Effect of sweet potato pectin on multilayer emulsion stability

Sweet potato (Ipomoea batatas) is a good alternative source of pectin which has the potential for stabilization of emulsion. This study aimed to optimize the extraction of pectin from sweet potato peels, and to investigate the effect of sweet potato pectin on multilayer emulsion stability. Response surface methodology was employed to optimize pectin extraction from sweet potato peels using citric acid. The factors included in the experimental design were temperature (60 - 100 °C), time (40 – 100 min) and pH (1 – 2). The yield of pectin was calculated on the basis of the sweet potato cell wall material. The degree of esterification (DE) of the pectin was analyzed using Fourier transform infrared spectroscopy. The extracted sweet potato pectin was incorporated in oil-in-water emulsion after homogenization using microfluidizer producing whey protein isolate-pectin multilayer emulsion. The effects of environmental conditions on the multilayer emulsion were studied by subjecting the emulsions to various conditions namely: 0 – 1.2 wt % pectin, pH 3 - 7 and 0 – 400 mM salt solution. The emulsion stability was characterized by determination of particle size, zeta-potential and creaming index (CI). The optimum conditions to extract the maximum yield of pectin of 65.8% were at extraction temperature 76°C, time 64 min and pH 1.2. The pectin was categorized as highmethoxyl pectin with DE of 58.5%. Decreasing of zeta-potential (+2.38 to –14.8 mV) showed the adsorption of pectin layer around the emulsion droplets. CI was the lowest (3.64%) at the highest pectin concentration (1.2 wt%) which showed great stability against creaming. Multilayer emulsion showed better stability at high pectin concentration and wide range of salt concentration compared to primary emulsion. Pectin addition largely improved the stability of emulsion especially at pH 4 and 5. Multilayer emulsion prepared using sweet potato pectin can be utilized to produce food emulsion with good stability against environmental pressure (pH and salt content) and can be further applied for controlled release of active ingredients in functional food and beverages

Extraction and characterisation of pectin from dragon fruit (hylocereus polyrhizus) peels

Pectins are complex carbohydrate molecules that are used in numerous food applications as a gelling agent, thickener, stabiliser, and emulsifier. Dragon fruit (Hylocereus polyrhizus) is one of the tropical fruits that belong to the cactus family, Cactaceae. Since the peels of dragon fruit are often discarded as waste, it would be an advantage to convert it into a value-added product such as pectin. The objective of this study was to investigate the extraction of pectin from dragon fruit peels under different extraction time using hot water extraction method. The dragon fruit peels were extracted using distilled water at 80 °C with different extraction time of 20, 40, 60 and 80 min. The extracted pectin was characterised by its yield, moisture and ash content, degree of esterification and antioxidant activity. Determination of moisture and ash content was conducted using AOAC standard method. The determination of the degree of esterification of pectin was performed using Fourier Transform Infrared Spectroscopy (FTIR). DPPH assay was used to determine the antioxidant activity of the pectin extract. Based on the result, the yield of pectin decreases (20.34 to 16.20 %) with the increase of extraction time, moisture contents were between 4 to 6 % while ash contents were between 7 to 10 %. Pectin from dragon fruit peels was determined as low methoxyl pectin and has high percentage of antioxidant activity with low value of inhibition concentration (IC50) (0.0063 to 0.0080 mg/mL). 60 min extraction sample exhibits the highest antioxidant activity (81.91 % at 40 μg/mL), followed by 80 min extraction (81.68 % at 40 μg/mL), 40 min extraction (81.38 % at 40 μg/mL) and 20 min extraction (81.31 % at 40 μg/mL)