Effects of extraction methods on the rheological properties of polysaccharides from onion (Allium cepa L.).

In this work we described the rheological properties of polysaccharides (HBSS, CHSS, DASS, CASS) sequentially extracted from onion (Allium cepa L.). Four onion polysaccharides (ACLPs) solutions resulted into significant differences on their rheological properties. ACLPs solutions showed non-Newtonian shear-thinning behavior over the range of 0.5-2.5%. At concentration of 1%, the apparent viscosity of CHSS was observed to be the highest. The apparent viscosity of ACLPs solutions decreased with the acidic pH (4.0) or alkaline pH (10.0) which was further declined at higher temperature (90 °C). After the addition of various salts, ACLPs had apparent differences on apparent viscosity. The G' (storage modulus) and G″ (loss modulus) of ACLP solutions were increased with increasing oscillation frequency. Moreover, the crossover value of oscillation frequency gradually decreased with increasing concentration of ACLPs. Our results exhibited that among the ACLPs, CHSS can be used as supplements in the food industry as thickening agent, gelling agent and stabilizer.

Antioxidant and antibacterial evaluation of polysaccharides sequentially extracted from onion (Allium cepa L.).

We investigated the antioxidant and antimicrobial potential of sequentially extracted onion polysaccharide fractions namely HBSS, CHSS, DASS and CASS. The different antioxidant assays indicated that ACLPs exhibited potentially appreciable antioxidant activity in a dose-dependent manner. Among all the fractions, CHSS rendered the highest antioxidant action towards ABTS radical cations (97.52%), Fe2+ chelating (98.94%) and superoxide anion radical scavenging (76.27%). Whereas, HBSS possessed the highest potential for DPPH radicals (93.68%), hydroxyl radicals (65.12%) as well as for reducing power (0.559). CASS exhibited the highest lipid peroxidation inhibition (86.43%), while, DASS showed the best ß-carotene bleaching inhibition (92.26%). Furthermore, regardless of the bacterial strain, DASS represented the strongest antibacterial activity on the basis of largest inhibition zone, the lowest minimal inhibitory concentration and maximum inhibition of bacterial growth in liquid medium. Overall results indicated that ACLPs hold a promise as potential natural antioxidant additives and antimicrobial agents for formulating the functional foods with potential applications in the medical and food industries.

Thermal and Antioxidant Properties of Polysaccharides Sequentially Extracted from Mulberry Leaves (Morus alba L.).

Polysaccharides from natural plant products are gaining considerable attention due to their multi-faceted health effects, as well their functional applications in food production. We reported the sequential extraction of mulberry leaf polysaccharides (MLPs) with hot buffer (HBSS), chelating agent (CHSS), dilute alkali (DASS) and concentrated alkali (CASS), in order to obtain polysaccharide fractions. Monosaccharide analysis proved that galactose (27.07%) and arabinose (25.99%) were the major sugars in HBSS, whereas arabinose (30.55%) was the major sugar in CHSS, and glucose was the major sugar in DASS (24.96%) and CASS (27.51%). The molecular weights of the polysaccharide fractions were 7.812 × 10³ (HBSS), 3.279 × 10³ (CHSS), 6.912 × 10³ (DASS), and 1.408 × 10³ kDa (CASS). HBSS and CASS showed the largest peak temperature and the highest endothermic enthalpy, respectively. Different antioxidant assays showed that the MLPs possessed appreciable antioxidant activities in a dose-dependent manner. At 5 mg/mL, HBSS and DASS possessed the largest 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH) radical scavenging activity (96.82%). HBSS exhibited the highest reducing power, and DASS rendered the strongest ABTS radical scavenging activity (99.69%). CHSS performed the best hydroxyl radical scavenging activity (64.22%) and Fe2+-chelating ability (96.36%). Our results suggested that MLPs could be a promising source of natural antioxidants for use in the food, pharmaceutical, and cosmetic industries.

Insights into physicochemical and functional properties of polysaccharides sequentially extracted from onion (Allium cepa L.).

Onion polysaccharides (ACLP) were sequentially extracted with four different solvents (hot buffer, chelating agent, dilute alkaline and concentrated alkaline) and obtained four fractions, named as HBSS, CHSS, DASS and CASS, respectively. The present studies characterized the ACLP concerning its physicochemical and functional properties. Monosaccharides analysis revealed that mannose (81.68%) was the dominant sugar in HBSS and galactose (67.59%) was the most in CASS. Similarly, CHSS and DASS possessed mannose and galactose as major sugar, which were 25.80% and 31.37%, 20.33% and 33.96%, respectively. The obtained molecular weight of ACLPs were 7.702×103 (HBSS), 4.690×103 (CHSS), 4.943×103 (DASS) and 1.390×103kDa (CASS). CASS resulted in the strongest solubility, fat-binding capacity, foam capacity and foam stability whereas, HBSS showed the highest thermal stability. DASS showed the best hygroscopicity and the best moisture retention was obtained by CHSS. Subsequently, the emulsifying activity and emulsifying stability were the highest for HBSS and the longest for of CASS, respectively. The rheological properties of CHSS exhibited the largest viscosity. Our results indicated that all factions could be considered as functional polysaccharides according to their respective characteristics, which have vast potential in food production.