**3.1 Materials and methods**

## *3.1.1 Experimental materials and site*

Field trials were conducted in Siaya and Busia counties of Kenya, in 2018/2019. Nineteen genotypes including seven Arabusta hybrids, six different backcross derivatives of Arabica to Arabusta hybrids, Congusta, Congensis, Arabusta cultivar, Robusta, *C arabica* (Batian) and *C arabica* (Ruiru 11) were evaluated. The Uganda tetraploids used in generating the interspecific hybrids were sourced from Uganda while the Robusta and Arabica genotypes are all from Coffee Research Institute-Ruiru, Kenya.

The trials were established at Siaya ATC (Siaya County) and KALRO Alupe (Busia County) both of which sites are located near the Lake Victoria basin in the low altitude zones suitable for planting Robusta coffee. Siaya lies between 0° 30 N′ and 0° 45′ E with an altitude that varies from 1,135 m to 1,500 m above sea level receiving a mean annual rainfall of 1,500 mm whereas Busia county lies between 0° 30 N′ and 34° 30' SE with an altitude that varies from 1241 m to 1343 m above sea level with mean annual rainfall of 1400 mm.

## **3.2 Sensory evaluation of coffee**

The evaluation of the sensory attributes was conducted by five trained judging panel using the procedures described by [64, 65]. A probate laboratory roaster was used in the roasting process and the roasted beans were left to rest for at least 8 hours before cupping. Green coffee beans were weighed before and after roasting

**55**

*Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and Their Arabusta Hybrids*

to be able to determine the roasting degree. After the 8 hours', the roasted beans were ground into individual cups ensuring that the whole sample was deposited into each cup. Each sample representing a specific genotype was placed into five cups. Samples were weighed to get 8.25 g and 150 ml of hot water was added per cup. The evaluation of the sensory attributes was conducted by five trained judges forming a panel using the procedures described by [65]. The descriptors measured included acidity, body, balance, fragrance/aroma, flavour, aftertaste, and prefer-

The attribute scores of clean cup, sweetness, and uniformity were each scored and a maximum of two points per cup was awarded getting a maximum score 10. These scores were added to the scores obtained from the other seven sensory attributes to constitute the total score. This would then reflect the total performance of genotypes regarding cup quality. The average score of a cupper was considered as

Two (2) grams of the dried green coffee powder from the green coffee bean was weighed and dried for 1 h at 105°C ± 2°C. Extraction was carried out after adding 100 mm of hexane to the coffee powder which was then in the soxhlet extraction apparatus [66]. Rota vapor was used to dry the extract and placing it an oven at105 ± 2°C to complete drying process. The extract was cooled and then weighed to get the final weight after evaporation. The drying process continued for another two hours weighing being undertaken at a 30-minute interval until there was no more than one milligram loss between successive weighing. Crude oil content was

then calculated by as the increase in weight of the extraction flasks [67].

*3.3.2 Extraction of caffeine, trigonelline and total chlorogenic acids (CGA)*

*3.3.3 Analysis of caffeine, trigonelline and total chlorogenic acids*

Caffeine, trigonelline and chlorogenic acids levels were determined using the protocols as provided by [68, 69] with slight modifications as described below.

HPLC system (Knaeur) equipped with a Super Co Discovery C-18 column was used to analyse caffeine and trigonelline and BDS HYPERSIL C-18 column used to analyse chlorogenic acids. Diode Array Detector was used to detect the three wavelengths, at 278 nm for caffeine, 266 nm for trigonelline and 324 nm for CGA. HPLC grade methanol (PANREAC) 35% was used as the mobile phase, distilled water 65%, acetic acid (PROLABO) 0.1%, at a flow rate of 1 ml/min under ambient temperature. The retention times of the trigonelline standard (Sigma Aldrich), CGA standard (Acros organics) and caffeine standard (99%) (Fischer Scientific) were used to calculate trigonelline, CGA and Caffeine quantities respectively. Calibration equations were used to calculate using the peak area of the slope [67].

The extraction and analysis of sucrose was done according to the method of [70] used by [67]. 0.2 g of the green coffee powder was added to 100mls of 96% ethanol under reflux. The extract was evaporated to dryness after filtering it using the Whatman filter paper number 42. Recovery of sucrose was done using 10mls

*DOI: http://dx.doi.org/10.5772/intechopen.95520*

**3.3 Biochemical compounds analyses**

*3.3.4 Extraction and analysis of sucrose*

*3.3.1 Extraction and quantification of crude oil*

ence as described by SCA.

a replication.

*Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and Their Arabusta Hybrids DOI: http://dx.doi.org/10.5772/intechopen.95520*

to be able to determine the roasting degree. After the 8 hours', the roasted beans were ground into individual cups ensuring that the whole sample was deposited into each cup. Each sample representing a specific genotype was placed into five cups. Samples were weighed to get 8.25 g and 150 ml of hot water was added per cup. The evaluation of the sensory attributes was conducted by five trained judges forming a panel using the procedures described by [65]. The descriptors measured included acidity, body, balance, fragrance/aroma, flavour, aftertaste, and preference as described by SCA.

The attribute scores of clean cup, sweetness, and uniformity were each scored and a maximum of two points per cup was awarded getting a maximum score 10. These scores were added to the scores obtained from the other seven sensory attributes to constitute the total score. This would then reflect the total performance of genotypes regarding cup quality. The average score of a cupper was considered as a replication.

### **3.3 Biochemical compounds analyses**

*Mineral Deficiencies - Electrolyte Disturbances, Genes, Diet and Disease Interface*

which in turn influence flavour [6, 53].

*2.2.4 Chlorogenic acids*

*2.2.5 Lipids/oils*

the beans [63].

Ruiru, Kenya.

**3.1 Materials and methods**

*3.1.1 Experimental materials and site*

level with mean annual rainfall of 1400 mm.

**3.2 Sensory evaluation of coffee**

in coffee [54]. Degradation of trigonelline during roasting results in niacin, nicotinamide and a wide range of aroma volatiles, that include pyridines and pyrroles

Chlorogenic acids (CGA) are the highest occurring polyphenols in coffee and form a significant part of coffee antioxidants [57, 58]. CGA belongs to hydroxycinnamic acids classes that comprise caffeic acid (3,4-hydroxycinnamic acid), ferulic acid (3-methoxy-4-hydroxycinnamic acid), p-coumaric (4-hydroxycinnamic acid), and sinapic acid (3,5-dimethoxy-4-hydroxycinnamic acid) [59]. CGA varies from 4% to 8.4% in Arabica coffee and between 7% to 14.4% in Robusta coffee whereas Arabusta hybrids have intermediate levels [60]. Maillard and Strecker's reaction cause chlorogenic acids to form pigments that affect taste and flavour [61].

Oil which is produced during roasting process, is the key determining factor of flavour and its quantity in the green bean is cultivar specific. The most important lipids in Arabica beans are the fatty acids that include the triacylglycerols, sterols, and tocopherols which are also found in vegetables [62]. Arabica coffee contains about 15% lipids compared to 10% in, Robusta coffee. Most lipids in the green coffee bean are located in the endosperm whereas the rest is found on the outer layer of

**3. Organoleptic attributes of arabusta hybrids from experimental data**

Field trials were conducted in Siaya and Busia counties of Kenya, in 2018/2019.

Nineteen genotypes including seven Arabusta hybrids, six different backcross derivatives of Arabica to Arabusta hybrids, Congusta, Congensis, Arabusta cultivar, Robusta, *C arabica* (Batian) and *C arabica* (Ruiru 11) were evaluated. The Uganda tetraploids used in generating the interspecific hybrids were sourced from Uganda while the Robusta and Arabica genotypes are all from Coffee Research Institute-

The trials were established at Siaya ATC (Siaya County) and KALRO Alupe (Busia County) both of which sites are located near the Lake Victoria basin in the low altitude zones suitable for planting Robusta coffee. Siaya lies between 0° 30 N′ and 0° 45′ E with an altitude that varies from 1,135 m to 1,500 m above sea level receiving a mean annual rainfall of 1,500 mm whereas Busia county lies between 0° 30 N′ and 34° 30' SE with an altitude that varies from 1241 m to 1343 m above sea

The evaluation of the sensory attributes was conducted by five trained judging panel using the procedures described by [64, 65]. A probate laboratory roaster was used in the roasting process and the roasted beans were left to rest for at least 8 hours before cupping. Green coffee beans were weighed before and after roasting

**54**

### *3.3.1 Extraction and quantification of crude oil*

Two (2) grams of the dried green coffee powder from the green coffee bean was weighed and dried for 1 h at 105°C ± 2°C. Extraction was carried out after adding 100 mm of hexane to the coffee powder which was then in the soxhlet extraction apparatus [66]. Rota vapor was used to dry the extract and placing it an oven at105 ± 2°C to complete drying process. The extract was cooled and then weighed to get the final weight after evaporation. The drying process continued for another two hours weighing being undertaken at a 30-minute interval until there was no more than one milligram loss between successive weighing. Crude oil content was then calculated by as the increase in weight of the extraction flasks [67].

#### *3.3.2 Extraction of caffeine, trigonelline and total chlorogenic acids (CGA)*

Caffeine, trigonelline and chlorogenic acids levels were determined using the protocols as provided by [68, 69] with slight modifications as described below.

#### *3.3.3 Analysis of caffeine, trigonelline and total chlorogenic acids*

HPLC system (Knaeur) equipped with a Super Co Discovery C-18 column was used to analyse caffeine and trigonelline and BDS HYPERSIL C-18 column used to analyse chlorogenic acids. Diode Array Detector was used to detect the three wavelengths, at 278 nm for caffeine, 266 nm for trigonelline and 324 nm for CGA. HPLC grade methanol (PANREAC) 35% was used as the mobile phase, distilled water 65%, acetic acid (PROLABO) 0.1%, at a flow rate of 1 ml/min under ambient temperature. The retention times of the trigonelline standard (Sigma Aldrich), CGA standard (Acros organics) and caffeine standard (99%) (Fischer Scientific) were used to calculate trigonelline, CGA and Caffeine quantities respectively. Calibration equations were used to calculate using the peak area of the slope [67].

#### *3.3.4 Extraction and analysis of sucrose*

The extraction and analysis of sucrose was done according to the method of [70] used by [67]. 0.2 g of the green coffee powder was added to 100mls of 96% ethanol under reflux. The extract was evaporated to dryness after filtering it using the Whatman filter paper number 42. Recovery of sucrose was done using 10mls

deionized water and 2mls of the extract mixed with 2mls Diethyl ether (AR) and the top layer was discarded after settling. The process was repeated three times and 1 ml of acetonitrile was added to 1 ml of the extract. Filtering was conducted using the 0.45 μm micro filter. HPLC system (Knaeur) equipped with a Eurospher 100–5 NH2 column and a refractive index detector was used to analyse sucrose. Acetonitrile HPLC grade (SCHARLAU) 75%, and distilled water 25% was used as the mobile phase at a flow rate 1 ml/min. The sucrose standard (Fischer Scientific) was used in quantifying the sucrose level through comparison of the retention peak of standards and sample peak the sucrose level calculated using the calibration equation.

### **3.4 Data analysis**

The bean grades, sensory data and biochemical data were subjected to Analysis of Variance (ANOVA) using GENSTAT statistical software version 18 and effects declared significant at 5%. The General Linear Model (GLM) was used.

$$\mathbf{Y}^{\star} = \mathbb{B}\_{\mathrm{o}} + \mathbb{B}\_{\mathrm{i}}\mathbf{X}\_{\mathrm{i}} + \mathbb{B}\_{\mathrm{z}}\mathbf{X}\_{\mathrm{z}} + \dots + \mathbb{B}\_{\mathrm{k}}\mathbf{X}\_{\mathrm{k}} + \mathbf{E}\_{\mathrm{i}}.\tag{1}$$

Where,

For each observation *i =* 1, …., *n.* where *n* is the observations of one dependent variable.

*Yˆ* = *j* th observation of the dependent variable.

*j* = 1,2, ….., k.

*X* = is the observation of the *j* th independent variable.

β = parameters to be estimated.

*Ei =* Distributed normal error.

Least Significance Difference was used to separate means [71]. Separate as well as combined analysis of variance was performed on data from the two sites. GENSTAT statistical software was used to compute correlation and to show relationship between sensory traits using the Pearson Correlation Coefficient.

### **3.5 Sensory performance**

Sensory traits significantly varied among the coffee genotypes tested across the two locations with Arabica genotype SL28 recording the highest Fragrance value and Robusta genotypes the lowest. Again as for Flavour, Arabica genotype, SL28 recorded the highest value whereas CV1 recorded the lowest (**Table 1**). Again, genotype SL28 recorded significantl higher values for Aftertaste in both sites. As for Acidity, Robusta genotypes had the lowest values but Arabica genotype SL 28 recorded the highest. Body value was high in both Arabusta hybrids and Arabica genotypes. For all the traits scored, Arabica genotype, SL28 recorded significantly higher values than all the rest, across the two locations (**Table 2**).

The genotypic effect varied significant for all the sensory traits with the exception of the environmental variations were significant for all the sensory trait whereas the G x E interaction was not significant for all the sensory traits measured (**Table 2**). Preference scored the highest maximum score, whereas acidity scored the lowest. (**Table 3**). The highest rated sensory attribute was Body, followed closely by Aroma whereas Flavour and Aftertaste had the lowest mean. Acidity and preference indicated that they had wider phenotypic variance than all the other sensory traits (**Table 3**).

**57**

**Genotypes**

ARH1 ARH4 ARH5 ARH6 ARH7

BC01 BC02 BC03 BC04 BC05 BC06

CV1 CV2 ARV Robusta Ruiru 11

Batian

SL28 LSD %CV

Ftest

**Table 1.**

*Sensory traits for coffee genotypes at KALRO-Alupe and Siaya ATC.*

7.7 7.6 8.1 0.3 0.7

S

S *Key: Bu- Busia Si- Siaya; Reproduced from PhD thesis, University of Nairobi.*

S

S

S

S

S

S

NS

7.5

S

S

S

S

S

S

3.6

1.8

2.3

2.5

2.4

2.0

2.7

1.6

7.5

1.1

3.1

1.5

1.9

0.7

0.9

0.4

0.3

0.5

0.3

0.4

0.3

0.4

0.4

7.5

0.3

0.6

0.3

0.4

1.5

2.4

8.2

7.9

8.2

8.0

8.1

7.8

8.2

7.9

7.5

7.9

7.9

8.3

7.9

85.9

86.2

7.9

7.5

7.9

7.3

7.9

7.4

8.1

7.6

7.5

7.2

7.2

7.2

7.2

81.8

83.8

7.2

7.3

7.0

7.3

7.0

7.5

7.2

7.5

7.5

7.3

7.4

7.4

7.3

82.0

80.6

**Fragrance**

**Bu** 7.5 7.4 7.8 7.5 7.6 7.4 7.5 7.8 7.6 7.7 7.6 7.6 7.4 7.4 6.8

6.9

7.2

7.0

7.1

7.1

7.0

6.9

7.2

7.5

7.0

7.0

7.1

7.0

79.5

79.1

7.6

7.4

7.3

7.5

7.3

7.4

7.4

7.7

7.5

7.4

7.4

7.4

7.4

82.2

82.0

7.2

7.2

6.8

7.4

6.9

7.2

6.9

7.5

7.5

7.4

7.0

7.3

6.7

81.4

78.7

7.1

7.2

6.7

7.4

6.6

7.2

6.7

7.6

7.5

7.4

7.3

7.3

6.6

81.7

78.2

7.4

7.4

7.0

7.4

6.8

7.5

6.8

7.6

7.5

7.4

7.0

7.4

6.9

82.3

79.0

7.4

7.6

7.3

7.6

7.1

7.6

7.4

7.7

7.5

7.8

7.4

7.7

7.4

83.7

81.6

7.5

7.4

7.2

7.5

7.2

7.5

7.4

7.5

7.5

7.4

7.1

7.4

7.2

82.3

81.2

7.7

7.1

7.3

7.3

7.3

7.3

7.5

7.5

7.5

7.2

7.4

7.4

7.4

81.6

82.3

7.5

7.3

7.2

7.3

7.1

7.3

7.0

7.5

7.5

7.2

7.2

7.3

7.1

81.4

80.6

7.4

7.2

6.9

7.3

6.8

7.3

6.9

7.6

7.4

7.4

7.0

7.4

6.9

81.6

79.3

7.6

7.5

7.4

7.7

7.2

7.6

7.4

7.7

7.7

7.7

7.3

7.7

7.4

83.5

82.0

7.4

7.3

7.3

7.4

7.3

7.4

7.4

7.5

7.6

7.6

7.4

7.5

7.4

82.2

81.8

7.3

7.5

7.2

7.7

7.1

7.5

7.1

7.8

7.5

7.6

7.1

7.6

7.2

83.5

80.5

7.5

7.2

7.0

7.4

6.9

7.2

7.0

7.6

7.4

7.3

7.0

7.4

7.0

81.5

79.8

7.0

7.4

7.0

7.6

7.1

7.4

7.2

7.7

7.5

7.4

7.2

7.4

7.1

82.4

80.1

**Si**

**Bu**

**Si**

**Bu**

**Si**

**Bu**

**Si**

**Bu**

**Si**

**Bu**

**Si**

**Bu**

**Si**

**Bu**

**Si**

**Flavor**

**Aftertaste**

**Acidity**

**Body**

**Balance**

**Preference**

**Total score**

*Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and Their Arabusta Hybrids*

*DOI: http://dx.doi.org/10.5772/intechopen.95520*


*Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and Their Arabusta Hybrids DOI: http://dx.doi.org/10.5772/intechopen.95520*

> **Table 1.**

*Mineral Deficiencies - Electrolyte Disturbances, Genes, Diet and Disease Interface*

deionized water and 2mls of the extract mixed with 2mls Diethyl ether (AR) and the top layer was discarded after settling. The process was repeated three times and 1 ml of acetonitrile was added to 1 ml of the extract. Filtering was conducted using the 0.45 μm micro filter. HPLC system (Knaeur) equipped with a Eurospher 100–5 NH2 column and a refractive index detector was used to analyse sucrose. Acetonitrile HPLC grade (SCHARLAU) 75%, and distilled water 25% was used as the mobile phase at a flow rate 1 ml/min. The sucrose standard (Fischer Scientific) was used in quantifying the sucrose level through comparison of the retention peak of standards and sample peak the sucrose level calculated using the calibration

The bean grades, sensory data and biochemical data were subjected to Analysis of Variance (ANOVA) using GENSTAT statistical software version 18 and effects declared significant at 5%. The General Linear Model (GLM) was

For each observation *i =* 1, …., *n.* where *n* is the observations of one dependent

th independent variable.

Least Significance Difference was used to separate means [71]. Separate as well as combined analysis of variance was performed on data from the two sites. GENSTAT statistical software was used to compute correlation and to show relationship between sensory traits using the Pearson Correlation Coefficient.

Sensory traits significantly varied among the coffee genotypes tested across the two locations with Arabica genotype SL28 recording the highest Fragrance value and Robusta genotypes the lowest. Again as for Flavour, Arabica genotype, SL28 recorded the highest value whereas CV1 recorded the lowest (**Table 1**). Again, genotype SL28 recorded significantl higher values for Aftertaste in both sites. As for Acidity, Robusta genotypes had the lowest values but Arabica genotype SL 28 recorded the highest. Body value was high in both Arabusta hybrids and Arabica genotypes. For all the traits scored, Arabica genotype, SL28 recorded significantly

The genotypic effect varied significant for all the sensory traits with the excep-

tion of the environmental variations were significant for all the sensory trait whereas the G x E interaction was not significant for all the sensory traits measured (**Table 2**). Preference scored the highest maximum score, whereas acidity scored the lowest. (**Table 3**). The highest rated sensory attribute was Body, followed closely by Aroma whereas Flavour and Aftertaste had the lowest mean. Acidity and preference indicated that they had wider phenotypic variance than all the other

th observation of the dependent variable.

higher values than all the rest, across the two locations (**Table 2**).

*Y* =β +β +β +…+β + kk i ˆ X X X E. 0 11 22 (1)

**56**

equation.

used.

Where,

*j* = 1,2, ….., k.

**3.5 Sensory performance**

sensory traits (**Table 3**).

*X* = is the observation of the *j*

β = parameters to be estimated. *Ei =* Distributed normal error.

variable. *Yˆ* = *j*

**3.4 Data analysis**


*Key: \*, \*\*, \*\*\* and NS represent significant at (P < 0.005), (P < 0.001), (P < 0.0001) and non-significant respectively. Reproduced from PhD thesis, University of Nairobi.*

#### **Table 2.**

*Mean squares for sensory traits of 17 coffee genotypes evaluated at Siaya ATC and KALRO-Alupe (Busia).*


#### **Table 3.**

*Variability of the sensory attributes for the 20 coffee genotypes.*

The biochemical attributes scored here, varied significantly among the genotypes with genotypes ARH2 and ARH3 scoring the highest levels of chlorogenic acids, caffeine, sucrose and Trigonelline contents (**Figure 1**). Arabica genotypes, Ruiru 11, Batian and SL28 gave the highest oil content values, whereas Robusta recorded the highest caffeine contents (**Figure 1**). In the two locations over the two seasons, there was variation in the biochemical composition of the Arabusta hybrids, backcrosses, Robusta and Arabica coffee genotypes evaluated here. Arabica coffee genotypes had the highest composition of sucrose, trigonelline and oils, whereas the Arabusta hybrids scored intermediate values between Arabica and Robusta. Robusta genotypes scored the highest caffeine and cholorogenic acid contents whereas Arabica scored the lowest (**Figure 2**).

The Arabusta hybrids had higher values of oil, sucrose and trigonelline contents than Robusta genotypes which contributed to a better cup quality. As noted elsewhere in this chapter, chlorogenic acids are involved in aroma formation and pigmentation of coffee whereas caffeine influences the mildness in the cup [72]. But higher levels of caffeine and chlorogenic acids lower the quality by infusing bitterness and the astringency taste in the coffee brew [64, 73]. The results reported here showed that, Arabica and Arabusta genotypes had higher levels of sucrose, oil and trigonelline contents than Robusta genotypes, that contributed to a better cup quality due to the aroma and flavor that these biochemical compounds produce. All the interspecific

**59**

compared to Robusta genotypes**.**

*from PhD thesis, University of Nairobi.*

and hybridization in coffee improvement programs**.**

**4. Conclusions**

**Figure 2.**

**Figure 1.**

*Nairobi.*

*Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and Their Arabusta Hybrids*

hybrids with the exception of ARH4 genotype recorded a 80% quality performance

*Biochemical composition for the Arabusta coffee hybrids, Backcrosses, Arabica and Robusta coffee. Reproduced* 

*Biochemical contents of twenty coffee genotypes in Busia and Siaya. Reproduced from PhD thesis, University of* 

Arabica and Arabusta genotypes evaluated in these experiments, confirmed that there is genetic variation for organoleptic, sensory and biochemical traits in coffee. Interspecific hybridization between *C. Arabica* and *C. canephora*, produced hybrids with improved sensory and organoleptic traits that were intermediate between the two species. Cup quality in coffee can be improved through selection

*DOI: http://dx.doi.org/10.5772/intechopen.95520*

*Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and Their Arabusta Hybrids DOI: http://dx.doi.org/10.5772/intechopen.95520*

#### **Figure 1.**

*Mineral Deficiencies - Electrolyte Disturbances, Genes, Diet and Disease Interface*

The biochemical attributes scored here, varied significantly among the genotypes with genotypes ARH2 and ARH3 scoring the highest levels of chlorogenic acids, caffeine, sucrose and Trigonelline contents (**Figure 1**). Arabica genotypes, Ruiru 11, Batian and SL28 gave the highest oil content values, whereas Robusta recorded the highest caffeine contents (**Figure 1**). In the two locations over the two seasons, there was variation in the biochemical composition of the Arabusta hybrids, backcrosses, Robusta and Arabica coffee genotypes evaluated here. Arabica coffee genotypes had the highest composition of sucrose, trigonelline and oils, whereas the Arabusta hybrids scored intermediate values between Arabica and Robusta. Robusta genotypes scored the highest caffeine and cholorogenic acid

**Attributes Minimum Maximum Mean Variance range Standard Error** Aroma 7.23 8.00 7.48 0.78 0.09 Flavor 6.93 8.00 7.28 1.08 0.10 Aftertaste 6.98 7.88 7.28 0.90 0.10 Acidity 6.90 8.08 7.31 1.18 0.10 Body 7.30 7.83 7.53 0.53 0.10 Balance 7.15 7.85 7.34 0.70 0.13 Preference 6.93 8.10 7.32 1.18 0.09

*Key: \*, \*\*, \*\*\* and NS represent significant at (P < 0.005), (P < 0.001), (P < 0.0001) and non-significant* 

*Mean squares for sensory traits of 17 coffee genotypes evaluated at Siaya ATC and KALRO-Alupe (Busia).*

**Source Rep Gen (G) Envt (E) G x E Error** Df 4 17 1 17 140 Fragrance 0.598 0.3514\*\*\* 0.73472\*\* 0.12296NS 0.096 Flavour 0.152 0.6629\*\*\* 2.6889\*\*\* 0.0793NS 0.102 Aftertaste 0.151 0.4416\*\*\* 7.4014\*\*\* 0.0911NS 0.106 Acidity 0.213 0.7609\*\*\* 2.6281\*\*\* 0.1524NS 0.113 Body 0.536 0.1769\*\*\* 0.6183\*\*\* 0.0926NS 0.102 Balance 0.202 0.3225NS 2.4019\*\*\* 0.1402NS 0.159 Preference 1.218 21.18\*\*\* 134.421\*\*\* 4.525NS 2.882

The Arabusta hybrids had higher values of oil, sucrose and trigonelline contents than Robusta genotypes which contributed to a better cup quality. As noted elsewhere in this chapter, chlorogenic acids are involved in aroma formation and pigmentation of coffee whereas caffeine influences the mildness in the cup [72]. But higher levels of caffeine and chlorogenic acids lower the quality by infusing bitterness and the astringency taste in the coffee brew [64, 73]. The results reported here showed that, Arabica and Arabusta genotypes had higher levels of sucrose, oil and trigonelline contents than Robusta genotypes, that contributed to a better cup quality due to the aroma and flavor that these biochemical compounds produce. All the interspecific

contents whereas Arabica scored the lowest (**Figure 2**).

*Reproduced from PhD thesis, University of Nairobi.*

*Variability of the sensory attributes for the 20 coffee genotypes.*

*respectively. Reproduced from PhD thesis, University of Nairobi.*

**58**

**Table 3.**

**Table 2.**

*Biochemical contents of twenty coffee genotypes in Busia and Siaya. Reproduced from PhD thesis, University of Nairobi.*

#### **Figure 2.**

hybrids with the exception of ARH4 genotype recorded a 80% quality performance compared to Robusta genotypes**.**

#### **4. Conclusions**

Arabica and Arabusta genotypes evaluated in these experiments, confirmed that there is genetic variation for organoleptic, sensory and biochemical traits in coffee.

Interspecific hybridization between *C. Arabica* and *C. canephora*, produced hybrids with improved sensory and organoleptic traits that were intermediate between the two species. Cup quality in coffee can be improved through selection and hybridization in coffee improvement programs**.**
