Pectin, a complex polysaccharide found in plant cell walls, plays a crucial role in various industries due to its functional properties. The diluted alkali-soluble pectin (DASP) fractions that result from the stepwise extraction of apples and carrots were studied to evaluate their structural and rheological properties. Homogalacturonan and rhamnogalacturonan I, in different proportions, were the main pectin domains that composed DASP from both materials. Atomic force microscopy revealed that the molecules of apple DASP were longer and more branched. A persistence length greater than 40 nm indicated that the pectin molecules deposited on mica behaved as stiff molecules. The weight-averaged molar mass was similar for both samples. Intrinsic viscosity values of 194.91 mL·g-1 and 186.79 mL·g-1 were obtained for apple and carrot DASP, respectively. Rheological measurements showed greater structural strength for apple-extracted pectin, whereas carrot pectin was characterized by a higher linear viscoelasticity limit. This comparison showed that the pectin fractions extracted by diluted alkali are structurally different and have different rheological properties depending on their botanical origin. The acquired insights can enhance the customized use of pectin residue and support further investigations in industries relying on pectin applications.

Phenylketonuria (PKU) is an autosomal recessive inherited disorder affecting one in every 10,000 to 15,000 newborn children in the US each year. PKU patients\' metabolism of an essential amino acid, phenylalanine (PHE), is impaired, resulting in concentrations of PHE in the circulating blood and brain that are potentially toxic. Individuals with PKU restrict dietary intakes of PHE by consuming medical foods formulated with low PHE concentrations. In this study, an alkaline serine protease (ASP) expressed in Bacillus licheniformis strain 2709, which is composed of >90% protein with a concentration of <0.25% PHE, was heat deactivated (becoming deactivated ASP (DASP)) and evaluated for safe use as an ingredient in foods, including medical foods. DASP was non-mutagenic with and without metabolic activation up to 5000 μg DASP/plate. 14-Day dietary studies supported a Maximum Tolerated Dose (MTD) of 115000 ppm DASP. In a 90-day dietary toxicity study, CRL SD CD® rats were administered 0, 28750, 57500, 115500 ppm DASP in the diet. No DASP-related adverse effects were observed at the high dose. As such, a No Observable Adverse Effect Level (NOAEL) of 115,500 ppm DASP or 6224.1 mg DASP/kg bw/day (males) and 7500.9 mg DASP/kg bw/day (females) was established.