Effects of Fatty Acid Addition on the Physicochemical Properties of Corn Starch

The effect of addition of six fatty acids (stearic, palmitic, myristic, oleic, palmitoleic, and myristoleic acid) on the gelatinization, glass transition, and retrogradation properties of corn starch as well as their complexing abilities with amylose were determined. Differential scanning calorimeter studies reflected that addition of fatty acids caused a 73–89% decrease in the gelatinization enthalpy compared to that of the native starch. Besides amylose-lipid formation, exotherm was determined at the same temperature range with the gelatinization endotherm. As a result, it was suggested that fatty acids complexed with amylose during gelatinization. Fatty acid addition significantly increased the glass transition temperature of starch gel. This was attributed to two reasons: the first is due to the physical cross-linking action of amylose–lipid complexes in starch-water system; the second may be due to the effect of uncomplexed fatty acids on water distribution in the gel structure as a result of their amphiphilic character. Thermal properties of amylose-lipid complexes were compared in order to determine the effect of fatty acid properties. It was found that the shorter chain length and unsaturation favored the complex formation but the complexes formed by longer and saturated fatty acids were more heat stable. Addition of fatty acids resulted in 73–90% and 47–71% reduction in the retrogradation enthalpy compared to native starch gels at 5°C and 21°C, respectively. The reduction in the retrogradation enthalpy was inversely related to the amylose-lipid complexing abilities of the fatty acids and it might be explained by the hindrance effect of uncomplexed fatty acids to the water distribution in the starch gel matrix.     

Characterization of Starch from Bread Aged at Different Temperatures

A series of bread samples stored at various temperatures (4°, 25°, and 40°C) were analyzed by differential scanning calorimetry (DSC) to determine if retrogradation (quantified by DSC enthalpy values) and storage temperature were correlated. The increase in enthalpy values during storage time was dependent on storage temperature. However, the rate of recrystallization was not linear at any of the temperatures studied. The net result was that the enthalpy values tended to converge with time, irrespective of storage temperature. Another effect of the increased storage temperature was an increase in the peak temperature (T_p) of the amylopectin endotherm. This indicates either that storage temperature affects the type of crystal being formed as the starch recrystallizes, or that annealing of crystals occurs at the higher storage temperatures. X-ray diffractometry of starch isolated from the crumb gave similar diffraction patterns indicating no difference in crystal type among the treatments. In addition, the DSC endotherm became sharper at the higher temperatures. Thus, the increase in T_p was apparently the result of annealing of the crystals at the higher storage temperatures.     

木聚糖酶对馒头品质的影响及抑制回生的机理研究

本试验主要研究木聚糖酶对馒头品质的影响,结果表明:添加30 mg/kg(以小麦粉为基准)木聚糖酶对馒头的改善效果较好,馒头的综合评分最高,达93分;馒头的硬度为1 658 g,胶着性为1 439,咀嚼性为1 391,分别比对照降低了48%、46%和44%;RVA分析表明,与对照相比,馒头皮黏度降低了344cP,馒头芯部黏度降低168 cP,说明添加木聚糖酶增大了馒头表皮和芯部的糊化程度;馒头贮藏过程中DSC分析表明,馒头的结晶熔融焓值由对照的3.05 J/g降低为1.99 J/g,说明木聚糖酶可以抑制馒头回生。相关性分析表明,馒头芯部糊化程度与贮存期间馒头的回生性质呈负相关。而RVA和DSC研究结果表明,添加木聚糖酶后小麦粉糊化温度降低,热焓值降低,小麦粉更易糊化,阐明了木聚糖酶能够抑制馒头回生的机理。     

Effect of freezing and frozen storage on the gelatinization and retrogradation of amylopectin in dough baked in a differential scanning calorimeter

Frozen and non-frozen dough were baked in a differential scanning calorimeter (DSC) pan (heated in the calorimeter at temperatures similar to those of the center of the crumb during baking) and were aged at different temperatures. Gelatinized dough (DSC-baked dough) was heated again in the DSC. This methodology permitted us to study the effects of dough freezing and frozen storage on gelatinization and retrogradation of starch. During storage of frozen doughs at −18 °C an increase in the gelatinization enthalpy after 150 day of storage was observed. At 230 days of frozen storage a decrease in the onset temperature and an increase in the gelatinization temperature range was also detected. An increase of starch retrogradation with time of storage in frozen conditions was observed. During the aging of dough baked in DSC, a higher retrogradation temperature range was detected together with a faster retrogradation of starch at low temperature of aging.     

支链聚合度对菠萝蜜种子淀粉热力学特性的影响及老化动力学分析

为了探究支链聚合度对淀粉老化的影响,利用差示扫描量热仪结合Avrami方程,研究不同支链聚合度菠萝蜜种子淀粉(jackfruit seed starch,JFSS)凝胶后贮藏过程中的老化焓变和老化动力学。结果表明:支链聚合度降低,JFSS凝胶后老化过程形成更多趋于有序排列的结晶,老化速率从0.336增加到0.513,不同聚合度JFSS成核方式为瞬间成核;随贮藏时间的延长,JFSS老化度增大;支链聚合度与Avrami指数呈显著正相关(p<0.05);支链重均聚合度与凝胶化焓呈极显著负相关(p<0.01),数均聚合度凝胶化焓呈显著负相关(p<0.05);支链重均聚合度与贮藏0~7 d的老化焓变均呈现显著负相关(p<0.05)。支链聚合度是影响淀粉贮藏过程中老化特性的重要结构因素。     

Investigation of physicochemical properties of breads baked in microwave and infrared-microwave combination ovens during storage

Staling of breads baked in different ovens (microwave, infrared-microwave combination and conventional) was investigated with the help of mechanical (compression measurements), physicochemical (DSC, X-ray, FTIR) and rheological (RVA) methods. The effect of xanthan-guar gum blend addition on bread staling was also studied. Xanthan-guar gum blend at 0.5% concentration was used in bread formulation. The gums were mixed at equal concentrations to obtain the blend. After baking, the staling parameters of breads were monitored over 5 days storage. During storage, it was seen that hardness, retrogradation enthalpies, setback viscosity, crystallinity values, and FTIR outputs related to starch retrogradation of bread samples increased, whereas FTIR outputs related to moisture content of samples decreased significantly with time. The hardness, retrogradation enthalpy, setback viscosity, and crystallinity values of microwave-baked samples were found to be highest among other heating modes. Using IR-microwave combination heating made it possible to produce breads with similar staling degrees as conventionally baked ones in terms of retrogradation enthalpy and FTIR outputs related to starch retrogradation. Addition of xanthan-guar gum blend decreased hardness, retrogradation enthalpy and total mass crystallinity values of bread samples showing that staling was delayed.     

Differential Scanning Calorimetry of Rice Starches

DSC thermograms from 5–135°C of eight rice starches, pretreated with sodium dodecyl benzenesulfonate (DoBS) to remove milled rice proteins, gave gelatinization endotherms with characteristic temperature ranges. Good positive correlations were found between gelatinization temperatures measured by DSC and photometry, and between gelatinization enthalpies and gelatinization temperatures. The enthalpy of the amylose-lipid endotherm at 90–97°C was less for two DoBS-prepared rice starches than for the same pronase-treated starches. The endotherm was absent in waxy starch, and its enthalpy followed the level of lipids extracted by cold water-saturated butanol (WSB). It was concluded that DoBS treatment removed and replaced some of the starch lipid. Although this DoBS did not form a complex with amylose that was observable by DSC, the adsorbed DoBS was extracted by hot WSB.     

Effect of different carbohydrases on fresh bread texture and bread staling

The effect of cellulase, xylanase and #-glucanase on the properties of wheat bread and its staling during storage was studied. The presence of the carbohydrases tested led to breads with high specific volume compared to the control. The texture profile analysis was greatly modified in that the firmness of bread crumb was reduced by all the carbohydrases. A kinetic study of the firmness along with the storage by the Avrami equation showed that the presence of carbohydrases produced softer crumbs and also reduced the rate of bread firming, although no great differences were found between enzymes. Since retrogradation of starch is one of most important factors related to bread staling, the modification of the amylopectin retrogradation was measured by scanning calorimetry. Those studies showed that all the carbohydrases decrease the starch retrogradation, and that the xylanases had the greatest effect. The simultaneous analysis of the firming and starch retrogradation results revealed that the anti-staling effect of xylanase might be due to the retardation in the starch retrogradation, while in the case of cellulase and #-glucanase some other mechanism should be implied in their anti-staling action.     

Retrogradation of waxy cornstarch studied by DSC

The retrogradation process of the biphasic endotherms Gr and M1r for waxy cornstarch was systematically investigated using differential scanning calorimetry (DSC). The high temperature endotherm M1r developed significantly within 2–5 h, while the retrograded endotherm Gr appeared after 5 h storage and increased with time. The single endotherm Gr was separated using an analytical software, and the enthalpy was found to be ∼36% of the total enthalpy of the retrograded starch. Compared to normal cornstarch (∼77% amylopectin content), the final retrogradation ratio of the waxy cornstarch was higher. Both the waxy and normal cornstarches investigated showed a similar pattern of retrogradation process, which developed quickly in the initial stage (up to 1 day) and then gradually came to a near‐constant value in the second stage (from 1 to 20 days).     

Firming of starch gels and amylopectin retrogradation as related to dextrin production by α-amylase

 The effect of dextrins produced by α-amylase on the firming and amylopectin retrogradation of wheat starch gels was studied. Different gel samples were prepared and included several ingredients, for example, α-amylase, vital gluten and glucoamylase. Amylopectin retrogradation, gel firming and the dextrin profile were analysed throughout a 5-day storage period. Both processes, i.e. firming and starch retrogradation, increased with time, and were not affected by the incorporation of gluten into the mixture. The well-known effect of α-amylase to retard bread crumb firming was also found to be relevant to starch gels. From the results obtained in this work, it seems that this anti-firming effect is not due to modifications of the starch but to dextrins produced by starch hydrolysis, since the effect did not occur when dextrins were removed by glucoamylase. Received: 30 December 1996     

DIFFERENTIAL SCANNING CALORIMETRY OF STARCH12

At high water-to-starch (2:1) ratios a single endotherm was obtained for starch gelatinization. As the water-to-starch ratio was decreased the endotherm area decreased and the peak developed a trailing shoulder. At high water-to-starch ratios birefringence is lost over a temperature range of about 7°C. That narrow range increases to about 30°C at a low water-to-starch ratio. Starch and flour gave essentially the same endotherm initiation temperatures. In low-water systems the second DSC peak is much smaller with starch than with flour. It appears that in a starch system, water migrates during gelatinization. In dough, gluten limits that migration. As the level of sucrose was increased in a dough, the transition temperature increased and the gelatinization temperature range decreased. At the levels found in bread doughs both sugar and salt increase starch gelatinization temperatures.     

Composition and physicochemical properties of starch from pearl millet grains

The physicochemical properties of starches isolated from three cultivars (ICTP 8203, ICMS 7703 and ICMH 356) of pearl millet grains were studied. The yield of the starch was in the range 53–56% on a whole grain basis. The starch granules were round or polygonal with numerous indentations and pores on their surface. The free, bound and total starch lipids ranged from 0.04 to 0.08%, from 0.40 and 0.47% and from 0.44 and 0.55%, respectively. In all starches, neutral lipids (NL) and phospholipids (PL), respectively, formed the major lipid class in the free and bound lipid extracts. The major fatty acid in the NL fraction being linolenic acid, whereas palmitic acid was the major fatty acid in PL and glycolipid fractions. The total amylose contents ranged from 28.8 to 31.9%, of which 14.6–17.2% were complexed by native lipid. The X-ray pattern was of the A-type. The intensities of the major diffraction peaks followed the order: ICMS > ICTP > ICMH. The swelling factor followed the order: ICTP > ICMH > ICMS. All three starches exhibited identical pasting temperatures, but they differed with respect to the Brabender viscosity at 95 °C (ICMH > ICTP > ICMS), and the extent of increase in viscosity during the holding cycle at 95 °C (ICMS > ICMH > ICTP). The gelatinization temperature ranges were: 61.2–70.5 °C (ICTP), 60.9–67.5 °C (ICMH) and 64.5–78.0 °C (ICMS). The enthalpy of gelatinization (cal g⁻¹) were: 2.7 (ICTP), 2.5 (ICMH), 3.5 (ICMS). The extent of hydrolysis by porcine pancreatic α-amylase and 2.2 n HC1 followed the order: ICTP > ICMH > ICTP. The percentage light transmission followed the order: ICTP > ICMH > ICMS. The stability towards freeze-thaw cycling followed the order: ICMS > ICMH > ICTP. The retrogradation endotherm was broader than the gelatinization endotherm (ICTP > ICMS > ICMH). In all starches, the melting temperature (T_p) of the retrogradation endotherm increased only marginally during storage. The increase in the enthalpy of retrogradation (ΔH_mR), however, was much higher in ICTP than in ICMS and ICMH.     

Chemical and physicochemical properties of dried wet masa and dry masa flour

Commercial ‘masas’ and dry ‘masa’ flours (DMFs) were evaluated for chemical composition, water retention capacity (WRC), gelatinization, retrogradation and X‐ray diffraction. Both masas and DMF had similar chemical compositions. The masas had higher soluble carbohydrate contents and lower WRCs than DMF. In the same way, DMFs had lower gelatinization temperatures and enthalpies of gelatinization than masas. These results were confirmed by X‐ray diffraction analysis showing a lower degree of crystallinity in DMFs than in masas. The melting temperature in retrogradated samples of both masas and DMFs had a tendency to increase as storage time increased. This increment was more apparent with the enthalpy of melting. These results were probably associated with crystal perfection during starch retrogradation, ie recrystallization of gelatinized starch occurred as a time‐dependent process. Copyright © 2003 Society of Chemical Industry     

Effect of damaged starch levels on flour-thermal behaviour and bread staling

The effect of the amount of damaged starch in two different flours (wheat and triticale) on the bread quality and its behaviour during storage has been analysed. Two wheat and one triticale flour cultivars were milled in a disc mill to obtain different levels of damaged starch. Differential Scanning Calorimetry (DSC) and Rapid Visco Analyser (RVA) were used to characterize the flour properties and TA-XT2 textural analyses were made on breadcrumb. The effect of the damaged starch content on the bread firming, the amylopectin retrogradation and starch-pasting properties were studied in order to establish any relationship between damaged starch and bread staling. DSC analysis showed that the damaged starch content changed the thermal behaviour of flour–water mixtures: the higher the levels of damaged starch the lower the starch-gelatinization enthalpy and the higher the melting enthalpy of amylose–lipid complexes. The amount of amylopectin retrogradation and breadcrumb firming increased with the damaged starch content at the beginning of storage time; however, differences were decreasing at final storage time. The flour viscosity during pasting decreased as their damaged starch content increased.     

茶叶乙醇提取物对蜡质玉米淀粉回生性质的影响

以蜡质玉米淀粉（waxy corn starch,WCS）为原料,研究不同添加量（1.0%、2.5%、5.0%、10.0%）茶叶乙醇提取物（ethanol extract of tea,EET）与WCS共糊化后的相互作用以及对其透光率、老化度、溶解度、膨胀度、凝胶强度、糊化及回生特性、结晶结构、微观结构及体外消化性能的影响。结果表明：EET的添加对WCS的理化性质、回生性质及体外消化性能影响显著。随着EET添加量的增加,WCS的溶解度、膨胀度逐渐增加,而WCS的凝胶强度逐渐下降;与对照组相比,当EET添加量为2.5%时,WCS的老化度、糊化焓值、回生焓值、回生率、1047/1022的比值以及相对结晶度均有所下降,说明WCS的回生受到显著抑制。此外,EET的添加导致WCS的消化性能下降,使WCS中的快消化淀粉含量下降,抗性淀粉的含量增加。因此,在淀粉类食品加工时,可适量加入EET,降低产品的回生程度,提高产品的感官品质并延长产品的保质期。     

Gelatinization and retrogradation of 6-year-old korean ginseng starches studied by DSC

Gelatinization and retrogradation characteristics of 6-year-old Korean ginseng starch with different grades were investigated using differential scanning calorimetry (DSC). The 1st and 3rd grade ginseng starches showed typical biphasic DSC endotherm while 2nd grade ginseng starch revealed monophasic DSC endotherm with relatively narrow transition temperature. Although Avrami exponents (n) of all ginseng starches were close to 1.0 (i.e., retrogradation of all ginseng starches at a single temperature have an instantaneous nucleation followed by rod-like growth of crystals), 1st and 3rd grade ginseng starches showed higher degree of retrogradation and faster retrogradation rate than 2nd grade ginseng starch. This indicates that 2nd grade ginseng starch has different gelatinization and retrogradation characteristics compare to 1st and 3rd grade ginseng starches, which may influence the occurrence of inner white, the main defect of red ginseng.     

茶多酚对小麦淀粉理化特性和面包品质的影响及机理

目的：研究茶多酚对小麦淀粉理化特性和面包品质的影响及机理。方法：分析茶多酚对小麦淀粉透光率、糊化特性、老化特性及微观结构等理化特性的影响;分析茶多酚对面包的比容、质构和颜色等品质指标的影响;采用分子动力学模拟技术,探究茶多酚与小麦淀粉的分子相互作用机理。结果：茶多酚可降低淀粉糊的透光率,促进淀粉的糊化,抑制淀粉的老化,改变淀粉凝胶的微观结构;不同添加量的茶多酚对面包的比容、质构及颜色影响差异明显;茶多酚通过影响分子内氢键与分子间氢键的形成而改变淀粉分子的空间构型,表没食子儿茶素没食子酸酯与淀粉分子的结合更稳定,氢键比例更高,结合自由能更低。结论：茶多酚具有改良小麦淀粉理化特性及面包品质的潜力。     

Gelatinization and Retrogradation Properties of Native and Hydroxypropylated Crosslinked Tapioca Starches with Added Sucrose and Sodium Chloride

The effects of sucrose and sodium chloride on the gelatinization and retrogradation of native and hydroxypropylated crosslinked tapioca starches were investigated by using Differential Scanning Calorimetry (DSC). Hydroxypropylated crosslinked tapioca starches showed low gelatinization temperature and enthalpy compared to the native tapioca starch. Sucrose and sodium chloride increased the gelatinization temperatures of all starch samples. The enthalpy to melt retrograded amylopectin of hydroxypropylated crosslinked tapioca starches were low, compared to that of the native starch. Sucrose did not have much effect on retrogradation of the starch, while sodium chloride decreased retrogradation of all starch samples.     

Pasting and Thermal Properties of Potato and Bean Starches

Starches from potato (Mainechip, ND651-9 and Commercial) and Navy and Pinto bean were isolated and the pasting and thermal properties examined. Analysis by Rapid Visco-Analyzer (RVA) showed potato starches had lower pasting temperatures, higher peak viscosity, and lower setback than bean starches. High intrinsic viscosity values obtained for the potato starch indicated higher average molecular weight for the potato starches compared to the bean starches. Characterization of thermal (gelatinization and retrogradation) properties of starches by Differential Scanning Calorimetry (DSC) showed that potato starches had sharp, well-defined gelatinization thermograms, while bean starches had broad, shallow thermograms with higher peak temperature (Tp). Potato starches required higher gelatinization enthalpies than bean starches. In comparison with gelatinization, the retrogradation thermograms of starches stored at three different temperatures (23,4 and −10°C) were broader and occurred at the lower temperatures. Compared to potato starches, Navy and pinto bean starches showed a higher retrogradation enthalpy at 4 and 23°C storage temperatures, but a lower enthalpy at −10°C.     

Influence of hydroxypropylation on retrogradation properties of native,defatted and heat-moisture treated potato starches

Recent studies have shown that defatting and heat-moisture treatment cause structural changes within the amorphous and crystalline regions of potato starch. Furthermore, the alkaline reagents (NaOH and Na₂SO₄) used during hydroxypropylation has been shown to cause structural changes within the amorphous and crystalline regions of native, defatted and heat-moisture treated starches. In this study, we have compared (using different techniques) the retrogradation properties of potato starch before and after physical (defatting and heat-moisture treatment), and chemical (alkaline treatment and hydroxypropylation) modification. Turbidity measurements showed that changes in turbidity during storage (4°C for 24 h and then at 40°C for 29 days) of native, defatted and heat-moisture treated gelatinized starch pastes were influenced by the interplay of two factors: (1) interaction between leached starch components (amylose–amylose, amylose–amylopectin, amylose–amylopectin), and (2) interaction between granule remnants and leached amylose and amylopectin. In alkali treated gelatinized native, defatted and heat-moisture treated starch pastes, turbidity changes on storage was influenced by aggregation of granule remnants. Hydroxypropylation decreased the rate and extent of increase in turbidity during storage of native, defatted and heat-moisture treated starches. The change in turbidity during storage of hydroxypropylated starch pastes was influenced by the interplay between: (1) steric effects imposed by hydroxypropyl groups on chain aggregation, (2) aggregation between small granule remnants, and (3) settling of large granule remnants beneath the path of the spectrophotometer beam. Stored gelatinized pastes of native, defatted and heat-moisture treated starches gave a `B' type X-ray pattern. A similar pattern was also observed after alkaline treatment, and hydroxypropylation. However, the X-ray intensity of the strong reflection at 5.2 Å decreased after alkaline treatment and hydroxypropylation. The retrogradation endotherm (monitored by differential scanning calorimetry) occurred after 2 days storage in native, defatted and heat-moisture treated starches. A similar trend was also observed after alkaline treatment. However, the retrogradation endotherm appeared only after 7 days in hydroxypropylated starches. The enthalpy of retrogradation in all starches decreased on alkaline treatment and hydroxypropylation.