http://www.paper.edu.cn Journal of Food Engineering 76 (2006) 420–426 Studies on the morphological, thermal and crystalline properties of starches separated from medicinal plants Shujun Wang a, Wenyuan Gao a,*, Haixia Chen a, Peigen Xiao b a The College of Pharmaceutical Science and Biotechnology, Tianjin University, Tianjin 300072, China b Institute of Medicinal Plant, Chinese Academy of Medical Sciences and Peking Union Medical College, Beijing 100094, China Received 6 January 2005; accepted 21 May 2005 Available online 25 July 2005 Abstract The starches separated from five different medicinal plants-Fritillaria (Fritillaria thunbergii Miq., Fritillaria ussurensis Maxim., Fritillaria pallidifloca Schrenk, Fritillaria cirrhosa D. Don and F. hupehensis Hsiao et K.C. Hsia) were investigated for morpholog- ical, thermal, crystal, swelling power, solubility and water-binding capacity properties. The thunbergii F. and ussurensis F. starches had a granule size ranging between 5 and 30 lm and the shape of the granules was oval and elliptic, while the other Fritillaria starches had the granule size from 5 to 40 lm and the granule shape varied from oval to irregular or cuboidal. The transition tem- peratures and enthalpy of gelatinization (DHgel) were determined using differential scanning calorimetry (DSC). Cirrhosa F. starch showed the highest DHgel values (9.18 J/g) while hupehensis F. starch showed the lowest values (5.90 J/g). All Fritillaria starches showed a typical B-type pattern with the degree of crystallinity of between 43.8% and 52.3%. Cirrhosa F. starch had the highest swelling power and the lowest solubility while the values for hupehensis F. starch were contrary. Hupehensis F. starch showed the highest water binding capacity and it was the lowest for pallidifloca F. starch. Ó 2005 Elsevier Ltd. All rights reserved. Keywords: Fritillaria; Starch; Morphology; Thermal; Crystallinity; Water binding capacity 1. Introduction have demonstrated that the major biologically active ingredients to relieve cough in the bulb are alkaloids with In the research of many medicinal plants, isolation, their types and contents varying in different Fritillaria purification and structure identification of small-mole- species (Li et al., 1999; Li, Li, & Lin, 1999; Li, Li, Lin, cule active ingredients were always the most important Chan, & Ho, 2000; Li, Lin, Chan, & Li, 2001; Lin, Li, task for the phytochemist. However, the macromolecules Li, & Chan, 2001). In addition, some non-alkaloid con- such as starch contained in these medicinal plants have stituents containing saponin, terpenoids, steroids, succi- hardly been studied and all wasted. Fritillaria (Chinese nic acid, thymidine, adenisine in different Fritillaria name Beimu), the bulbs of various species of the genus species have also been identified (Ruan, Zhang, & Wu, Fritillaria (Liliaceae), has been used as anti-tussive and 2002). However, the starch contained in the bulb of expectorant herbs using the Chinese name: Beimu in tra- Fritillaria has been ignored and discarded. As we ditional Chinese medicine for more than 2000 years. reported earlier, the main component in the bulbs of Various chemical and pharmacological studies on Beimu Fritillaria species is starch occupying approximately 80% content in the total biomass (Gao, Fan, & Paek, 1999). Starches from different botanical sources, such as * Corresponding author. Tel.: +86 222 740 1483; fax: +86 228 740 1895. corn, rice, wheat and potato, have been studied fully E-mail address: [email protected] (W. Gao). for several centuries (Singh, Singh, Kaur, Sodhi, & Gill, 0260-8774/$ - see front matter Ó 2005 Elsevier Ltd. All rights reserved. doi:10.1016/j.jfoodeng.2005.05.041 转载 中国科技论文在线 http://www.paper.edu.cn S. Wang et al. / Journal of Food Engineering 76 (2006) 420–426 421 2003). The physical properties of the native starch such 2.4. Thermal properties as morphological, thermal, rheological and crystal prop- erties were much different from each other due to the Thermal characteristics of isolated starches were inner structure of the starch granule. These properties studied by using a differential scanning calorimeter- directly decided the application of starch in the food DSC204, HP (NETZSCH, Germany) equipped with a and drug industry. In order to make good use of Fritil- thermal analysis station. Starch (3.5 mg, dry weight) laria medicinal plant resources and widen their indus- was loaded into a 40 ll capacity aluminium pan trial application, we investigated the starch contained (Mettler, ME-27331) and distilled water was added with in the Fritillaria by means of modern analytical technol- the help of Hamilton microsyringe to achieve a starch– ogy for the first time. water suspension containing 70% water. Samples were The objective of the present study was to investigate hermetically sealed and allowed to stand for 1 h at room the morphological, thermal and crystal properties of temperature before heating in the DSC. The DSC ana- starches separated from different bulbs of Fritillaria lyzer was calibrated using indium and an empty alumin- medicinal plant. ium pan was used as reference. Sample pans were heated at a rate of 10 °C/min from 20 to 120 °C. Onset temper- ature (T0); peak temperature (Tp); conclusion tempera- 2. Materials and methods ture (Tc) and enthalpy of gelatinization (DHgel) were calculated automatically (Kaur, Singh, & Sodhi, 2002). 2.1. Materials The gelatinization temperature range (R) was computed as (Tc À T0) as described by Vasanthan and Bhatty Fritillaria thunbergii Miq., Fritillaria ussurensis Max- (1996). Enthalpies were calculated on a starch dry basis. im., Fritillaria pallidifloca Schrenk, Fritillaria cirrhosa The peak height index (PHI) was calculated by the ra- D.Don and Fritillaria hupehensis Hsiao et K.C. Hsia tion DH/(Tp À T0) as described by Krueger, Knutson, were provided by Meiwei TCM company (Anguo, Hebei Inglett, and Walker (1987). province, China) and were identified by Professor Gao Wenyuan, Tianjin University, China. 2.5. X-ray powder diffraction measurements 2.2. Starch isolation Monochromatic Co-Ka radiation (wavelength = 1.789 A˚ ) was produced by a XÕPert PRO X-ray powder Fritillaria from different geographical origins were diffractometer (PANalytical, Holland). The Fritillaria washed and comminuted to powders with a plant starch powders were packed tightly in a rectangular alu- micro-muller which were sieved with 160 mesh sifter minum cell (20 · 20 mm, thickness 0.15 cm). The sam- and then kept in a desiccator. The dried powders were ples were exposed to the X-ray beam from the X-ray extracted with 95% ethanol by cold immersion method generator running at 40 kV and 40 mA. The scanning re- for 24 h. The supernatant was removed and the settled gions of the diffraction angle 2h were 4–35°, which cov- solid layer was resuspended in 95% ethanol and the cold ered most of the significant diffraction peaks of the immersion lasted for 24 h once again. The resulting sus- starch crystallites. The other operation conditions were pension was filtrated with a G4 type anti-acid filter. The as follows: step size, 0.0330°, scan step time, 30.8451 s, residue was washed with 95% alcohol for several times, PSD length, 2.12°, divergence slit size, 0.2177°, specimen allowed to dry at room temperature. The dried residue length, 10.00 mm. Duplicate measurements were made powder was resuspended with distilled water again and at ambient temperature. Radiation was detected with a again till the supernatant was transparent. The starch proportional detector. was then collected and dried at room temperature for further use. 2.6. Determination of the degree of crystallinity 2.3. Morphological properties The degree of crystallinity of samples was quantita- tively estimated following the method of Nara and Scanning electron micrographs were obtained with an Komiya (1983). A smooth curve which connected peak environmental scanning electron microscope (ESEM, baselines was computer-plotted on the diffractograms Philips XL-3). Starch samples were suspended in ace- (Fig. 1). The area above the smooth curve was taken tone to obtain a 1% suspension. One drop of the as the crystalline portion, and the lower area between starch-acetone suspension was applied on a glass slide. smooth curve and the linear baseline which connected The starch was coated with gold powder to avoid charg- the two points of the intensity 2h of 30° and 4° in the ing under the electron beam after the acetone volatilized. samples was taken as the amorphous section. The upper An accelerating potential of 30 kV was used during diffraction peak area and the total diffraction area over micrography. the diffraction angle 4–30° 2h were integrated using 中国科技论文在线 http://www.paper.edu.cn 422 S. Wang et al. / Journal of Food Engineering 76 (2006) 420–426 viewed by SEM. Scanning electron micrographs of the starch granules from different Fritillaria species were illustrated in Fig. 2. The granule size of the thunbergii F. starch was vari- able and ranged from 5 to 30 lm. The average granule size ranged from 5 to 15 lm for small and 20–30 lm for large thunbergii F. starch granules. The average size and shape of usssurensis F. and thunbergii F. starch gran- ules was same (Fig. 2(a)–(d)). The granule surface ap- peared smooth, round or elliptic-shaped. These two Fritillaria starches showed the presence of a fairly large number of large-sized, elliptic-shaped granules. How- ever, the granule size of the pallidifloca F. starch was Fig. 1. Calculation of the relative degree of the crystallinity. more variable and ranged from 5 to 40 lm. The average granule size of pallidifloca F. starch ranged between 5 Smadchrom software (Morgan and Kennedy Research, and 20 lm for small and 25–40 lm for large granules. Australia). The ratio of upper area to total diffraction The shape of starch granule was elliptic and irregular. was taken as the degree of crystallinity. The moisture The pallidifloca F.