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2. Materials and methods​The methods of hydration and DSC procedures are a​modification of those previously described. (Takigami,​Takigami, & Phillips, 1993, 1994). A Perkin?Elmer DSC​II equipped with cooling apparatus was used to measure the​phase transitions of the sorbed water in the samples which​were cooled from 25 to 2908C at 108C/min and subsequently​heated to 258C at a rate of 108C/min. The temperature​scale and heats of fusion were calibrated using distilled​water and indium as the standard materials.​After DSC measurements, the sample pans were pricked​with a pin to remove water from the samples, which were,​thereafter, dried under reduced pressure for 30 min at​1108C, then left overnight at room temperature. After​weighing the water content was determined and Wc defined​as​Wc.g=g. .​Weight of water .g. in polysaccharide​Weight of dry polysaccharide .g.​It is possible to distinguish between non-freezing water​(Wnf), freezing-bound water (Wfb) and free water (Wf)​from the individual transitions or shape of the transitions,​​and these are connected by the relationship​Wc . Wnf 1 Wfb 1 Wf​3. Results and discussion​A representative set of DSC heating curves for kappacarrageenan​(E407) is shown in Fig. 1, and for PES​(E407a) in Fig. 2. The Wc values are listed in the figure.​The systems are first cooled to 2808C and slowly warmed.​At Wc 0.35 for kappa-carrageenan and Wc 0.22 for PES, no​transition is observed, indicating that at this water content​the water is bound to the hydrophilic groups and is non-​Food Hydrocolloids 14 (2000) 609?613​0268-005X/00/$ - see front matter q 2000 Elsevier Science Ltd. All rights reserved.​PII: S0268-005X(00)00040-0​www.elsevier.com/locate/foodhyd​* Corresponding author.​610 S. Takigami et al. / Food Hydrocolloids 14 (2000) 609?613​Fig. 1. DSC heating curves for water?kappa-carrageenan (E407) systems.​Fig. 2. DSC heating curves for water?PES (E407a) systems.​freezing. As the value of Wc is increased, both systems show​the presence of at least two broad transitions, due to the​melting of free water (at temperature Tf) and freezingbound​water (at temperature Tfb). As Wc is increased Tfb​shifts towards Tf and eventually overlaps in each of the​systems. We have used this value where overlap occurs of​the bound water melting temperature with that of free water​as an indication of the relative abilities of individual polysaccharides​to bind water (Takigami et al., 1994). It is​immediately evident by direct observation of Figs. 1 and 2​that kappa-carrageenan retains water in a bound form​more effectively than PES. The task is to quantify this​difference.​Immediately following the first heating and cooling cycle,​the procedure was repeated, but we did not observe any​significant change in the transitions, indicating that both​systems can readily form stable and reversible thermodynamic​traps for water. The melting of the freezing-bound​water is an endothermic process. The freezing process​however is exothermic. Fig. 3 shows the typical behaviour​of both systems on cooling. More than one transition are​evident both at water contents 0.58 and 0.6, which are​subsequently masked as the water content is increased. It​would appear, therefore, that within the broad transitional​S. Takigami et al. / Food Hydrocolloids 14 (2000) 609?613 611​Fig. 3. DSC cooling curves for water?PES (E407a) systems.​Fig. 4. The relationship of melting temperature with water content for PES​(E407a) and kappa-carrageenan (E407). (W) For bound water for E407a;​(A) free water for E407a; (K) overlapped water for E407a; (X) bound water​for E407; (B) free water for E407: (O) overlapped water E407.​envelope, there are several metastable states of water, due to​the water interacting and being ‘bound’ within various sites​within the polysaccharide structure. The unsymmetrical​curves, even at high water contents, show that the freeand​bound water exist alongside each other.​The overall behaviour can more readily be identified in​Fig. 4, which directly compares the behaviour of the two​carrageenan systems. Whereas the temperature of freezing​of the free water is constant with an increase in Wc (the value​of Tfb moves up, to approach that of free water. Following​the sorption of the non-freezing water at the hydrophilic​groups of the framework polysaccharide structure, as Wc​increases, the freezing-bound water builds up as a structured​entity and retains its distinctive character from free water.​The enthalpy of melting of this structured water remains less​than that of free water throughout (due to defects introduced​into the freezing-bound ice. The free water, on the other​hand, melts near 08C in the form of hexagonal ice, because​in the free form there is no interference by the carrageenan​structure.​As was previously shown, it is possible to calculate the​amounts of the various types of water at increasing Wc​values (Takigami et al., 1993, 1994), as shown in Figs. 5​and 6. In comparison with other polysaccharides we have​studied, the ability of PES to strongly bind water is low.​There is an initial build-up of non-freezing water to 0.5 g​water per gram PES, which does not change with water​content. This value represents the complete hydration of​the sugar skeleton and corresponds to ,13 moles of​water in the non-frozen state per disaccharide unit. This​water is bound tightly by the OH and other ionic sites.​The amount of bound water, while increasing with water​content remains low particularly for PES. At Wc 1.5, for​example, kappa-carrageenan bind at least twice the amount​of water than PES, and continues to increase beyond Wc​2.8, whereas PES is saturated at Wc 1.5. Table 1 shows a​comparison of kappa-carrgeenan and PES with other polymer​systems.​The gel?sol transition has been compared for kappacarrageenan​and PES (Tanaka et al., 1996), and demonstrates​that the presence of cellulose in PES leads to a​lower gel?sol transition temperatures. More heat absorption​612 S. Takigami et al. / Food Hydrocolloids 14 (2000) 609?613​Fig. 5. The amounts of various types of water as a function of water content​for PES (E407a). (X) Non-freezing water; (A) bound water; (K) free water;​(W) total freezing water.​Fig. 6. The amounts of various types of water as a function of water content​for kappa-carrageenan (E407). (X) Non-freezing water; (A) bound water;​(K) free water; (W) total freezing water.​​

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好好努力,迎接新的开始回复: 可以帮忙翻译一下吗?我顶～～～

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好好努力,迎接新的开始回复: 可以帮忙翻译一下吗?楼主你不是在开玩笑吧。。。。

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白天看中国股市，晚上看中国足球！回复: 可以帮忙翻译一下吗?楼主先翻出来，让大家帮忙改如何？。。。

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回复: 可以帮忙翻译一下吗?不开玩笑是我的弟弟让我帮忙翻译的.我汗,姐姐英语一蹋糊涂.他真是看走了眼睛.我今天如何交代啊??难受

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好好努力,迎接新的开始回复: 可以帮忙翻译一下吗?有好心人帮我翻译一段也可以我可以有所交代啊

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好好努力,迎接新的开始回复: 可以帮忙翻译一下吗?在做毕设？。。。

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回复: 可以帮忙翻译一下吗?专业性有些强。。。翻出来还不如不翻呢。。。强要非专业的翻，至少也给个word list吧。。。还是找找专业论坛吧。。。

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回复: 可以帮忙翻译一下吗?在做毕设？。。。点击展开... 对的,.聪明是毕设.他说就简单翻译一下就行了

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好好努力,迎接新的开始回复: 可以帮忙翻译一下吗?这个没法简单翻译，专业英语简单翻译就是错的翻译。这段1000多字，拿去外边翻译公司估计至少400块，汗。。。我是看得一头雾水，类似专业的朋友帮帮忙吧。

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