Subcritical water-assisted fish gelatin hydrolysis for astaxanthin-loaded fish oil emulsion stability.

Though gelatin emulsifying properties have been intensively studied, how low-molecular-weight (LMW) fish gelatin affects astaxanthin (AST)-loaded fish oil emulsion stability remains elusive. In this study, subcritical water hydrolysis (SWH)-modified LMW fish gelatin (SWHG) was produced from 110 °C to 180 °C and used to enhance the AST steadiness in oil/water emulsions in the presence of an emulsifier, lecithin. In the prepared emulsions, the surface charge increased while droplet size decreased with the decrease in gelatin MW due to the reduced thickness of the adsorbed gelatin membrane. LMW gelatin and lecithin could form a firm-absorbed layer on the droplet surface by electrostatic interaction between amide groups of gelatin molecules and phosphate groups of lecithin, thus stabilizing the emulsions. SWHG improved the creaming stability of the emulsions and hindered the oxygen- and light-induced AST degradation for 11 months compared to high MW gelatin. Whereas, the control emulsion showed noticeable phase separation after two weeks of storage. These findings prove the advantage of the SWH approach and propose the use of SWHG in oil-in-water emulsions for AST stabilization.

In vitro characterization of bioactive compounds extracted from sea urchin (Stomopneustes variolaris) using green and conventional techniques.

This study investigated the in vitro bioactivities of extracts obtained from viscera, spines, shells, and gonads of Stomopneustes variolaris using subcritical water extraction (SWE) at 110 °C, 150 °C, 190 °C, and 230 °C and Soxhlet extraction. The highest amounts of phenolics (22.68 ± 0.05 mg GAE/g), flavonoids (27.11 ± 0.10 mg RE/g), and proteins (40.25 ± 0.84 mg BSA/g) were recorded from gonads at 230 °C, whereas maximum sugar content (23.38 ± 1.30 mg glucose/g) was in viscera at 150 °C. Gonads at 230 °C exhibited the highest DPPH activity (78.68 ± 0.18%), whereas viscera at 150 °C exhibited the highest ABTS+ (98.92 ± 1.27%) and protein denaturation inhibition activity (37.13 ± 9.94%). Viscera at 110 °C claimed the highest amylase inhibition (42.46 ± 0.83%), and spines at 150 °C had the highest anticancer activity (IC50 = 767.47 µg/mL). SWE achieved superior results in bioactive compound recovery and detected higher levels of bioactivities (p < 0.05). Results suggest processing sea urchin extracts via SWE has potential application to the food and pharmaceutical industries.