Step 1: Understanding the Concept:
Traditional fermented cider production requires specialized apple cultivars possessing specific chemical compositions.
Step 2: Detailed Explanation:
Cider apple varieties are categorized based on their tannin (polyphenol) and malic acid concentrations into bittersweet, bittersharp, sharp, and sweet types.
High tannin content ($> 0.2\text{--}0.4\%$) is essential in cider making to impart body, astringency, bitterness, color development, and natural microbial/antioxidant stability to the beverage.
Step 3: Final Answer:
Hence, apples used for cider making should have a high content of tannin.