Value-added products from squid (loligo formosana) ovary and pen: characterization and application in food systems

Abstract

Characteristics and functional properties of squid (Loligo formosana) ovary (SO) were studied. Protein (18.64±0.51%) and carbohydrate (7.44+0.2%) were found as the major constituents. Albumin (79.02+0.79%) was the dominant protein of SO, followed by glutelin-1 (8.31±0.62%) and globulin (6.68+0.08%). Nevertheless, prolamin and glutelin-2 constituted approximately 1% of total proteins. SO was rich in non-essential amino acids (52.26%) and polyunsaturated fatty acid (PUFA, 43.76±0.84%). SO lipids had high amount of docosahexaenoic acid (C22:6) (28.59%). When SO powder (SOP) was prepared and tested, foaming capacity (FC) and stability (FS) of foam from SOP were increased with increasing concentration up to 8% (p < 0.05). When partial hydrolysis of SO using 1% Alcalase or 1% papain at different hydrolysis times was conducted to improve the foaming properties, SO hydrolysate (SOH) prepared by Alcalase for 30 min (SOH-A1-30) showed the highest FC (236%). The SOH-Al-30 powder showed high solubility and surface hydrophobicity with slightly larger particle size than that of SOP. SOH-Al-30 preheated at 60 °C showed the highest FC (300%). Therefore, foaming properties of SOP could be enhanced with partial hydrolysis and appropriate pre-treatment. Ultrasonication at amplitude 70% for 30 min was the optimized condition using central composite design (CCD) in combination with response surface methodology (RSM). Surface hydrophobicity of ultrasonicated SOP (USOP) was increased by 28%. Solubility, total sulfhydryl group and mean particle size of SOP was decreased after ultrasonication. FC of USOP was increased by 83.3%, compared to the control and the lowest liquid drainage was attained. USOP foam showed uniformly distributed smaller sized bubbles with a thick lamella. Thus, ultrasonication at appropriate condition enhanced foaming properties SOP. The addition of USOP to replace the egg white powder (EWP) at different substitution levels (0-100%) in cake was studied. Highest elastic modulus (G') and average bubble size of batter was obtained with the addition of 100% USOP. Cake added with 100% USOP showed higher volume and lower baking loss, when compared to the control cake (100% EWP). The lowest values of hardness, gumminess and chewiness were noticeable for cake containing 100% USOP (p<0.05), in which oil phase was distributed in gluten matrix uniformly. Cake added with 100% USOP had higher overall likeness score (p<0.05). Thus, addition of 100% USOP resulted in the production of cake with superior quality and increased overall acceptance by consumers. Serine protease inhibitors from SO (SOSPI) were extracted and characterize. Optimal extraction condition included 0.45 M NaCl for 1 h. After heat treatment at 70 °C for 10 min, the highest specific activity was obtained. The major SOSPIS were present as monomer with molecular weight of 9.10 and 10.27 kDa. Autolysis study of bigeye snapper surimi revealed that myosin heavy chain was more retained with coincidentally lower trichloroacetic acid-soluble peptide content as the level of SOSPI increased. Surimi added with 1% SOSPI showed the highest gelling property with increased water holding capacity. Breaking force of gel from surimi from Indian mackerel increased when SOSPI levels increased up to 2%. However, EWP showed higher efficiency in increasing breaking force of resulting surimi gel. TCA- soluble peptide content and expressible moisture content of surimi gel decreased when the levels of SOSPI and EWP increased (p<0.05) but resulted in lower whiteness. Highly connected and denser microstructure was observed for surimi gel added with 2% EWP as compared to that containing 2% SOSPI. The SOSPI had no negative effect on sensory attributes and could serve as the alternative protein additive to improve gel strength of surimi. Chitosan from squid (Loligo formosana) pens was also prepared and characterized. Firstly, ultrasonication condition was optimized for deproteinization of squid pen using CCD. Squid pen ultrasonicated at amplitude 69% for 41.46 min at the solid/solvent ratio of 1: 18 yielded 34% (w/w) chitin with the lowest remaining protein. When the resultant chitin was subjected to deacetylation at different temperatures and times, yield and degree of deacetylation (DDA) of chitosan was in the range of 65-50% (w/w) and 78-90%. Intrinsic viscosity and molecular weight (MW) of chitosan was in the range of 3.2-6.52 dL/g and 1.2 x105-3.2 x105 Dalton, respectively. DDAs of chitosan produced by deacetylation at 130 °C for 2 h (CH130-2) determined using FTIR and 'H-NMR were nearly same (87 and 89%, respectively). CH130-2 stabilized the emulsion under the mimicked pH condition of gastrointestinal tract. It could form gel entrapping oil in simulated in vitro gastrointestinal tract. Therefore, it could be used as dietary fiber to control the adsorption of fat/oil in the human digestive tract. Chitooligosaccharide (COS) produced using various non-specific enzymes named lipase, pepsin and amylase was characterized. COS produced by 8% (w/w) lipase (COS-L) showed the maximum FRAP and ABTS radical scavenging activity than those prepared using other enzymes. COS-L had the average MW of 79 kDa, intrinsic viscosity of 0.41 dL/g and water solubility of 49%. COS-L showed antibacterial activity against both pathogenic and food born bacteria. When COS-L was incorporated into sardine surimi gel at various concentrations (0-3%), the highest breaking force and deformation of gel were obtained at 1% COS-L (p<0.05). WHC of gel was increased as COS-L was added up to 2% (p<0.05). Gel added with 1% COS-L had the denser network with higher connectivity than the control. COS-L increased likeness score for all sensory attributes of gel as compared to control. When gel incorporated with 1% COS-L was stored at 4 °C, textural properties and whiteness were maintained and the lower PV, TBARS and microbial growth were obtained in surimi gel during 10 days of storage at 4 °C. Thus, incorporation of 1% COS-L could improve gel properties of sardine surimi gel as well as preserved the gel during extended storage. Overall, squid processing waste, squid pen and ovary, could be used to extract various value-added bioactive compounds. They might be used to improve the quality and retard quality loss of various food products during extended storage.