## 1 Introduction  
Muscat Hamburg grapes (_Vitis vinifera_ L. cv. Muscat Hamburg) have been grown in Tianjin for more than one hundred years due to the advantageous properties of this type of grape including: wide adaptability, strong disease resistance, high yield, easy management and strong flavor. Muscat Hamburg grapes are commonly consumed as both table grapes and grapes for winemaking, and the grape flavor characteristics make them very popular in the region. Muscat Hamburg wine (a dry white wine) was initially produced by the Tianjin Dynasty Winery in the 1980s. This type of wine was highly awarded in worldwide wine competitions. Since then, the production of Muscat Hamburg wine has dramatically increased, and currently, approximately 5000 tons is produced every year (95% of which is white wine, 2% is red wine and 3% is sparkling wine).  
There are two main and popular techniques used in making fresh Muscat Hamburg wines in China including classical white-winemaking and red-winemaking techniques. However, these two types of Muscat Hamburg wine cannot meet the demand of consumers for the high-quality wine. The reason for the lack of consumer appreciation of these wines as high-quality wines appears to be due to the fact that the content of phenolic substances in white wine is lower, and the wine has a poorer mouthfeel as well as a lower beneficial compounds (polyphenols) due to the reduced involvement of the grape skin in the white-winemaking process [1,2]. On the other hand, the red-winemaking process, which includes daily (1-3 times) pumping over in air, results in a lower content of aroma compounds. Indeed, the effect of the phenolic compounds in wine quality has been studied extensively in recent years in many different types of wine regions [3,4]. Therefore, the demand from the market has driven research into elucidating the factors that affect the quality of wines and developing new winemaking techniques and new types of wine. Wine quality is mainly assessed by three factors, the color, aroma and taste of the wine. Different fermentation technologies can be used to improve these quality characteristics to suit consumer preferences.  
Carbonic maceration is widely used to produce wine with novel characteristics. The technique has been used in France for more than 80 years [5], and it exploits a process that takes place naturally inside grape berries stored intact in an anaerobic environment. After carbonic maceration, the final product has a richer flavor and superior aromatic qualities [6] with a higher content of phenolic compounds [5], which are desirable to consumers. Carbonic maceration techniques have been used with many grape varieties, including Gamay, Tempranillo, Monastrell, Airen, Syrah, and Tinta Miuda grapes [5, 6, 7, 8, 9, 10]. However, to the best of our knowledge, there are no studies applying this technique to Muscat Hamburg grapes.  
Therefore, the main objective of this study is to determine the influence of carbonic maceration compared with classical red and white wine fermentation techniques on the color, aroma and sensory properties of Muscat Hamburg wine compared with classical red and white wine fermentation techniques. Results from this work will improve our comprehension in carbonic maceration wine fermentation technique used in Muscat Hamburg grapes to enhance the quality of Muscat Hamburg wine.