Unravelling the structure of serum pectin originating from thermally and mechanically processed carrot-based suspensions
2018
Santiago, Jihan Santanina J. | Kyomugasho, Clare | Maheshwari, Shashikant | Jamsazzadeh Kermani, Zahra | Van de Walle, Davy | Van Loey, Ann M. | Dewettinck, Koen | Hendrickx, Marc E.
The molecular structure of pectin, a cell wall polysaccharide in fruits and vegetables, greatly determines its functionality. Owing to its solubility characteristics, pectin is naturally present in the particle and liquid (serum) phase of plant-based dispersions (e.g. purées) that can influence product functionality. The objective of the present study was to investigate the structure of serum pectin obtained from carrot purées, differently processed by a combination of mechanical tissue disintegration (blending and high pressure homogenization) and heat treatments (high and low temperature). Serum phases, isolated from the purées, were lyophilized and served as the starting material for isolation of the pectic polysaccharides as alcohol insoluble residues. Physico-chemical characterization revealed that different processing combinations of carrot purées can generate serum pectins with specific structural properties. Differences in the molecular weight of carrot serum pectic polysaccharides were observed depending on the sequence of heat and mechanical treatments. Subsequent partitioning of carrot serum pectic polysaccharides into rhamnogalacturonan I (RGI) and homogalacturonan (HG)-rich fractions using hot alkaline and mild acid conditions, respectively, revealed the composition and molecular characteristics of the serum pectin subdomains. The RGI-rich fractions were mainly characterized by high concentrations of neutral sugars (arabinose, galactose, and rhamnose) and exhibited branch-like structures in solution under cryo-SEM. HG-rich fractions, on the other hand, were characterized by highly linear galacturonic acid-rich pectin and exhibited strand-like structures under cryo-SEM. Knowledge of these structural changes can be useful in exploring the functionalities of carrot serum pectic polysaccharides.
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