Step 1: Understanding the Concept:
Jelly preparation relies on the formation of a stable pectin-sugar-acid gel network.
For a fruit to be suitable for making jelly, it must naturally contain a sufficient concentration of both pectin (to form the structural matrix) and organic acids (to lower the pH and facilitate pectin precipitation).
Step 2: Detailed Explanation:
Assertion A Analysis: Guava (Psidium guajava) is widely recognized as one of the best and most ideal fruits for commercial and home-scale jelly preparation.
The resulting jelly is clear, attractive, and holds its shape perfectly. Thus, Assertion A is correct.
Reason R Analysis: The fruit pulp of guava (especially when slightly under-ripe or firm-ripe) contains high levels of high-methoxyl pectin and organic acids (mainly citric and malic acid).
The acid lowers the pH to the optimum range ($3.0 - 3.4$), which neutralizes negative charges on pectin molecules, allowing them to cross-link and form a firm gel network with sucrose.
Because guava naturally contains these optimal amounts of both pectin and acid, no external addition of pectin is required to set the jelly.
Thus, Reason R is correct, and it directly explains why guava is an ideal fruit for jelly making.
Step 3: Final Answer:
Both statements are correct, and R provides the scientific rationale for A, making (A) the correct choice.