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To develop a ready-to-drink (RTD) milk coffee that retains the original coffee flavor, the effects of manufacturing processing conditions on retronasal-aroma (RA) odorants were investigated by gas chromatography-olfactometry (CharmAnalysis™) using an RA simulator (RAS). Twenty-nine of 33 odorants detected in the RAS effluent (RAS odorants) were identified. The detected odorants were classified into 19 odor-description groups. The total odor intensity (charm value, CMV) of all coffee RAS odorants decreased approximately 68% following pH adjustment, whereas the total CMV increased 6% to 7% following ultra-high-temperature sterilization. The total CMV ratio (about 83%) of the milk coffee produced using a new blending-after-sterilization (BAS) process without pH adjustment of the coffee was greater than that (approximately 56%) prepared using a conventional blending-before-sterilization (BBS) process with pH adjustment. In BAS-processed milk coffees, the total CMV ratio (91%) with infusion (INF)-sterilized reconstituted milk (r-milk) was greater than that (83%) of plate (PLT)-sterilized r-milk. Principal component analysis of odor-description CMVs indicated that the effect of coffee pH adjustment on odor characteristics was greater than that of sterilization, that BAS and BBS samples differed, and that BAS milk coffee prepared using INF sterilization was more similar to homemade milk coffee (blending unsterilized coffee without pH adjustment with PLT-sterilized milk) than milk coffee prepared using PLT sterilization. In conclusion, the BAS process using INF sterilization is superior for manufacturing RTD milk coffee that retains odor characteristics similar to targeted homemade milk coffee. PRACTICAL APPLICATION: Ready-to-drink milk coffee beverages produced using conventional blending-before-sterilization methods do not retain their original coffee flavor following adjustment of the pH of the coffee during manufacturing. The use of newly developed blending-after-sterilization methods, by contrast, produces ready-to-drink milk coffee with an aroma more similar to that of homemade milk coffee, as demonstrated using an analytical system for characterizing food product aromas. The blending-after-sterilization process is now being used in Japan to produce ready-to-drink milk coffee beverages.

To develop a ready‐to‐drink (RTD) milk coffee retaining the original coffee flavor, the effects of processing conditions during manufacture on retronasal‐arma (RA) compounds from the milk coffee were investigated by gas chromatography‐mass spectrometry using an RA simulator (RAS). Thirteen of 46 detected compounds in the RAS effluent (RAS compounds) decreased significantly following pH adjustment of coffee (from pH 5.1 to 6.8) and 5 compounds increased. RAS compounds from coffee tended to decrease through the pH adjustment and subsequent sterilization. Significantly higher amounts of 13 RAS compounds were released from the milk coffee produced using a blending‐after‐sterilization (BAS) process without the pH adjustment than from that using a blending‐before‐sterilization (BBS) process with the pH adjustment. In BAS‐processed milk coffee, significantly lower amounts of 8 high‐volatility compounds and 1H‐pyrrole were released from coffee containing infusion‐sterilized (INF) milk than from coffee containing plate‐sterilized (PLT) milk, whereas 3 low‐volatility compounds were released significantly more from coffee using PLT milk. Principal component analysis revealed that the effect of the manufacturing process (BAS, BBS, or homemade (blending unsterilized coffee without pH adjustment with sterilized milk)) on milk coffee volatiles was larger than that of the sterilization method (INF or PLT) for milk, and that the sterilization method could result in different RAS volatile characteristics in BAS and homemade processes. In conclusion, a BAS process was found to be superior to a BBS process for the manufacture of an RTD milk coffee that retains volatile characteristics similar to that of a homemade milk coffee. Ready‐to‐drink (RTD) milk coffee manufactured using the conventional blending‐before‐sterilization process does not retain its original coffee flavor due to pH adjustment of the coffee during the process. The new blending‐after‐sterilization (BAS) process enabled the production of RTD milk coffee whose volatiles are closer to that of homemade milk coffee, as demonstrated by the results of RAS‐GC‐MS analysis. The BAS process has already been applied to the manufacture of RTD milk coffees in Japan.

To develop a ready-to-drink (RTD) milk coffee that retains the original coffee flavor, the effects of manufacturing processing conditions on retronasal-aroma (RA) odorants were investigated by gas chromatography-olfactometry (CharmAnalysis™) using an RA simulator (RAS). Twenty-nine of 33 odorants detected in the RAS effluent (RAS odorants) were identified. The detected odorants were classified into 19 odor-description groups. The total odor intensity (charm value, CMV) of all coffee RAS odorants decreased approximately 68% following pH adjustment, whereas the total CMV increased 6% to 7% following ultra-high-temperature sterilization. The total CMV ratio (about 83%) of the milk coffee produced using a new blending-after-sterilization (BAS) process without pH adjustment of the coffee was greater than that (approximately 56%) prepared using a conventional blending-before-sterilization (BBS) process with pH adjustment. In BAS-processed milk coffees, the total CMV ratio (91%) with infusion (INF)-sterilized reconstituted milk (r-milk) was greater than that (83%) of plate (PLT)-sterilized r-milk. Principal component analysis of odor-description CMVs indicated that the effect of coffee pH adjustment on odor characteristics was greater than that of sterilization, that BAS and BBS samples differed, and that BAS milk coffee prepared using INF sterilization was more similar to homemade milk coffee (blending unsterilized coffee without pH adjustment with PLT-sterilized milk) than milk coffee prepared using PLT sterilization. In conclusion, the BAS process using INF sterilization is superior for manufacturing RTD milk coffee that retains odor characteristics similar to targeted homemade milk coffee. PRACTICAL APPLICATION: Ready-to-drink milk coffee beverages produced using conventional blending-before-sterilization methods do not retain their original coffee flavor following adjustment of the pH of the coffee during manufacturing. The use of newly developed blending-after-sterilization methods, by contrast, produces ready-to-drink milk coffee with an aroma more similar to that of homemade milk coffee, as demonstrated using an analytical system for characterizing food product aromas. The blending-after-sterilization process is now being used in Japan to produce ready-to-drink milk coffee beverages.

To develop a ready-to-drink (RTD) milk coffee retaining the original coffee flavor, the effects of processing conditions during manufacture on retronasal-arma (RA) compounds from the milk coffee were investigated by gas chromatography-mass spectrometry using an RA simulator (RAS). Thirteen of 46 detected compounds in the RAS effluent (RAS compounds) decreased significantly following pH adjustment of coffee (from pH 5.1 to 6.8) and 5 compounds increased. RAS compounds from coffee tended to decrease through the pH adjustment and subsequent sterilization. Significantly higher amounts of 13 RAS compounds were released from the milk coffee produced using a blending-after-sterilization (BAS) process without the pH adjustment than from that using a blending-before-sterilization (BBS) process with the pH adjustment. In BAS-processed milk coffee, significantly lower amounts of 8 high-volatility compounds and 1H-pyrrole were released from coffee containing infusion-sterilized (INF) milk than from coffee containing plate-sterilized (PLT) milk, whereas 3 low-volatility compounds were released significantly more from coffee using PLT milk. Principal component analysis revealed that the effect of the manufacturing process (BAS, BBS, or homemade (blending unsterilized coffee without pH adjustment with sterilized milk)) on milk coffee volatiles was larger than that of the sterilization method (INF or PLT) for milk, and that the sterilization method could result in different RAS volatile characteristics in BAS and homemade processes. In conclusion, a BAS process was found to be superior to a BBS process for the manufacture of an RTD milk coffee that retains volatile characteristics similar to that of a homemade milk coffee.Ready-to-drink (RTD) milk coffee manufactured using the conventional blending-before-sterilization process does not retain its original coffee flavor due to pH adjustment of the coffee during the process. The new blending-after-sterilization (BAS) process enabled the production of RTD milk coffee whose volatiles are closer to that of homemade milk coffee, as demonstrated by the results of RAS-GC-MS analysis. The BAS process has already been applied to the manufacture of RTD milk coffees in Japan.

To develop a method for evaluating and designing the retronasal aroma of espresso, sensory evaluation data was correlated with data obtained from gas chromatography/olfactometry (GC/O, CharmAnalysis™) and from an electronic nose system αFOX4000 (E-nose). The volatile compounds of various kinds of espresso (arabica coffee beans from 6 production countries: Brazil, Ethiopia, Guatemala, Colombia, Indonesia, and Tanzania; 3 roasting degrees for each country: L values, 18, 23, and 26) were collected with a retronasal aroma simulator (RAS) and examined by GC/O and E-nose. In addition, sensory descriptive analysis using a 7-point scale for RAS effluent gas was performed by 5 trained flavorists using sensory descriptors selected based on the frequency in use and coefficient of correlation. The charm values of 10 odor descriptions obtained from GC/O analysis exhibited the significant (P < 0.05) differences among both roasting degrees and origins. Also, linear discriminant analysis (LDA) on the E-nose-sensor resistances and factor analysis on the sensory evaluation scores showed that the differences of aroma characteristics among the roasting degrees were larger than those among the origins. Based on an artificial neural network (ANN) model applied to the data from GC/O analyses and sensory evaluations, the perceptual factor of the RAS aroma was predicted to be mainly affected by sweet-caramel, smoke-roast, and acidic odors. Also, 3 metal oxide semiconductor sensors (LY2/Gh, P30/1, and T40/1) of E-nose were selected for analyses of RAS aroma and correlated with the sensory descriptive scores by the ANN to support sensory evaluation.

A sampling method to isolate headspace volatiles of freshly brewed drip coffee using a solid-phase microextraction fiber (fiber type: divinylbenzene/carboxen/polydimethylsiloxane) in a short time (2 min) immediately after extraction has been developed. Volatile compounds and potent odorants obtained from each headspace aroma of various arabica coffee extracts (3 production countries: Ethiopia, Tanzania, and Guatemala; 3 roasting degrees for each country: L26, L23, and L18) using the sampling method were examined by gas chromatography/mass spectrometry (GC/MS) and GC/olfactometry (GC/O, CharmAnalysis). The results of principal component analysis (PCA) using the data of GC/O analysis showed that the aroma profile of Ethiopian coffee was discriminately different from those of Tanzanian coffee and Guatemalan coffee. In addition, it was suggested from the factor loading of the PCA that 4-(4'-hydroxyphenyl)-2-butanone (raspberry ketone; sweet-fruity odor) characterized the aroma profile of freshly brewed Ethiopian coffee. Therefore, the 4-(4'-hydroxyphenyl)-2-butanone was quantified in the 9 kinds of coffee extracts. Ethiopian coffee extract of the lightly roasted degree (roasting degree: L26) contained the highest amount of this component, while it was only a little over the reported threshold. In the sensory test, the headspace aromas of Tanzanian and Guatemalan coffees in which 4-(4'-hydroxyphenyl)-2-butanone was added were, respectively, discriminated from not added samples, and "sweet" odor was selected as an odor description that assessors found similarity between the added Tanzanian or Guatemalan coffee aroma and the Ethiopian coffee aroma. It was suggested that 4-(4'-hydroxyphenyl)-2-butanone made some detectable change on total aroma profile even though the added amount was only near threshold level.

Headspace volatiles of freshly brewed drip coffee were investigated by gas chromatography/mass spectrometry (GC/MS) and gas chromatography/olfactometry (GC/O, CharmAnalysis) analyses. For this purpose, a solid-phase microextraction (SPME) sampling method for the headspace volatiles of freshly brewed drip coffee was developed. SPME fiber coated with divinylbenzene (DVB)/carboxen/polydimethylsiloxane (PDMS) was selected from 6 types, and sampling time was determined at 2 min. The headspace coffee volatiles stayed constant in proportion for the first 2 min to keep the freshness of the brewed coffee aroma. Using this sampling method, the headspace volatiles of freshly brewed drip coffee (Ethiopian arabica coffee, roast degree: L value; 23) were examined by GC/MS and GC/O analyses. From the GC/O results, 1-(3,4-dihydro-2H-pyrrol-2-yl)-ethanone (nutty-roast odor) and 4-(4'-hydroxyphenyl)-2-butanone (raspberry ketone, sweet-fruity odor) were newly detected as components in the aroma of coffee.