Starch is a polymer compound formed by the polymerization of glucose molecules. Currently, mainstream commercial starch can be divided into three categories based on its source: grain starch, legume starch, and rhizome starch. Amylose and amylopectin are the two main components of starch, and their amylose content varies depending on the source and variety of starch. There are also some starches in nature that are almost entirely composed of branched starch, namely waxy starch. As an important renewable and environmentally friendly resource, starch and its derivatives are widely used in industries such as food, textiles, papermaking, pharmaceuticals, plastics, adhesives, etc. However, due to the inherent defects of starch, such as insoluble in water, high gelatinization temperature, and easy retrogradation after gelatinization, its application in industry is greatly limited. Therefore, the study of starch modification is of great significance.

酶法改性澱粉顆粒是在澱粉糊化溫度以下修飾澱粉的一種改性方法。澱粉改性後，其顆粒形態、分子結構、晶型、結晶度、溶解度、糊化特性以及流變學性質等發生改變，可達到改善澱粉的加工特性並提高其應用價值的目的。江南大學食品學院，食品科學與技術實驗室，食品與營養協同創新，食品聯合實驗室的翟一潭、柏玉香、金征宇*等人通過綜述澱粉顆粒酶法改性前後結構與性質的變化，以及改性所需的澱粉酶種類、方法等。

Enzymatic modification of starch granules is a modification method that modifies starch below the gelatinization temperature. After starch modification, its particle morphology, molecular structure, crystal form, crystallinity, solubility, gelatinization characteristics, and rheological properties undergo changes, which can improve the processing characteristics of starch and enhance its application value. Zhai Yitan, Bai Yuxiang, Jin Zhengyu * and others from the School of Food Science, Jiangnan University, the State Key Laboratory of Food Science and Technology, the Collaborative Innovation Center for Food Safety and Nutrition, and the International Joint Laboratory of Food Safety reviewed the changes in the structure and properties of starch granules before and after enzymatic modification, as well as the types and methods of amylase required for modification.

天然澱粉以顆粒的形式貯存於植物的各個器官中，主要由直鏈澱粉和支鏈澱粉構成。直鏈澱粉呈線性結構，幾乎沒有分支，相對分子質量介於105～106之間，支鏈澱粉呈高度分支的簇狀結構，相對分子質量在107～109之間。天然澱粉顆粒由交替出現的“生長環”的無定形層和半結晶層組成，厚度在100～400 nm之間。其中，無定形區主要由直鏈澱粉分子構成，半結晶區主要由支鏈澱粉分子構成；半結晶區中又包含結晶片層和非晶片層。澱粉顆粒這種特殊的無定形區和半結晶區交替出現的排列方式，使得其對光產生了特殊的折射現象，即“偏光十字”。

Natural starch is stored in various organs of plants in the form of granules, mainly composed of amylose and amylopectin. Amylose starch exhibits a linear structure with almost no branching, with a relative molecular weight between 105 and 106. Branched starch exhibits a highly branched cluster structure with a relative molecular weight between 107 and 109. Natural starch particles are composed of alternating amorphous and semi crystalline layers of "growth rings", with a thickness ranging from 100 to 400 nm. Among them, the amorphous region is mainly composed of linear starch molecules, while the semi crystalline region is mainly composed of branched starch molecules; The semi crystalline zone also includes crystalline and amorphous layers. The alternating arrangement of amorphous and semi crystalline regions in starch particles results in a special phenomenon of refraction towards light, known as the "polarized cross".

溶脹力和溶解度

Swelling force and solubility

α-澱粉酶和葡萄糖澱粉酶混合水解澱粉顆粒形成的多孔澱粉比相應的原澱粉具有更高的溶脹力和溶解度。經過兩次濕熱預處理後再用混合酶水解製備的多孔小麥澱粉溶解度和溶脹力分別高於天然澱粉和隻經過兩次濕熱預處理的澱粉樣品。這種現象與酶水解後無定形區域的直鏈澱粉浸出有關，從而導致澱粉樣品的溶解度增加。

α- The porous starch formed by the mixed hydrolysis of starch particles by amylase and glucoamylase has higher swelling power and solubility than the corresponding raw starch. After two wet heat pre-treatments, the porous wheat starch prepared by mixed enzyme hydrolysis has higher solubility and swelling power than natural starch and starch samples that have only undergone two wet heat pre-treatments. This phenomenon is related to the leaching of amylose in the amorphous region after enzymatic hydrolysis, resulting in an increase in the solubility of the starch sample.

糊化特性

Gelatinization characteristics

由於對澱粉顆粒的改性在非糊化條件下進行，所以改性澱粉仍然保留了糊化特性，並且酶對澱粉顆粒的修飾會改變其糊化溫度和糊化焓。分支酶修飾木薯澱粉顆粒引起改性澱粉糊化起始溫度、糊化峰值溫度和糊化焓升高。糊化起始溫度的升高是由於澱粉顆粒的形態發生了變化，以及直鏈澱粉發生重結晶。糊化焓的提高表明改性使澱粉顆粒結構的穩定性提高。

Due to the modification of starch particles under non gelatinization conditions, the modified starch still retains its gelatinization characteristics, and enzyme modification of starch particles can change their gelatinization temperature and enthalpy. The modification of cassava starch granules by branching enzymes resulted in an increase in the gelatinization starting temperature, gelatinization peak temperature, and gelatinization enthalpy of the modified starch. The increase in gelatinization starting temperature is due to changes in the morphology of starch particles and the recrystallization of amylose. The increase in gelatinization enthalpy indicates that modification enhances the stability of starch particle structure.

流變性能

Rheological properties

脫支酶對澱粉顆粒的修飾會降低糊化過程中的峰值黏度，但降低程度與澱粉來源有關。在相同的條件下使用脫支酶修飾馬鈴薯澱粉和玉米澱粉顆粒，改性馬鈴薯澱粉峰值黏度顯著下降了56%，而改性玉米澱粉峰值黏度僅降低了15%。澱粉的峰值黏度主要與直鏈澱粉含量、支鏈澱粉的支鏈長度分布以及澱粉中的某些基團和脂質等成分有關。

The modification of starch particles by debranching enzymes can reduce the peak viscosity during the gelatinization process, but the degree of reduction is related to the source of starch. Under the same conditions, using debranching enzymes to modify potato starch and corn starch granules significantly reduced the peak viscosity of modified potato starch by 56%, while the peak viscosity of modified corn starch only decreased by 15%. The peak viscosity of starch is mainly related to the content of amylose, the distribution of branch chain length of branched starch, and certain functional groups and lipids in starch.