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Milk is often subjected to technological treatments which have impacts on the structure of milk constituents and the characteristics of rennet curds. In this paper, the influence of the dairy fat structure on the biochemical and textural characteristics of curds coagulated by an extract of Calotropis procera leaves was studied. Standardized milks were reconstituted with the same contents in protein (35 g·kg− 1) and fat (35 g·kg− 1) but with different structures of fat i.e. homogenized anhydrous milk fat (HAMF), homogenized cream (HC) and non-homogenized cream (NHC). As expected, the size distributions of fat globules in the different milks were different. After their coagulations by the plant extract, the physico-chemical characteristics of the curds and respective wheys were determined. No difference was observed in the coagulation time between the three milks but the whey removed more quickly from HAMF and HC curds than NHC-curd. The biochemical analyses of curds revealed a lower content in dry matter and fat in the NHC-curd compared to HAMF- and HC-curds. Otherwise, the NHC-whey exhibited the highest amount of fat. Observations by confocal microscopy showed that the fat globules were homogenously distributed and well trapped in the protein networks of HAMF- and HC-curds. In the NHC-curd, the fat globules were located in whey pockets, with less connectivity with the protein network. The textural analysis showed that the NHC-curd was more elastic, soft and adhesive than HAMF- and HC-curds. Homogenization significantly reduced the loss of fat during cheese manufacturing and conferred specific textural characteristics to the curds coagulated by an extract of Calotropis procera.

International audience; Milk is often subjected to technological treatments which have impacts on the structure of milk constituents and the characteristics of rennet curds. In this paper, the influence of the dairy fat structure on the biochemical and textural characteristics of curds coagulated by an extract of Calotropis procera leaves was studied. Standardized milks were reconstituted with the same contents in protein (35 g·kg−1) and fat (35 g·kg−1) but with different structures of fat i.e. homogenized anhydrous milk fat (HAMF), homogenized cream (HC) and non-homogenized cream (NHC). As expected, the size distributions of fat globules in the different milks were different. After their coagulations by the plant extract, the physico-chemical characteristics of the curds and respective wheys were determined. No difference was observed in the coagulation time between the three milks but the whey removed more quickly from HAMF and HC curds than NHC-curd. The biochemical analyses of curds revealed a lower content in dry matter and fat in the NHC-curd compared to HAMF- and HC-curds. Otherwise, the NHC-whey exhibited the highest amount of fat. Observations by confocal microscopy showed that the fat globules were homogenously distributed and well trapped in the protein networks of HAMF- and HC-curds. In the NHC-curd, the fat globules were located in whey pockets, with less connectivity with the protein network. The textural analysis showed that the NHC-curd was more elastic, soft and adhesive than HAMF- and HC-curds. Homogenization significantly reduced the loss of fat during cheese manufacturing and conferred specific textural characteristics to the curds coagulated by an extract of Calotropis procera.

Cheese is used to preserve the essential constituents of milk (protein, fat, vitamin and minerals).[1] In West Africa, a traditional cheese named “wara” is manufactured using an extract of Calotropis procera leaves, a small latex tree growing naturally in tropical and subtropical areas of Africa and Asia.[2,3] The aim of this study was to investigate the biochemical composition and mineral profile of curds manufactured using an extract of dried leaves of Calotropis procera as coagulant in comparison with curd obtained using chymosin. We have reconstituted milks at 10% dry matter using a low heat skimmed milk powder and distilled water. After milk coagulation by Calotropis procera extract (at 75°C) or chymosin (at 30°C), the curds and respective wheys were recovered for biochemical analysis. Sodium, potassium, magnesium and calcium contents were determined. The microstructure of curds were also observed by scanning electron microscopy. The contents in dry matter, ash and protein were more important in the curds manufactured using Calotropis procera extract compared to those made using chymosin. However, the two curds exhibited similar contents in minerals. The calcium content was considered as high in both curds probably because the pH did not decreased during manufacturing by fermentation. The difference of coagulation temperatures did not seem to affect the mineral contents of the curds. By microscopic observation, the protein network appeared well organized in chymosin curds compared to those obtained using Calotropis procera. At high magnification, the casein micelles were observed in both curds. The results obtained in this paper support that the consumption of traditional dairy products especially cheese can be a good source of mineral supplementation mostly in population whose diet is poor in these elements.

Dans les pays en développement, quels que soient le climat et lesespèces animales domestiquées, le lait et ses dérivés occupent leplus souvent une place importante dans la vie quotidienne et constituentun vecteur indéniable de développement. La diversité des pratiques,des outils et des produits nis est considérable et implique unensemble d’acteurs le long des chaînes d’approvisionnement. Parfoismenacés par les dynamiques en cours de la mondialisation, le lait etses dérivés représentent néanmoins une valeur patrimoniale inestimable.Outre leur rôle nutritif incontesté, ces produits ont souvent unrôle clé dans la microéconomie et le développement territorial, avecde multiples modèles selon les contraintes et les opportunités locales.L’objectif de ces rencontres, qui font suite à la 1re édition organisée àRennes (France) en 2014 (colloque6.inra.fr/lait2014), est de favoriser leséchanges d’expériences autour de la diversité des modèles de développementlaitier observés à l’échelle de la planète, de rassembler toutes lesinitiatives et réseaux impliqués, de mesurer l’importance des femmes etdes jeunes dans ces dynamiques et de m@ieux cerner le rôle des politiquespubliques pour accompagner cet essor.Aboutir ensemble à une meilleure coordination des actions autour dulait dans les pays en voie de développement, et notamment à des projetsconjoints de recherche, de formation ou d’appui est la principaleambition de ces rencontres.; La chymosine est l’enzyme communément utilisée pour coaguler le lait en fromagerie mais des coagulants d’origine microbienne et végétale existent aussi. Ces derniers présentent l’avantage d’être accessible et facile d’utilisation même à l’échelle artisanale.En Afrique de l’Ouest, les feuilles et tiges de l’arbuste Calotropis procera sont utilisées dans la fabrication d’un fromage traditionnel appelé « wagachi » qui signifie en langue peulh « gâteau de lait ».Ce fromage est utilisé en remplacement de la viande ou du poisson dans nombre de mets traditionnels. L’importance de sa consommation incite à mener des travaux dans le but d’améliorer la qualité du produit.

Chymosin is the major enzyme used in cheesemaking but latex enzymes are also used. The aim of this work was to characterize the composition and the structure of dairy gel obtained by an extract of Calotropis procera leaves in comparison with those obtained by chymosin. The biochemical and mineral compositions of the curds and the cheese yields obtained by using Calotropis procera extract or chymosin were relatively similar. Quantitative and qualitative evaluations of proteolysis after milk coagulation, determined by the non-protein nitrogen content and chromatography coupled to mass spectrometry, indicated that Calotropis procera extract was more proteolytic than chymosin and that κ-casein was proteolyzed. The main consequence of proteolysis by Calotropis procera extract or chymosin was the formation of a similar and regular network with the presence of aggregates of casein micelles. These results support that Calotropis procera extract can be used as effective coagulant in cheesemaking.

Dans les pays en développement, quels que soient le climat et lesespèces animales domestiquées, le lait et ses dérivés occupent leplus souvent une place importante dans la vie quotidienne et constituentun vecteur indéniable de développement. La diversité des pratiques,des outils et des produits nis est considérable et implique unensemble d’acteurs le long des chaînes d’approvisionnement. Parfoismenacés par les dynamiques en cours de la mondialisation, le lait etses dérivés représentent néanmoins une valeur patrimoniale inestimable.Outre leur rôle nutritif incontesté, ces produits ont souvent unrôle clé dans la microéconomie et le développement territorial, avecde multiples modèles selon les contraintes et les opportunités locales.L’objectif de ces rencontres, qui font suite à la 1re édition organisée àRennes (France) en 2014 (colloque6.inra.fr/lait2014), est de favoriser leséchanges d’expériences autour de la diversité des modèles de développementlaitier observés à l’échelle de la planète, de rassembler toutes lesinitiatives et réseaux impliqués, de mesurer l’importance des femmes etdes jeunes dans ces dynamiques et de m@ieux cerner le rôle des politiquespubliques pour accompagner cet essor.Aboutir ensemble à une meilleure coordination des actions autour dulait dans les pays en voie de développement, et notamment à des projetsconjoints de recherche, de formation ou d’appui est la principaleambition de ces rencontres.; Chymosin is the common enzyme used in cheese making worldwide but other enzymes especially from vegetable origin also exist. In West Africa, an extract of the shrub Calotropis procera, is traditionally used to make a local soft cheese named Wagashi. This cheese, produced and marketed by women, is an interesting source of incomes. The aim of this study was to understand the milk coagulation mechanism by an extract of Calotropis procera leaves in comparison with chymosin. A standard manufacturing process was set up for making both Calotropis procera and chymosin curds. The contents in dry matter, ash and total nitrogen were more important for the curds manufactured using Calotropis procera (310,9; 31,1 and 231,9 g.Kg-1, respectively) compared to those made using chymosin ( 305,7; 25,5 and 207,8 g.Kg-1, respectively). The whey liquid dry matter was also more important when Calotropis procera extract was used. In spite of these composition differences considered as small, both types of curds can be classified as rennet curds strongly mineralized. Analysis by chromatography coupled to tandem mass spectrometry showed an increasing number of peptides coming from -caseins hydrolysis identified in the whey liquids: 96 when using Calotropis procera extract and 47 when using chymosin as coagulant. The proteolysis of this casein molecule explains the milk coagulation observed in both cases. The observation of the two curds by scanning electron microscopy have revealed regular networks with the presence of aggregates of casein micelles. These results support that Calotropis procera extract can be used as effective coagulant in cheese manufacturing with technological adaptations to take in consideration and specific organoleptic and textural specifies.