶的硬度随着紫薯粉添加量的增加而降低，因为弹性在紫薯粉的添加量为10%的时候达到最大值。对谷物图像的测试表明了生面团的稳定性随着紫薯粉的添加量逐渐增长到达30%时从18.0减少到最小值7.8。紫薯粉对面条的结构性质和烹煮有减弱的作用，但是在添加量小于15%时不会对加盐面条的制作质量产生剧烈的影响。实际应用紫薯粉可以作为谷类粉的代替品，它可以在颜色和营养方面提高产品的质量。含盐面条中加入部分替代小麦粉的15%的紫薯粉会使面条表现出诱人的粉红色，并且有最好的烹煮性质，这样就对形成既有特别的颜色又有良好的抗氧化性的食物提供了依据。INTRODUCTIONThe purple sweet potato (PSP) is originated in theAndes and widely grown in South America for centuries.In the past few years, it was developed in Korea, Japan, New Zealand and other countries to meet the growing demand in the health food markets (Philpott et al. 2003). Although PSP was imported to China in recent years, its production increased 50% per year in China (Zhang et al.2009).PSP and its prod- uctshave become more and more popular among consumers. PSPhas an intens epurplecolor in t he tubers because of the accumulation of anthocyanins (Terahara et al. 2004). The anthocyanins of PSP possess biological functions such as scavenging free radicals, antimutagenicity, anticarcinogen activity and antihypertensive effects (Smith et al. 2000; Oki et al. 2002; Katsube et al. 2003; Tsuda 2008). PSP can be pro- cessed into our that is less bulky and more stable than theperishable fresh root. PSP our (PSPF) can serve as a substi- tute for cereal ours, especially for people diagnosed with celiac disease. Some cultivars in Japan have been utilized in a variety of processed commercial products, such as natural food colorants, bread, noodles, juices, confectionary and fer- mentedbeverages(SteedandTruong2008).PSPFcanbeused to enhance food products through color, avor, sweetness and nutrient. The color tone of foods affects peoples appetite and sig- nicantly determines their enjoyment of foods (Auvray and Spence 2008). Public concerns about the safety of synthetic pigments in food have led to increasing attention to natural pigments. Natural colorants, such as anthocyanins, caro- tenoidsandbetalains,cannotonlyenhancethesensoryprop- erties of food products, but also functionally improve nutritional quality because of their potential role as natural antioxidants. Anthocyanins which are widely existed in theJournal of Food Processing and Preservation ISSN 1745-4549709Journal of Food Processing and Preservation 37 (2013) 709716 2012 Wiley Periodicals, Inc.plant kingdom,present a spectrum from red to blue-green in color,satisfyingconsumersdemandforfoodcolors(Caiet al. 2001;Stintzing and Carle 2004). Salted noodle products are the traditional food in many regions of Asia.It is mainly used as an energy source because of their high carbohydrate content. However, traditional noodlesaremadefromsimpleingredients(wheatour,water and salt) and are claimed to lack other essential nutritional components, such as dietary ber, vitamins and minerals (Choo and Aziz 2010). In addition, the protein has a low amount of the essential amino acid lysine. Salted noodle product is considered to be an excellent vehicle for supple- ments with vitamins, minerals and dietary bers. Thus, it could be appropriately designed as a functional food if healthy components could be incorporated into its formula- tion (Borneo andAguirre 2008). Several investigations have been conducted on the extrac- tion and biological function of PSP anthocyanins (Oki et al. 2002; Philpott et al. 2003; Terahara et al. 2004; Steed and Truong 2008). Maruf et al. (2010) reported the impact of a-amylase and maltodextrin on physicochemical and anti- oxidant capacity of spray-dried PSPF. However, little or no work has been done to determine the physicochemical prop- erties of PSPF blended with wheat our and their inuence on the texture and color of salted noodles. Theobjectiveof thisstudywastoinvestigatethepossibility of blending PSPF in wheat our to make salted noodles. Besides, the inuence of PSPF on thermal, pasting and rheo- logical properties of blends would also be investigated.引言紫薯起源于安第斯山脉 ，并且在几个世纪里在美国有了广泛的种植。在过去的几年里，为了满足人们在食品市场上对健康的需求，紫薯在韩国，日本，新西兰和其他国家得到了不错的发展。尽管紫薯是在最近几年里引入中国的，但是它的产量却以每年50%的速度增加。紫薯和它附属的根茎越来越受到消费者的喜爱。紫薯的块茎呈深紫色是由于花青素的积累，紫薯中的花青素具有许多生物功能，例如可以清除自由基，抑制突变，抗癌，防止高血压的功效。紫薯可以处理添加到面粉中，它比那些新鲜的易腐烂的根体积更小，性质更稳定。紫薯可以作为谷类面粉的替代品，尤其对那些正在治疗的腹泻病人。在日本一些紫薯品种被加工成各种各样的商品投入市场，例如用作面包，面条，果汁，甜点和发酵型饮料的天然着色剂Raw MaterialsCommercial wheat ours (Pengtai 3,450) were purchased from Zhong Liang Flour Mills Company (Qinhuangdao, China). Proximate analysis (dry basis d.b. ) was performed according to American Association of Cereal Chemists (AACC)methodsintriplicate.Thecontentsof crudeprotein, ash,fat and ber were 13.3,0.17,1.5 and 0.2% (w/w),respec- tively. PSPF was purchased from Tian Heyuan Company (Suzhou, China), and the contents of crude protein, ash, fat and ber were 5.7, 2.65, 0.93 and 3.1% (w/w), respectively. Wheat our and PSPF were blended in ratios of 100:0, 95:5, 90:10, 85:15, 80:20, 75:25 and 70:30 by weight, with wheat our as control.PSP Starch and PigmentPSP starches and pigments were extracted to examine their effect on thermal and pasting properties of blends, respec- tively. PSP starch was extracted according to the methods of Collado and Corke (1999) and the content of starch extractwas 98.6% (d.b.). PSP pigment extraction followed Zhang et al. (2009) with minor modication. PSP pigment was extracted from PSPF using citric acid. The extract was clari- ed by alcohol that precipitated polysaccharide and other impurities. The supernatant was vacuum concentrated after puried by macroporous resin NKA-9 (Nankai University, Tianjin,China).Thepigmentpowderwasobtainedbyfreeze- drying. Solution of PSP pigment was prepared by dissolving 1 g of pigment powder in 100 mL of deionized water before vortexing to obtain homogeneity.Thermal PropertiesGelatinization of samples was measured using a Pyris 1 Dif- ferential Scanning Calorimeter (Perkin-Elmer, Boston, MA) according to the methods of Gunaratne and Corke (2007) with some modications.The samples were weighed directly into an aluminum pan,and pure deionized water or pigment solution (our : water = 1:2,w/v) was added.The percentage of PSP pigment in wheat our was 0.02% (w/w). Pans were sealed and allowed to stand for 24 h at 4C for distribution of water. The scanning temperature range and the heating rate were 30100C and 10C/min. All tests were performed in triplicate.Pasting PropertiesThe pasting properties of samples were measured using a rapid viscosity analyzer (RVA) Super-3 (Newport Scientic, Warriewood, New South Wales, Australia). Suspensions of samples in pure deionized water or pigment solution (a con- centration of 13% w/w for dry material) were prepared in the RVA canisters. The percentage of PSP pigment in wheat our was 0.05% (w/w). A programmed heating and cooling cycle was set for 13 min, where it was rst held at 50C for 1.0 min, then heated to 95C at the rate of 12C/min, further heldat95Cfor2.5 min,thencooledto50Cattherateof 12C/ min,andheldat50Cforanother1.0 min.Theviscositieswere presented in rapid viscosity units (RVU). All tests were per- formed in triplicate.Gel Texture AnalysisGel texture properties were determined on the gels made from the RVA testing using a TA-XT2 Texture Analyzer (Stable Micro Systems, Godalming, England) under texture prole analysis (TPA) mode. After RVA testing, the paddle was removed immediately, and the paste in the canister was coveredbyParalm(TopGroup,Shanghai,China)andstored at 4C for 24 h before testing. The speed of pretest, test and posttest was 1.0, 1.0 and 0.8 mm/s, respectively, to a distance of 10 mm with a 5-mm cylindrical probe. All tests were per- formed in triplicate.BLENDS OF PURPLE SWEET POTATO FLOUR-WHEAT FLOUR S. SHAN ET AL.710 Journal of Food Processing and Preservation 37 (2013) 709716 2012 Wiley Periodicals, Inc.Farinograph AnalysisWater absorption, dough development time, dough stability anddegreeofsofteningweredeterminedbyfarinograph(Bra- benderInstruments,Duisburg,Germany)accordingtoAACC (2000)method54-21.Alltestswereperformedintriplicate.Salted Noodles PreparationTheblends(100 g)weremixedwith34 mLof 2%(w/w)NaCl solution to make salted noodles. The mixture was automati- cally stirred for 5 min using mixer to obtain dough. After resting for 30 min in the sealed plastic bag at room tempera- ture, the dough was then sheeted through the roll gap of 1.2, 1.0 and 0.8 mm for six times, respectively, then cut into 2.0-mm wide noodles using a domestic-type electric noodle machine (JMTD 168/140, Beijing, China). The noodles were dried at room temperature for around 12 h.Cooking Properties and Texture AnalysisCooking of noodles followed the previous methods with some modications (Wu and Corke 2005; Sui et al. 2006). The dried noodles (M1, g) were cooked in boiling water (500 mL) for 4 min.After cooking, 200 mL of the remaining water was further boiled for evaporation in a beaker (M0, g) until 20 mL was left. The beaker with left water was dried in an oven at 105C until constant weight (M2, g). Boiled loss (BL) was calculated as: BL (%) = 2.5(M2M0)/(M1 1W) 100, where W = weight of moisture in dried noodles. All analysis was conducted at least in triplicate. All texture properties were analyzed with a TA-XT2i TextureAnalyzer (Stable Micro Systems).For tensile strength analysis, the instrument was equipped with the probe of A/SPR. The distance between the parallel rollers was 30 mm. Thetestspeedwas1.0 mm/stoadistanceof60 mm.Forcom-pression analysis, the instrument was equipped with the probe of A/LKD.The test speed was 0.8 mm/s to the strain of 90%.ForTPAanalysis,theinstrumentwasequippedwiththe probe of HDP/PFS.The test speed was 0.8 mm/s to the strain of 70%, and the interval time was 1 s. At least six times was tested for each group.Color AnalysisThe Hunter color parameters L*,a* and b* were measured by a colorimeter CR-400 (Minolta, Osaka, Japan). Color results were expressed as tristimulus parameters (L*, a* and b*). H (hue angle = arctan b*/a*) indicates sample color (0 or 360 = red; 90 = yellow; 180 = green; 270 = blue), and C (Chroma = a*2 + b*21/2)indicatescolorpurityorsaturation. Color characteristics of noodles were determined on their surface. All measurements were performed at least in triplicate.Statistical AnalysisDatawereanalyzedwithStatisticalPackagefortheSocialSci- ences (SPSS) version 13.0 (SPSS Inc.,Chicago,IL) using one- way analyses of variance.Signicance was dened at P 0.05 by using Duncans test.RESULTS AND DISCUSSIONThermal AnalysisThe thermal properties of wheat our as inuenced by PSP starch, PSP pigment and varying amounts of PSPF are pre- sented in Table 1. There was a signicant increase (P 0.05) in gelatinization temperatures (To,Tp and Tc) of wheat our with addition of 0.02% PSP pigment, but the inuence of 10% PSP starch was not statistically signicant. Increase inTABLE 1. GELATINIZATION TEMPERATURES (ONSET, PEAK, CONCLUSION) AND ENTHALPIES OF BLENDS AS COMPARED WITH WHEAT FLOURSamples To (C) Tp (C) Tc (C) DH (J/g)Wheat our 60.56 0.19a 66.45 0.40a 70.45 0.34ab 3.33 0.20e 10% PSP starch 60.61 0.22a 66.39 0.17a 70.08 0.05a 3.06 0.13d 0.02% PSP pigment 63.71 0.48c 68.54 0.30c 71.88 0.19c 3.78 0.08f PSPF 77.75 0.72d 82.32 0.23d 87.02 0.16d 2.10 0.04a PSPF substitution (%) 5 62.54 0.33b 66.23 0.23a 69.69 0.13a 2.71 0.03d 10 62.88 0.50b 67.16 0.60b 70.71 0.36b 2.59 0.03c 15 62.75 0.31b 67.32 0.12b 70.88 0.36b 2.59 0.01c 20 62.69 0.38b 67.57 0.01b 71.59 0.07c 2.58 0.03c 25 62.43 0.41b 67.56 0.23b 71.47 0.26c 2.51 0.03c 30 62.36 0.46b 67.73 0.24b 71.82 0.52c 2.41 0.02bEach value is presented as mean standard deviation (n = 3). Means within each column with different superscript lower case letters (ad) differ signicantly (P 0.05). PSP, purple sweet potato; PSPF, purple sweet potato our.S. SHAN ET AL. BLENDS OF PURPLE SWEET POTATO FLOUR-WHEAT FLOUR711Journal of Food Processing and Preservation 37 (2013) 709716 2012 Wiley Periodicals, Inc.thelevelsof PSPFupto30%increasedthepeaktemperatures (Tp) of blends from 66.45 0.40 to 67.73 0.24C, but decreased the melting enthalpies. The PSPF showed the high gelatinization temperatures (To, Tp and Tc were 77.75 0.72,82.32 0.23 and 87.02 0.16C,respectively), which were signicantly (P 0.05) higher than that of wheat our (60.56 0.19,66.45 0.40 and 70.45 0.34C). The different gelatinization temperatures and melting enthalpiesamongtheblendscouldbeattributedtothediffer- ent chemical compositions, which largely determined the thermal properties of wheat our. Kim and Walker (1992) reported that hydroxyl groups from various additives could be important to gelatinization properties and could increase gelatinization temperatures. Spies and Hoseney (1982) illus- trated that the effect of polyhydroxy compounds on starch gelatinization could be attributed to competition for water between starch and polyhydroxy compounds,which resulted in the change of water activity. The anthocyanidins found in PSP have a typical avonoid structure(Kenjirouet al.2008).Thepatternofanthocyanidin iscomplex,owingtothenumberandpositionofhydroxyland methoxyl groups on the basic anthocyanidin skeleton and positionsatwhichsugarsareattached,theextentofsugaracy- lation, and the identity of the acylating agent (Nyman and Kumpulainen2001;Kahkonenet al.2003;Queirozet al.2009, Oliveira et al. 2010). The presence of anthocyanidins and bersinPSPFledtocrystallizationformedbyspecicinterac- tion between wheat starch and hydroxyl groups.Thus,higher temperatures would be required to break down the starch granules,resultinginenhancedgelatinizationtemperatures.Pasting PropertiesThe pasting viscosity properties of samples are listed in Table 2.Replacementwith10%PSPstarchshowedincreaseinpasting viscosities, while 0.05% PSP pigment decreased the viscosities signicantly (P 0.05). Adding PSPF decreased thepastingviscositiesof blendstovariousextents.Asthesub- stitutionlevelof PSPFincreasedupto30%,thepeakviscosity (PV) decreased from 344 2.76 to 197 0.2 RVU. Osun- dahunsi and Fagbemi (2003) reported that the low viscosity indicatedourwithhighenzymaticactivity,whichresultedin low water-holding capacity. From RVA data, there was a decreasingtrendinbreakdown(BD)rangedfrom145 0.12 to97 0.26RVUastheproportionof PSPFincreasedfrom5 to 30%. However, low levels of PSPF increased BD (at 5 and 10% of 145 0.12 and 141 1.21 RVU, respectively) com- pared with wheat our (132 1.24 RVU), and high levels of PSPFdecreasedBD.Setback(SB)wasaderivativeof nalvis- cosity (CPV) and PV and showed similar trend with BD.The low SB at higher levels indicated a lower tendency for retro- gradation during cooling. Different food additives in the system could alter the pasting behavior. It was reported that polyhydroxy com- pounds could signicantly alter the pasting properties of wheat starch, and pH could also be an important factor that affected the pasting properties (Zhu et al. 2008). The antho- cyanidinsofPSPwoulddegradeintoaseriesofrelatedchemi- cal ingredients such as carboxylic acid and aldehyde when subjected to heating, which lowered the pH in system (Seeram et al.2001).Bao and Corke (2002) reported that low pH could result in viscosity reduction of pasting for rice ours.ThiswasalsoinagreementwithGunaratneandCorke (2007), who found that the slight erosion of the amorphous region of starch granules by acid molecules could result in weaker starch granules, which were more deformable in shearing. The short chains were just t for enhancing the interactions between starch molecules. Furthermore, the complicatedcompositionssuchasproteinsandbersinPSPF hindered the starch from swelling with water molecules andTABLE 2. PASTING CHARACTERISTICS OF BLENDS AS COMPARED WITH WHEAT FLOUR*Samples PV (RVU) HPV (RVU) BD (RVU) CPV (RVU) SB (RVU)Wheat our 344 2.76g 212 2.22f 132 1.24d 367 1.64f 154 0.22d 10% PSP starch 374 2.14h 219 2.14f 154 0.12f 382 2.20g 163 0.14e 0.05% PSP pigment 329 2.18f 185 1.41e 144 0.29e 364 1.73f 179 0.29fg PSPF substitution (%) 5 331 2.14f 185 2.14e 145 0.12e 367 2.20f 182 0.14g 10 303 2.83e 162 1.14d 141 1.21e 337 2.14e 175 0.20f 15 268 0.56d 135 0.06c 133 0.16d 297 0.58d 163 0.05e 20 244 2.11c 120 1.23b 124 0.07c 269 0.14c 149 0.26c 25 217 1.41b 108 0.93a 109 0.89b 235 1.41b 128 0.81b 30 197 0.2