Advances in Food Science and Engineering

5

Authors: Ayuba L., Agboire S., Gana A.K., Ishaq M., Aliyu U., Affiniki G., Manjang J. I.

The potential of using castor oil as an antibacterial agent was investigated on three species of bacteria chiefly responsible for throat, skin and enteric infections. Staphylococcus aureus was used as the test organism for skin bacteria, the throat bacteria used was Streptococcus viridans, while for enteric bacteria, Shigella dysenteriae was used. Castor oil was extracted by cold pressing of seed kernels. The extract obtained was assayed for antimicrobial activity on the in-vitro growth of test organism using direct inoculation, paper disc method. These were soaked in the castor oil for 1 hour. The soaked discs were then placed on prepared plates each containing the test bacteria, the antimicrobial effect of the castor oil was observed by measuring the zone of inhibition of the agent against the test bacteria. The result showed that castor oil is highly effective against all the bacteria species tested; the zone of inhibition measured, showed that Staphylococcus aureus is more susceptible to the oil than the other bacteria with a range of 11-13mm while Streptococcus viridans had a range of 8-10mm and the least was Shigella dysenteriae which had a range of 3-6mm. The result obtained implies that castor oil can be used in the control of wounds, skin infections, throat infections and in the treatment of stomach unrest caused by these bacteria species.

6

Authors: Samira Nair, Nebia Bouzidi Maghraoui

Honey is a nutritious product that is produced by honey bees. Its composition depends highly on the type of flowers utilised by the bee as well as the climatic conditions. This study was intended to evaluate the quality parameters of ten honey samples, from various regions in NorthWest of Algeria. The physicochemical property of the honeys [moisture, electrical conductivity, hydroxymethylfurfural, pH, acidity (free, total and lactone), reducing sugars, apparent sucrose, insoluble material, ash, and diastase activity] was determined. The moisture shows values of 14.21±0.18 % and 16.59±0.12%. The water insoluble material content ranged between 0.01 ± 0.03 to 0.67 ± 0.07%. The reducing sugars were between 66.3 ± 0.37 and 88 ± 0.23 %, mean percentages of apparent sucrose were 6.54 ± 0.23%. Honey samples showed an appropriate diastase number with an average of 12.35 ± 0.24, and their HMF (hydroxymethylfurfural) content ranging from 5.65 ±0.37 to 37.42 ± 0.55 mg/kg, Conductivity values ranged from 10 ± 0.54 to 606 ± 2.45 µS/cm. The ash content ranged from 0.019 ± 0.01% to 0.37 ± 0.05%. All honeys were acidic, having a pH in the range 3.7 ± 0.03– 4.78 ± 0.05. The average values for free acidity in samples were between 10 ± 0.22 and 25 ± 0.5 meq/kg. Lactonic acidity ranges were from 2 ± 0.15 to 5 ± 0.15 meq/kg. Total acidity ranged from 12 ± 0.37 to 30 ± 0.65 meq/kg. All the samples were found to meet all major national and international honey specifications.

11

Authors: Fernanda Rosa Assis, Rui Manuel Santos Costa de Morais, Alcina Maria Miranda Bernardo de Morais

The aim of the present work was to study the effects of the osmotic dehydration (OD) on the mass transfer kinetics of the microwave drying (MWD) and some quality parameters of apple cubes. The fit of several mathematical models was tested to describe the drying. A comparison between MWD and hot air drying (HAD) was performed. Apple cubes were osmotically treated with 60ºBrix sucrose or sorbitol solutions at 60ºC and dried at a microwave power between 160 and 850 W. Overall, the increase of the microwave power from 160 to 500 W resulted in an increase of the water loss rate, shown by the A parameter of modified Page’s model, of 123 and 155% for samples osmotically dehydrated with sucrose and sorbitol solutions, respectively. The OD tends to increase the drying rate, but the osmotic agent used did not have any effect. The modified Page's model described well the drying kinetics and MWD was faster than HAD. The water activity of the osmotically dehydrated product was reduced to below 0.4 after MWD at 500 W. The MWD of control samples resulted in a loss of 39% and 28% of the total phenolic content and the antioxidant activity, respectively. For osmotically dehydrated samples, a loss of around 75% was observed for both these quality parameters after the osmotic treatment.