Drying conditions of black tea using superheated steam (SHS) were optimized based on a central composite design (CCD) of response surface methodology (RSM). The effects of independent variables (temperature and time) towards the total phenolic content (TPC), scavenging free radical ability, ferric-reducing antioxidant power assay and sensory attributes (infusion colour, aroma, flavour and astringency) were analysed using regression polynomial equations. Analysis of variance (ANOVA) showed that a quadratic model fitted the experimental design well, with a p-value less than 0.05 and a highest coefficient of 0.9474. The optimum drying conditions were achieved at 166.7oC and 21.2 minutes where the experimental values were in accordance with predicted values, with percentage errors (PE) less than 10%. Temperature (140oC – 180oC) was concluded to have the most significant effect and showed a positive direction in most responses. This effect was definitely able to support the application of a SHS dryer for the quality production (antioxidant and sensory properties) of black tea.

Osmotic dehydration of chestnut slices in sucrose was optimized for the first time by Response Surface Methodology (RSM). Experiments were planned according to a three-factor central composite design (α=1.68), studying the influence of sucrose concentration, temperature and time, on the following parameters: volume ratio, water activity, color variation, weight reduction, solids gain, water loss and normalized moisture content, as well as total moisture, ash and fat contents. The experimental data was adequately fitted into second-order polynomial models with coefficients of determination (R2 ) from 0.716 to 0.976, adjusted-R2 values from 0.460 to 0.954, and non-significant lacks of fit. The optimal osmotic dehydration process conditions for maximum water loss and minimum solids gain and color variation were determined by the “Response Optimizer” option: 83% sucrose concentration, 20 °C and 9.2 hours. Thus, the best operational conditions corresponded to high sugar concentration and low temperature, improving energy saving and decreasing the process costs.

The objectives of this study were to make yoghurt from camel milk and determine its physicochemical, microbiological and sensory qualities. The quality of camel milk yoghurt was compared with cow milk yoghurt and all parameters were analyzed following standard procedures. Yoghurt of acceptable consistency was made from camel milk using 1.2% gelatin, 5% bovine skim milk powder, 1.5 ml/L of calcium chloride, 40 ml/L of maple strawberry syrup and 6% yoghurt culture (YF-L811) and by incubating the milk at 42°C for 18 h. The average values for moisture, ash, syneresis, pH, titratable acidity and total solids of camel milk yoghurt were 83.4%, 1.13%, 58%, 4.37, 1.255% lactic acid and 16.7%, respectively. The corresponding values for cow milk yoghurt were 80.6%, 0.71%, 56%, 4.67, 0.865% lactic acid and 19.5%, respectively. The titratable acidity of camel milk yoghurt was significantly higher (P<0.05) than cow milk yoghurt; however, no significant difference was observed between the two yoghurt types for the other parameters. Coliforms were not detected in both yoghurt types. The sensory analysis showed that cow milk yoghurt was more preferred by the panellists than camel milk yoghurt. Production of yoghurt from camel milk using the same procedure as for cow milk yoghurt proved to be difficult.  Further research is called for to improve the acceptability of camel milk yoghurt using locally available and acceptable flavouring agents. Research needs to be conducted to optimize the operating parameters and standardize the production procedures of camel milk yoghurt in the future.

The potential of pineapple peel as a source of cellulose nanocrystals was evaluated. Peels skin from fresh-cut fruit was used as raw material. These residues were purified to remove pigments, lipids and hemicellulose, and a bleaching process for delignification was carried out for 4-6 h. All resulting products were characterised for their lignin, hemicellulose, cellulose and ash contents using standard techniques. Dry matter at the end was low (ca. 50%) compared with the raw material (ca. 90%). The process applied resulted in ca. 20% (m/m) of purified cellulose (ca. 80% purity), with ineligible levels of lignin and hemicellulose present, especially when using 6h of bleaching. The purified cellulose was subject to acid hydrolysis for nanocrystal extraction with two testing times, 30 and 60 minutes. These cellulose nanocrystals had small sizes (< 1000 nm), with high variability and negative zeta potential values. The time of extraction did not affect the nanocrystals’ chemical and physical properties. The use of 6 h of bleaching treatment during purification was shown to be more effective than 4 h. Pineapple peel was demonstrated to be a good source of cellulose for the production of cellulose nanocrystals. 

The objectives of this study were to optimize the conditions for cell growth and exopolysaccharides (EPS) production by using pure and mixed microbial cultures of Streptococcus thermophilus and Lactobacillus bulgaricus, and to evaluate the antioxidant and antibacterial activities of EPS in vitro. The mixed cultures of two strains showed a higher cell growth whereas the higher EPS production was detected in pure culture with S. thermophilus. The optimal medium were determined as follows (g/l): sucrose 50, yeast extract 10, KH2PO4 3 , MgSO4.7H2O 0.05 and pH initial 6.5 at 30°C. Under the optimized conditions, the values of dry cell weight (DCW) and EPS were 5.2± 0.8 g/l and 56.8 ± 0.62 mg/ml, respectively.  The EPS demonstrated a positive antioxidant potential on DDPH radical scavenging. The agar diffusion assay showed that purified EPS exhibited antibacterial activities against tested pathogens such as Escherichia coli ATCC 250922 and Staphyloccocus aureus ATCC 250923 at (62-1000) μg/mL. In conclusion, EPS have an antioxidant activity and could have applications in the food industry.