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Liu J.,Southwest University | Chen J.,Southwest University | Dong N.,Southwest University | Ming J.,Southwest University | And 4 more authors.
Food Chemistry | Year: 2012

The degree of substitution (DS) markedly affects the properties of carboxymethyl starch (CMS). The conventional methods for the DS determination are time-consuming and not environment friendly. Fourier transform mid-infrared (FT-MIR) spectroscopy coupled with partial least squares (PLS) regression is applied to determine the DS of CMS in the present study. Calibration models with direct titration as the reference method were optimised by cross validation. A PLS regression model with a coefficient of determination (R 2) of 0.9593 and root-mean-square error of cross validation (RMSECV) of 0.0141 was obtained in the spectral range from 500 to 4000 cm -1. The prediction set gave a coefficient of determination (R 2) and root-mean-square error of prediction (RMSEP) of 0.9368 and 0.0228, respectively. The results obtained in this study indicate that FT-MIR spectroscopy can be used as an easy, rapid, and novel tool to quantitatively predict the DS of CMS. © 2011 Elsevier Ltd. All rights reserved. Source

Shen X.L.,Southwest University | Shen X.L.,China Agricultural University | Wu J.M.,Southwest University | Chen Y.,China Rural Technology Development Center | And 3 more authors.
Food Hydrocolloids | Year: 2010

Antimicrobial biodegradable films have been prepared with sweet potato starch by incorporating potassium sorbate or chitosan. Films incorporated with potassium sorbate ≥ 15% or chitosan ≥ 5% were found to have an anti-Escherichia coli effect. Staphylococcus aureus could be effectively suppressed by incorporation of chitosan at ≥10%. Whereas potassium sorbate lowers the tensile strength and elongation at break, and raises the oxygen permeability, water vapor permeability and water solubility, chitosan has the opposite effect. Fourier Transform Infrared (FT-IR) spectra analysis revealed that starch crystallinity was retarded by potassium sorbate incorporation and that hydrogen bonds were formed between chitosan and starch. This explained the modification of the mechanical and physical properties of the films by the incorporation of these two antimicrobial agents. © 2009 Elsevier Ltd. All rights reserved. Source

Guan Y.,Southwest University | Ye F.,Southwest University | Liu J.,Southwest University | Zhao G.,Southwest University | Zhao G.,Chongqing Sweet Potato Engineering and Technology Center
Journal of Agricultural and Food Chemistry | Year: 2013

The interaction between ε-polylysine (ε-PL) and anionic polysaccharides has gained considerable attention recently because of its scientific impact on the stability and appearance of liquid food systems. The purpose of this study was to characterize the interactions between ε-PL and carboxymethyl sweet potato starch (CSS) using isothermal titration calorimetry (ITC), electrical charge, and turbidity measurements. The results showed that the interaction between ε-PL and CSS was electrostatic and mainly dependent on the molar ratio of amino groups in ε-PL to carboxyl groups in CSS. Additionally, the interaction between ε-PL and CSS was also associated with pH, degree of substitution (DS) of CSS, and ionic strength of the system. For the interaction of ε-PL with high DS (>0.235) CSS, three states of the ε-PL/CSS mixture were observed as transparent, turbid, and precipitated with a successive increase in amino/carboxyl molar ratio. Distinguishingly, a transparent mixture could be obtained for CSS with low DS (0.114) at a sufficiently high amino/carboxyl molar ratio. The present study provided basic guidance in designing liquid food systems containing both ε-PL and CSS. © 2013 American Chemical Society. Source

Liu J.,Southwest University | Wena Y.,Southwest University | Dong N.,Southwest University | Lai C.,Southwest University | And 3 more authors.
Food Chemistry | Year: 2013

Fourier transform mid infrared (FT-MIR) spectroscopy combined with chemometrics techniques were developed for classification and quantification of cheaper starches (potato and sweet potato starch) in lotus root powder (LRP). By performing principal component analysis (PCA), it was possible to distinguish between adulterated and non-adulterated LRP. The coefficient of determination (R2) and standard deviation ratio (SDR) of calibration set were found to be 0.9587-0.9898 and 3.63-10.2, depending on the pretreatment of spectra. The external validation set gave a coefficient of determination (R2) and standard deviation ratio (SDR) of 0.9810 and 5.47, respectively. Moreover, the limit of detection (1%), the limit of quantification (3%), reasonable recovery (92.3-101.5%), satisfactory intra-assay (2.9-5.5%) and interassay (11.0-13.5%) precision illustrated the good performance of the present method. The results obtained in this study indicate that FT-MIR spectroscopy can be used as an easy, rapid and novel tool to detect the LRP adulterated with cheaper starches. © 2013 Elsevier Ltd. All rights reserved. Source

Peng Z.,Southwest University | Li J.,Southwest University | Guan Y.,Southwest University | Zhao G.,Southwest University | And 2 more authors.
LWT - Food Science and Technology | Year: 2013

This work focuses on the impact of carriers on the physicochemical properties, antioxidant capacities and biological components of spray-dried purple sweet potato flours. The optimal carrier addition of maltodextrin (MD), β-cyclodextrin (β-CD) and their combination (MD/β-CD, 5/1) were 30, 10 and 24 g/100 g in terms of flour yield. Compared to the flour without carrier, flours with carriers had higher values in L*, fluidity, water solubility index, glass transition temperature, lower values in chroma, water absorption index and water holding capacity. The influence intensity of carriers on the physicochemical properties of flours followed the sequence of MD > MD/β-CD> β-CD. The flours with carriers were more dispersive and had smoother surface than flour without carrier. The addition of carrier had little effects on flours' sorption isotherm and the Halsey model presents the best goodness-of-fit to all flours. The flour with MD had higher retention rate of anthocyanins, flavonoids and total phenolics than flours without and with other carriers. The flour with MD has higher antioxidant activity (DPPH test) than flours with MD/β-CD or β-CD. © 2012 Elsevier Ltd. Source

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