Effect of heating strategies on whey protein denaturation--Revisited by liquid chromatography quadrupole time-of-flight mass spectrometry.
Previous standards in the area of effect of heat treatment processes on milk protein denaturation were based primarily on laboratory-scale analysis and determination of denaturation degrees by, for example, electrophoresis. In this study, whey protein denaturation was revisited by pilot-scale heating strategies and liquid chromatography quadrupole time-of-flight mass spectrometer (LC/MC Q-TOF) analysis. Skim milk was heat treated by the use of 3 heating strategies, namely plate heat exchanger (PHE), tubular heat exchanger (THE), and direct steam injection (DSI), under various heating temperatures (T) and holding times. The effect of heating strategy on the degree of denaturation of β-lactoglobulin and α-lactalbumin was determined using LC/MC Q-TOF of pH 4.5-soluble whey proteins. Furthermore, effect of heating strategy on the rennet-induced coagulation properties was studied by oscillatory rheometry. In addition, rennet-induced coagulation of heat-treated micellar casein concentrate subjected to PHE was studied. For skim milk, the whey protein denaturation increased significantly as T and holding time increased, regardless of heating method. High denaturation degrees were obtained for T >100°C using PHE and THE, whereas DSI resulted in significantly lower denaturation degrees, compared with PHE and THE. Rennet coagulation properties were impaired by increased T and holding time regardless of heating method, although DSI resulted in less impairment compared with PHE and THE. No significant difference was found between THE and PHE for effect on rennet coagulation time, whereas the curd firming rate was significantly larger for THE compared with PHE. Micellar casein concentrate possessed improved rennet coagulation properties compared with skim milk receiving equal heat treatment.
Department of Food Science, Science and Technology, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark.
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Akkerman
Arla Foods Strategic Innovation Centre, Rørdrumvej 2, DK-8220 Brabrand, Denmark.
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Rauh
Arla Foods Strategic Innovation Centre, Rørdrumvej 2, DK-8220 Brabrand, Denmark.
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Christensen
Arla Foods Strategic Innovation Centre, Rørdrumvej 2, DK-8220 Brabrand, Denmark.
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Johansen
Department of Food Science, Science and Technology, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark.
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Hammershøj
Department of Food Science, Science and Technology, Aarhus University, Blichers Allé 20, DK-8830 Tjele, Denmark. Electronic address: lbl@food.au.dk.
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Larsen
D002853:Chromatography, Liquid; D012085:Chymosin / Q000378:metabolism; D005511:Food Handling; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D007782:Lactoglobulins / Q000737:chemistry; D013058:Mass Spectrometry; D008823:Micelles; D010865:Pilot Projects; D011489:Protein Denaturation; D000067796:Whey / Q000737:chemistry*; D000067816:Whey Proteins / Q000737:chemistry*
D007782:Lactoglobulins; D008823:Micelles; D000067816:Whey Proteins; C025350:rennet; D012085:Chymosin
direct heat exchange; indirect heat exchanger; rennet-induced coagulation; whey protein denaturation