EFFECT OF CERTAIN CHEMICALS IN WATER ON THE FLAVOR OF BREWED COFFEE^a

Abstract

Organoleptic studies of odor-producing impurities which might impair the taste of water supplies and coffee brewed therefrom have been conducted and taste thresholds of six odor-producing chemicals and four non-volatile compounds used in water treatment have been estimated. These experiments supplement earlier work by Lockhart, Tucker, and Merritt (2) which was concerned with threshold levels of inorganic ions normally present in water supplies.Ammonia, chlorine, hydrogen sulfide, phenol and the ortho-and parachlorophenols were selected as typical examples of odor-producing impurities found in some municipal water supplies.It was assumed that coffee-making equipment and china would retain traces, at least, of chemicals used for cleansing and that coffee brew might contain water softening compounds in appreciable amounts. Disodium dihydrogen versenate, commonly used as a sequestering agent, and Calgon, were selected as representative water-softeners. Trisodium phosphate, a heavy duty cleanser, and Tide, an all-purpose detergent, were also included in this phase of the experiment. Threshold levels were determined for the selected compounds in water and in coffee brew made from water solutions of the respective chemicals. Effect of these chemicals on the flavor o f the brewed coffee was also noted.Solutions of the chemicals were prepared with redistilled water in terms of parts per million. Residual chlorine was determined in water heated by the method for preparation of standard coffee brew (2). Threshold values were reported in terms of residual chlorine. Variable losses of hydrogen sulfide made reliable estimates of thresholds in treated coffee brew unfeasible. The negligible losses of ortho-and parachlorophenol during brewing were confirmed by the use of standard curves obtained with a Beckman Model DU Quartz Spectrophotometer.Concentrations chosen for triangle tests were such that the odd sample would be identified by more than 35% but less than 1 0 % of the judges.The coffee used was one selected from several as an acceptable brand. I t was a Silex-grind type and vacuum-packed in one-pound cans. The coffee brew was prepared in Silex glass coffee makers by the method previously used (2). Controls were brewed with redistilled water and treated samples were brewed with the solutions described above. EXPERIMENTAL Method. Organoleptic panels of 21-22 experienced judges participated in difference tests of the triangle type. Since panel members were selected from among the depart-' Contribution No. 328 from the Department of Food Technology, Massachusetts Institute of Technology, Cambridge, Mass. 5 75

Taste Thresholds of Halogens in Water

“…the present study with those reported by others is diffi cult because of gross differences in methodology, testing conditions, and criteria for threshold definition. Campbell et al 6 reported a taste threshold for chlorine residual of 5.2 mg/1 in redistilled water, using the triangle test method and the chlorine concentration related to 50 per cent above chance correct response as the threshold.…”

“…Campbell et al 6 reported the taste threshold of chlorine in redistilled water as 5.2 ppm. In their re view, McKee and Wolf7 credit Um-benhauer8 with the statement that objectionable tastes and odors were not produced with residual chlorine concentrations as high as 2.0 ppm.…”

“…The poorer water qual ity in Town Lake water is reflected especially in the chlorine doses and, to a smaller extent, the iron dosage and required hardness removal. 6. The main factor apparently causing poorer water quality in the The halogens that are sometimes used as water disinfectants can leave undesirable tastes and odors.…”

Initial Test of a Subsurface Constructed Wetland with Green Sorption Media for Nutrient Removal in On-site Wastewater Treatment Systems

“…Ammonia is another important parameter usually monitored in routine wastewater treatment. Ammonia in water can be tasted at levels of about 34 ppm (Campbell et al 1958). The presence of elevated ammonia levels in raw water can result in moldy, earthy-tasting water that may interfere with the operation of manganese-removal filters (Dieter and Möller 1991).…”

Assessment of research and development (R and D) needs in ammonia safety and environmental control

“…The threshold of odor in domestic water supplies is 5 mgj£ (t~cKee and Wolf 1971). Humans can taste NH 3 in coffee at 35 mg/t (Campbell et al 1958). Concentrations >40 mg/£ were acutely toxic to aquatic plants (Klussman et al 1970).…”