TY - JOUR

T1 - Structure modification of stirred fermented milk gel due to laccase-catalysed protein crosslinking in a post-processing step

AU - Mokoonlall, Aryama

AU - Pfannstiel, Jens

AU - Struch, Marlene

AU - Berger, Ralf Günter

AU - Hinrichs, Jörg

N1 - Funding information: This research project was supported by the German Ministry of Economics and Technology (via AiF) and the FEI (Forschungskreis der Ernährungsindustrie e.V., Bonn) Project AiF 17475 N . The authors thank Stefan Nöbel for his invaluable comments, Lin Du for performing part of the experiments and Luc Mertz and Berit Würtz for their technical assistance.

PY - 2015/11/2

Y1 - 2015/11/2

N2 - Laccases are a promising candidate for crosslinking milk proteins in stirred fermented milks. It was applied in a post-processing step due to its acidic pH optimum reported in literature for rebodying of the gel and an improvement in structure. A laccase preparation from Trametes versicolor had a lower oxidation activity in ultrafiltration permeate than in model buffer systems, and a pH optimum of 4.5. It was applied to stirred skim milk gels but no significant change in the storage modulus or apparent viscosity of yoghurt occurred. Confocal laser scanning micrographs showed a more porous structure of the milk gel. Some fresh cheese samples had improved rheological properties. A competing crosslinking activity and peptidolytic activity was assumed and smaller peptides were detected in acidified milk by fluorescence. Mass spectrometry of the laccase preparation returned mainly laccase sequences. Although this does not exclude proteases, it indicates that the radical mechanism of laccases may lead to protein degradation. Industrial Relevance: Enzymatic modification of milk proteins can alter the structure of fermented milk gels and even create new structures. Rheological properties can be improved via crosslinking, thus reducing costs due to the addition of protein powders or stabilisers. An innovative approach to combining biotechnology and food science and engineering is investigated. The study is interesting for both enzyme manufacturers and dairy companies as it aims to at least partially fill the knowledge gap between enzymology and their real-world application in dairy products. However, enzymatic treatment is an additional step and also incurs costs which should be taken into account.

AB - Laccases are a promising candidate for crosslinking milk proteins in stirred fermented milks. It was applied in a post-processing step due to its acidic pH optimum reported in literature for rebodying of the gel and an improvement in structure. A laccase preparation from Trametes versicolor had a lower oxidation activity in ultrafiltration permeate than in model buffer systems, and a pH optimum of 4.5. It was applied to stirred skim milk gels but no significant change in the storage modulus or apparent viscosity of yoghurt occurred. Confocal laser scanning micrographs showed a more porous structure of the milk gel. Some fresh cheese samples had improved rheological properties. A competing crosslinking activity and peptidolytic activity was assumed and smaller peptides were detected in acidified milk by fluorescence. Mass spectrometry of the laccase preparation returned mainly laccase sequences. Although this does not exclude proteases, it indicates that the radical mechanism of laccases may lead to protein degradation. Industrial Relevance: Enzymatic modification of milk proteins can alter the structure of fermented milk gels and even create new structures. Rheological properties can be improved via crosslinking, thus reducing costs due to the addition of protein powders or stabilisers. An innovative approach to combining biotechnology and food science and engineering is investigated. The study is interesting for both enzyme manufacturers and dairy companies as it aims to at least partially fill the knowledge gap between enzymology and their real-world application in dairy products. However, enzymatic treatment is an additional step and also incurs costs which should be taken into account.

KW - Fermented milks

KW - Laccase

KW - Post-processing

KW - Protein modification

UR - http://www.scopus.com/inward/record.url?scp=84961878117&partnerID=8YFLogxK

U2 - 10.1016/j.ifset.2015.10.006

DO - 10.1016/j.ifset.2015.10.006

M3 - Article

AN - SCOPUS:84961878117

VL - 33

SP - 563

EP - 570

JO - Innovative Food Science and Emerging Technologies

JF - Innovative Food Science and Emerging Technologies

SN - 1466-8564

ER -