Heat treatment of milk may cause whey proteins and caseins to form aggregates. These soluble and micellar aggregates and their other properties (size, composition, shape, etc.) can affect the techno-functionalities to...Heat treatment of milk may cause whey proteins and caseins to form aggregates. These soluble and micellar aggregates and their other properties (size, composition, shape, etc.) can affect the techno-functionalities to the milk, conferring interesting or negative features depending on the application in dairy industries. In this study, we propose a new approach to characterise those protein aggregates. SDS-agarose electrophoresis is followed by the calculation of a retention factor (Rf) for each protein spot. Rf allows milk aggregates to be compared qualitatively under the same conditions. This method could be transposed to the dairy industry for a better knowledge of the milk subsequent to heat treatment.展开更多
The Lactococcus diversity in cow and goat raw milk was investigated. To do so, a protocol had to be established for the specific enumeration of lactococci. Eight agar media and one control medium were analysed to comp...The Lactococcus diversity in cow and goat raw milk was investigated. To do so, a protocol had to be established for the specific enumeration of lactococci. Eight agar media and one control medium were analysed to compare their proficiency in evaluating the Lactococcus population in raw milk: M17 Nal, Elliker, modified Elliker, PCA + milk, modified KCA, modified Chalmers, Turner, FSDA. The M17 medium was used as reference. Eighteen pure strains were tested on these media for their selectivity towards lactococci: six Lactococcus species or subspecies, three Leuconostoc, three Enterococcus, two Lactobacillus, one Streptococcus thermophilus, one Pseudomonas fluorescens, one Escherichia coli and one Staphylococcus aureus. All these bacteria were chosen for their regular presence in raw milk. The KCA medium proved to be the most selective towards lactococci, on condition that 1) we discriminated the colonies using the catalase test and 2) we subtracted the Enterococcus population counted on BEA. However, it was not possible to separate the Streptococcus from the Lactococcus colonies on KCA. The “Lactococcus-like” population including these two genera was estimated at a mean level of 3.18 log(cfu)/mL and 4.14 log(cfu)/mL in cow and goat raw milk respectively. This is consistent with the data already published.展开更多
文摘Heat treatment of milk may cause whey proteins and caseins to form aggregates. These soluble and micellar aggregates and their other properties (size, composition, shape, etc.) can affect the techno-functionalities to the milk, conferring interesting or negative features depending on the application in dairy industries. In this study, we propose a new approach to characterise those protein aggregates. SDS-agarose electrophoresis is followed by the calculation of a retention factor (Rf) for each protein spot. Rf allows milk aggregates to be compared qualitatively under the same conditions. This method could be transposed to the dairy industry for a better knowledge of the milk subsequent to heat treatment.
基金the RMT(“Réseau Mixte Technologique”)“Fromages de Terroir”the CASDAR project“FloracQ”(Ministère de l’Agriculture et de la Pêche,Chambre d’agriculture du cantal).
文摘The Lactococcus diversity in cow and goat raw milk was investigated. To do so, a protocol had to be established for the specific enumeration of lactococci. Eight agar media and one control medium were analysed to compare their proficiency in evaluating the Lactococcus population in raw milk: M17 Nal, Elliker, modified Elliker, PCA + milk, modified KCA, modified Chalmers, Turner, FSDA. The M17 medium was used as reference. Eighteen pure strains were tested on these media for their selectivity towards lactococci: six Lactococcus species or subspecies, three Leuconostoc, three Enterococcus, two Lactobacillus, one Streptococcus thermophilus, one Pseudomonas fluorescens, one Escherichia coli and one Staphylococcus aureus. All these bacteria were chosen for their regular presence in raw milk. The KCA medium proved to be the most selective towards lactococci, on condition that 1) we discriminated the colonies using the catalase test and 2) we subtracted the Enterococcus population counted on BEA. However, it was not possible to separate the Streptococcus from the Lactococcus colonies on KCA. The “Lactococcus-like” population including these two genera was estimated at a mean level of 3.18 log(cfu)/mL and 4.14 log(cfu)/mL in cow and goat raw milk respectively. This is consistent with the data already published.
