Characteristics of the fruit

FormaTION

The formation of the apex and shoulders. At the apex of the chestnut, remnants of the stigma can be found in a browned state, which may affect the attractiveness of the product. The shape of the apex varies greatly among different chestnut varieties. All forms occur, ranging from sharply pointed apices to broadly, saddle-shaped shoulders. This characteristic can be particularly useful for distinguishing varieties (e.g., Nagymarosi 37 – pointed, Nagymarosi 38 – shouldered).

The hilum

At the base of the chestnut there is a lighter brown, dull-surfaced navel area, the so-called “hilum” (or “scar”), whose pattern, shape, and size can be used as a varietal characteristic. A large hilum is especially characteristic of Castanea crenata and its derived cultivars (e.g., Iharosberényi 57 has a large hilum).

SHELL

The shell may be completely smooth or ribbed from the base toward the apex, and in rare cases wavy (among Italian marroni cultivars, several have ribbed shells). The shell color varies by variety, ranging from yellowish-brown to dark brown. Ribbed types often show reddish streaks. Lighter-colored shell varieties tend to have a better taste and higher market appeal, while darker-colored ones have a stronger, more rustic flavor; confectionery products made from them also have a darker color.

SIZE

Of the fruit’s length, width, and thickness, width is the most important, as commercial standards classify and grade the product based on this dimension. According to the Hungarian standard, chestnuts larger than 30 mm are classified as First Class. In international evaluation, sizes above 32 mm are accepted as “marroni” quality. Some cultivars are characterized by large fruit size, which is influenced by the conditions of each growing season and the production site. A characteristic feature of the varieties is the proportion of large “marroni” fruits in the annual yield. This is determined by the number of nuts per burr. Cultivars producing “marroni” quality typically develop only 1–3 nuts per burr. In Italian cultivation practice, cultivars are also described in percentage terms, indicating the share of their yield that qualifies as “marroni” quality.

BURR

The branching and length of the spines on the burr are varietal characteristics. Chestnut varieties with sparse spines may be more susceptible to infestation by the chestnut weevil. The shell thickness ranges from 0.3 to 0.9 mm depending on the variety, and this trait affects the proportion of edible kernel obtained from the fruit. Higher-quality chestnut varieties tend to have thinner shells (for example, the Nagymarosi varieties).

Pellicle

The degree of penetration of the inner skin (pellicle) is one of the most important quality traits affecting market value and is characteristic of each variety. Varieties that produce a higher proportion of double nuts are disadvantageous in this regard, because each nut has its own complete inner skin, which makes peeling very difficult. Even in single-nut fruits, it is desirable that the pellicle does not penetrate deeper than 2–3 mm.