Sugar-free cola has sweet taste but no "soul"? This food expert found the scientific basis

When you are feeling down, will a cup of cola or coffee with sugar bring you happiness and satisfaction? However, excessive intake of sugar can have a negative impact on health, leading to obesity, diabetes, high blood pressure and other diseases. It is reported that reducing sugar has become a major trend in healthy living worldwide, and my country's "14th Five-Year Plan" has also put forward corresponding initiatives.

Many male friends love to drink cola, but they are worried about getting fat. What should they do? The birth of sugar substitutes solved this problem, and sugar-free cola came into our view! However, why do sugar-free cola and classic cola with sugar substitutes taste sweet but "lose their soul" and have different tastes? What is the molecular mechanism behind this? Professor Chen Zhongxiu's team from the School of Food and Bioengineering at Zhejiang Gongshang University found that the molecular structure of sugar substitutes is different from that of sucrose, and their reaction with water is also different, which leads to the phenomenon that we feel the taste is different when we drink sugar-free cola.

Chen Zhongxiu

Studying sweetness perception

Different sweeteners react with water to form different hydration shell structures. This structural difference causes different degrees of disturbance in the hydrogen bond network of the solvent water, which may affect the conformational changes of the receptor protein. When binding to the sweet taste receptors on the taste bud cells, sweet molecules with different hydration levels exhibit different binding constants, binding sites, and thermodynamic parameters during the binding process. At the same time, the kinetic parameters of the binding, such as the binding rate and the energy of the transition state formed, are also different. These factors work together to affect the dynamic perception of sweeteners, resulting in different taste experiences.

The difficulty in studying the dynamic perception mechanism of sweetness lies in how to experimentally obtain transient information of ligand interaction in the "living" state. Chen Zhongxiu's research group used the fast kinetic technology of stopped-flow spectroscopy and the "sweet cell" model of sweet receptor gene expression based on the food sensory science research platform to study the transient response kinetic curves of sweet cells after various sweeteners stimulated them, providing an experimental basis for in-depth interpretation of the dynamic perception mechanism of sweetness.

This research not only has theoretical significance in the study of sweetness perception mechanism, but also has guiding significance for the design of sugar substitute application formulas in food systems. This project was awarded the National Natural Science Foundation of China in 2023, which is also the third National Natural Science Foundation of China general project obtained by Chen Zhongxiu's research team in this field.

From Chemistry to Food Science

Chen Zhongxiu's scientific research journey was not smooth sailing. When she first entered the School of Food Science and Technology of Shangda University, she, who had a background in chemistry, faced the challenge of how to combine chemical knowledge with food science. Due to differences in disciplinary backgrounds and lack of scientific research resources, she needed to build her own food tower little by little from the foundation. "Food sensory science relies a lot on subjective descriptions, but I hope to use non-subjective physical and chemical methods to interpret the sensory quality of food and explore the chemical mechanism of food sensory at the molecular level." So, she innovatively combined chemistry and food science, opening up a unique research path.

Chen Zhongxiu's scientific research is a mixture of ice and fire. She is full of passion and can still maintain prudent and rational thinking and the quality of studying hard. Since she joined the University of Commerce in 2005, she has always adhered to the belief that "scientific research is done by doing, not by sitting", and has been determined to solve scientific problems. She joked that chemists do physical work, and these rough hands are a symbol of their diligence.

However, in reality, there are not enough researchers who can really settle down and do in-depth research like Chen Zhongxiu. "The outside world is always complicated, and society's demand for scientific research is also changing. As a scientific worker, we must face the needs of economic and social development and do meaningful and practical scientific research." Chen Zhongxiu's scientific research started with "sweetness" and has been rooted in the laboratory for 20 years. At present, her achievements and discoveries have covered food sensory and food nutrition-related chemical mechanisms. Faced with different assessment mechanisms and evaluation standards in different periods, she often encourages her graduate students to keep a quiet heart, have determination, and do scientific research that they really love and is beneficial to society.

The inheritance of "sweet business"

For many years, as the director of the Department of Food Quality and Safety at Shangda, Chen Zhongxiu has been actively guiding undergraduates to enter the laboratory as early as possible, consciously allowing them to participate in research projects, understand scientific research trends, and implant innovative genes into students' blood.

"In class, teachers focus on imparting theoretical knowledge, but participating in laboratory work can cultivate our practical ability to discover, analyze and solve problems, which is more meaningful," said Feng Qian, a junior student in the Food Safety Department.

"I require that all scientific research laboratories in the Food Safety Department be open to undergraduate students, and graduate students must warmly welcome undergraduate students to join us! In this process, undergraduate students are also allowed to change laboratories, which reflects that they are thinking, choosing, and exploring their own interests." Chen Zhongxiu said, "Undergraduates and graduate students grow together" is an important concept in the talent training system for the food safety major at Shangda.

Chen Zhongxiu and his graduating students

Zhu Yike, a senior student in the Department of Food Safety, said: "Professor Chen's classes are very valuable. You have to spend time and effort to absorb and master them." When Chen Zhongxiu first came to Shangda, she found that undergraduates lacked certain chemical knowledge to understand the complex food system, so she began to explore new course designs. She conducted in-depth research on food chemistry-related textbooks and course structures in domestic universities, combined with the learning situation of students in her school, and finally creatively designed the course "Molecular Food Science" after ten years of hard work. In specific teaching practice, Chen Zhongxiu is good at integrating world-leading subject information, current food hotspots, and even new discoveries just made by the school laboratory, hoping to open students' horizons and keep pace with the times and the world. In 2023, "Molecular Food Science" was recognized as the second batch of national first-class undergraduate courses.

"Have a happy life and do scientific research happily." Whether in life or in scientific research, Chen Zhongxiu's sunny attitude subtly influences her students. "If you encounter difficulties, we will solve them together. The sofa in my office is always waiting for you." She always said this to her students gently.

Today, Chen Zhongxiu's "sweet" career continues. As the head of the Molecular Food Science Laboratory of Shangda University, she leads students to conduct multidisciplinary research in the fields of food, chemistry and materials, and has made outstanding contributions to promoting the development of food perception science and the food industry.

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