A guava-like flavour occurring in some South African Chenin blanc and Colombard dry white wines was investigated. Headspace volatiles of some of these wines, as well as those of fresh guava fruits, were analysed by means of a gas chromatograph equipped with a "sniffer-detector". In contrast to the headspace concentrate of guava fruits, no single fraction with a typical guava flavour was found in the wines analysed.The pattern recognition system "ARTHUR" was therefore used to investigate relationships between the more important wine volatiles and the intensity of a guava-like flavour of a set of wines originating from the same Chenin blanc must. Sensory scores for this flavour were used in both category and continuous property analysis in each case. Category and correlation to property plots were used to elucidate the results. Several promising variables and ratios between variables were singled out for further investigation, notably ethyl butyrate and the ratios ethyl butyrate/ethyl decanoate and ethyl butyrate/ethyl octanoate.
Pattern recognition and simple factorial analyses were applied to chemical profiles determined on wines resulting from an experiment in which the effect of grape solids, assimilable nitrogen, bentonite and fermentation temperature levels as well as culture aeration on total fermentation time was investigated. It was found that fermentation times of the untreated Chenin blanc must could be shortened considerably by increasing grape solid levels and/ or nitrogen as well as temperature. However, it was established that the speeding up of fermentation at sub-optimal assimilable nitrogen levels leads to wines relatively high in higher alcohols and low in esters.
The effect of four yeast strains, two levels of grape solids, two nitrogen levels and three fermentation temperatures viz. 10°, 13° and 15° C on total fermentation time (TFT) and wine quality was studied in a factorial experiment by employing a nitrogen deficient Chenin blanc must. It was found that the presence of solids, addition of nitrogen and fermenting at 15° C decreased TFT dramatically. Nitrogen was the only factor which also increased wine quality, the other two having a detrimental effect. At optimum levels of nitrogen, yeast strains WE 452 and WE 500 (VORI collection) reduced TFT without detrimentally affecting wine quality. In the case of WE 452, no solids should be present and fermentation conducted at 10° C -13° C, and in the case of WE 500, traces of solids should be present and a fermentation temperature of between 13° C -15° C should be utilized. Under these conditions WE 452 and WE 500 reduce TFT from C.76 days to as few as C.30 and C.15 days respectively.
The occurrence of killer factor amongst yeast strains in the Viti cultural and Oenological Research Institute (V 0 RI) yeast collection was studied. From a total of 96 strains, 85 were Saccharomyces cerevisiae of which 7 strains were killer, 9 neutral and 69 sensitive. These included some imported strains. On agar, no killer action was detected at wine pH. In fermentation studies using four grape cultivars, it was shown that where the killer yeast population was less than approximately 2,5% fermentation was not affected. At higher levels the killer yeast, in some instances, took over and completed fermentation, but the total fermentation time was never longer than that of the killer strain on its own. It was concluded that the use of a yeast strain should not hinge on its killer character but rather on its oenological characteristics.
A Chenin blanc and a Colombar vineyard was sprayed with copperoxychloride (CuOCI) in different spraying programs. A laboratory trial was conducted where copper in different concentrations was added to grape must and fermented. Copper concentrations were determined in musts and wines, fermentation curves established and wine quality assessed. Results show that spraying a vineyard with CuOCI for 5 or 6 consecutive sprays up to 14 or 3 days before harvest respectively caused copper concentrations of 13-44 mg// in the settled musts. Spraying a vineyard at 14 + 7 + 3 days before harvest yielded a must with a copper concentration of 16 mg//. These musts as well as a must to which 10 mg/ I of copper was added, underwent slower fermentation than their respective controls. Wine quality was seriously impaired. It is concluded that the closer to harvest the last copper spray is applied, the more problems will be encountered.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.
hi@scite.ai
10624 S. Eastern Ave., Ste. A-614
Henderson, NV 89052, USA
Copyright © 2024 scite LLC. All rights reserved.
Made with 💙 for researchers
Part of the Research Solutions Family.