The steam volatile components of Californian green bell peppers (Capsicum annuum var.

Commercial Delicious apple essence was extracted to yield an oil with a strong apple-like aroma.This oil was separated into its components with high-resolution packed and opentubular gas chromatographic columns. Fiftysix compounds were identified, mainly by a combination of mass spectrometry and gas-chromatographic retention data. While many of these compounds contribute to over-all Delicious apple essence aroma, the main components directly associated with characteristic apple-like aroma were ethyl 2-methylbutyrate, hexanal, and 2-hexenal.

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A simple technique for measurement of olfactory thresholds of odorous materials is described. Sensitivity and reproducibility of the method was good, but many precautions must be taken to insure reliability of results. Olfactory thresholds for a number of pure compounds, several of which were identified in potatoes, are presented. In general, sulphur compounds and short-chain unsaturated aldehydes gave the lowest and highest thresholds, respectively. The thresholds of a homologous series of saturated aliphatic aldehydes decreased progressively with increase in chain length from C , to Clo. Similar results were obtained with a series of unsaturated aldehydes. Thresholds of some of the more potent compounds were less than 0.1 of a part per 109 parts of water.

Olfactory thresholds of a series of compounds previously identified in Brewers Gold Hop Oil are given. Thresholds of the oxygenated components ranged from 0.3 to 28 parts per 10° while those of the hydro‐carbon fraction ranged from 6 to 140 parts per 10°. For solutions of hop oil in water, myrcene accounted for about 58% of the total odour intensity of the whole oil and 85% of the odour of the hydrocarbon fraction. The oxygenated fraction amounted to about 1/7 of the whole oil but contributed about 1/3 of total odour intensity.

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The synthesis, mass spectra, and infrared spectra are described for four new 2-methoxy-3-alkylpyrazines with alkyl groups hexyl, propyl, isopropyl, and ethyl. The odor thresholds of the hexyl, propyl, isopropyl, and ethyl compounds were found to be 1, 6, 2, and 425 parts of compound per 1012 parts of water, respectively. The odor character of these four compounds compared to that of the known bell pepper component 2-methoxy-3-iso-butylpyrazine are described as very similar for the hexyl and propyl, moderately similar for the isopropyl, and not similar for the ethyl. The related