Characteristics and Gel Properties of Gelatin from Goat Skin as Influenced by Alkaline-pretreatment Conditions

Characteristics and properties of gelatin from goat skin pretreated with NaOH solutions (0.50 and 0.75 M) for various times (1 to 4 days) were investigated. All gelatins contained α-chains as the predominant component, followed by β-chain. Gelling and melting temperatures of those gelatins were 23.02°C to 24.16°C and 33.07°C to 34.51°C, respectively. Gel strength of gelatins increased as NaOH concentration and pretreatment time increased (p<0.05). Pretreatment for a longer time yielded gelatin with a decrease in L*-value but an increase in b*-value. Pretreatment of goat skin using 0.75 M NaOH for 2 days rendered the highest yield (15.95%, wet weight basis) as well as high gel strength (222.42 g), which was higher than bovine gelatin (199.15 g). Gelatin obtained had the imino acid content of 226 residues/1,000 residues and the gelatin gel had a fine and ordered structure. Therefore, goat skin gelatin could be used as a potential replacer of commercial gelatin

Composite films based on chitosan and epigallocatechin gallate grafted chitosan: Characterization, antioxidant and antimicrobial activities

The effect of chitosan-epigallocatechin gallate conjugate (CS-EGCG) at various ratios (10:0, 9:1, 8:2, 7:3, 6:4 and 5:5, w/w) and glycerol (30 and 50%, w/w) on mechanical, barrier and optical properties of CS films and CS/CS-EGCG composite films was studied. CS films added with 30 or 50% glycerol (CS-30G or CS-50G, respectively) had high tensile strength and elongation at break. Generally, CS/CS-EGCG composite films had higher resistance to light transmission than CS films (p < 0.05). With augmenting concentrations of CS-EGCG, films with lower lightness (L*) and higher redness (a*) and yellowness (b*) were obtained. Therefore, among composite films, those with CS/CS-EGCG ratio of 8:2, containing 30 or 50% glycerol, were selected for further analyses in comparison to CS films. Composite films, regardless of glycerol levels, showed higher antioxidant and antimicrobial activities as compared to CS films (p < 0.05). Overall, CS/CS-EGCG (8:2) composite films had satisfactory physical properties with increased antimicrobial and antioxidant activities and could serve as promising packaging for food shelf-life extension

ผลของสภาวะการสกัดต่อสมบัติเคมีกายภาพและสมบัติฟิล์มของเจลาตินจากหนังปลาตาหวาน (Priacanthus macracanthus) และการใช้เจลาตินเพื่อเตรียมเป็นแผ่นฟิล์มที่มีสารสกัดกานพลูเป็นส่วนผสม

Prince of Songkla Universit

Properties of composite film based on bigeye snapper surimi protein and lipids

Lipids were incorporated into bigeye snapper surimi protein films through emulsification using Tween-20 as a surfactant to form protein/lipid composite films. The effects of lipid types (palm oil, butter or shortening) and concentrations (0-100% glycerol substitution) on film properties were investigated. Additionof lipids up to 75% glycerol substitution resulted in the improved water vapor barrier, lowered tensile strength (TS) and increased elongation at break (EAB) of the composite film (P<0.05). However, an increase in TS was observed with increasing lipid concentration, plausibly caused by increasing protein aggregation in film matrix. Transparency of films was decreased with increasing lipid concentrations used (P<0.05), especially for those added with solid lipids. Generally, the mechanical properties and water resistance of surimi protein films incorporated with palm oil were superior to those modified with butter or shortening. An increase in Tween-20, nonionic surfactant, might be associated with the decrease in non-disulfide covalent cross-links in the film. Scanning electron microscopic study revealed that dispersion of palm oil in the film was more uniform than that of butter and shortening. This might contribute to the varying properties of resulting films

Quality changes of shrimp cracker covered with fish gelatin film without and with palm oil incorporated during storage

Abstract Impact of fish gelatin film incorporated without and with palm oil on the quality changes of fried shrimp cracker stored for 15 days at room temperature was investigated, in comparison with nylon/linear low-density polyethylene (nylon/LLDPE) film. The moisture content and water activity of shrimp cracker packaged with all films increased during storage (p < 0.05). The lowest moisture content and water activity were found in the sample packaged with nylon/LLDPE film throughout the storage (p < 0.05). Sample packaged with fish gelatin films incorporated with palm oil generally had lower moisture content than those without oil added during the first 12 days of storage (p < 0.05). During 15 days of storage, shrimp cracker packaged with nylon/LLDPE film generally had the lower PV and TBARS value as well as volatile compounds, except for n-nonanal, than those stored in fish gelatin films, regardless of oil incorporation. The decrease in crispiness and increase in toughness occurred in all samples during the 15 days of storage. Nevertheless, the lower changes were observed in the sample packaged with nylon/LLDPE film. Overall, gelatin film showed excellent oxygen barrier property, which was associated with the retardation of lipid oxidation. The incorporation of oil into gelatin film could lower WVP, but negatively increased oxygen permeability of the resulting film. Thus, the improvement of gelatin film is still required

Protein Hydrolysates from Pacific White Shrimp Cephalothorax Manufactured with Different Processes: Compositions, Characteristics and Antioxidative Activity

Hydrolysates from Pacific white shrimp (Litopenaeus vannamei) cephalothorax were prepared using various hydrolysis processes, and their chemical composition, characteristics as well as antioxidative activity were studied. Those processes consisted of autolysis (AU), hydrolysis using Alcalase at 0.5% (0.5A) or 1.0% (1.0A) and autolysis, followed by Alcalase hydrolysis at 0.5 and 1.0% (AU+0.5A and AU+1.0A). All the hydrolysate samples had higher protein contents (86.04-89.24%) and lower amounts of ash (7.46-11.26%) and lipids (0.43-0.64%), compared to those of cephalothorax (P<0.05). The highest yield (54.04%) and protein recovery (84.15%) were observed in the AU+1.0A sample, which had the maximum degree of hydrolysis (DH) (44.93%) (P<0.05). All the hydrolysates had glutamic acid/glutamine (115.80-121.69 mg/g dry sample), aspartic acid/asparagine (84.04-90.28 mg/g dry sample), arginine (63.27-68.62 mg/g dry sample) and leucine (58.67-68.07 mg/g dry sample) as the dominant amino acids. Based on gel filtration chromatography, the hydrolysates with higher DH showed higher proportions of smaller peptides (<1355 Da). When the antioxidant activities of the hydrolysates were determined, the AU+1.0A sample had the highest ferrous ion chelating activity, ABTS radical scavenging activity and ORAC value, compared to the others (P<0.05). However, the highest ferric reducing antioxidant activity and DPPH radical scavenging activity were obtained for the 1.0A and AU samples, respectively (P<0.05). Furthermore, the AU+1.0A sample showed higher inhibitory activity against DNA damage induced by peroxyl radicals than the 1.0A and AU samples. Therefore, different hydrolysis processes directly affected the protein recovery, chemical composition and antioxidant activities of the hydrolysates from shrimp cephalothorax

สมบัติและการใช้ฟิล์มชีวภาพนาโนคอมพอสิทระหว่างเจลาตินและนาโนเคลย์

Gelatin from splendid squid (Loligo formosana) skin extracted at different temperatures (50-80 °C) and their corresponding films were characterized. Gelatin extracted at 80 °C showed the highest yield (45.3%, dry weight basis) with relatively higher free amino group content (P<0.05). However, gelatin extracted at 50 °C (G50) had the highest gel strength (P<0.05). G80 had the higher a* value, compared with others (P<0.05). When films from those gelatins were prepared, tensile strength (TS) and elongation at break (EAB) of films decreased, but water vapor permeability (WP) increased (P<0.05) as the extraction temperature increased. Increase in transparency value with coincidental decrease in lightness was observed with increasing extraction temperatures. Thermogravimetric analysis (TGA) indicated that film prepared from G80 (F80) exhibited the higher heat susceptibility and weight loss. Loosen structure was observed in film prepared from gelatin with increasing extraction temperatures. Gelatins obtained from bleached (0-8% H2O2 w/v) squid skin and films from those gelatins were characterized. Gelatin from skin bleached with higher H2O2 concentrations had higher yield, lower free amino group and carbonyl group contents than the control gelatin (P<0.05). Gel strength of gelatin generally decreased as H2O2 concentrations increased (P<0.05). Gelatin prepared from skin bleached with 2% H2O2 showed the highest L", but lowest AE*-values (P<0.05). H2O, at higher concentrations yielded gelatin with increasing b*value. TS and WVP of films decreased, but EAB increased (P<0.05) as the concentration of H2O2 increased. TGA indicated that heat susceptibility and weight loss of different films varied with H2O2 concentrations. Rougher surface was obtained in gelatin films prepared from skin bleached with H2O2 concentrations above 4%. The impacts of hydrophilic and hydrophobic montmorillonite (MMT) nanoclays at various levels (0-10%, w/w) on properties of tilapia skin gelatin films were investigated. Generally, mechanical properties were improved by the addition of Cloisite Nat in the range of 0.5-5% (w/w). The lowest WVP was observed for films incorporated with Cloisite Nat and Cloisite 20A at a level of 1% (w/w) (P<0.05). Wide angle X-ray diffraction (WAXD) and scanning electron microscopic (SEM) analyses revealed the intercalated/exfoliated structure of films. Homogeneity and smoothness of film surface decreased with the addition of both nanoclays. The incorporation of nanoclays enhanced the rigidity and heat stability of films. Tilapia skin gelatin films incorporated with hydrophilic and hydrophobic nanoclays with the aid of homogenization using different pressure levels (1000 to 4000 psi) and passes (2 and 4) were characterized. YM, TS and EAB of films decreased and WVP increased with increasing pressure levels and number of passes. Films incorporated with Cloisite 20A exhibited the lower WVP than those with Cloisite Nat Transparency of films increased when homogenization pressure and number of passes increased. Nanocomposite films prepared using homogenization had exfoliated structure, whilst those prepared without homogenization exhibited intercalated structure. TGA and DSC analyses indicated that thermal stability of nanocomposite films varied with homogenization condition. Effects of various pHs (4-8) of film forming suspensions (FFS) on the properties of nanocomposite film based on tilapia skin gelatin and Cloisite Nat were investigated. In general, mechanical and water vapor barrier properties of nanocomposite films were improved when FFS having pH 6 was used. Intercalated/exfoliated structure of nanocomposite films was revealed by WAXD analysis. Homogeneity and smoothness of film surface were obtained for nanocomposite films with pH 6 as confirmed by SEM micrographs. Thermal stability of nanocomposite films varied with different pH levels. Effects of ethanolic extract from coconut husk (EECH) at 0-0.4% (w/w) on properties of films and nanocomposite films from tilapia skin gelatin were investigated. YM, TS and EAB of both films decreased with addition of EECH (P<0.05). The lowest WVP was obtained for gelatin film and nanocomposite film containing 0.05% and 0.4% EECH (w/w), respectively (P<0.05). Generally, a* value of films increased (P<0.05) with increasing levels of EECH, regardless of nanoclay incorporation. Intercalated or exfoliated structure of nanocomposite films was revealed by WAXD analysis. Based on SEM analysis, the rougher surface was found when EECH was added. EECH had varying impact on thermal stability of films. When tilapia and squid skin gelatin films and nanocomposite films incorporated without and with EECH were used to cover mackerel meat powder, quality changes were monitored in comparison with that covered with polyethylene (PE) film and the control (without covering) during storage of 30 days at 28-30 °C. The powder covered with nanocomposite film incorporated with EECH at 0.4% (w/w) (SGF-Na-EECH) generally had the lower moisture content than those covered with other gelatin films throughout the storage. The lower PV, TBARS, TVB and pH were observed for SGF-Na-EECH sample than PE sample and the control (P<0.05). Based on SPME-GCMS analysis, SGF-Na-EECH sample contained the lower volatile lipid oxidation products. Higher overall likeness score was observed for SGF-Na-EECH sample on day 30 of storage. Therefore, fish and squid gelatins could be used as biomaterials for film preparation. The improvement of film properties could be achieved by incorporation of nanoclay, especially in combination with EECH. The film could extend the shelf-life of dried mackerel powder, mainly via the prevention of lipid oxidation.เจลาตินจากหนังหมึกกล้วย (Loligo formosana) สกัดที่อุณหภูมิ 50-80 องศาเซลเซียสและนําไป วิเคราะห์ การทดลองพบว่าเจลาตินที่สกัดด้วยอุณหภูมิ 80 องศาเซลเซียสให้ yield สูงสุดคือร้อยละ 45.3 โดย น้ําหนักแห้ง รวมทั้งปริมาณ free amino group สูงสุด (P<0.05) อย่างไรก็ตามเจลาตินที่ได้จากการสกัดที่ อุณหภูมิ 50 องศาเซลเซียสให้ค่า gel strength สูงสุด เมื่อนํามาเตรียมฟิล์มและทดสอบพบว่าเมื่ออุณหภูมิสูงขึ้น ค่า tensile strength (TS) และ elongation at break (EAB) ของฟิล์มมีค่าลดลงในขณะที่ค่าการต้านการซึมผ่าน ไอน้ําเพิ่มขึ้น นอกจากนี้อุณหภูมิที่เพิ่มขึ้นส่งผลให้ความใสของฟิล์มเพิ่มขึ้น และจากการทดสอบทางความร้อนโดย Thermogravimetric analysis (TGA) พบว่าที่อุณหภูมิในการสกัด 80 องศาเซลเซียส ฟิล์มที่ได้ทนต่อความร้อน เจลาตินที่ทําการฟอกสีโดยใช้ Hy0) (0-896w/v) จากการทดสอบพบว่าเมื่อความเข้มข้นของ Hy0) เพิ่มขึ้น yield มีค่าสูงขึ้น รวมทั้งปริมาณของ free amino group และ carbonyl group มีค่าลดลงเมื่อเทียบกับ Control gelatin รวมทั้งค่า gel strength มีค่าลดลง ที่ความเข้มข้นร้อยละ 2 พบว่า L* มีค่าสูงสุดในขณะที่ AF" มีค่าต่ําสุด เมื่อความเข้มข้นของ Hy02 สูงขึ้นพบว่า b* มีค่ามากขึ้นด้วย ค่า TS และ WVP ของฟิล์มลดลง ขณะที่ EAB เพิ่มขึ้น ความเข้มข้นของ Hy02 เกินร้อยละ 4 ส่งผลให้ผิวของฟิล์มมีความขรุขระเพิ่มมากขึ้น ทั้งนี้มีการศึกษาผลจากการเติม hydrophilic และ hydrophobic montmorillonite (MMT) นาโนเคลย์ ที่ปริมาณ 0-10%, w/w ต่อสมบัติของฟิล์มเจลาตินที่ได้จากหนังปลานิล พบว่านาโนเคลย์ Choisite Na* สามารถ ปรับปรุงสมบัติเชิงกลของฟิล์ม เมื่อเติมในปริมาณร้อยละ 0.5-5 โดยน้ําหนัก ทั้งนี้พบว่า WVP มีค่าต่ําสุดเมื่อเติม Cloisite Na และ Cloisite 20A ร้อยละ 1 โดยน้ําหนัก การศึกษาโครงสร้างและสัณฐานวิทยาของฟิล์มโดย Wide angle X-ray diffraction (WAXD) และ scanning electron microscopic (SEM) แสดงการกระจายตัวของ เคลย์เป็นแบบ intercalated/exfoliated ความสม่ําเสมอและความเรียบของพื้นผิวฟิล์มลดลงเมื่อเติมนาโนเคลย์ ในปริมาณมากขึ้น และการเติมนาโนเคลย์ส่งผลให้ความแข็งและเสถียรภาพทางความร้อนของฟิล์มมีค่าเพิ่มขึ้น ต่อมาได้ศึกษาผลของการ homogenization ต่อสมบัติของฟิล์มเจลาตินจากหนังปลาที่เติม hydrophilic และ hydrophobic นาโนเคลย์ ซึ่งสภาวะที่ใช้คือ pressure levels (1000 ถึง 4000 psi) และ passes (2 และ 4) พบว่าค่า YM IS และ EAB ลดลงในขณะที่ค่า WVP เพิ่มขึ้น เมื่อเพิ่ม pressure level และ pass ฟิล์มที่เติม Cloisite 20A ส่งผลให้ค่า WP ต่ํากว่าเมื่อเติม Cloisite Na นอกจากนี้การเพิ่ม homogenization pressure และ pass ส่งผลให้ฟิล์มใสขึ้น การกระจายตัวของนาโนเคลย์เป็นแบบ exfoliated การศึกษาผลของค่า pH (4-8) ของ film forming Suspensions (FFS) ต่อสมบัติของนาโนคอมพอสิท ฟิล์ม พบว่าสมบัติเชิงกลและ WVP ดีขึ้นเมื่อ FFS มี pH เท่ากับ 6 และการกระจายตัวของเคลย์เป็นแบบ Intercalated/exfoliated นอกจากนี้พบว่าเสถียรภาพทางความร้อนของฟิล์มมีความแตกต่างกันเมื่อใช้ pH ต่างกัน ทั้งนี้การเติม ethanolic ที่สกัดได้จาก coconut husk (EECH) ปริมาณร้อยละ 0-0.4 (w/w) ส่งผลให้ค่า YM TS and EAB ของฟิล์มลดลง ค่า WVP ของฟิล์มเจลาตินและฟิล์มนาโนคอมพอสิทมีค่าต่ําที่สุดเมื่อเติม EECH ปริมาณร้อยละ 0.05 และ 0.4 ตามลําดับ ค่า o” ของฟิล์มเพิ่มขึ้นเมื่อเติม EECH มากขึ้น นอกจากนี้พบว่าการ กระจายตัวของเคลย์เป็นแบบ Intercalated หรือ exfoliated และจากการวิเคราะห์โดย SEM พบว่าพื้นผิวฟิล์มมี ความขรุขระเพิ่มขึ้นเมื่อเติม EECH เมื่อนําฟิล์มนาโนคอมพอสิทที่เติม EECH มาบรรจุเนื้อปลา mackerel และเก็บรักษาที่สภาวะ 28-30 องศาเซลเซียส เป็นเวลา 30 วันและนําไปตรวจสอบคุณภาพเทียบกับการบรรจุในฟิล์มที่ไม่เติม EECH ฟิล์มพอลิเอ ทิลีน (PE) และตัวอย่างควบคุมที่ไม่บรรจุในฟิล์ม พบว่า ฟิล์มนาโนคอมพอสิทที่ผสม EECH ปริมาณร้อยละ 0.4 โดยน้ําหนัก (SGF-Na-EECH) มีปริมาณความชื้นต่ํากว่าฟิล์มเจลาตินอื่น นอกจากนี้พบว่า PV TBARS TVB และ pH ในตัวอย่าง SGF-Na-EECH ต่ํากว่าใน PE และตัวอย่างควบคุม จากการวิเคราะห์ SPME-GC-MS พบว่าตัวอย่าง SGF-Na-EECH ให้ volatile lipid oxidation products ในปริมาณต่ํ

Enhancement of Hydrophobicity of Fish Skin Gelatin via Molecular Modification with Oxidized Linoleic Acid

Fish gelatin possesses hydrophilicity in nature since it contains a few hydrophobic amino acids and a large portion of hydrophilic amino acids. Low hydrophobicity of fish gelatin results in poor water vapor barrier and water resistance of gelatin films. This can limit its usage as packaging material. To overcome this drawback, the molecular attachment of hydrophobic domains can effectively improve the hydrophobicity of fish gelatin. In this study, fish skin gelatin modified with oxidized linoleic acid (OLA) prepared under various conditions using different molar ratios of OLA/free amino group content was characterized. When OLA was prepared at 60 and 80°C for various oxidation times (0–24 h), the peroxide value (PV) increased continuously up to 9 and 12 h when reaction was performed at 80 and 60°C, respectively. Consequently, the PV decreased until the end of the reaction (24 h). Thiobarbituric acid reactive substances (TBARS) of OLA were increased sharply up to 12 h, regardless of reaction temperatures. Thus, primary and secondary lipid oxidation products mainly occurred within the first 12 h. As gelatin was modified with different OLA at various OLA/free amino group molar ratios, the one modified with OLA prepared at 60°C for 24 h at a molar ratio of 10 : 1 had the highest increases in surface hydrophobicity and carbonyl content with the coincidentally lowest free amino group content, compared with control gelatin (without OLA modification). Fourier transforms infrared (FTIR) spectra also reconfirmed the presence of fatty acid covalently attached to resulting gelatin. Therefore, OLA could be used to modify gelatin and increase its hydrophobicity