No abstract

To take full advantage of computer monitoring and control systems already in existence in many breweries, there is a need for reliable and inexpensive on-line sensors. Prior to the development of any system for production scale conditions, the underlying principles of the method of measurement adopted have to be investigated.Work at the laboratory (1.5 Litre and 11 Litre), pilot (30 Litre) and experimental brewery (100 hi) scales of fermentation has demonstrated that a good correlation exists between evolved CO2 and changes in specific gravity. During the period from the onset of CO2 evolution to the end of a fermentation, it was found that evolved CO2 yield was ca. 1.0 gCO2/ Litre/degree gravity drop. Metering systems based on evolved CO2 determination are nonintrusive, simple to install and cost effective.

This study was performed in the aim to evaluate nine different extracts from Tunisian Lycium arabicum for their total phenolic and total flavonoid contents, phytochemical analyses as well as their antioxidant and anti-lipase activities. The in vitro antioxidant property was investigated using three complementary methods (DPPH, ferric reducing antioxidant power (FRAP), and β-carotene-linoleic acid bleaching assays) while anti-lipase activity was evaluated using 4-methylumbelliferyl oleate method. From all of the tested extracts the most potent found to be the polar MeOH extracts especially those of stems and leaves. In order to investigate the chemical composition of these extracts and possible correlation of their constituents with the observed activities, an UHPLC/HR-ESI-MS/MS analysis was performed. Several compounds belonging to different chemical classes were tentatively identified such as rutin and kampferol rutinoside, the major constituents of the leaves, and N-caffeoyltyramine, lyciumide A, N-dihydrocaffeoyltyramine as well as fatty acids: trihydroxyoctadecadienoic acid and hydroxyoctadecadienoic acid isomers were detected abundantly in the stems. These results showed that the MeOH extracts of stems and leaves of L. arabicum can be considered as a potential source of biological active compounds.

The time course of the extraction of a-acids by liquid carbon dioxide was investigated and it has been established that there are two zones with greatly differing rates of extraction. The rate in the first zone is governed by 'solubility' effects, while in the second zone the rate is limited by 'diffusions!' effects. Consequently the rate of extraction in the first zone depends upon the flow rate of liquid carbon dioxide while that in the second zone depends upon the time of extraction. The effects on extraction performance of the depth of the bed of hops and the extent of milling were also explored.

The quality of beers bittered with liquid CO2 and ethanoi extracts derived from fresh and deteriorated hops and the percentage utilization of alpha-acids therefrom were comparable. The importance of using analytical methods which measure bitterness substances per se is emphasized.