Thermal processing modulates starch and non-starch macromolecules digestibility in chestnut: Structural...

Area of Science:

• Food Science and Technology
• Nutritional Science
• Agricultural Processing

Background:

• Chestnut processing predominantly uses thermal methods, creating a nutritional paradox due to high glycemic index (GI).
• High GI foods conflict with low-GI dietary recommendations, necessitating research into processing impacts on chestnut GI.
• Understanding the mechanisms behind GI variations in cooked chestnuts is crucial for product development.

Purpose of the Study:

• To systematically evaluate the expected glycemic index (eGI) of chestnuts processed using four conventional cooking methods.
• To elucidate the underlying mechanisms responsible for the observed differences in eGI among various cooking methods.
• To provide insights for optimizing chestnut processing to achieve lower GI values.

Main Methods:

• Evaluation of four conventional cooking methods: boiling, steaming, baking, and frying.
• Analysis of chestnut structure, texture profile analysis (TPA), and 1H low-field nuclear magnetic resonance (LF-NMR).
• Correlation of physical and structural properties with determined eGI values.

Main Results:

• Moist-heat processed chestnuts (boiled: 81.40, steamed: 86.67) exhibited higher eGI than dry-heat processed chestnuts (baked: 69.47, fried: 69.85).
• Baked and fried chestnuts showed superior textural integrity and restricted starch accessibility.
• Water phase transitions, indicated by changes in immobilized (A21) and free (A22) water content, were identified as key determinants of chestnut GI.

Conclusions:

• Water phase transitions during cooking significantly influence the glycemic index of chestnuts.
• Dry-heat processing methods preserve textural integrity and reduce starch accessibility, leading to lower eGI.
• Targeted processing optimization based on water phase transitions can facilitate the development of low-GI chestnut products.