Fresh chestnut manufacturers explain why candied chestnuts stick to their skins—likely due to these seven reasons.

Fresh chestnut manufacturers explain why candied chestnuts stick to their skins—likely due to these seven reasons.

When eating candied chestnuts, we often encounter a common issue: after peeling the shell, it’s difficult to remove the inner skin and the chestnut kernel. This phenomenon is referred to as “hupi” on JD.com. The term for hupi varies across regions, with different words used—such as “hu,” “lu,” “hu,” or “nian”—to describe it. So why does this sticky skin occur?

First, it is related to the chestnut’s place of origin.

Overall, northern chestnuts are easier to peel than their southern counterparts, while southern chestnuts—especially the “vegetable chestnuts”—tend to have a sticky inner skin. In the north, particularly in the Jingdong region, chestnuts are very easy to shell. When peeled, the soft inner skin adheres to the shell, leaving behind smooth, polished chestnut kernels.

Second, it is related to the chestnut variety.

Even within the same region in northern China, not all chestnuts fail to stick to their shells, and very few varieties naturally adhere to their husks.

Third, it is related to the maturity of the chestnuts.

When harvested while still immature, the flesh is very tender; chestnuts candied in this manner tend to be smaller, softer, shriveled, and less sweet. The inner skin adheres tightly to the nut, resulting in a sticky peel. In contrast, chestnuts that fall naturally to the ground or are picked at full maturity exhibit far less stickiness.

Fourth, it is related to the size of the chestnuts.

At the same location and for the same chestnut variety, standard-sized nuts are less likely to exhibit skin adhesion, whereas medium- and small-sized nuts are more prone to this issue.

Fifth, it is related to the moisture content of chestnuts.

In general, chestnuts with high moisture content are prone to developing a sticky skin, whereas low‑moisture chestnuts exhibit significantly less of this issue. Freshly harvested chestnuts, compared with candied ones, tend to show less stickiness due to the drying effect of ambient air over time or to moisture loss during the candying process.

Sixth, it is related to the sugar-coating method.

During the sugar-coating process, drum-type pans are more prone to sticking than vertical pans; low‑concentration sugar can cause chestnuts to become sticky, and the sugar is less likely to adhere to the shells before the moisture has evaporated.

Seventh, it is related to the temperature at the time of delamination.

In some regions, chestnuts can be easily peeled when freshly roasted, with the inner skin coming off readily; however, once cooled, they tend to stick together.

During the actual sugar-coating process, vendors should analyze the causes of skin adhesion and, depending on the specific circumstances, take corrective or compensatory measures to minimize this issue and ensure smooth sales at the store.