Properties of bovine gelatin cross-linked by a mixture of two oxidases (horseradish peroxidase and glucose oxidase) and glucose

ABSTRACT

A mixture comprising horseradish peroxidase (HRP), glucose oxidase, and glucose was used to cross-link bovine gelatin via dityrosine formation. Suitable HRP, glucose oxidase, glucose addition levels, and reaction time were studied with single-factor trials, and selected as 100 U, 1 U, 0.025 mmol/g protein, and 3 h, respectively. Electrophoretic and circular dichroism analyses showed that the cross-linked gelatin contained high levels of polymerized proteins, had a typical triple helix structure at 5°C, but a more ordered secondary structure at 40°C. In comparison with bovine gelatin, the cross-linked gelatin had better colloidal stabilization in dispersion through the formation of aggregates of smaller hydrodynamic radius (73.3 versus 97.2 nm) and more negative zeta-potential (–8.15 versus –5.88 mV), showed enhanced thermal stability with a higher decomposition temperature (323.7°C versus 320.8°C), but less mass loss (50.10% versus 50.90%) and formed gels with shorter gelation time (14.1 versus 34.1 min) and stronger gel strength (increased by 12–14%).

RESUMEN

Se utilizó una mezcla compuesta de peroxidasa de rábano picante (HRP), glucosa oxidasa y glucosa para entrecruzar gelatina bovina mediante la formación de tirosina. Se estudiaron los HRP, la glucosa oxidasa, los niveles de adición de glucosa y el tiempo de reacción más adecuados con ensayos de un solo factor y seleccionados como 100 U, 1 U, 0,025 mmol/g de proteína y 3 h, respectivamente. Los análisis electroforéticos y de dicroísmo circular mostraron que la gelatina entrecruzada contenía muchas proteínas polimerizadas, tenía una estructura típica de triple hélice a 5°C aunque una estructura secundaria más ordenada a 40°C. En comparación con la gelatina bovina, la gelatina entrecruzada tenía una mayor estabilización coloidal en dispersión mediante la formación de agregados con radios hidrodinámicos más pequeños (73,3 frente a 97,2 nm) y más potencial zeta negativo (–8,15 frente a –5,88 mV), mostró una estabilidad termal mejorada con una mayor temperatura de descomposición (323,7°C frente a 320,8°C) aunque menos pérdida de masa (50,10% frente a 50,90%), podía formar geles con un menor tiempo de gelificación (14,1 frente a 34,1 min) y una mayor resistencia del gel (mejorada de 12–14%).

KEYWORDS:

• Bovine gelatin
• horseradish peroxidase
• glucose oxidase
• cross-linking
• secondary structure
• functional property

PALABRAS CLAVE:

• gelatina bovina
• peroxidada de rábano picante
• glucosa oxidasa
• enlaces cruzados
• estructura secundaria
• propiedad funcional

Acknowledgement

The authors thank the anonymous reviewers and editors for their valuable advice.

Disclosure statement

No potential conflict of interest was reported by the authors.

Additional information

Funding

This study was funded by the National Natural Science Foundation of China [Project No. 31371738], the Program of International Science & Technology Cooperation of Heilongjiang Province [Project No. WB13C102], and the Innovation Foundation for Postgraduate of Northeast Agricultural University [Project No. YJSCX14061].

Notes on contributors

Yan-Ping Han

Miss YP Han is studying at Northeast Agricultural University, and will shortly complete her MD in Food Science and Technology under the direction of Prof. XH Zhao. Her work focuses on enzymatic modification of gelatin and application of the modified gelatin.

Xin-Huai Zhao

Prof. XH Zhao complected his MD and PhD in Food Science and Chemistry from Northeast Agricultural University and Ocean University of China, respectively. He has been working at Northeast Agricultural University for more than 30 years, and has more than 200 research publications on different domains of food chemistry. His work mostly focuses on modification and bioactivities of food proteins/peptides, health benefits of phytochemicals, and application of food microorganism for bioconversion and biodegradation.