PRODUCING VINEGAR FROM UNMARKETABLE DATES OF THREE LIBYAN CULTIVARS USING DOUBLE STAGE FERMENTATION METHOD

This work investigated producing vinegar from unmarketable 'Taleese', 'Athwi' and 'Hellawi' Libyan date cultivars. Sugar was extracted from 'Athwi' and 'Talees' dates by soaking in distilled water at 1:3 (w/w) for 10 hours and pressing while 'Hellawi’ dates were mixed with distilled water at the similar ratio, heated at 80°C and agitated for 2 hours and pressed. Total soluble solids (TSS) of solutions obtained from the three cultivars were 16.5, 17.4 and 25.0 °Brix, respectively. Solutions were adjusted to 15.5°Brix and 8 litre of solution of each cultivar were fermented in 15L setup equipped with an airlock. Baker’s yeast was added and solutions were incubated at room temperature averaging 22°C. The process lasted 9 days, afterward aerobic acetification was carried out by adding virgin date vinegar at 10% (v/v) and solutions were kept under same conditions. Weekly measurements of titratable acidity (TA) and alcohol percentage were made until alcohol content dropped below 1%. The process lasted 60 days for 'Taleese' and 'Athwi', while 'Hellawi' took additional 11 days. Both fermentations were described by linear relations (R2 >0.97). In the anaerobic reaction, cultivars were significantly different in their alcohol percentages and TSS but were similar in acidity and pH. In the aerobic fermentation, no significant differences in TA, pH but significant different in alcohol residues and TSS were recorded. Moreover, sensory evaluation of the three kinds of vinegar was made on acidity, taste, and acceptance; again no significant differences were recorded. Color analysis in Hue angle, Chroma and L* were also made, vinegar of the three cultivars were significantly different; 'Hellawi' vinegar was much darker than 'Athwi' and 'Talees'. Quantification of acetic acid showed its contents above 5% (v/v), representing nearly 85% of total acids. The study demonstrated the potential of producing good quality vinegar from unmarketable Libyan dates

In-situ estimation of respiration and transpiration rates of stored fruits and vegetables

The use of a direct method for measuring respiration and transpiration rates may lead to better storage control systems and closer observation of storage losses. A laboratory scale environmental chamber was constructed and provided with a fan and adjustable louver to obtain variable ventilation flow rates. Flow rates were determined using a pressure sensor and fan characteristic curves which were determined experimentally. A regression equation representing the flow rate versus pressure relation was derived and used for estimating the flow rates throughout the study.Respiration and transpiration were simulated using precision heat sources ranging from 15 to 105W in 15W interval and an evaporative pad. Measured wet and dry bulb temperatures and ventilation flow rates were used for the estimation of heat and moisture generated inside the chamber. The work was performed in two parts. In the first, precision heat sources were used and the heat balance equation components were solved.In the second part, heat and moisture were generated inside the chamber, heat and moisture balance equations as well as psychrometric equations were solved. (Abstract shortened by UMI.

Respiratory response of healthy and diseased potatoes (Solanum tuberosum L.) under real and experimental storage conditions

This study investigates respiration rate of potatoes (Solanum tuberosum L.) under real and experimental storage conditions. Real storage conditions were obtained by building a small-scale storage facility equipped with two independent storage bins including all controls. Each bin was filled with 2.5 metric tons of potatoes and these were stored for five months. Temperature, relative humidity, air flowrate and other operational parameters were collected. Also, mass loss and CO2 analyses were performed.A heat and moisture balance was applied to quantify heat and moisture rates produced by potatoes and were converted to respiration rates as CO 2 produced (ml.kg-1.h-1). Evaporation rates were also determined (g.kg-1.h -1). The balance was mainly applied on data collected from specific periods in which steady conditions were imposed; heaters and humidifiers were turned off and fans were operated to circulate air at a given flowrate for more than 8 h/day over a two month period. Respiration rates were determined as rates of heat produced (W) with stability and acceptable accuracy for a relatively large facility. Respiration rates were converted to CO2 production (ml.kg-1.h-1), and these agreed fairly with ranges reported in the literature. Simultaneously, respiration rates were measured by in-store CO2 analysis, and later they were measured under laboratory conditions using a closed gas analysis system. Comparing these with rates obtained by the heat and moisture balance, the later were slightly higher. Mass losses were also obtained by both weight losses and moisture balance; results from the two methods were quite similar and comparable with those reported in the literature.Under experimental conditions, respiration rates were measured for healthy, diseased and sprouted tubers using a gas analysis method. This experiment demonstrated the need for a more extensive investigation of disease development and its relation to respiration rates, and the need for a faster and more convenient gas analysis system. (Abstract shortened by UMI.