Coffee bean treatment method and coffee beans

Abstract

Provided are: a coffee bean treatment method by which acrylamide can be reduced without causing deterioration in taste and aroma; and coffee beans. This coffee bean treatment method comprises heating coffee beans at a temperature lower than a temperature of at least 40ºC at which a first crack is generated. Moreover, according to these coffee beans, the pH of a liquid extracted with water does not show a tendency to decrease compared to the case in which beans are subjected only to roasting, and the concentration of acrylamide in the coffee beans is at most 90% compared to the case in which beans are subjected only to roasting.

Description

Coffee bean processing method and coffee beans

[0001] The present invention relates to a method for treating coffee beans and to coffee beans.

[0002] Cooking food is known to improve palatability through changes in taste, aroma, and texture, as well as safety and shelf life through sterilization. It is also known that various complex chemical changes occur, resulting in the production of not only healthy nutrients but also harmful substances. For example, the presence of acrylamide has been reported in many foods cooked at high temperatures (see Non-Patent Document 1), raising concerns about its adverse health effects. Acrylamide is also considered to be neurotoxic and genotoxic (Ministry of Agriculture, Forestry and Fisheries, Health Effects of Acrylamide), and the International Agency for Research on Cancer (IARC) has classified it as "probably carcinogenic to humans (Group 2A)." Along with potatoes (such as potato chips and French fries) and cereals (processed grain foods), coffee is a typical food of greatest concern for acrylamide exposure, due to its frequent daily consumption.

[0003] Many mechanisms for acrylamide formation in cooked foods have been proposed, but the most important is a chemical reaction pathway between free asparagine and reducing sugars at high temperatures of 120°C or higher (see Non-Patent Document 2). As with other foods, various studies have been conducted on the reduction of acrylamide in coffee.

[0004] For example, it has been described that the acrylamide content in roasted beans can be reduced by administering to green coffee beans an asparagine-degrading enzyme that converts asparagine to aspartic acid (see Patent Document 1). It has also been described that the acrylamide content can be reduced by administering to extracted coffee liquid an acrylamide-degrading enzyme that converts acrylamide to acrylic acid (see Non-Patent Document 3). Roasting using superheated steam (see Non-Patent Document 4) or under vacuum (see Non-Patent Document 5) has also been performed.

[0005] Special Publication No. 2006-503592

[0006] E. Tareke et.al: Analysis of Acrylamide, a Carcinogen Formed in Heated Foodstuffs. J Agric Food Chem. 2002:50:4998-5006D.S. Morttram, B.L. Wedzich, A.T. Dodson: Acrylamide is formed in the Maillard reaction. Nature 419 (2002) pp. 448-449D.K.Bedade, Y.B.Sutar, R.S.Singhal, Chitosan coated calcium alginate beads for covalent immobilization of acrylamide: process parameters and removal of acrylamide from coffee. Food Chem, 275(2019), pp.95-104P.Rattanarat, N.Chindapan, S.Devahastin, Comparative evaluation of acrylamide and polycyclic aromatic hydrocarbons contents in Robusta coffee beans roasted by hot air and superheated steam. Food Chem, 341(2021), Article 128266M.Anese, M.C.Nicoli, G.Verardo, M.Munari, G.Mirolo, R.Bortolomeazzi, Effect of vacuum roasting on acrylamide formation and reduction in coffee beans. Food Chem, 145(2014), pp. 168-172

[0007] The method described in Patent Document 1 was able to reduce the acrylamide content in roasted beans, but the process was complicated and deterioration in taste and aroma was observed. The method described in Non-Patent Document 3 also resulted in deterioration in taste and aroma. Non-Patent Document 4 achieved a reduction in acrylamide only in deep roasting compared to conventional hot air roasting, but resulted in deterioration in taste and aroma. Furthermore, the method described in Non-Patent Document 5 achieved a reduction in acrylamide by approximately 50% compared to roasting under atmospheric pressure, without causing deterioration in taste and aroma, but the effect was limited to moderate roasting.

[0008] Furthermore, coffee beans have a very hard structure, making it difficult to treat the green beans before roasting to reduce acrylamide, making it one of the most difficult foods to reduce acrylamide in. However, roasting is the only way to obtain the unique taste and aroma of coffee. Furthermore, since most coffee products are sold as roasted beans, instant coffee, or ready-to-drink brewed coffee, it has been thought that there is little room for consumers to reduce acrylamide.

[0009] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a method for treating coffee beans that can reduce acrylamide without causing deterioration in taste or aroma, and to provide the coffee beans.

[0010] The present invention was made to solve the above-mentioned problems, and the inventors discovered that the problems of the present invention can be solved by heating coffee beans at a predetermined temperature, and completed the present invention. The gist of the present invention is as follows.

[0011] [1] A method for processing coffee beans, comprising a heating treatment step of heating coffee beans at a temperature of 40°C or higher but lower than the temperature at which a first crack occurs. [2] The method for processing coffee beans according to [1], comprising a roasting step of roasting the coffee beans, wherein the heating treatment step is carried out before the roasting step. [3] The method for processing coffee beans according to [1], comprising a roasting step of roasting the coffee beans, wherein the heating treatment step is carried out after the roasting step. [4] The method for processing coffee beans according to [1], comprising a roasting step of roasting the coffee beans, wherein the heating treatment step comprises a first heating treatment step carried out before the roasting step and a second heating treatment step carried out after the roasting step. [5] The method for processing coffee beans according to any one of [2] to [4], wherein the heating treatment step is carried out until the acrylamide concentration in the coffee beans is 90% or less compared to coffee beans that have been subjected to only the roasting step. [6] Coffee beans obtained from the same green beans, wherein the acrylamide concentration in the coffee beans is 90% or less compared to coffee beans immediately after being subjected to only a roasting process. [7] The coffee beans according to [6], wherein the liquid extracted with water is not accompanied by a decrease in pH caused by rancidity. [8] The coffee beans according to [6] or [7], wherein the free asparagine concentration is 29 mg / 100 g or less. [9] Coffee beans treated by the coffee bean treatment method according to any of [1] to [4].

[0012] According to the present invention, acrylamide can be reduced without causing deterioration in taste or aroma.

[0013] The coffee bean processing method and coffee beans according to the present invention will be described in detail below.

[0014] [Method for Treating Coffee Beans] The method for treating coffee beans of the present invention includes a heating treatment step of heating the coffee beans at a temperature of 40° C. or higher but lower than the temperature at which a first crack occurs.

[0015] (Coffee Beans) The coffee beans used in this embodiment are not limited to a particular variety, and various varieties can be used. A mixture of multiple varieties may also be used. There are many different species and cultivars of coffee trees (Coffea canefera), but the main varieties cultivated commercially are Arabica and Canefera (Robusta). Hybrid varieties have also been developed by crossbreeding Arabica and Robusta. In this embodiment, the variety is not particularly limited, but the above varieties are preferred.

[0016] In this embodiment, the term "coffee beans" is used to encompass both "coffee cherries" and "coffee beans." "Coffee cherries" refer to coffee fruits from which the skin and pulp have not been removed. Furthermore, "coffee beans" refer to coffee cherries from which the skin and pulp have been removed. Hereinafter, in this specification, "coffee cherries" may be simply referred to as "cherries," and "coffee beans" may be simply referred to as "beans." Furthermore, the coffee beans subjected to the treatment method of the present application are a group of coffee beans, and raw beans from that group are referred to as "the same raw beans."

[0017] To turn the harvested "fruits" into "beans," various refining processes are required, and although the refining process methods vary depending on the region, the main ones used are the dry process (natural), the wet process (washed), and the pulped natural. The beans used in this invention are not limited by these refining processes.

[0018] Furthermore, the moisture content of the beans used in this embodiment is not particularly limited. In most cases, beans are dried to a moisture content of 9-12% at the production site before being exported. Therefore, even when using beans produced at our own coffee farm (Stream Coffee Farm, Kagoshima City), beans with a similar moisture content can be used. In many cases, beans that have undergone post-harvest refining processes are roasted as is. Furthermore, while pre-processing such as decaffeination and aging / fermentation may be performed as needed, the beans used in the present invention may or may not undergo such pre-processing.

[0019] (Heating Treatment Step) The coffee bean processing method of the present invention includes a heating treatment step in which coffee beans are heated at a temperature of 40°C or higher but lower than the temperature at which a first crack occurs. The heating treatment step involves heating the coffee beans for a certain period of time at a temperature of 40°C or higher but lower than the temperature at which a first crack occurs. The temperature at which a first crack occurs can be determined, for example, by experimentally heating a portion of the coffee beans to be processed. The method for performing the heating treatment step is not particularly limited. There are three types of heat transfer: conductive heat, convective heat, and radiant heat. However, when heat is actually transferred to food, it is transferred in a complex combination of these three types. In this embodiment, the method of heat transfer in the heating treatment step is not particularly limited. Furthermore, a wide variety of equipment can be used, including direct flame, charcoal fire, electric equipment, gas equipment, and induction heating equipment. The heating treatment step is performed separately from the roasting step described below, either before or after the roasting step, and is therefore different from the heating in the roasting step and the slow cooling after the roasting stop in the roasting step.

[0020] During the heating treatment step, the coffee beans may be left unwrapped, or may be wrapped in food wrap film (trade name Saran Wrap (registered trademark)), aluminum foil, a plastic bag with a zipper (trade name Ziploc (registered trademark)), etc. Furthermore, the coffee beans may be wrapped in a special film, the air removed, and the bag sealed before being vacuum-cooked.

[0021] The temperature in the heating process is at least 40°C but lower than the temperature at which the first crack occurs. By heating coffee beans for a certain period of time at a temperature at least 40°C but lower than the temperature at which the first crack occurs, the color of the coffee beans changes over time from their initial light green to yellow and then brown. In the case of coffee cherries, several cherries are removed at regular intervals during heating, threshed (the skin, pulp, mucilage, parchment, and silverskin are removed from the coffee cherries), and the beans are removed to confirm the color change. The rate at which coffee beans change color due to heating is affected by the temperature and whether or not they are threshed. For example, when roasted at a normal high temperature of 185 to 250°C, it takes about 7 days at 90°C for the cherries to reach the color immediately after the first crack occurs. In the case of beans, it takes about 10 days at 90°C and about 14 days at 70°C. When coffee beans are roasted, complex chemical reactions occur, resulting in changes in the color of the beans and their distinctive taste and aroma. This is primarily due to the Maillard reaction, which occurs between various amino acids, which are components of coffee beans, and reducing sugars such as glucose and fructose. The main pathway for acrylamide production is the Maillard reaction between free asparagine, an amino acid, and reducing sugars. By measuring the changes in the free asparagine and acrylamide concentrations over time in coffee beans subjected to heating, the concentration of free asparagine decreased and the concentration of acrylamide increased in the early stages of heating. Therefore, it is inferred that the color change of the coffee beans during heating is due to the Maillard reaction.

[0022] The heating temperature may be at least 40°C lower than the temperature at which the first crack occurs, regardless of whether the heating treatment is performed before or after roasting the coffee beans. The preferred temperature range has a lower limit of 70°C or higher, and more preferably 90°C or higher. The upper limit is preferably 150°C or lower, and more preferably 120°C or lower. The heating treatment step is preferably carried out until the acrylamide concentration is 90% or lower, preferably 25% or lower, and more preferably 0.0% (below detection) compared to beans that have been subjected to only a roasting step without a heating treatment step.

[0023] First, an embodiment of heating pre-roasted coffee beans will be described. Acrylamide is generated by heating pre-roasted coffee beans for a certain period of time at a temperature of 40°C or higher but lower than the temperature at which the first crack occurs. The acrylamide generated by heating at a temperature of 40°C or higher but lower than the temperature at which the first crack occurs reaches a peak concentration by maintaining heating and then decreases over time, thereby reducing the acrylamide concentration in the coffee beans.

[0024] As mentioned above, the main pathway for the generation of acrylamide is the Maillard reaction between free asparagine, a type of amino acid, and reducing sugars. By heating coffee beans at a temperature of 40°C or higher but lower than the temperature at which the first crack occurs, the concentration of free asparagine in green beans (beans before roasting) can be reduced. By lowering the concentration of free asparagine, the generation of acrylamide can be suppressed, and acrylamide in coffee beans can be reduced.

[0025] (Roasting Process) By roasting the coffee beans that have undergone the heating process, the components contained in the coffee beans undergo chemical changes, resulting in the development of coffee's unique flavors, such as a volatile aroma, bitterness, sourness, and sweetness. The "roasting process" refers to the roasting of coffee beans that is typically carried out, and involves, for example, placing raw beans at room temperature in a roaster heated to a predetermined temperature, heating the coffee beans through steaming and dehydration processes, and then heating them to a temperature at which a first or second crack occurs, or above the temperature at which a second crack occurs, until the desired roasting level is reached. Once the desired roasting level is reached, heating is terminated and the beans are cooled to stop the chemical reaction. In typical roasting, the time from placing the raw beans in the roaster to finishing heating is less than 20 minutes, and approximately 1.5 x 10 ８ ~3.0 x 10 ８ However, the calorific value is not limited to these values ​​and can be changed as appropriate depending on the type of coffee beans and the roasting method.

[0026] In this embodiment, there is no particular limit to the set time between the heating treatment step and the roasting step; the roasting step may be performed immediately after the heating treatment step, or a fixed time interval may be set. In this embodiment, the roasting method is not particularly limited. For example, a drum-type or fluidized bed-type roaster can be used for agitation-type roasting. Furthermore, a direct-fire, semi-hot air, or hot air-type roaster can be used for heating-type roasting.

[0027] Roasting can be performed at any commonly used temperature. For example, the temperature can be gradually increased from room temperature up to 250°C depending on the roasting level. When roasting begins, coffee beans gradually expand, during which chemical changes affecting taste and color occur within the beans. At the same time, carbon dioxide and water vapor are generated. Eventually, the beans are unable to withstand the increased internal pressure, causing their cells to break down and produce a popping sound. This sound, called the first crack, generally occurs around 200°C. As roasting continues, the first crack subsides, but the chemical reaction and expansion continue, further destroying the cells, and the evaporation of fats and oils produces a popping sound. This sound, called the second crack, generally occurs around 220°C. The start and end points of the first and second cracks are one indicator of the roast level, such as light, medium, or dark roast. The temperature at which roasting stops is called the "temperature at the end of roasting."

[0028] The Agtron Scale is an objective indicator for determining the roast level of beans during roasting and after roasting has stopped. This method uses a food-grade spectrophotometer manufactured by Agtron, Inc., USA, to measure the roast level of coffee. Furthermore, there is also the Agtron Color Disc, a simple method that does not require a spectrophotometer, which classifies beans into eight color levels, from low roast level #95 to high roast level #25. In the present invention, the acrylamide reduction effect of heating is confirmed by comparing coffee beans that have only undergone the roasting process. Therefore, for example, to ensure that the roast levels of the compared samples are as similar as possible, the roast level of beans during roasting can be confirmed by changes in their state due to the first and second cracks, and the roast level of beans after roasting can be confirmed by using the Agtron Color Disc. By using the same Agtron Color Disc, the roast level after roasting can be consistent. It is generally known that the acrylamide concentration in roasted beans is higher the lighter the roast and decreases the darker the roast. Therefore, the effect of heating to reduce acrylamide concentration can be confirmed by measuring the acrylamide concentration using the same Agtron color disc judgment as beans roasted without the heating treatment process of the present invention. Therefore, when measuring the acrylamide concentration of beans of the same roast level using the Agtron color disc judgment, if one bean has a lower acrylamide concentration than the other, it can be said that the coffee bean treatment method of the present invention has been applied. Note that the degree of roasting is not particularly limited in the present invention, and any degree of roasting is acceptable.

[0029] As described above, free asparagine is reduced by heating coffee beans at a temperature of 40° C. or higher but lower than the temperature at which the first crack occurs, and the free asparagine concentration is reduced to below detection level by continuing to heat the beans at a temperature of 40° C. or higher but lower than the temperature at which the first crack occurs. Roasting beans with reduced free asparagine concentrations can suppress the production of acrylamide by the Maillard reaction, thereby reducing acrylamide in the roasted coffee beans.

[0030] Although the above description concerns a method of processing coffee beans in which a roasting step is carried out after a heating step of coffee beans, the heating step of coffee beans may also be carried out after the roasting step of coffee beans. In this case, there is no particularly limited set time between the roasting step and the heating step, and the heating step may be carried out immediately after the roasting step, or a fixed time interval may be set. Even when beans that have been previously roasted are heated for a fixed time at a temperature of 40°C or higher but lower than the temperature at which the first crack occurs, the acrylamide concentration can be reduced.

[0031] Furthermore, the heating treatment step is not limited to either before or after the roasting step, and may include a first heating treatment step performed before the roasting step and a second heating treatment step performed after the roasting step, and the heating treatment steps may be performed before and after the roasting step. The first heating treatment step and the second heating treatment step may be performed in the same manner as the heating treatment step described above.

[0032] [Coffee beans subjected to a heating treatment process] Coffee beans that have been subjected to a roasting process in addition to the heating treatment process of the present invention have an acrylamide concentration of 90% or less compared to coffee beans that have been subjected to only the roasting process. Furthermore, it is preferable that the liquid extracted from the coffee beans with water does not suffer from the decrease in pH that occurs due to rancidity. Note that "immediately after only the roasting process" refers to within 72 hours from the point in time when heating is stopped and the beans are cooled to room temperature after reaching the desired roasting level during the roasting process described above.

[0033] Acrylamide in roasted coffee beans is known to naturally decrease during storage. For example, it has been reported that the acrylamide concentration decreased from 203 μg / kg to 147 μg / kg (72.4%) after storage at room temperature for 7 months (T. Delatour et al.: Improved sample preparation to determine acrylamide in difficult matrices such as chocolate powder, cocoa, and coffee by liquid chromatography tandem mass spectroscopy. J Agri Food Chem. 2004 Jul 28;52(15):4625-31). It has also been reported that storage at 10-12°C for three months reduced the acrylamide content from 285 μg / kg to 200 μg / kg (70.2%), and that storage for six months reduced it by 40-65% (K. Hoenicke, R. Gatermann: Studies on the stability of acrylamide in food during storage. Journal of AOAC International Vol. 88, No. 1, 2006, 268-273). However, it is also known that long-term storage can significantly impair the taste and aroma (I. Lantz, R. Ternite, J. Wilkens, K. Hoenicke, H. Guenther, G. H. D. van der Stegen: Studies on acrylamide levels in roasting, storage, and brewing of coffee. Mol Nutr Food Res 2006, 50: 1039-1046). Mechanisms of deterioration of roasted beans over time include, for example, rancidity.

[0034] <Ranization> When the fatty acids that make up fats and oils are oxidized by air, they become highly unsaturated fatty acids, which, when further oxidized, break down into lower fatty acids with 6 to 9 carbon atoms, causing the oil to have an unpleasant smell (rancid odor) and a drop in pH. The rate at which this deterioration due to oxidation progresses is relatively slow, and it takes 7 to 8 weeks at room temperature for the oil to change enough to be noticeable.

[0035] In the present embodiment, the pH of the liquid extracted from coffee beans whose acrylamide concentration has been reduced by the heating treatment step and the roasting step is not significantly different from that of the liquid extracted from beans that have been subjected to only the roasting step, and therefore the occurrence of rancidity can be suppressed, and an increase in sourness can be prevented.

[0036] For example, when the pH of tap water, a liquid (control) obtained by extracting coffee beans that had been roasted at a normal high temperature (temperature at the end of roasting: approximately 220°C, roasting time: approximately 15 minutes) with water, and a liquid obtained by extracting coffee beans obtained by heating the same coffee beans at 90°C for two and seven days were measured, the pH values ​​were 6.64±0.01, 5.65±0.08, 5.44±0.01, and 5.58±0.02 for the tap water, control, 2-day heating, and 7-day heating samples, respectively, indicating that heating coffee beans roasted at a normal high temperature at 90°C does not result in a decrease in pH. Incidentally, the pH of beans roasted at a normal high temperature and then frozen and stored for six months was 5.59±0.02, while the pH of beans stored at room temperature for six months after roasting was clearly reduced to 5.12±0.00. The pH was measured by grinding 10 grams of coffee beans to a medium size (particle size of approximately 0.6 to 0.71 mm, according to the All Japan Coffee Culture Association standard) and extracting them using a paper filter drip method with 130 ml of tap water at approximately 80°C. The extract was allowed to cool to approximately 45°C before the pH was measured. A PH60 pH tester manufactured by APERA INSTRUMENTS, Inc. was used to measure the pH.

[0037] Furthermore, the acrylamide concentration in the coffee beans is 90% or less compared to beans that have been subjected to only a roasting process without being subjected to a heating treatment. As described above, according to the coffee bean processing method of the present invention, the acrylamide concentration can be reduced by heating, and therefore the acrylamide concentration in the heat-treated coffee beans can be reduced to 90% or less compared to beans that have been subjected to only roasting without being subjected to a heating treatment. The acrylamide concentration in the coffee beans is preferably 90% or less, more preferably 25%, and most preferably 0.0% (below the detection limit) compared to beans that have been subjected to only roasting without being subjected to a heating treatment.

[0038] Furthermore, the concentration of free asparagine in coffee beans is preferably 29 mg / 100 g or less. As described above, free asparagine generates acrylamide through the Maillard reaction. Therefore, reducing the concentration of free asparagine in coffee beans can suppress the generation of acrylamide. The concentration of free asparagine is preferably 20 mg / 100 g or less, more preferably 10 mg / 100 g or less, and most preferably 1 mg / 100 g (detection limit) or less.

[0039] The present invention will be explained in more detail below with reference to examples, but the present invention is not limited to the following examples.

[0040] Example 1: Measurement of Changes in Acrylamide Concentration Over Time When Coffee Beans Were Heated at 90°C The acrylamide concentration of coffee beans was measured after heating at 90°C for 2, 7, 14, and 21 days. The green beans used were Arabica imported from Brazil and purchased from a coffee bean retailer. Approximately 200 g of green beans were sealed in a Ziploc® bag and wrapped in aluminum foil to form a single sample, for a total of four samples. A T-fal Lacra Cooker Compact electric pressure cooker was used as the heating device. The experiment began with the low-temperature cooking mode selected, the set temperature set to 90°C, and the maximum cooking time settable for 22 hours. During the 21-day experimental period, the setting was reset immediately after or before the set time expired, and heating continued. The samples after heating were kept refrigerated until the end of the heating experiment. After the heating experiment was completed, all samples were delivered in a refrigerated state to the testing center (Japan Food Functional Analysis Research Institute, Inc.) as soon as possible, and measurement operations were started within 72 hours at the latest after the samples were shipped. Acrylamide concentration measurements were performed using liquid chromatography-mass spectrometry. The detection limit for acrylamide concentration was 0.01 ppm. The acrylamide concentration measurement results are shown in Table 1. The peak acrylamide concentration was reached two days after the start of heating, and the percentages shown are those assuming the acrylamide concentration to be 100%.

[0041] <Method of preparing measurement samples> The samples were prepared by grinding and mixing the heated coffee beans in a mill mixer to homogenize them. 1 g of this analysis sample was placed in a centrifuge tube and the internal standard solution (acrylamide) was added. １３ C ３A solution of 1000 mg ... １３ C ３ ;75→78 m / z <Calculation formula>

[0042]

[0043] Example 2: Measurement of Changes in Free Asparagine Concentration Over Time When Coffee Beans Were Heated at 70°C or 90°C The free asparagine concentrations of coffee beans were measured when the beans were heated at 70°C for 7, 14, 21, and 28 days. The free asparagine concentrations of coffee beans were also measured when the beans were heated at 90°C for 2, 7, 14, 21, and 28 days. As in Example 1, the beans used were imported from Brazil. The heating method was also the same as in Example 1, using the low-temperature cooking mode of a T-fal electric pressure cooker. The packaging of approximately 200 g of raw beans for each sample, the continuous heating operation, and the measurement procedure at the testing center were all performed in the same manner as in Example 1. The free asparagine concentrations were measured using an automated amino acid analysis method. The detection limit for free asparagine concentration was 1 mg / 100 g. The measurement results for free asparagine concentrations are shown in Table 2. The percentages shown are those when the free asparagine concentration in the raw beans before heating is taken as 100%. The automated amino acid analysis was commissioned to a testing center (Japan Food Functional Analysis Research Institute, Inc.) and was performed using their own testing method.

[0044]

[0045] When heated to 90°C, the concentration of free asparagine was detected up to two days after heating but was not detected after seven days, and in Example 1, the acrylamide concentration increased after two days of heating and decreased after seven days. This suggests that acrylamide is produced in the presence of free asparagine, and that acrylamide decreases when the free asparagine is depleted. Therefore, if the concentration of free asparagine can be reduced, the generation of acrylamide in coffee beans can be suppressed.

[0046] Example 3: Measurement of Changes in Acrylamide Concentration Over Time in Coffee Beans Roasted at 90°C and Roasted to Immediately After the First Crack. The beans used and the heating method were the same as in Example 1. Approximately 200 g of green beans were used per sample. After heating for 2, 7, 14, 21, and 28 days, each sample was roasted. The roasting was performed using a KAKACOO Coffee Roaster and an IWATANI Eco Premium portable stovetop, set at medium heat. To ensure that each sample was roasted to the same degree as possible and to achieve a light roast with a high acrylamide concentration, the roasting operation was stopped immediately after the first crack (so that the roasting temperature reached approximately 200°C). The roasted beans were quickly cooled using an EC Hometec single-layer coffee bean cooling device. The Agtron Color Disc value for the beans roasted immediately after the first crack was equivalent to #95. The acrylamide levels in the roasted coffee beans were measured using the same method as described in Example 1. The results are shown in Table 3. The acrylamide levels in beans that were only roasted without being subjected to a heating treatment (beans two days (48 hours) after cooling) were also measured, and the percentages shown are those relative to the acrylamide level in beans that were only roasted, taken as 100%.

[0047]

[0048] The amount of heat given to green beans when they were heated at 90°C for two days is expressed as heat (J) = weight of green beans (g) x temperature (°C) x time (seconds) (room temperature is 20°C), and is calculated as follows: heat (J) = 200 x (90 - 20) x 48 x 60 x 60 = approximately 2.4 x 10 ９is 1.24 × 10 per kg １０ In addition, assuming that the temperature of the beans rises linearly as a linear function from immediately after roasting until the roasting is stopped, and assuming that the roasting time is 20 minutes, the amount of heat required for roasting is: Heat (J) = 200 x (200 - 20) x 1 / 2 x 20 x 60 = 2.16 x 10 ７ 1.08 x 10 per kg ８ Thus, in order to reduce the acrylamide concentration to about 90% or less, a heat amount about 100 times that required for the roasting process was required.

[0049] Example 4: Measurement of change over time in acrylamide concentration when coffee beans roasted until just after the first crack were heated at 90°C. The green beans used in Example 1 were roasted according to the roasting method of Example 3. Each sample weighed approximately 200 g of green beans, and each sample was roasted. Roasting was stopped immediately after the first crack, and the roasted and cooled beans were sealed in Ziploc® bags and heated at 90°C for 1, 2, or 7 days according to the procedure of Example 1. The acrylamide concentration of the coffee beans after heating was measured. The Agtron Color Index values ​​of the beans for each heating period were all equivalent to #95. The results are shown in Table 4.

[0050]

[0051] Example 5: Measurement of change over time in acrylamide concentration when coffee beans roasted until just after the second crack were heated at 90°C. The green beans used were the same as those used in Example 1, and the roaster and cooler used were the same as those used in Example 3. Roasting was performed according to the roasting method of Example 3, with the roasting stopped just after the second crack. The roasted beans were subjected to a heating treatment at 90°C for 3 and 7 days according to the procedure of Example 1. The acrylamide concentration of the coffee beans after the heating treatment was measured. The Agtron Color Index values ​​of the beans for each heating period were all equivalent to #45. The results are shown in Table 5.

[0052]

[0053] Example 6: Measurement of Changes in Acrylamide Concentration Over Time When Coffee Beans Roasted Immediately After the Second Crack Are Heated at 150°C The raw beans used in Example 1 were roasted according to the roasting method of Example 3. Approximately 200 g of raw beans were roasted per sample. Because each sample was also used for sensory evaluation, it was roasted immediately after the second crack (at a roasting temperature of approximately 220°C), when the acidity and bitterness were balanced, rather than immediately after the first crack, when only the acidity is prominent, and then cooled according to Example 3. The Agtron Color Disc value of the beans roasted immediately after the second crack was equivalent to #45. Each sample was then heated at 150°C for 10, 30, 60, and 120 minutes. A Panasonic NE-BS1200 household steam oven was used for heating. Preheating was performed in oven mode, and the roasted beans were placed on a square tray on the lower shelf. The acrylamide concentration of the coffee beans after heating was measured. The results are shown in Table 6. The acrylamide concentration of beans that were only roasted (beans one day (24 hours) after cooling) was also measured, and the percentage is shown, assuming the acrylamide concentration of beans that were only roasted as 100%. The Agtron Color Index values ​​of the beans for each heating time were all equivalent to #45.

[0054]

[0055] The time required to reduce the acrylamide concentration of coffee beans after the roasting process to 78.6% by heating was 10 minutes at 150°C, and the amount of heat given to the coffee beans after the roasting process was calculated as follows: (J) = 1.56 × 10 ７ is 7.8 × 10 per kg ７ In addition, the amount of heat required for roasting is 2.35 x 10, assuming that the roasting time is 20 minutes. ７ 1.18 x 10 per kg ８Thus, in order to reduce the acrylamide concentration of roasted coffee beans to 90%, the amount of heat applied can be reduced compared to when a heating treatment is performed before the roasting process. Furthermore, in Example 6 (heating at 90°C), it took three days to reduce the acrylamide concentration to 21.4%, but in Example 7 (heating at 150°C), it was confirmed that this could be achieved in just 120 minutes.

[0056] <Sensory Evaluation> To evaluate the presence or absence of changes in both acidity and bitterness, dark roasted beans (roasted immediately after the second crack) with a balanced acidity and bitterness were used instead of lightly roasted beans (roasted immediately after the first crack) with a pronounced acidity. For the coffee, 10 g of beans were medium-ground (particle diameter approximately 0.6-0.71 mm, according to the All Japan Coffee Culture Association standard) and extracted using a paper filter drip method with 130 ml of tap water at approximately 80°C. As a control, an extract from beans roasted at a normal high temperature was used. For the sensory evaluation, four healthy adult subjects who regularly drink coffee drank the coffee and rated the acidity and bitterness on a scale of 1 to 5, with 3 representing a slight increase in the taste quality of the beans roasted at a normal high temperature, 4 representing a slight increase, 5 representing a strong increase, 2 representing a slight decrease, and 1 representing a strong decrease.

[0057] Example 7: Sensory test of beans roasted to just after the second crack after heating at 90°C for 7 days The green beans used were the same as those used in Example 1, and the heating process was carried out in the same manner as in Example 1. After the heating process, the beans were roasted to just after the second crack using the same method as in Example 5. An extract was prepared using the coffee beans roasted to just after the second crack, and a sensory evaluation was carried out. The results are shown in Table 7. The acrylamide concentration of the coffee beans roasted after the heating process was 0.12 ppm, which was 85.7% of the acrylamide concentration of coffee beans that were only roasted (acrylamide concentration of coffee beans that were only roasted: 0.14 ppm).

[0058]

[0059] Example 8: Sensory test of coffee beans roasted until just after the second crack and then heated at 90°C for 3 days and 7 days The green beans used were the same as those used in Example 1, and roasted until just after the second crack in the same manner as in Example 5. Then, a sensory test was performed using coffee beans that had been heated at 90°C in the same manner as in Example 1. The results are shown in Table 8.

[0060]

[0061] Example 9: Sensory test of coffee beans roasted until just after the second crack and then heated at 150°C for 120 minutes A sensory test was conducted using the coffee beans from Example 6 that had been roasted and then heated for 120 minutes. The results are shown in Table 9.

[0062]

[0063] Reference Example 1: Sensory Test of Coffee Beans Roasted to Just After the Second Crack and Stored Frozen for 6 Months, and Coffee Beans Stored at Room Temperature for 6 Months Green beans were harvested from our own coffee farm and roasted to just after the second crack using the same method as in Example 3. The roasted beans were divided into two groups: one group was placed in a Ziploc® bag and stored frozen for 6 months until testing, and the other group was placed in a glass container (500 ml soda glass sealed bottle manufactured by MUJI) and stored at room temperature away from direct sunlight for 6 months. For reference in the sensory evaluation, the pH of the liquid extracted with water from the coffee beans of each group after 6 months of storage was also measured. The liquid was extracted using the paper filter drip method described above, and the pH was measured using a PH60 pH tester manufactured by APERA INSTRUMENTS, Inc. The results are shown in Table 10.

[0064]

[0065] All subjects rated the beans stored at room temperature for six months after roasting as having an unpleasant rancid smell and a distinct sour taste, with the sweetness and bitterness characteristic of coffee having disappeared.

[0066] The present invention can reduce acrylamide in coffee beans without causing deterioration in taste or aroma, and therefore can be suitably used as a product with little impact on health.

Claims

1. A method for processing coffee beans, comprising a heating treatment step of heating coffee beans at a temperature of 40°C or higher but lower than the temperature at which a first crack occurs.

2. The method for processing coffee beans according to claim 1, further comprising a roasting step of roasting the coffee beans, and the heating treatment step is carried out before the roasting step.

3. The method for processing coffee beans according to claim 1, further comprising a roasting step of roasting the coffee beans, and the heating treatment step is carried out after the roasting step.

4. A method for processing coffee beans as described in claim 1, comprising a roasting step of roasting the coffee beans, and the heating treatment step comprises a first heating treatment step carried out before the roasting step and a second heating treatment step carried out after the roasting step.

5. A method for treating coffee beans described in any one of claims 2 to 4, wherein the heating treatment step is carried out until the acrylamide concentration in the coffee beans is 90% or less compared to coffee beans that have been subjected to only the roasting step.

6. Coffee beans obtained from the same raw beans, in which the acrylamide concentration in the coffee beans is 90% or less compared to coffee beans immediately after being subjected to only a roasting process.

7. Coffee beans according to claim 6, in which the liquid extracted with water does not experience a drop in pH caused by rancidity.

8. Coffee beans according to claim 6 or 7, having a free asparagine concentration of 29 mg / 100 g or less.

9. Coffee beans treated by the method for treating coffee beans according to any one of claims 1 to 4.

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