When ingested, pectin can lower serum cholesterol levels in humans. Pectin is degraded by fecal bacteria in the colon. We examined the release of methanol (MeOH) by this degradation. A 0.2% glucose (2 g/L) mixture was used as the control medium. A pure culture of pectinolytic Erwinia carotovora was the control bacterium. The chief substrates were, in set 1, 0.2% pectin (2 g/L) and, in set 2, 0.1% glucose (1 g/L) and 0.1% pectin (1 g/L). Cultures of fecal bacteria and E carotovora grew for 72 h in each of the solutions. By 72 h the fecal flora culture in set 1 cleaved 30% of the possible methoxyl groups on pectin. The fecal flora in set 2 cleaved 90.7% of all possible methoxyl groups. Balance studies suggest that all of the free MeOH comes from methoxyl groups on pectin. This study demonstrates that fecal bacteria are capable of degrading pectin to release MeOH.

Summary: Dietary intake of cholesterol has been linked to coronary heart disease. The effect of grapefruit pectin (Cirrus puradisi) on plasma cholesterol, triglycerides, very low-density lipoprotein cholesterol, low-density lipoprotein cholesterol, highdensity lipoprotein cholesterol, and the low-density lipoprotein: high-density lipoprotein cholesterol ratio was studied. The study design was a 16-week double-blind, crossover (placebo or pectin) using 27 human volunteers screened to be at medium to high risk for coronary heart disease due to hypercholesterolemia. The study did not interfere with the subjects' current diet or lifestyle. Grapefruit pectin supplementation decreased plasma cholesterol 7.6%, low-density lipoprotein cholesterol 10.8%, and the low-density lipoprotein: high-density lipoprotein cholesterol ratio 9.8%. The other plasma lipid fractions studied showed no significant differences. We conclude that a grapefruit pectin-supplemented diet, without change in lifestyle, can significantly reduce plasma cholesterol.

There is substantial evidence that natural vitamin B-6 exists largely in a bound form. It has been shown that the principal modes of binding represents an interaction of pyridoxal and/or pyridoxal phosphate with protein moieties. The nature and extent of binding of different forms of the vitamin in orange juice was investigated. Studies employing ultracentrifugation, ultrafiltration and, membrane dialysis of this food product suggested binding to a molecule of less than 3,500 daltons molecular weight. Binding was resistant to protease treatment although susceptible to heat-acid hydrolysis. Separation of pyridoxal, pyridoxine, and pyridoxamine species of the vitamin by ion exchange chromatography was followed by fluorometric analysis with and without preparative hydrolysis. Extensive and equal binding of both pyridoxal and pyridoxine was observed by this method. Thus, the binder(s) of vitamin B-6 in orange juice is a small dialyzable molecule which is heat stable, binds both pyridoxal and pyridoxine and is non-protein in nature.

The influence of dietary pectin on iron absorption and retention was studied in rats. Basal diet with low and normal iron levels were fed with and without addition of 2% citrus pectin. After 40 days rats were fasted for 24 hours and were given 59Fe in dilute HCl with or without 2% pectin by gavage. Whole-body counting techniques were employed to monitor 59Fe absorption and turnover. Rats maintained on low iron diet absorbed and retained a much higher proportion of 59Fe than rats maintained on normal level of iron. Dietary pectin at the level fed in this study had no influence on iron uptake and/or turnover in rats.