From Biosynthesis to Application: The Fascinating World of Potato Starch
by Jorge Luis Alonso with ChatGPT
This study, conducted by the Zhejiang Academy of Agricultural Sciences (China), identifies the biodiversity of starch content, structure and physicochemical properties, particularly amylose and amylopectin content, molecular and granular structure, gelatinization, retrogradation, swelling power, solubility and digestibility of potatoes in the last decade. This is a summary of its contents.
Introduction
Potato, a major non-cereal food crop native to the Andes, ranks fourth in global production after corn, wheat and rice. With China as the leading producer, potatoes are not only a rich source of nutrients, but are also used to produce starch-based materials with a range of benefits.
Starch, which accounts for 15–20% of the potato’s weight, is a polymeric carbohydrate composed of amylose and amylopectin whose physicochemical properties are determined by the molecular and granular structure of potato starch. Its biosynthesis is a highly complex process involving several enzymes. Importantly, modified potato starch is widely used in various industries such as food packaging and medical materials.
This review aims to provide an updated summary of the structure, function, biosynthesis and applications of potato starch in both food and non-food areas.
Biodiversity of Potato Starch
Between the two major polysaccharides that make up starch, the amylopectin molecule is significantly larger than the amylose molecule, and minor components such as protein, lipid, and ash are present in small amounts.
The amount of starch in potatoes varies between varieties and growing areas, with environmental factors playing an important role. For example, amylose content can vary from a minimum of 11.4% to a maximum of 36.6% depending on these factors.
Potato variety and growing region also determine the amylose/amylopectin ratio, while lipid, protein and ash are other minor components of potato starch.
Structure of Potato Starch
As mentioned above, potato starch consists of two types of molecules called amylose and amylopectin, which are composed of glucose linked by glycosidic bonds. Amylose is composed of α-(1→4) glycosidic linkages, while amylopectin has a higher number of α-(1→6) glycosidic linkages. Amylose forms single helix structures, while amylopectin has an extra chain extending from the starch monomer at position 6, forming a double helix structure. The length of the starch structure depends on the number of units forming amylose and amylopectin.
Amylopectin contains a high number of branches and phosphate ester groups, while the length of the amylose chain varies significantly among potato varieties. In addition, the molecular structure of potato starch can be affected by environmental conditions. To describe the chains, those with a degree of polymerization (DP) of less than 100 are categorized as amylopectin chains, while those with a DP of 100 or more are mainly referred to as amylose chains.
Physicochemical Properties of Potato Starch
The physicochemical properties of potato starch include its pasting, gelatinization and retrogradation properties. Pasting properties are measured using the Rapid Viscosity Analyzer (RVA), which helps determine peak viscosity, hot paste viscosity, cool paste viscosity, breakdown, setback, and pasting temperature.
These properties are influenced by a number of factors including variety, growing conditions and the amount of starch in suspension. Compared to other starches, potato starch has lower hot paste viscosity and paste temperature, but higher peak viscosity, cool paste viscosity, breakdown and setback.
The gelatinization and retrogradation properties are measured by differential scanning calorimetry. These properties vary between potato varieties and growing regions. During gelatinization, starch chains expand and melt into a disordered state.
Retrogradation is the process by which these disordered chains recombine into an ordered crystalline structure.
Biosynthesis of Potato Starch
To make potato starch, several enzymes work together in a part of the cell called the amyloplast. These enzymes include AGPase, SSs, SBE and DBE. GWD and PWD also help with the process by adding phosphate groups to the starch.
AGPase is unique in that it exists both inside and outside the amyloplast. PGM is an enzyme that starts the starch-making process by converting α-glucose-6-phosphate to α-glucose-1-phosphate. Then, AGPase and ATP help convert α-glucose-1-phosphate to ADP-glucose, which is used to build long chains of glucose molecules with the help of SSs.
SSs add more glucose units to the chains, which can then be converted into branches by SBE or trimmed by DBE. AGPase is the first enzyme involved in starch biosynthesis and the amount of starch produced is directly related to its activity.
There are two main types of SSs in potatoes: GBSS and SSS. GBSS is responsible for the formation and extension of amylose chains. There are two forms of GBSS in potatoes, GBSSI and GBSSII, with GBSSI accounting for 95% of GBSS.
Application of Potato Starch
Potato starch is a highly versatile and environmentally friendly material that has gained popularity in the food and pharmaceutical industries. It can be used to make a variety of foods such as pasta, bread, chips and French fries. It’s also a popular thickening agent and a substitute for sugar and fat in many foods, such as yogurt.
Importantly, potato starch is also an excellent option for environmentally friendly packaging materials such as film. By adding materials such as glycerin, cellulose and gelatin, the packaging can be made more functional. By using potato starch-based packaging materials, we can contribute to a better environment and reduce harm to people.
For those looking for an easy way to make a positive contribution to the environment, consider switching to potato starch-based products.
Conclusion
Potato starch is crucial for carbohydrate researchers because of its unique properties and potential applications. The composition, structure, and enzymes involved in its synthesis significantly affect its properties. However, there is a limited understanding of potato starch metabolism and enzyme functions, which calls for further research in this area. It is important to prioritize the study of potato starch granule structure to better comprehend its properties, alongside the development of fully biodegradable materials for food packaging. Additionally, researchers should explore new modification technologies to improve their safety and utilization.
Source: Tong, C., Ma, Z., Chen, H., & Gao, H. (2023). Toward an understanding of potato starch structure, function, biosynthesis, and applications. Food Frontiers, 00, 1– 21.
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