Process Development and Characteristics of Biocalcium from Skipjack Tuna (Katsuwonus pelamis) Eyeball Scleral Cartilage

Abstract

Scleral cartilage biocalcium (SCBC) powder from skipjack tuna (Katsuwonus pelamis) eyeball scleral cartilage (STESC) was produced using hexane and isopropanol (1:1) for defatting, followed by protein removal using alcalase at different concentrations (1.5–4.5%) for various times (0–180 min). Calcined scleral cartilage (CSC) was also prepared and characterized. The lowest fat remaining in STESC was attained after 6 cycles of defatting (P < 0.05). The use of 1.5% alcalase for 90 min resulted in the highest soluble protein removal, while showed the lowest loss in hydroxyproline. Higher value of calcium (39.90%), phosphorus (18.97%) and L* (87.97) were detected in the CSC powder, compared to SCBC powder (23.28%, 10.99% and 81.77, respectively) (P < 0.05). However, a*, b*, and ∆E* of CSC powder were lower than SCBC counterpart. The mean particle sizes of both powders had a negligible difference (P > 0.05). XRD-diffractogram of both powders confirmed the presence of hydroxyapatite. CSC showed the loss of water, amide I, II, III, and other organic functional group peaks in Fourier transform infrared spectra. Also, smaller number and abundance of volatile compounds were found in CSC powder. STESC showed a higher calcium solubility in gastrointestinal tract than CSC (P < 0.05). Therefore, scleral cartilage of tuna eyeball could be used as an alternative source for producing biocalcium.