No abstract

Rennet covers only 30% of the world's cheese production because the availability of calf stomach becomes limited (FAO, 2016). This lack has suggested the search for animal, vegetable or microbial enzyme substitutes. Among the alternative animal enzymes, chicken pepsin. In order to study the chicken pepsin stability over time, chicken proventriculus, whole or incised into four parts or incised into slices, without or with salt addition distributed into six different lots, were dried under partial vacuum (47°C, 800 mbar). The effects of the incision or not, as well as the addition or not of salt, and storage time of dried proventriculus, on the coagulant activity of pepsin extracts (expressed in equivalents Rennet Units) were studied. The six batches pepsin residual activities determined immediately after drying operation expressed the relative yield in the fresh state before storage. They were between 50% for proventriculus cut into four parts without salt addition and 18% for proventriculus with salt addition.After 54 days of storage, the residual activity was relatively distinct for proventriculus cut into four parts without salt addition : 35.5% and for the proventriculus incised into slices with salt addition of 4.7%. Salt seemed to have caused a great loss of activity during salting. In addition, the incision effect combined to salt addition showed a remarkable loss of activity. During the storage period, the pepsin residual coagulant activity showed better stability of partially vacuum-dried proventriculus cut into four parts and unsalted.

The present work was carried out in order to study the antimicrobial activity of A. herba-alba extracts and their application as food preservative. A crude extract was prepared by steeping of the dry leaves of A. herba-alba in phosphate buffer. In order to obtain an enriched fraction in active molecules, a series of ammonium sulfate precipitation (ASP) was carried out. Extracts showed antibacterial activity against E. feacalis, M. leteus and L. monocytogenes strains. The best activity is noted for the precipitate obtained at ammonium sulfate precipitation of 60% (ASP60), with inhibition zones of 23.67 ± 0.44 mm for the E. feacalis and M. leteus strains and 18.00 ± 0.67 mm for L. monocytogenes. This extract shows a MIC (minimum inhibitory concentration) of 0.23 and 0.9 mg/ml for E. feacalis and L. monocytogenes, respectively. The application of ASP60 on "Takammérite", traditional fresh cheese as preservative, cause a significant slowdown in microbial growth under refrigeration during 15 days of storage.