Oxidized Caffeic Acid Cross-linked Whey Protein Films: Thermal Properties, Light Transmittance, Water Barrier Properties and in vitro Digestibility

Abstract

Abstract: Oxidized caffeic acid (OCA) was employed to induce cross-linking in whey protein-based films. The thermal properties, light transmittance, water barrier properties, and in vitro digestibility of the resultant whey protein films were analyzed. OCA at 2% and 4% (based on protein content) application levels was incorporated into 6 g/100 mL heat-denatured (90 ℃) whey protein isolate (WPI) solutions before casting to form films. The protein cross-linking behavior and film functionality were characterized by electrophoresis, differential scanning calorimetry (DSC), and thermogravimetry. The results showed that OCA promoted whey protein cross-linking primarily via disulfide bonds and partial non-reducible covalent bonds, leading to an improved thermal stability of the resultant films. OCA treatment significantly lowered the light transmittance and transparency, but slightly reduced the water vapor permeability (WVP) of the films. The in vitro digestion experiments carried out using pepsin and pancreatin showed that hydrolysis of the films was inhibited when higher concentrations of OCA were incorporated.

Key words: edible films, whey protein isolate, oxidized caffeic acid, cross-linking, thermal properties, light transmittance, water vapor permeability, digestibility

References

[1] BALDWIN E A, HAGENMAIER R, BAI J. Edible coatings and films to improve food quality[M]. New York: CRC Press, 2011: 13-77.
[2] KHWALDIA K, PEREZ C, BANON S, et al. Milk proteins for edible films and coatings[J]. Critical Reviews in Food Science and Nutrition, 2004, 44(4): 239-251.
[3] ANKER M, STADING M, HERMANSSON A M. Effects of pH and the gel state on the mechanical properties, moisture contents, and glass transition temperatures of whey protein films[J]. Journal of Agricultural and Food Chemistry, 1999, 47(5): 1878-1886.
[4] KINSELLA J E, WHITEHEAD D M. Proteins in whey: chemical, physical, and functional properties[J]. Advances in Food Nutrition Research, 1989, 33: 343-439.
[5] MCHUGH T H, KROCHTA J M. Plasticized whey protein edible films: water vapor permeability properties[J]. Journal of Food Science, 1994, 59(2): 416-419.
[6] MILLER K S, KROCHTA J M. Oxygen and aroma barrier properties of edible films: a review[J]. Trends in Food Science and Technology, 1997, 8(7): 228-237.
[7] JANJARASSKUL T, KROCHTA J M. Edible packaging materials[J]. Annual Review of Food Science and Technology, 2010, 1:415-448.
[8] MILLER K S, CHIANG M T, KROCHTA J M. Heat curing of whey protein films[J]. Journal of Food Science, 1997, 62(6), 1189-1193.
[9] GALIETTA G, GIOIA L D, GUILBERT S, et al. Mechanical and thermomechanical properties of films based on whey proteins as affected by plasticizer and crosslinking agents[J]. Journal of Dairy Science, 1998, 81(12): 3123-3130.
[10] USTUNOL Z, MERT B. Water Solubility, mechanical, barrier, and thermal properties of cross-linked whey protein isolate-based films[J]. Journal of Food Science, 2004, 69(3): 129-133.
[11] YILDIRIM M, HETTIARACHCHY N S. Properties of films produced by cross-linking whey proteins and 11S globulin using Transglutaminase[J]. Journal of Food Science, 1998, 63(2):248-252.
[12] F?RGEMAND M, OTTE J. QVIST K B. Cross-linking of whey proteins by enzymatic oxidation[J]. Journal of Agricultural and Food Chemistry, 1998, 46(4), 1326-1333.
[13] LAEMMLI U K. Cleavage of structural proteins during the assembly of the head of bacteriophage T4[J]. Nature, 1974, 227(5259): 680-685.
[14] NUTHONG P, BENJAKUL S, PRODPRAN T. Characterization of porcine plasma protein-based films as affected by pretreatment and cross-linking agents[J]. International Journal of Biological Macromolecules, 2009, 44(2): 143-148.
[15] FANG Y, TUNG M A, BRITT I J, et al. Tensile and barrier properties of edible films made from whey proteins[J]. Journal of Food Science, 2002, 67(1): 188-193.
[16] HAN J H, FLOROS J D. Casting antimicrobial packaging films and measuring their physical properties and antimicrobial activity[J]. Journal of Plastic Film and Sheet, 1997, 13(4): 287-298.
[17] American Society for Testing and Materials. Annual book of ASTM standards[S]. Philadelphia, PA, USA: ASTM. 1989.
[18] MA Y, XIONG Y L. Antioxidant and bile acid binding activity of buckwheat protein in vitro digests[J]. Journal of Agricultural and Food Chemistry, 2009, 57(10): 4372-4380.
[19] STRAUSS G, GIBSON S M. Plant phenolics as cross-linkers of gelatin gels and gelatin-based coacervates for use as food ingredients[J]. Food Hydrocolliods, 2004, 18(1): 81-89.
[20] KIM S J, USTUNOL Z. Thermal properties, heat sealability and seal attributes of whey protein isolate/lipid emulsion edible films[J]. Journal of Food Science, 2001, 66(7): 985-990.
[21] BARRETO P L M, PIRES A T N, SOLDI V. Thermal degradation of edible films based on milk proteins and gelatin in inert atmosphere[J]. Polymer Degradation and Stability, 2003, 79(1):147-153.
[22] RATTAYA S, BENJAKUL S, PRODPRAN T. Properties of fish skin gelatin film incorporated with seaweed extract[J]. Journal of Food Engineering, 2009, 95(1):151-157.
[23] MARTUCCI J F, RUSECKAITE R A. Tensile properties, barrier properties, and biodegradation in soil of compression—molded gelatin-dialdehyde starch films[J]. Journal of Applied Polymer Science, 2009, 112(4): 2166-2178.
[24] SCHMIDT V, GIACOMELLI C, SOLDI V. Thermal stability of films formed by soy protein isolate sodium dodecyl sulfate[J]. Polymer Degradation and Stability, 2005, 87(1): 25-31.
[25] KROLL J, RAWEL H M, ROHN S. Reactions of plant phenolics with food proteins and enzymes under special consideration of covalent bonds[J]. Food Science and Technology Research, 2003, 9(3): 205-218.
[26] BALANGE A K, BENJAKUL S. Effect of oxidised phenolic compounds on the gel property of mackerel (Rastrelliger kanagurta) surimi. LWT–Food Science and Technology, 2009, 42(6): 1059-1064.