过氧化氢改性苹果渣膳食纤维的研究

【目的】研究过氧化氢对苹果渣膳食纤维的改性作用，为提高苹果渣可溶性膳食纤维含量、改善苹果渣理化性质提供一种简单高效、成本低廉的方法。【方法】采用不同pH和浓度的过氧化氢溶液处理果汁厂苹果渣，经醇沉、干燥、粉碎后，制得过氧化氢改性苹果渣。研究pH及过氧化氢浓度对改性苹果渣得率、膳食纤维组成及含量、物理性质及结构特性的影响。其中，膳食纤维组成及含量包括总膳食纤维（Total dietary fibre, TDF）含量、不可溶性膳食纤维（Insoluble dietary fibre, IDF）含量、可溶性膳食纤维（Soluble dietary fibre, SDF）含量，物理性质包括改性苹果渣持水力、膨胀力、持油力、堆积密度、颜色，结构特性包括改性苹果渣热稳定性、超微结构，并检测改性苹果渣中过氧化氢残留量。【结果】（1）过氧化氢溶液的pH对苹果渣理化结构性质具有显著影响。过氧化氢溶液浓度相同时，经酸性（pH 3.8）、中性（pH 7）过氧化氢处理的苹果渣，TDF含量、持水力、膨胀力、持油力均有不同程度的提高，而SDF含量、堆积密度较原果渣无显著变化，颜色变暗。经碱性（pH 11.5）过氧化氢处理的苹果渣，SDF含量显著提高，持水力、膨胀力、颜色等理化性质均得到极大改善，堆积密度增加，TDF含量较未处理苹果渣有所提高。热重及超微分析结果表明，酸性、中性过氧化氢处理后苹果渣热稳定性及超微结构与原果渣相比无明显差异，碱性过氧化氢处理后苹果渣热稳定性下降，超微结构变得紧密平滑。（2）过氧化氢溶液浓度对苹果渣理化结构性质也具有显著性影响。在pH为11.5的碱性条件下，使用不含过氧化氢的溶液处理后，苹果渣理化结构性质与经酸性、中性过氧化氢处理的苹果渣相似。随着过氧化氢浓度逐渐升高，苹果渣SDF含量逐渐增加，SDF含量由3.30%增加到19.02%-28.32%，提高476%-758%，膨胀力、颜色逐渐改善，堆积密度增加，持水力先上升后下降，苹果渣得率、TDF、IDF含量逐渐下降，持油力未得到改善。此外，随着过氧化氢浓度升高，苹果渣结构性质也发生变化，苹果渣热稳定性逐渐降低，结构变得更加松碎。（3）过氧化氢残留量检测结果表明，过氧化氢在处理过程中可完全分解除去，改性苹果渣中无残留。【结论】碱性过氧化氢处理可作为一种清洁高效的提高苹果渣SDF含量并改善苹果渣理化性质的改性方法，改性效果与过氧化氢pH及浓度密切相关。

Apple Pomace Dietary Fibre Modification by Hydrogen Peroxide

【Objective】The aim of this study was to explore the effect of hydrogen peroxide modification on the dietary fibre in apple pomace, and provide a simple, effective and cheap method to increase the content of soluble dietary fibre and improve physicochemical properties of apple pomace. 【Method】Different pHs and concentrations of hydrogen peroxide were used to treat the apple pomace which obtained from juice factory. After precipitating by ethanol, drying and grinding, the hydrogen peroxide modified apple pomace was obtained. The physicochemical and structural properties of apple pomace were studied, such as yield, total dietary fibre (TDF) content, insoluble dietary fibre (IDF) content, soluble dietary fibre (SDF) content, water holding capacity, swelling capacity, oil holding capacity, bulk density, colour, thermostability and microstructure. Hydrogen peroxide residue in modified apple pomace was also determined. 【Result】pH of hydrogen peroxide solution could significantly impact the physicochemical and structural properties of apple pomace. In treatment with the same concentration of the hydrogen peroxide, TDF content, water holding capacity, swelling capacity, oil holding capacity of apple pomace were increased in different degrees by acidic (pH 3.8) or neutral (pH 7) hydrogen peroxide treatments, however, there was no significant change in the content of SDF and bulk density. The colour of apple pomace became dark. In alkaline (pH 11.5) hydrogen peroxide treatment, the content of SDF was significantly increased, the water holding capacity, swelling capacity and colour were also improved significantly, the bulk density and TDF content were increased compared with the untreated apple pomace. Through analysis of the thermostability and microstructure, there was no significant difference between modified and untreated apple pomace in thermostability and microstructure in treatments with acidic or neutral hydrogen peroxide, while the thermal property became less stable and the structure became dense and smooth in treatment with alkaline hydrogen peroxide. The concentration of hydrogen peroxide solution could also significantly impact the physicochemical and structural properties of apple pomace. In alkaline conditions (pH 11.5), when using 0% hydrogen peroxide solution treatment, the physicochemical and structural properties of apple pomace were similar to the acidic and neutral hydrogen peroxide treated products. With the increase of hydrogen peroxide concentration, the SDF content was increased from 3.30% to 19.02%-28.32%, increased by 476%-758%, the swelling capacity and the colour of apple pomace were improved, the bulk density were also increased, the water holding capacity was rised firstly and then decreased, the yield, TDF content, and IDF content were decreased, but oil holding capacity was not improved. Moreover, the structural properties of apple pomace were also changed. The thermostability was reduced and the structure became more fragmented with the increase of hydrogen peroxide concentration. The result of hydrogen peroxide residue showed that hydrogen peroxide could be removed completely during the process of treatment, without any residue. 【Conclusion】Alkaline hydrogen peroxide modification could be used as a clean and effective method to increase the content of soluble dietary fibre in apple pomace and improve the physicochemical properties of apple pomace. The effect of modification was closely related to pH and concentration of hydrogen peroxide.