Gelatinization and Retrogradation of Potato Starch-Water Mixtures Treated with High Hydrostatic Pressure

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1 High Pressure Bioscience and Biotechnology 280 Proceedings of the 4 th International Conference on High Pressure Bioscience and Biotechnology, Vol. 1, , 2007 Gelatinization and Retrogradation of Potato Starch-Water Mixtures Treated with High Hydrostatic Pressure Kiyoshi Kawai* 1, Ken Fukami 2, Shigenobu Koseki 3, and Kazutaka Yamamoto 3 1 Tokyo University of Technology Institution, School of Bionics, Katakura, Hachioji, Tokyo Japan. 2 San-ei Sucrochemical Co. Ltd., 24-5 Kitahama-cho, Chita, Aichi Japan 3 National Food Research Institute, Kannondai, Tsukuba, Ibaraki Japan * kawai@bs.teu.ac.jp Received 27 November 2006/Accepted 4 December 2006 Abstract Potato starch-water mixtures (10 to 70 % w/w) were treated with high hydrostatic pressure (HHP) up to 1.2 GPa, and then gelatinization and retrogradation properties were investigated by differential scanning calorimetry (DSC). DSC thermograms for HHP-treated samples showed various characteristic thermal behaviors depending on the treatment pressure and starch content, and enthalpy changes for gelatinization ( H gel ) and regelatinization of retrograded starch ( H retro ) of each HHP-treated mixture were evaluated. From the changes of H gel and H retro, the physically modified states of HHP-treated potato starch-water mixtures were classified as follows: no change, partial gelatinization, complete gelatinization, partial gelatinization and retrogradation, and complete gelatinization and retrogradation. Keywords: high hydrostatic pressure, potato starch, gelatinization, retrogradation, differential scanning calorimetry 1. Introduction The use of high hydrostatic pressure (HHP) has been realized in the food industry, because HHP treatment enables to produce foods of high quality with retained color and flavor, and novel texture. In fact, some HHP-processed foods have been launched on the market [1,2]. For further development, many efforts have been devoted. It has been known that gelatinization of starch can be achieved not only by heating starch with water but also by HHP treatment. Pressure-gelatinized starch has different gelatinization and retrogradation properties from heat-gelatinized one. For example, pressure-gelatinized starch maintains its granular structure [3-5], and shows lower quantity of released amylose [4,5], lower the initial rate of enzymatic reactivity [6], and lower swelling ability [4] than heat-gelatinized one. In addition, there are some studies that retrogradation was observed immediately after HHP treatment [3,7,8]. The gelatinization and retrogradation properties of HHP-treated starch-water mixtures have been investigated in terms under various conditions (treatment pressure, temperature and time) and composition of starch-water mixture (botanical sources of starch and starch content). Effects of treatment pressure, temperature, and time on pressure gelatinization have been extensively investigated, and pressure-temperature diagrams [9-11] and time courses of pressure gelatinization [5,11,12] have been presented. In contrast, there has been little study on the effect of starch content on pressure gelatinization of starch-water mixture, and thus, there was no systematic experimental conclusion such as a state diagram (treatment pressure

2 281 vs. starch content). In addition, little is known on the gelatinization and retrogradation properties of HHP-treated potato starch, because potato starch is more resistant to pressure than other starches (e.g., corn, waxy corn, rice, wheat, and pie) [3,6-8,13-18]. The purpose of this study was to understand effects of treatment pressure (0.4 to 1.2 GPa) and starch content of potato starch-water mixtures (10 to 70 % w/w) on the gelatinization and retrogradation properties by differential scanning calorimetry (DSC). State diagram (treatment pressure vs. starch content) of potato starch-water mixtures was presented. 2. Materials and methods Potato starch was purchased from Hokuren, Japan. The starch (50 to 200 mg) was put into a polymer pouch (7 2 cm), and then distilled water was added to prepare 50 to 70 % starchwater mixtures. For preparing 10 to 40 % mixtures, 2 % (w/w) heat-gelatinized waxy corn starch-water mixture was used instead of water in order to prevent the sedimentation of potato starch during pressure treatment [5]. The sample was heat-sealed and set in a HHPgenerating system (HPS-1400: Teramecs Co. Ltd., Japan). The temperature of pressure medium (50 % (v/v) castor oil-ethanol mixture) was kept at 40 C with an equipped heater in order to avoid crystallization of water in the sample during HHP treatment [19]. Pressure was built up at approximately 0.1 GPa/min and held at a treatment pressure for 60 min. After the HHP treatment, pressure was released to ambient pressure at 0.1 GPa/min. Gelatinization and retrogradation properties of HHP-treated sample were investigated by using a DSC (Diamond DSC: Perkin-Elmer Co. Ltd., USA). Empty stainless steal pan was used as a reference, and the temperature and heat flow were calibrated with indium and distilled water. HHP-treated sample (10 to 30 mg) was put into the steal pan, and then the starch content was adjusted below 30 % (w/w) by adding distilled water. The DSC measurement was performed at heating rate of 10 C/min in the temperature range of 10 to 120 C. DSC thermogram was analyzed by using Thermal Analysis Pyris Software interfaced with the DSC. The values of H gel (enthalpy change for heat gelatinization) and H retro (enthalpy change for re-gelatinization of retrograded starch) were evaluated from the peak area in the endothermic peak of gelatinization and re-gelatinization of retrograded starch, respectively. In the case that the endothermic peaks of the heat gelatinization and regelatinization of retrograded starch overlapped, both H gel and H retro were evaluated by deconvolution of the overlapped curve into two endothermic peaks with the analytical software. 3. Results and discussion The values of H gel were plotted against the treatment pressure in Fig. 1. It was confirmed that the values of H gel decreased with increased treatment pressure and decreased starch content. Non-treated starch showed H gel = 20 ± 2 J/g, and thus HHP-treated samples showing H gel < 18 J/g were judged as partially or completely gelatinized ones. Although there have been many studies on pressure gelatinization of potato starch-water mixtures, a little has been known on the treatment pressure required for complete gelatinization because potato starch is much more resistant to pressure than the starches of other botanical sources [3,6-8,13-18]. It was demonstrated that 10 to 50 % mixtures were gelatinized completely by HHP treatment in the pressure range of 0.7 to 1.2 GPa.

3 282 The values of H retro were plotted against the treatment pressure in Fig. 2. It was found that 30 to 60 % mixtures retrograded. The higher the starch content was, retrogradation was observed at higher treatment pressure. In comparison with the results in Fig. 1 and Fig. 2, it was noted that retrogradation was observed when H gel was below 12 J/g. This indicates that a certain amount of gelatinized part induced by HHP treatment was required for the progress of retrogradation. At each starch content, H retro reached a plateau value and the values increased with increased starch content. This agrees with the starch content dependences of retrogradation for heat-gelatinized starch-water mixtures; the degree of retrogradation increased with increased starch content in the starch content range of 30 to 60 % (w/w) [20-22]. It has been reported that retrogradation was observed immediately after HHP treatment [3,7,8], although the mechanism has been unclear at this stage. In order to understand the mechanism of retrogradation of HHP-treated starch more in detail, further study will be necessary ΔH gel (J/starch-g) ΔH retro (J/starch-g) Fig. 1 Effect of treatment pressure on H gel of potato starch-water mixtures. The number in the figure indicates the starch content of each sample. Fig. 2 Effect of treatment pressure on H retro of potato starch-water mixtures. The number in the figure indicates the starch content of each sample Fig. 3 State diagram of potato starch-water mixtures (treatment pressure vs. starch content). From the changes of H gel and H retro, the physically modified states of HHP-treated potato starch-water mixtures were classified as follows: cross, no change ( H gel 18 J/g and H retro = 0 J/g); open circle, partial gelatinization ( H gel < 18 J/g and H retro = 0 J/g); closed circle, complete gelatinization ( H gel = 0 J/g and H retro = 0 J/g); open circle embedded into square, partial gelatinization and retrogradation ( H gel < 18 J/g and H retro > 0 J/g); closed circle embedded into square, complete gelatinization and retrogradation ( H gel = 0 J/g and H retro > 0 J/g) Starch content (% w/w)

4 283 From the changes of H gel and H retro, the physically modified states of HHP-treated potato starch-water mixtures were classified as follows: no change ( H gel 18 J/g and H retro = 0 J/g), partial gelatinization ( H gel < 18 J/g and H retro = 0 J/g), complete gelatinization ( H gel = 0 J/g and H retro = 0 J/g), partial gelatinization and retrogradation ( H gel < 18 J/g and H retro > 0 J/g), and complete gelatinization and retrogradation ( H gel = 0 J/g and H retro > 0 J/g). The classifications were presented as a state diagram of potato starch-water mixtures (treatment pressure vs. starch content) in Fig. 3. Physically modified states of HHP-treated potato starch-water mixtures will be overviewed by this state diagram. It has been difficult to control the degree of gelatinization, but HHP treatment enables to do so as shown in Fig. 1. Furthermore, starch products with partial gelatinization and retrogradation have been required as modified starches, especially as resistant starch [23-25]. Combined use of HHP treatment and the state diagram will realize the production of the modified starches with controlled gelatinization and/or retrogradation. 4. Conclusion Effects of treatment pressure and starch content of potato starch-water mixtures on the gelatinization and retrogradation properties was investigated, and then, a state diagram (treatment pressure vs. starch content) of potato starch-water mixtures was presented. A foreseeable extension of this research would involve investigating the effects of treatment temperature and time on the starch properties and clarification of the mechanism of gelatinization and retrogradation induced by HHP treatment. 5. References [1] Suzuki, A. (2002) High pressure-processed foods in Japan and the world. in: Trends in High pressure Bioscience and Biotechnology (Hayashi, R., Eds), pp Elsevier science B. V., Amsterdam, The Netherlands. [2] Sasagawa, A. and Yamazaki, A. (2002) Development and industrialization of pressure-processed foods. in: Trends in High pressure Bioscience and Biotechnology (Hayashi, R., Eds), pp Elsevier science B. V., Amsterdam, The Netherlands. [3] Stute, R., Klingler, R.W., Boguslawski, S., Eshtiaghi, M.N. and Knorr, D. (1996) Effects of high pressures treatment on starches. Starch/Stärke. 48, [4] Douzals, J.P., Perrier-Cornet, J.M., Gervais, P. and Coquille, J.C. (1998) High-pressure gelatinization of wheat starch and properties of pressure-induced gels. J. Agric. Food Chem. 46, [5] Stolt, M., Oinonen, S. and Autio, K. (2001) Effect of high pressure on the physical properties of barely starch. Innov. Food Sci. Emerg. Technol., 1, [6] Selmi, B., Marion, D., Perrier Cornet, J.M., Douzals, J.P. and Gervais, P. (2000) Amyloglucosidase hydrolysis of high-pressure and thermally gelatinized corn and wheat starches. J. Agric. Food Chem. 48, [7] Hibi, Y., Matsumoto, T. and Hagiwara, S. (1993) Effect of high pressure on the crystalline structure of various starch granules. Cereal Chem. 70, [8] Katopo, H., Song, Y. and Jane, J. (2002) Effect and mechanism of ultrahigh hydrostatic pressure on the structure and properties of starches. Carbohydr. Polym. 47, [9] Rubens, P. and Heremans, K. (2000) Pressure-temperature gelatinization phase diagram of starch: an in situ fourier transform infrared study. Biopolym. 54, [10] Douzals, J.P., Perrier-Cornet, J.M., Coquille, J.C. and Gervais, P. (2001) Pressure-temperature phase transition diagram for wheat starch. J. Agric. Food Chem. 49, [11] Bauer, B.A. and Knorr, D. (2005). The impact of pressure, temperature and treatment time on starches: pressure-induced starch gelatinisation as pressure time temperature indicator for high hydrostatic pressure processing. J. Food Eng. 68, [12] Bauer, B.A. and Knorr, D. (2004) Electrical conductivity: A new tool for the determination of high hydrostatic pressure-induced starch gelatinisation. Innov. Food Sci. Emerg. Technol. 5,

5 [13] Muhr, A.H. and Blanshard, J.M.V. (1982) Effect of hydrostatic pressure on starch gelatinization. Carbohydr. Polym. 2, [14] Muhr, A.H., Wetton, R.E. and Blanshard, J.M.V. (1982) Effect of hydrostatic pressure on starch gelatinization, as determined by DTA. Carbohydr. Polym. 2, [15] Douzals, J.P., Marechal, P.A., Coquille, J.C. and Gervais, P. (1996) Microscopic study of starch gelatinization under high hydrostatic pressure. J. Agric. Food Chem. 44, [16] Bauer, B.A. Hartmann, M., Sommer, K. and Knorr, D. (2004) Optical in situ analysis of starch granules under high pressure with a high pressure cell. Innov. Food Sci. Emerg. Technol. 5, [17] Błaszczak, W., Fornal, J., Valverde, S. and Garrido, L. (2005) Pressure-induced changes in the structure of corn starches with different amylase content. Carbohydr. Polym. 61, [18] Błaszczak, W., Valverde, S. and Fornal, J. (2005) Effect of high pressure on the structure of potato starch. Carbohydr. Polym. 59, [19] Smeller, L. (2002) Pressure-Temperature phase diagram of biomolecules. Biochim. Biophys. Acta, 1595, [20] Hoover, R. (1995) Starch retrogradation. Food Rev. Int. 11, [21] Miles, M.J., Morris, V.J., Orford, P.D. and Ring, S.G. (1985) The roles of amylase and amylopectin in the gelation and retrogradation of starch. Carbohydr. Res. 135, [22] Orford, P.D., Ring, S.G., Carroll, V., Miles, M.J. and Morris, V.J. (1987) The effect of content and botanical source on the gelation and retrogradation of starch. J. Sci. Food Agric. 39, [23] Escarpa, A., González, M.C., Mañas, E., García-Diz, L. and Saura-Calixto, F. (1996) Resistant starch formations: standardization of a high pressure autoclave process. J. Agric. Food Chem. 44, [24] Bauer, B.A. Wiehle, T., and Knorr, D. (2005) Impact of high hydrostatic pressure treatment on the resistant starch content of wheat starch. Starch/Stärke. 57, [25] Chung, H., Lim, H.S. and Lim, S. (2006) Effect of partial gelatinization and retrogradation on the enzymatic digestion of waxy rice starch. J. Cereal Sci. 43,

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