http://depot.umc.edu.dz/handle/123456789/10037 2026-06-01T14:36:33Z http://depot.umc.edu.dz/handle/123456789/14829 Formulation, fabrication et caractérisation de fromages frais aux laits de dromadaire et de chèvre. Bouras, Biya; Aissaoui Zitoun ép Hamama, Ouarda This study aims to improve the coagulation of camel milk for the production of fresh cheese by using goat's milk and various rennet substitutes. First, we studied the raw materials used, including the raw composition of camel and goat milk and the characteristics of camel rennet, goat rennet and chicken pepsin. Then, we studied the optimization of flocculation and coagulation parameters mainly pH and temperature with milk alone and camelgoat milk mixed with different formulations using response surface methodology (RSM). The optimum points obtained will be used for the manufacture of fresh cheese with enzymatic coagulation and with mixed coagulation by adding mesophilic lactic bacteria. The chemical and mineral analysis of camel milk and goat milk showed the specificity of the composition of camel milk in comparison with cow milk mainly in terms of protein, fat and total solids, lactose and even in chloride, sodium and copper. On the other hand, the characterization of the enzymatic extracts of camel rennet, goat rennet and chicken pepsin revealed variable protein contents and coagulant activities and good coagulant strength, respectively 1/4166.67, 1/2531.64, 1/6153.85. The optimization of the flocculation and coagulation time made it possible to highlight the specific optimum points according to the enzymatic extract used, the type of milk and the formulation tested. It appears that each enzyme acts differently on the coagulation of milk depending on the pH and the temperature, and even when we are under the same conditions, each enzyme gives a specific coagulum. Overall, the pH ranges from 5 to 6.7 and the temperature from 30°C to 42°C. At the level of the manufacture of fresh cheese, twelve formulations were produced and characterized, according to the proportions of camel and goat milk (75/25, 50/50, 25/75) and the type of enzyme. The best cheese yields of enzymatically coagulated fresh cheeses are those of camel rennet cheese with 19.3±0.9% of the FD25, goat rennet cheese with 13.45±0.5% of the FC25, chicken pepsin cheese with 16.65± 1.0% of FP25 and microbial coagulating agent cheese with 18.3±0.4% of FM50. Most of the cheeses obtained can be classified according to the food codex as soft and semi-fat. In rheological terms, the cheeses produced are quite firm. Cheese gel with camel rennet behaves like a dilating coagulum while those produced with chicken pepsin behave like a pseudoplastic coagulum. Whereas, cheeses produced with goat rennet and microbial coagulant behave as a dilating and pseudoplastic coagulum. This clearly shows the effect of the type of enzyme on the coagulation of the camel-goat milk mixture. In addition, electron microscope observations showed the specificity of each coagulum according to the enzymatic extract tested and according to the proportion of goat milk added to camel milk. The difference is noted in the number and diameter of the pores and the appearance of their compactness. Moreover, the statistical analysis of the amino acid concentration results revealed a significant difference (P<0.05) between most of the different formulations with the dominance in the cheeses of histidine. Finally, the best enzymatically coagulated cheeses according to sensory tests are the FD50, FC75, FP50 and FM25 formulations with an overall acceptability score on a score of 15 from 7.85±2.34 (FM25) to 10.05±3.81 (FC75). Finally, the physico-chemical characterization of the best four mixed coagulation formulations (FD50B, FC75B, FP50B and FM25B) gave cheeses with a total solids content of 25.66±0.5% to 43.55±1.2% and Fat/TS of 30.47±2.7 to 49.85±0.16 with a significant difference (P <0.05) for all parameters analyzed. From a sensory point of view, it should be noted that the addition of ferment has clearly resulted in more characteristic and more appreciated cheeses. The results obtained tend and converge towards the possibility of using camel rennet, goat rennet and chicken pepsin in cheese processing based on camel milk mixed with goat milk, taking into account the specific optimum points for each enzyme and each formulation. 2023-06-18T00:00:00Z http://depot.umc.edu.dz/handle/123456789/14801 Analyse de la composition chimique et évaluation des propriétés biologiques des huiles essentielles de trois plantes aromatiques et médicinales (Thymus willdenowii, Aloysia citriodora et Cymbopogon citratus) et impact de leur incorporation dans le yaourt étuvé. Benguedouar, Karima; Barkat, Malika; Bencharif-Betina, Soumeya The characterization of three essential oils (EOs) of aromatic and medicinal plants : thyme (T. willdenowii), verbena (A. citriodora) and lemongrass (C. citratus) and their incorporation into yogurt were the subject of this study. A survey of Internet users via Google Forms revealed that a high percentage did not use EOs in cooking or drinking. Analysis of the chemical composition by GC/MS revealed citral with its two isomers E-citral (38.6%) and Z-citral (29.89%) for citronella, and E-citral (34.43 %) and Z-citral (27.85%) for verbena and linalool (89.55%) for thyme. The essential oil extraction yields are 1.23±0.23%, 0.83±0.35% and 0.83±0.27% respectively for lemongrass, thyme and verbena. Thyme has a higher antiradical activity than verbena and lemongrass as well as the highest content of phenolic compounds (405.67±13.08 µg GAE/mL of yogurt). A strong inhibition of pathogenic bacteria such as B. cereus, S. enteritidis, P. aeruginosa and E. coli is obtained with thyme EO. Lemongrass EO has proven to be the most inhibitory of lactic acid bacteria in yoghurt: L. bulgaricus and S. thermophilus. The antioxidant and antibacterial activities of verbena EO were weak. However, it showed an interesting inhibitory activity of the butyrylcholinesterase enzyme, just after lemongrass EO.The inhibitory activity of the α-amylase, urease and tyrosinase enzymes was weak for the EOs studied. The evaluation of the cytotoxic effect of EOs on Artemia salina larvae did not show any cytotoxicity. The incorporation of essential oils into yogurt at a dose of 25 µL/L maintained satisfactory microbiological quality of the products. The physico-chemical analysis of the different yogurts revealed a decrease in pH throughout the cold storage period. However, the pH values, significantly are elevated in yogurts incorporated essential oils of lemongrass and verbena. The incorporation of essential oils of lemongrass and thyme significantly increased the antioxidant potential of these yogurts on the seventh day of storage evaluated by the CUPRAC test, as well as on the 21st day of storage for the yogurt incorporating the essential oils of thyme evaluated by the test ORAC. The antioxidant potential of lactic acid bacteria increased after their fermentation with the different EOs studied. HPLC analysis of the organic acids and aromas produced revealed an increase in the production of lactic and citric acid at the end of cold storage for yogurts containing verbena and lemongrass essential oils. The three HEs also stimulated the production of the acetaldehyde aroma from the first day of storage. The evaluation of the phenolic compounds content of the formulated yogurts revealed an increase of these compounds in the lemongrass EO yogurt on the first day and in the thyme yogurt on the seventh day of storage. The yogurt incorporated with verbena EO was the most appreciated by the panel of tasters, followed by the yogurt incorporating lemongrass and thyme EO. 2023-07-11T00:00:00Z http://depot.umc.edu.dz/handle/123456789/14653 Étude in vitro des propriétés probiotiques des bactéries lactiques d’origine apicole et essai de formulation d’un sorbet fonctionnel à base de fruits et de Psyllium. Meradji, Meriem; Kharroub, Karima The honeybee Apis mellifera intermissa hosts significant microbial biodiversity, with associated microorganisms showing exciting potential in the agro-food industry. These microorganisms represent a valuable resource for isolating novel strains of lactic acid bacteria with proven probiotic potential. This thesis focuses on the investigation of new indigenous lactic cultures with probiotic properties, isolated from the digestive tract of Apis mellifera intermissa and its honey, using cultural methods. A total of 141 presumptive lactic acid bacteria (LAB) isolates were obtained from five bees and two samples of fresh honey. Among them, 19 isolates were found to be acidresistant. Their polyphasic characterization identified them as belonging to four species: Fructobacillus fructosus, Apilactobacillus kunkeei, as well as Lactobacillus kimbladii and/or Lactobacillus kullabergensis. The isolated strains were then subjected to a series of in vitro tests to evaluate their probiotic properties and select the most effective ones. The results revealed significant variations in viability under simulated gastrointestinal conditions, as well as differences in autoaggregation and hydrophobicity levels. Broth cultures assessed using the disk diffusion method, demonstrated variable antibacterial activity against five human pathogenic strains. However, only the neutralized and catalase-treated supernatants of Fructobacillus fructosus ML20 and Apilactobacillus kunkeei U21 inhibited the growth of Escherichia coli, Bacillus cereus, and Staphylococcus aureus. Ten out of fourteen strains selected for their antibacterial activity demonstrated a significant ability to reduce cholesterol levels. The safety of the lactic strains was confirmed in vitro by the absence of hemolytic activity and biogenic amine production, along with variable sensitivity profiles to 13 tested antibiotics. Finally, a functional fruit-based frozen dessert was developed by incorporating the probiotic strain Fructobacillus fructosus ML20, selected for its interesting functional properties. Three formulations were tested: a standard one with an industrial stabilizer, a second with psyllium, and a third derived from the psyllium-based formulation by adding the ML20 strain. Although the melting kinetics favored the standard formulation, no significant differences were observed between the first two formulations in terms of physicochemical parameters, and the psyllium sorbet was preferred in sensory analysis. The ML20 strain demonstrated satisfactory viability in the product under simulated gastrointestinal conditions and after 30 days at -18 °C.These results highlight its industrial potential, particularly in the functional food sector. 2025-05-14T00:00:00Z http://depot.umc.edu.dz/handle/123456789/13649 Smen/Dhan, beurre fermenté traditionnel Boussekine, Rania; Barkat, Malika In Algeria, a wide variety of fermented dairy products are traditionally prepared, these products are part of the Algerian heritage and represents a cultural, medicinal and economic importance. Among these products, Smen or Dhan is a naturally fermented butter made by traditional methods. A Better knowledge of this product in terms of technological, physicochemical and microbiological know-how represents a scientific interest in order to control its health and organoleptic qualities and also for its valorization. The first part of this study was to investigate the place and use of this product in the Algerian culture as well as to identify the traditional methods used for its preparation. A survey was conducted on 880 households in 7 regions of the South and East of Algeria. The results revealed that this product is known by the majority of the surveyed population and prepared at household level according to empirical methods. The production of Smen is mainly intended for home consumption or marketed informally. Two different preparation modes are used depending on the surveyed regions. Households from Batna, Khenchela and Setif proceed directly with butter salting, while in the Biskra, Jijel, El Oued and Ouargla regions, a different process is used which first involves a heat-treatment of the butter followed by the addition of one or more ingredients. After packing in a traditional ceramic container (Ezzir) and other containers, a maturation step is applied with a long duration varying from one month to several years. This product is consumed as an additive to enhance the taste and aroma of some traditional dishes (couscous/other) and is also used in traditional medicine. In the second part of this work, we studied the microbial diversity and its implication in the Smen maturation. To reach this goal, 15 Smen samples (final products) produced in households were collected from different regions in Algeria, while microbial dynamics were investigated for one Smen preparation. The culture-dependent approach allowed the evaluation of the hygienic and sanitary quality, and the molecular identification of lactic acid bacteria (rRNA16S) and yeasts (D1-D2-rRNA26S region). The culture-independent technique (metabarcoding) using illumina-Miseq sequencing, targeting the V3-V4 region of RNA16S (BL) and the ITS2 region of RNA26S (yeasts), was also carried out, in order to identify microbial species that leave their genetic fingerprints (DNA). Results showed that all hygiene and safety criteria were satisfactory for these Smen products. Molecular identification of LAB and yeasts isolates showed that the samples were highly diverse in microflora. Among the total isolates LAB (121), 82 strains were chosen for molecular identification, the results showed that they belong to 11 species and 4 genera. regarding yeast isolates (102), 48 strains were identified to belong to 15 species and 11 genera. Significant divergences were observed between the two techniques used, the independent culture revealed the most imposing species (Lactococcus lactis and Streptococcus salivarius subsp. thermophilus), these later were not isolated by dependent culture approach, which revealed that the species of lactobacilli and enterococci were the most represented in the collected Smen samples. Regarding fungal diversity, several key species involved in Smen manufacturing and maturation were identified by the two approaches, i.e., Geotrichum candidum, Wickerhamiella pararugosa, Kluyveromyces lactis, Yarrowia lipolytica, Kluyveromyces marxianus, Torulaspora delbrueckii, Clavispora lusitaniea et Rhodotorula mucilaginosa. In addition to these results, a new species of Moniliella sp., was isolated which sequence gene (D1/D2-rRNA26S) represents 95% of similarity with Moniliella dehoogii its closest phylogenetic. Finally, the third part of this work was the analysis of volatile compounds by GC-MS and their dynamic during Smen maturation, as well as to highlight the nature of correlations between the volatile compounds and microbial diversity. 81 volatile organic compounds belonging to different families have been identified: Esters (20), ketones (20), aldehydes (13), fatty acids (12), alcohols (7), furans (3), terpenes (2), styrene (1) and other compounds (3). Volatile compound diversity and their abundances were highly related to maturation time and lipolysis degree as well as to the nature of autochthonous microbiota for which several correlations were noted between volatile compounds and identified species. Smen/Dhan is a territory product with an ethnic name and know-how passed down through generations. It would therefore be very interesting to create cooperatives that could market this product in a formal way, with a specific property label. It could help local producers to improve the quality and safety of the product. The selection of some LAB and yeast strains for Smen on an industrial scale, would also be interesting for its quality attributes. 2022-06-09T00:00:00Z