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  Effect of hydration on the gel structure of microparticulated whey protein added yoghurts: investigations by rheology and LR-NMR
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Ophav

 Ophav:
Mutaf, Gülsüm1, Forfatter
Ipsen, Richard Holstein1, Vejleder
Larsen, Flemming Hofmann1, Vejleder
Tilknytninger:
1Det Biovidenskabelige Fakultet, København, Danmark
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 Abstract: Microparticulated whey proteins (MWPs) are mimicking the sensory perception of fat due to their particle sizes and/or their surface and rheological properties. Janhøj and Ipsen (2006) showed that heat treatment had little effect on the functionality of microparticulated whey proteins. This implies that the MWPs do not actively promote structure formation in acid milk gels as the homogenized fat globules do. The effect of hydration time (24h, 1h or 0.25 h) of microparticulated and native whey protein concentrates on the gel structure of stirred yoghurt was investigated by pH, rheology and LR-NMR experiments.Large whey protein microparticulates are seen to inhibit the gelation process and result is longer gelation times. They also give weak and low viscous yoghurt gels as well as high syneresis values presumably due to disruption of the coagulum. Fine native whey protein (Lacprodan) particles give shorter gelation times than the microparticulates possibly due to easier protein-protein, protein-water interactions. Lacprodan also gives firmer and thicker gels and lower syneresis values than the microparticulates, if it is added before the heat treatment. G’ (elastic modulus), QRS model and the syneresis values might be correlated for 24 h and 1 h hydrated samples and firmness of the yoghurt gel is seen to be positively correlated with its thickness and inversely correlated with the whey expulsion.When added to milk after heat treatment and hydrated for 0.25 h, the powders are not denatured, integrated into the protein network and they can not bind enough water due to the lack of heat treatment and this result in high whey expulsions. Two very different components and a non-homogeneous system are achieved by the end of acidification in LR-NMR. Containing microparticulates lead to extremely different behavior than including fine particles during acidification in LR-NMR. Microparticulates are seen to inhibit the protein-water or protein-protein interactions by being "inert" and result in independent behavior of pre-hydration, if large enough aggregates are involved. The native whey protein Lacprodan samples in LR-NMR are affected more than the microparticulates when decreasing the hydration time from 24 h to 1h. The optimized model system is seen to represent the “real yoghurt” system in LR-NMR. Increase in temperature leads to more mobile water components. The yoghurt samples tend to give similar water components with the acidified milk drink samples. Large aggregates could also result in a three component yoghurt system at 20°C presumably due to the samples’ looseness caused by the large microparticulates in it, which also led to the highest mean syneresis value among all the samples.
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Thesis-Gulsum_Mutaf.pdf (Hovedtekst)
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Bogmærk denne post: https://diskurs.kb.dk/item/diskurs:31598:1
 Type: Speciale
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Sprog: English - eng
 Datoer: 2009
 Sider: 81 pages
 Publiceringsinfo: København, Danmark : Institut for Fødevarevidenskab
 Indholdsfortegnelse: -
 Note: Food Science and Technology, Food Science and Technology
 Type: Speciale
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