Low methoxyl pectins from lime peel

To prepare low methoxyl pectin (LMP) from lime peel, acid deesterification at pH 0.5 for 9 hr at 60°C and for 5 hr at 70°C; sodium hydroxide deesterification at 5°C and at pH 10.5 with continuous addition of alkali for 1–2 hr; and ammonia deesterification at 25°C and at pH 10.5 for 2–3 hr or at pH 11.7 for 1–2 hr were suitable. Such LMP had ∼4.5% methoxyl groups and a molecular weight of 40 000–70 000. Precipitation at pH 0.5 to 1.5 after saponification resulted in LMP having good gelling characteristics; precipitation at pH 4.5, as recommended hitherto, impaired the gelling property. Saponification titre values of the pectin being deesterified and a rapid gel test, based on the sensitivity of the pectin to the calcium, are described to follow the degree of deesterification. The gel test is also indicative of the gelling property of the pectin.