Transglutaminase at a concentration of 10 kU/kg of protein and degraded chitosan were used for glycosylation and crosslinking of caseinate at a fixed molar ratio of the acyl acceptor to the acyl donor of 3:1, a protein concentration of 50 g/L, a pH 7.5 at 37 o C, and a reaction time of 4 h. Electrophoretic and chemical analyses showed glycosylation and crosslinking of caseinate. Glycosylated and crosslinked caseinate (GC-caseinate) contained glucosamine at 12.77 g/kg of protein, and the protein fraction had fewer reactable amino groups than original caseinate (0.58 vs. 0.64 mol/kg of protein). GC-caseinate exhibited an enhanced surface hydrophobicity, in vitro digestibility, water-binding capacity, and rheological properties, with poor protein dispensability and emulsification activity, but a similar oilbinding capacity and emulsion stability, compared with original caseinate. GC-caseinate also exhibited better properties than transglutaminase-crosslinked caseinate. Glycosylation and crosslinking was effective for better water-binding and rheological properties of caseinate.

Structure and property changes of soybean protein isolates resulted from the glycation and cross-linking by transglutaminase and a degraded chitosan Cambios en la estructura y en las propiedades del aislado de proteína de soja como resultado de la glicación y reticulación mediante transglutaminasa y chitosán degradado A glycated and cross-linked soybean protein isolate (GC-SPI) with the glucosamine content of 19.40 g/kg protein was prepared by using SPI, transglutaminase, and a degraded chitosan under fixed conditions, aiming to assess modified properties and potential application of GC-SPI. GC-SPI has less reactable -NH 2 groups than SPI (0.38 versus 0.48 mol/kg protein), and is verified by electrophoretic analysis to be a glycated and cross-linked protein product. Infrared spectroscopy and circular dichroism analyses demonstrate that GC-SPI contains more -OH groups, and has a more open secondary structure. In comparison with SPI, GC-SPI has higher surface hydrophobicity but lower in vitro digestibility due to protein cross-linking, and exhibits greater water-and oil-binding capacities (9.9 versus 6.4 and 3.7 versus 2.0 kg/kg protein). It is concluded that the glycation and cross-linking confer an open structure and modified properties of SPI, and GC-SPI is a potential ingredient with better hydration and oil-binding than SPI.Keywords: soybean protein isolate; degraded chitosan; transglutaminase; secondary structure; property Se preparó aislado de proteína de soja glicada y reticulada (GC-SPI) con un contenido de glucosamina de 19,40 g/kg de proteína utilizando SPI, transglutaminasa y chitosán degradado sometido a condiciones determinadas con el objetivo de estudiar las propiedades modificadas y las aplicaciones potenciales de GC-SPI. GC-SPI obtuvo menos grupos reactivos de tipo NH 2 en comparación con SPI (0,38 frente a 0,48 mol/kg de proteína) y se verificó mediante análisis electroforético para ser un producto proteínico glicado y reticulado. La espectroscopía infrarroja y el análisis de dicroísmo circular mostraron que el GC-SPI contiene más grupos OH y tiene una estructura secundaria más abierta. En comparación con SPI, GC-SPI tiene una mayor superficie de hidrofobia aunque una menor digestibilidad in vitro debido a la reticulación proteínica, además exhibe una mayor capacidad de retención de agua y de aceite (9,9 frente a 6,4 y 3,7 frente a 2,0 kg/kg de proteína). En conclusión, la glicación y la reticulación conceden una estructura abierta y unas propiedades modificadas en SPI. Además GC-SPI se trata de un ingrediente potencial con una mejor hidratación y capacidad de retención que SPI.Palabras clave: aislado de proteína de soja; chitosán degradado; transglutaminasa; estructura secundaria; propiedad