Therefore, the extraction conditions (temperature, time, and pH) should be carefully controlled to achieve the desired pectin quality. However, some degradation reaction such as de-esterification and depolymerization will occur. This treatment allows the extraction and the solubilization of the pectin. Usually, the extraction of the pectin is achieved by acid treatment at high temperature, using hydrochloric acid, nitric acid or sulfuric acid. Viscosity is affected by molecular weight, degree of methylation, concentration and temperature. Viscous-flow properties are very important during the production and applications of pectin and the higher the molecular weight is, the higher is its viscosity, the better is its grade. Pectins with DE less than 50% are considered to be LM pectins. Commercial pectin preparations are divided into low-methoxyl (LM) and high-methoxyl (HM) pectins according to the degree of esterification (DE). The primary structural feature of this polysaccharides is a linear chain of poly-α-(1→4)-D-galacturonic acid with varying degrees of methyl esterification (DE). Citrus peels are reported to be good source of pectin which is widely used in the food industry for it gel-forming properties which depends on its degrees of methyl esterification DE and molecular weight. Pectin has also several physiological and biological functions, such as stimulation of phagocytes and macrophages, spleen cells proliferation and reduction of serum cholesterol. Many works reported that citrus pectin have inhibitory effects on fibroblast growth factor signal transduction, suppression of LPS-induced inflammatory responses and preventive effect on cancer growth and metastasis. These substances are the major component of the middle lamella and of the primary cell walls of fruit tissues. Pectin substances are present in practically all fruits and vegetables. The molecular weight varied from 1.538 x10 05 to 2.47x10 05 g/mol for grapefruit pectin and from 1.639 x10 05 to 2.471 x10 05 g/mol for orange pectin. This later was determined using four equations Huggins equation, kramer, Schulz-Blaschke and Martin equation. The molecular weight was calculated using Mark-Houwink-Sakurada equation which describes its relationship with intrinsic viscosity. Moreover, both peels allow the obtainment of a high methoxyl pectin with DE >50%. Results showed that the pectin yield was higher using the residual peels.
The aim of this study is the evaluation the effect of extraction conditions on pectin yield, degree of esterification “DE” and on molecular weight “Mw”. Organic acid (citric acid) and mineral acid (sulfuric acid) were used in the pectin extraction. The peels are used under two states: fresh and residual (after essential oil extraction). Orange ( Citrus sinensis) and grapefruit ( Citrus paradise) peels were used as a source of pectin, which was extracted under different conditions.
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