Physicochemical and Functional Properties of the Protein–Starch Interaction in Chinese Yam PDF

Received: 10 March 2022 | Revised: 7 November 2022 | Accepted: 5 December 2022 DOI: 10.1002/fsn3.3189 ORIGINAL RESEARCH Physicochemical and functional properties of the protein–­starch interaction in Chinese yam Yelin Shao1 | Ruize Jiao1 | Yingyin Wu1 | Fangcheng Xu2 | Yan Li2 | Qiaojun...

Received: 10 March 2022 | Revised: 7 November 2022 | Accepted: 5 December 2022 DOI: 10.1002/fsn3.3189 ORIGINAL RESEARCH Physicochemical and functional properties of the protein–­starch interaction in Chinese yam Yelin Shao1 | Ruize Jiao1 | Yingyin Wu1 | Fangcheng Xu2 | Yan Li2 | Qiaojun Jiang2 | Liang Zhang3 | Linchun Mao1,4 1 College of Biosystems Engineering and Food Science, Zhejiang Key Laboratory of Abstract Agro-­Food Processing, Key Laboratory of Protein–­starch interaction has an important impact on the properties of starchy foods Agro-­Products Postharvest Handling of Ministry of Agriculture and Rural Affairs, rich in protein, but the contribution of the interaction to Chinese yam still remains Zhejiang University, Hangzhou, China unclear. This study aimed to characterize the physicochemical and functional proper- 2 Department of Agriculture and Biotechnology, Wenzhou Vocational ties related to the possible interaction between starch and protein in Chinese yam. College of Science and Technology, Differential scanning calorimetry and rapid viscosity analyzer results revealed that Wenzhou, China 3 the gelatinization temperature increased in protein and starch cross-­linked powder, Wencheng Institution of Modern Agriculture and Healthcare Industry, while the peak viscosity and the setback viscosity decreased. The swelling power and Wenzhou, China solubility at 80°C and 95°C decreased with increasing protein ratio in the powder. 4 Ningbo Research Institute, Zhejiang In vitro starch digestibility test indicated that a high protein ratio could rapidly re- University, Ningbo, China duce digestible starch, but increase both slowly digestible starch and resistant starch. Correspondence Protein could act as the physical barrier toward starch against heating and digestion Linchun Mao, College of Biosystems Engineering and Food Science, Zhejiang to exert the influence on starch properties. Fourier transform infrared spectroscopy Key Laboratory of Agro-­Food Processing, test revealed the interaction between protein and starch. These results revealed the Key Laboratory of Agro-­Products Postharvest Handling of Ministry of role of protein–­starch interaction and provided beneficial information for the utiliza- Agriculture and Rural Affairs, Zhejiang tion of Chinese yam. University, Hangzhou, China. Email: [email protected] KEYWORDS Yan Li, Department of Agriculture and Biotechnology, Wenzhou Vocational Chinese yam, digestive properties, physicochemical properties, protein, starch College of Science and Technology, Wenzhou, China. Email: [email protected] Funding information Key R & D projects of Zhejiang Province, Grant/Award Number: 2020C02046; Key scientific and technological innovation agricultural projects of Wenzhou, Grant/ Award Number: ZN2019001; Zhejiang University-­Wencheng Joint Research Center of Health Industry, Grant/Award Number: Zdwc2202 This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. © 2023 The Authors. Food Science & Nutrition published by Wiley Periodicals LLC. Food Sci Nutr. 2023;11:1499–1506.  wileyonlinelibrary.com/journal/fsn3 | 1499 1500 | SHAO et al. 1 | I NTRO D U C TI O N 2.2 | Yam powder preparation Starch and protein played important roles in the nutritional quality and Yam powder was prepared referring to Xie et al. (2011). The yam processing characteristics of foodstuffs (Zhu et al., 2019). Therefore, tubers were cut and mixed with deionized water (1:2) in a blender the interaction, physicochemical, and digestive properties of starch (FL1928; Fuling Technology Co., Ltd), stirred at a speed of 15,294 g and protein have become a hot topic of food research. For example, for 2 min, and then dried in a fume hood (40°C) for 48 h. Protein and starch–­protein powders could be used to formulate new functional starch content of the yam powder was 14.0% and 78.0%, respectively. foods, including bakery products, snack food, baby food, and des- serts, and showed their rich functionality, significant bioactivity, and superior nutritional value (Yang et al., 2019). The interaction between 2.3 | Starch extraction starch and protein has an important influence on the overall texture, stability, and taste of the food, which mainly depends on the thermal The method of our previous study (Shao et al., 2020) was applied. properties (Li et al., 2007; Likitwattanasade & Hongsprabhas, 2010). Cut tubers were homogenized with the same weight of deionized This was mainly because the protein was closely combined with the water in the blender. The slurry was filtered through a 200-­mesh starch granules or distributed in the gaps of the starch granules by hy- sieve with the residue washed twice with distilled water and the fil- drogen bonds, van der Waals forces, and electrostatic, which affected trate stood for 2 h. Then, the supernatant was decanted, and the the reaction process of starch in water and heat (Zhu et al., 2019). The precipitated starch layer was resuspended with deionized water. interactions of components from different crops have also attracted After repeating eight times, the starch was resuspended in ethyl al- attention, such as molecule interactions of whey protein with potato cohol and dried at 45°C for 24 h (about 10% moisture), and collected starch (Guo et al., 2021; Lin et al., 2022; Liu et al., 2021). In addition, by filtration through a 100-­mesh sieve. protein could interfere with the starch digestion process by blocking enzyme-­binding sites and ultimately promote starch malabsorption (Oates, 1997). Starch digestibility and glycemic index were affected 2.4 | Protein isolation by protein, which in turn influenced sugar level management strate- gies and human health (Lal et al., 2021). Therefore, the in-­depth study The isolation of yam protein was referred to Hu et al. (2018). Tubers on starch–­protein interaction could help to understand and improve were washed, cut, peeled, and mixed with distilled water (pH 9.0). the quality of starch-­based foods. After stirring at 20°C for 30 min, the mixture was centrifuged at A subspecies of Chinese yam (Dioscorea opposita Thunb.) was 2655 g for 20 min. Then, the supernatant was filtered through a recently reported due to its low amylose content and related phys- double-­layer cloth using 2 M HCl and magnetically stirred for 1 h. icochemical and structural properties (Shao et al., 2020). The high The slurry was then centrifuged at 5000 rpm for 30 min at 20°C. content of protein was expected to play an important role in the nu- The precipitate was dissolved in distilled water, with pH adjusted to tritional and edible quality of the yam. There have been studies on 7.0, then ultrafiltered and lyophilized to prepare the protein. Chinese yam starch, including native starch, resistant starch, hydro- thermally treated starch (Yu et al., 2021; Zou et al., 2020). However, the contribution of protein and its interaction with starch to the phys- 2.5 | Mixture of starch and protein icochemical and digestive properties of the yam still remain unclear. The purpose of this study was to explore the interaction be- Protein was mixed with starch at various ratios of 0%, 10%, and 20% tween starch and protein by confocal laser scanning microscopy and (w/w), and the mixtures were evenly vibrated and shaken. For sub- Fourier transform infrared spectroscopy. The physicochemical and sequent tests, the yam powder or mixtures were stirred in water for functional properties related to the possible interaction between 10 min to obtain sufficient dispersion. starch and protein were evaluated in terms of gelatinization and pasting properties, solubility, swelling power, and starch digestibil- ity. The information covered in this study would help us to better 2.6 | Differential scanning calorimetry (DSC) understand the interaction mechanism between yam starch and protein, and to make effective use of yam resources. The gelatinization properties of samples were analyzed by Mettler DSC 1 professional thermal analyzer (ZCEC-­130263F, Mettler-­Toledo, Switzerland) according to Shao et al. (2020). The sample (5 mg, 10% 2 | M ATE R I A L S A N D M E TH O DS water content) and water (10 mg) were sealed in an aluminum crucible. After equilibration at 4°C for 24 h and then at room temperature for 2.1 | Materials 1 h, the crucible was held at 20°C for 1 min in the DSC furnace and then heated from 20°C to 110°C at a rate of 10°C/min. The data ob- Tubers of Chinese yam (Wennuo No.1) were obtained from tained included the onset temperature (To), the peak temperature (Tp), Wencheng County, Wenzhou City, Zhejiang, China in October 2019. the conclusion temperature (Tc), and the crystal melting enthalpy (ΔH). SHAO et al. | 1501 2.7 | Rapid viscosity analysis (RVA) 2.10 | Confocal microscopic characterization A modular compact rheometer (MCR 302, Anton Paar, Austria) About 500 mg of powders and 5 ml of distilled water were mixed, was used to measure the pasting properties according to Shao stirred, and heated in 100°C water bath for 15 min to obtain a paste. et al. (2020). The pasting temperature (PT), peak viscosity (PV), Powders were double-­stained and pasted with fluorescent dyes breakdown viscosity (BV), cold paste viscosity (CV), final viscos- (0.25 g/dl Rhodamine B and 0.01 g/dl FITC, in acetone) in the dark for ity (FV), and setback viscosity (SV) were obtained from the profile. 5 min. The stained section was covered carefully with a cover glass. SV = FV –­CV. Then, fluorescence images were captured with confocal laser scan- ning microscopy (CLSM; Leica TCS SP8). Two excitation wavelengths of 543 nm helium–­neon laser and 488 nm argon–­krypton laser were 2.8 | Swelling power and solubility test used to reflect the fluorescence of protein and starch, respectively (Nagano et al., 2008). The distribution and cross-­link of protein and The powder slurry (2% w/v) was heated in a shaking water bath at starch could be observed from the images. 80°C or 95°C for 30 min and then cooled to room temperature. After centrifugation at 1699 g for 15 min, the supernatant was dried at 105°C for 2 h (Shao et al., 2020). 2.11 | Fourier transform infrared spectroscopy The swelling power and solubility of the powder were calculated as follows: Absorbance spectra of samples were recorded on an FTIR spectrom- Solubility (SOL, %) eter (Ava tar370; Nicolet). Samples were prepared using 6% (w/w) pow- = Weight of dried supernatant × 100∕weight of powder der dispersed in KBr pellets. All powders were dried at 105°C for 24 h, then compressed with KBr, and 256 scans were recorded with a resolu- Swelling power (%) tion of 4 cm−1 and frequency from 400 to 4000 cm−1 (Shao et al., 2020). = (weight of wet sediment × 100)∕weight of powder × (100% − SOL%) 2.12 | Statistical analysis 2.9 | In vitro starch digestion Data were expressed as means ± standard deviation of three repli- The method of Englyst et al. (1992) was applied to digest starch cations and performed one-­way analysis of variance (ANOVA) with in powders in vitro. Powder (0.5 g) with 5 ml of distilled water Duncan's multiple range test (SSR) for statistical analysis by SPSS 25.0 was well mixed, stirred, and maintained in 100°C bath for 30 min, statistical software (Statistical Graphics Corp., Princeton, NJ). When then cooled down to 25°C. The mixture was added with 3 ml of the p value was