الفهرس 
AcknowledgementOnly 14 pages are availabe for public view
 |  | from | 166 |  |  |
| | | from | 166 | | |
Abstract
In the present study a total of random 160 pasteurized and Falahy butter samples (80 samples each) were bought from different localities in Assuit city. The sensory assessment for pasteurized and Falahy butter samples showed that62.5, 78.75% of samples exceeded score 90 (excellent) and 37.5, 21.25% had score (80-89). The mean values of peroxide index, TBRA reactive substances and acid index were (0.39±0.02, 0.44±0.03 meq/kg), (0.46±0.03, 0.51±0.02 mg MDA/Kg) and (0. 67±0.01, 0.82±0.02 mg KOH/g) for pasteurized and Falahy butter samples, respectively which revealed that all samples were acceptable with the absence of both hydrolytic and oxidative types of rancidity.
The mean values of the microbiological evaluation were (1.3x105 ± 1.6x104, 8.8x106 ± 1.3x104), (1x105 ± 2.3x104, 3.2x105 ± 3.3x104), (5.7x104 ± 1.3x104, 9.4x104 ± 2x104), (1.5x104 ± 3x103, 2.8x104 ± 4.5x103) and (1.3x103 ± 3.3x102, 1.6x104±4.2x103) CFU/g for total colony, Psychrotrophic, lipolytic, yeast and mold counts in pasteurized and Falahy butter samples, respectively. The results revealed the substandard production and storage conditions which calls for improvement of butter production modern technologies and awareness creation about the hygienic production, processing and handling of butter.
Moreover, nanoemulsions of Clove and RosemaryEOs were prepared and then characterized by Zeta sizer, FTIR and TEM. Finally, the effect of Clove and RosemaryEOs and their nanoemulsions on the quality of butter was studied by monitoring chemical, microbiological and sensory characteristics of the product over refrigerated storage.The droplet sizes of the CNE and RNE were 131.6 and 116.1 nm, respectively, whereas those by TEM were spherically shaped with average sizes of 87.92 and 77.43 nm and polydispersity indices (PDI) of 0.52 and 0.36, respectively.
Antimicrobial activity of the CEO, CNE, REO and RNE was determined against Gram positive (Staphylococcus aureus) and Gram negative (Escherichia coli) bacterial strains using minimum inhibitory concentration (MIC). MIC of both EO against Staph.aureuswere 0.5 and 1% but against E. coli was 1% and 1.5%. Also, MIC of clove and rosemary NEs against Staph.aureus were 0.25%, 0.5% and against E. coli was 0.5%, 1% respectively.
Overall sensory evaluation showed that the order of preference was control followed by RNE, CNE, REO and CEO. However, at the end of storage period CNE and RNE flavored butter had the fair grade, while the other flavored samples were judged as poor.
The chemical composition of stored butter samples at 5 ºCfor 5 weeks was significantly affected. The acid value increased significantly from0.33 to 1.6 mg KOH/g of fat at the end of the storage period which indicate that butter underwent lipolysis. The values of parameters indicating fat oxidation (peroxide value and TBA value) increased significantly during storage (from 0.23 to 1.25 meqO2 /kg of fat and from 0.007 to 0.78 mg malondialdehyde/kg, respectively).
Referring to storage time, the considered microbial analysis (total bacterial, psychrotrophic, lipolytic bacterial count, yeast and mold count) underwent a gradual increase until the end of storage. TBC was 7x103cfu/g,and reached 9x106cfu/g, the average psychrotrophic count was 2x104cfu/g and reached 4x107cfu/g, lipolytic count was 1.7x103cfu/g and become 7.1x106cfu/g, while yeast and mold count began with 1x105 cfu/g ,4x104 cfu/g and reachedto 4x106 cfu/g , 5x107 cfu/g , respectively at the endofstorage.
Clove, Rosemary oils and their NEs were shown to have strong antibacterial and antioxidant activities, Addition of CEO, CNE, REO and RNE significantly (P≤0.05) controlled the growth of total bacterial, psychrotrophic, lipolytic bacterial count, yeast and mold count when compared to the control samples. Compared to the control, CNE supplemented butter was the best, followed by RNE, CEO then REO. In terms of chemical parameters,CNE, RNE showed the highest antioxidant activity, when compared to the control and the others groups.