Abstract
Pectin is a kind of natural and complex carbohydrates which is extensively used in food, chemical, cosmetic, and pharmaceutical industries. Fresh sunflower (Helianthus annuus L.) heads were utilized as a novel source of pectin extracted by ammonium oxalate. The conditions of the extraction process were optimized implementing the response surface methodology. Under optimal extraction parameters (extraction time 1.34 h, liquid–solid ratio 15:1 mL/g, ammonium oxalate concentration 0.76% (w/v)), the maximum experimental yield was 7.36%. The effect of spray-drying and freeze-drying on the physiochemical properties, structural characteristics, and antioxidant activities was investigated by FT-IR spectroscopy, high performance size exclusion chromatography, and X-ray diffraction. The results showed freeze-drying lead to decrease in galacturonic acid (GalA) content (76.2%), molecular weight (Mw 316 kDa), and crystallinity. The antioxidant activities of pectin were investigated utilizing the in-vitro DPPH and ABTS radical-scavenging systems. This study provided a novel and efficient extraction method of sunflower pectin, and confirmed that different drying processes had an effect on the structure and properties of pectin.
Highlights
Pectin is a kind of natural and complex carbohydrates which is extensively used in food, chemical, cosmetic, and pharmaceutical industries
On the other hand, during the drying process of fresh sunflower heads, polysaccharides and proteins undergo a complex browning driven by oxygen and higher temperature to produce a substance called melanin pigment, whose presence influences the sensory quality of pectin[12]
To determine the effect of extraction time on pectin yield, the extraction was performed for 0.5–3 h, with the liquid–solid ratio of 15:1 mL/g, and the ammonium oxalate concentration at 0.4% (w/v) at 85 °C (Fig. 1a)
Summary
Pectin is a kind of natural and complex carbohydrates which is extensively used in food, chemical, cosmetic, and pharmaceutical industries. This study provided a novel and efficient extraction method of sunflower pectin, and confirmed that different drying processes had an effect on the structure and properties of pectin. Conventional methods of extracting sunflower pectin generally rely on dry sunflower h eads[4,6,7] and require harsh acid and high liquid–solid ratio (25:1–60:1)[6,8] Such a way could certainly lead to acidic degradation of pectin, the large amount waste of ethanol and serious environment pollution due to the acidic solid waste[9]. Fresh sunflower heads were extracted by subcritical water to obtain LMP with ideal color by subcritical water extraction[14], but the obtained pectin had low Mw. Muthusamy et al.[15] based on response surface method of genetic algorithm and artificial neural network model to extracted dry sunflower heads, and the pectin yield was 29.5%. There is no study on the effect of drying methods on physiochemical properties of pectin from pectin from fresh sunflower heads (SFHP)
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