S. Lactoperoxidase activity and thiocyanate content were monitored in the milks of seven individual cows and six goats during lactation. Lactoperoxidase activity exhibited a cyclic pattern with alternating peaks and troughs throughout lactation. Extremely large variations were observed between and within animals. For example, lactoperoxidase activity ranged from 0n05-5n60 U\ml for one cow on different sampling days. Variations between cows were also large, ranging from 0n98-5n1 U\ml on a specific sampling day. Mean lactoperoxidase activity in cows ranged from 1n5-2n7 U\ml with an overall mean of 2n3p1n0 U\ml while the thiocyanate concentration ranged from 6n0-10n2 µg\ml with an overall average of 8n5p5n1 µg\ml. Lactoperoxidase activity means for goats ranged from 0n04-0n16 U\ml with a grand mean of 0n1p0n06 U\ml while the thiocyanate content means ranged from 6n6-8n2 µg\ml with a grand mean of 7n0p2n59 µg\ml. There was no correlation between lactoperoxidase activity and thiocyanate content in either cows' (R# l 0n011) or goats' (R# l 0n015) milk. These experiments have revealed that lactoperoxidase activity is affected by many factors including the individual animals, species, feed and stage of lactation. Therefore the exogenous supply of thiocyanate and hydrogen peroxide needed to activate the lactoperoxidase system for raw milk preservation will vary in quantity depending on these factors.

No abstract

The extent to which lactoperoxidase (LP) activity was affected while varying the concentration of various compounds normally present in the reaction medium was investigated. LP activity increased with increasing concentrations of 2,2′‐azino‐bis‐3‐ethylbenz‐thiazoline‐6‐sulphonic acid (ABTS) but decreased with increasing thiocyanate concentrations. Maximum activity was at 0.1 mm for peroxide. Activity increased in the presence of lactose, whey protein concentrate, sodium, magnesium and calcium chlorides, but decreased in the presence of casein. Activity was similar in either acetate or phosphate buffers but higher in either citrate or succinate buffers. These compounds influence LP activity and should be considered when optimum activity conditions are being established.

Soixante-douze cobayes âgés de 6 mois, pesant en moyenne 555,00 ± 58,25 g et répartis de manière aléatoire en 4 lots de 15 femelles et 3 mâles par lot ont été mis en croisement durant 31 jours à l'Université de Dschang afin d'évaluer leurs performances de reproduction. Tous les animaux recevaient ad libitum Pennisetum purpureum associé à 20 g d'une des rations RR0 (Témoin), RR8, RR10 et RR12 contenant 0, 8, 10 et 12% de farine de feuilles de manioc (FFM) respectivement. Les résultats ont montré que la complémentation n'a affecté (P>0,05) ni la croissance pondérale, ni les paramètres de reproduction. Toutefois, les femelles recevant la ration RR8 ont enregistré les taux de fertilité (100%), de fécondité (206,67%) et de viabilité au sevrage (100%) les plus élevés par rapport aux femelles des autres rations. L'augmentation de la FFM dans la ration a réduit (P<0,05) les pertes de poids au terme du sevrage. La complémentation à 10% de FFM a amélioré (P<0,05) les GT (356,56 g) et GMQ (4,99 g) pendant la gestation. L'incorporation de la FFM dans la ration a amélioré les performances de reproduction des cobayes.

The lactoperoxidase system (LP-system) is an acceptable chemical method for raw milk preservation, especially in rural areas where refrigeration facilities are absent to farmers. Milk production in most African countries is dominated by small-scale traditional production systems using low yielding local breeds. Therefore, processors who operate in such situations must rely on small volumes of milk from many farmers. Application of the LP-system prolongs the shelf life of raw milk and also encourages grouping of farmers hence facilitating milk collection by processors. The application of the LP-system is a recent preservation method for milk in Cameroon whose efficiency has been proven. Therefore, need arose for further studies on the influence of this method on milk processing as well as the quality dairy products. The LP-system was activated by adding 10 ppm sodium thiocyanate and 8.5 ppm sodium percarbonate to fresh milk. Yoghurt and Bambui cheese were processed separately from treated and untreated (control) milk samples. Yogurt was produced from both the treated and the control milk samples at 2%, 3%, 4% and 5% (v/v) culture levels. Yogurt samples were analysed for acidity, protein content and dry matter content while cheese was analysed for butterfat and moisture content. Statistical tests were conducted by Analysis of Variance using the Fisher's test. Simple organoleptic assessments were conducted to compare yogurt and cheese from the treated and the control milk. Activation of the LP-system delayed lactic acid formation in yogurt during incubation and storage leading to increased energy consumption during processing and an improved keeping quality during storage. LPsystem treatment reduced the overall organoleptic quality of yogurt while it improved on that of Bambui cheese. Dry matter content and fat content of yogurt were not significantly affected by LP-system treatment (P<0.05). LP-system treatment did not also affect the moisture and fat content of cheese but slightly improved on its yield.