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Laboratory evaluation of the effects of processing methods, treatment and coffee cultivar on chemical composition and in vitro digestibility of coffee pulp

Getachew Gebru1, Beyene Chichaibelu2 and Jess D. Reed3

1 Lecturer, Department of Animal Science, Alemayu University of Agriculture, P. O. Box 138, Dire Dawa, Ethiopia.

2 Professor of Animal Science and Dean of the Graduate School, Alemaya University of Agriculture, P. O. Box 138, Dire Dawa, Ethiopia.

3 Formerly Animal Nutrition Scientist, International Livestock Centre for Africa, P. O. Box 5689, Addis Ababa, Ethiopia.


Abstract
Introduction
Materials and methods
Results and discussion
Conclusion
References


Abstract

Experiments were conducted to study: (1) the effect of dry processing of coffee cherries and ensiling with urea on the chemical composition and in vitro digestibility of coffee pulp, and (b) the effect of variety of fibre and phenolic components. Zero, 40, 50 and 60 grams of urea were dissolved in a litre of water and added to dry-processed coffee pulp (DCoP) (1 litre/kg of air-dried DCoP) sealed in plastic bags (3 replicates) and incubated for 15 and 30 days.

The experiment on the relationship of variety to chemical composition was studied on the wet processed pulp. Fourteen varieties of coffee cherry were collected from high and low altitudes in Kaffa Administrative Region.

Treatment level had a significant effect (P<0.05) on the neutral detergent fibre (NDF), acid detergent Fibre (ADF) and content of soluble phenolics. Nitrogen (N) and content of soluble phenolics showed a significant increase at 5 and 10% levels respectively. However, urea treatment did not alter the in vitro dry-matter digestibility (IVDMD).

There was a large difference in the content of soluble phenolics (15-41%), potassium, iron and manganese. There was a trend for the content of phenolics to increase in varieties harvested at higher altitude. NDF showed negative and positive correlation with the soluble phenolics and insoluble proanthocyanidins respectively. Varietal and environmental effects on the nutritive value of coffee pulp appear to be of considerable importance.

Introduction

The low productivity of livestock in Ethiopia, which has the largest animal population in Africa, is caused in part by poor nutrition. Though natural grasslands are important feed resources, their present capacity to support increased livestock productivity is reduced by their low yield and poor quality. Seasonal growth pattern of the grasslands and high grazing pressure further limit the availability of herbage. Lack of feed resources often imposes a major constraint on animal production, particularly during the dry season. Rapid development of improved pasture and cultivated forages is not always possible because of limitations imposed by technical, economic and human factors. Therefore animal production must be integrated with crop production and allied processing agro-industries.

It is anticipated that mechanization will increase cultivated land area in Ethiopia devoted to food production, and that this will increase the availability of agro-industrial by products some of which can find use as feed as-is or as components in compounded feeds. However, the bulk of the available by-products are presently not effectively utilised amongst other resources due to inadequate knowledge of their value in feeding systems. The potential use of the by-products is also determined by the time and place they become available and the alternative use. Use of by-products ensures that ruminant animals are complementary rather than competitive with man in meeting their feed requirement.

Coffee is an agricultural crop of significant economic importance in Ethiopia. Coffee pulp is the major primary byproduct from the processing of coffee cherries. The bean is the main crop. After processing the pulp and hull are either dumped or utilised rather unproductively. Better utilisation of the byproducts could make the cultivation and processing of coffee more economical. For years the only use for coffee pulp has been as a fertilizer for the coffee plant, a practice dictated more by the lack of alternative usage of the pulp than by its effectiveness as a fertilizer. Coffee pulp should be considered as a means of alleviating the scarcity of animal feed.

Different approaches have been used to improve the nutritive value of various coffee residues, such as physical (grinding, heating and drying) and chemical treatments (calcium, and sodium hydroxide) and their combination have been used to eliminate the anti-nutrition physiological factors such as caffeine, and tannins. The economics of AIBP treatment should not be viewed only in relation to increased livestock production. Sustaining animal production during periods of fodder shortage and preventing death due to starvation has economic advantage (Jayasuriya, 1984).

The chemical treatment of fibrous residues using urea has been known for some time now. Enzyme urease hydrolyses urea and releases ammonia. Ammonia in water is an alkali that can improve the digestibility of low quality roughages (Sundstol, 1981).

Fresh coffee pulp is an abundant by-product, but its nutritive value as an animal feed is limited by the presence of anti-nutritive physiological factors like caffeine and tannins. If adverse effects could be eliminated by physical or chemical treatments then the utilisation of nutrients in the pulp could increase. Sodium hydroxide and sodium metabisulfite have been used and with some success. However chemical treatment of feeds in the tropics is restricted by costs, availability and necessary machinery, available technical ability and safety. urea seems promising in this line, because it is cheap and easy to get and has minimal hazards.

It is also essential to understand how much of the variation in the nutritive value of coffee pulp is attributed to the effect of processing methods. Genetic and environmental factors may also affect the nutritive value of coffee pulp. In order to develop feeding systems which utilise coffee pulp as a main ingredient of the ration, factors which affect nutritive value need to be determined.

The objectives of this study were to determine the effect of cherry variety, processing method and treatment on chemical composition and in vitro digestibility of coffee pulp.

Materials and methods


Experiment 1: Urea treatment of dry-processed coffee pulp.
Treatment procedure
Sample processing and method of analysis
Experiment 2: Laboratory evaluation of wet-processed pulp obtained from 15 cultivars of coffee cherries in Ethiopia.
Separation of the pulp from the cherries
Preparation of the pulp for analysis
Chemical Analysis
Statistical analysis


Experiment 1: Urea treatment of dry-processed coffee pulp.

Coffee pulp: Source and processing procedure. Pulp was obtained from coffee-processing centre of the Ministry of Coffee and Tea Development in Gelemso, Hararge, Eastern Ethiopia. Coffee cherries are processed by the dry method. The cherries are left on the tree to dry. The dried cherries are collected and mechanically separated into the bean and other fractions.

Treatment procedure

40, 50, 60 grams of urea were dissolved in l litre of water. The urea solutions were applied at the rate of 1 litre/kg of air dried pulp. The 1 kg lots of pulp were thoroughly mixed and transferred into plastic bags. The bags were tightly closed and left at room temperature, for a 15 and 30 days reaction period. The control (water treated) was stored in similar manner.

Sample processing and method of analysis

The contents of all bags were removed, oven dried at 60°C for 25 hrs, ground to pass a 1 mm screen and bottled for chemical analysis at the ILCA nutrition laboratory. All samples described were assayed for IVDMD, NDF, ADF and ADF-lignin (Goering and Van Soest, 1970), omitting decahydronaphtalene and sodium sulfite in the NDF procedure (Van Soest and Robertson, 1980).

Hemicellulose was estimated as the difference between NDF and ADF contents. DM and ash were analysed by the methods of the AOAC (1980). Nitrogen and N in NDF (NDF-N) were determined by the macro-kjeldahl procedure using sodium sulfate and copper sulphate in the digestion mix and collecting the distillate in a boric acid solution. Phenolics and tannins soluble in aqueous acetone were determined by a gravimetric procedure based on precipitation with ytterbium acetate (Reed et al, 1985). All determinations were conducted in duplicate.

Proanthocyanidins that are insoluble in neutral detergent were determined by methods described by Bate-Smith (1973) as modified by Reed et al, (1982). Five milligram of NDF were placed in a test tube, 5 ml of 5% concentrated HCL in a n-butanol were added and tubes heated at 95°C for one hour. Absorbance was read at 550nM using UV-VIS spectophometry. If Proanthocyanidins were present in the NDF, the n-butanol-HCL solution turned red. Results were expressed at A550 per gram NDF.

Experiment 2: Laboratory evaluation of wet-processed pulp obtained from 15 cultivars of coffee cherries in Ethiopia.

Description of experimental materials

Ripe coffee cherries of selected coffee cultivars (Table 1) were collected from two coffee plantation projects in Kaffa Administrative Region and were brought to ILCA laboratory (Addis Ababa, Ethiopia) for studies involving the chemical analysis of the pulp and fractionation of the components of the fruit.

Separation of the pulp from the cherries

The pulp was separated from the beans manually. Following separation, the pulp was transferred into plastic bags, labelled and frozen until the time of analysis.

The coffee beans (containing mucilage + hulls) were washed to remove the mucilage and then dried in a forced draft oven for 5 days. The dried beans plus hull were threshed by hand and separated by using an electrically operated seed blower. The weight of the beans and hulls were recorded for each cultivar.

Preparation of the pulp for analysis

The pulp from each cultivar was weighed and the weight recorded. It was then oven-dried at 60°C for 24 hours, ground to pass 1 mm sieve and bottled for laboratory analysis.

Table 1. List of coffee cultivars used in the study.

Identification

Area of collection

Remark

7440B

Bebeka


7440G

Gummar


744G

Gummar


75227G

Gummar


75227B

Bebeka


7454B

Bebeka


744B

Bebeka


741G

Gummar


741B

Bebeka


O.C.B

Bebeka

Native unimproved cultivars

O.C.G

Gummar

Native unimproved cultivars

74112B

Bebeka


74112G

Gummar


74158G

Gummar


74165G.

Gummar


Chemical Analysis

NDF, ADF and N were determined as stated under experiment 1. Lignin was determined by treating ADF with sulphuric acid (Goering and Van Soest, 1970). Proanthocyanidins that en insoluble in neutral detergent, phenolics and tannins that are soluble in aqueous acetone were determined by methods as described in experiment 1.

Statistical analysis

Pearson correlation coefficients were calculated to estimate correlation between NDF, ADF, Lignin, soluble phenolics and Insoluble proanthocyanidins.

Results and discussion


Experiment 1: Effect of dry processing and urea treatment.
Utilisation of the research results
Problems concerned with full utilisation of the research results - Extension and research linkage


Experiment 1: Effect of dry processing and urea treatment.

Chemical composition of dry-processed pulp is compared to wet-processed in Table 2. Pulp obtained from the dry method of processing coffee cherries shows a high level of NDF, ADF and Lignin. This suggests that the material has low nutritive value. The dry processing of cherries results in a by-product comprising mucilage, hulls and pulp. The presence of the hulls or the parchment along with the pulp contributes to the high content of fibre components. Coffee hull is reported to have high concentration of lignin, pentoses and hexoses (Murillo et al, 1977). Phenolic compounds show a higher concentration in the dry-processed pulp. These compounds can form insoluble complexes with proteins and may reduce OM and N digestibility (Getachew et al, unpublished data).

Table 2. Chemical composition of the dry and wet processed pulp (% DM)


Dry processed

Wet processed

Crude protein

11.12

10.6

Crude Ash

7.09

4.8

NDF

57.14

29.5

ADF

52.08

25.7

Lignin

16.40

5.6

Insoluble proanthocycanins*

20.00

11.5

Soluble phenolics

32.48

24.6

Calcium

.422

.554

Phosphorus

.153

.116

* expressed as A550/g NDF

The urea-treated and ensiled pulp had a strong odour at opening. Mould presence was detected in all samples ensiled, but it was only severe in the un-treated pulp. The reason for the mould growth could be inadequate seal and presence of air in the ensiled material.

The ensiled material showed a dark brown colour as opposed to the light brown colour of the material before ensiling. The colour change could possibly arise from reactions such as phenolic condensation or condensation of aldehydes formed by sugars with nitrogenous bases (Maillard reaction). N in complexes formed by Maillard reaction is unavailable to the animal and thus reduce the utilisation of the feed.

The urea treatment effects on the chemical composition and IVDMD are shown in Table 3. Treatment level had a significant effect (P<0.05) on the content of CP and soluble phenolics but no significant effects were observed on other parameters. Subdivision of the urea level sum of squares showed a linear trend of the effects of treatment level on nitrogen, lignin and soluble phenolics.

Treatment time had a significant effect on NDF, lignin and insoluble proanthocyanidins. The 15 days treatment time had lower contents of NDF, lignin and insoluble proanthocyanidins. Different roughages show varying responses to ammonia treatment (Coxworth et al, 1976; Arnason and Mo, 1977). Cereal straws are very different than coffee pulp in the type of lignin and susceptibility of alkali treatment. Also urea is not as effective as other alkalis. The inferiority of urea treatment could also be due to reaction of ammonia with carbon dioxide to form ammonium carbonate which reduces the efficiency of urea treatment (Mason and Owen, 1986).

Table 3. Chemical composition and in vitro dry matter digestibility of urea treated and untreated pulp.




% DM




CP

NDF

Lignin

soluble Phenolics

in vitro Digestibility

Urea level (g/Kg DM)

0

11.5

64.0

20.2

33.0

47.3

40

15.6

61.9

20.3

30.3

51.4

50

16.8

66.1

21.3

27.1

49.0

60

17.2

64.8

21.6

30.0

47.9

Significance

*

*

NS

*

NS

Treatment days

15

15.6

62.6

9.9

31.2

49.9

30

14.9

65.9

21.8

29.3

47.8

Significance

NS

**

**

NS

*

* p<0.05
NS = Not significant

Experiment 2. Variation in the chemical composition of coffee pulp among several Ethiopian coffee cherry cultivars processed wet.

The yield of fractions from cherries of eight randomly selected cultivars is shown in Table 4; the yield of coffee pulp on dry matter basis represents 28% of the weight of the whose fruit. The variation in content of DM, N. NDF, ADF and lignin was low (Table 5) but the range in content of soluble phenolics was large, between 15 and 41%. Altitude did not have a large effect on the composition of coffee pulp although there was a tendency (Table 6) for fibre components to be lower and soluble phenolics and insoluble proanthocyanidins to be higher in cultivars grown at higher altitudes. It appears that cultivars had a greater effect on the composition of pulp than the altitude.

Table 4. Average yield of fractions from cherries of eight randomly selected cultivars.

Fractions

0 % (Range)

Coffee pulp

27.38 (25 - 31)

Coffee hulls

17.50 (15.5 - 20)

Beans

51.68 (40 - 62)

Table 5. Chemical composition of the pulp from 15 coffee cultivars.


Composition (% DM)

Cultivar

DM

N

NDF

Lignin

ADF

Soluble phenolics

Insoluble proanthocyanidins A 550/g NDF

7440B

87.5

1.7

28.0

4.7

23.7

30.5

8.3

7440G

86.9

1.6

31.1

8.1

27.8

15.9

14.3

744G

87.3

1.9

26.8

4.2

23.2

24.3

9.3

75227G

88.8

1.5

22.5

6.9

28.4

18.8

14.5

75227B

86.0

1.5

32.5

7.0

28.3

24.8

14.1

7454B

87.7

1.7

32.1

8.6

29.0

21.0

12.2

744B

87.4

1.7

28.9

6.9

25.5

23.6

10.0

741G

87.1

1.9

26.5

2.9

23.0

25.7

10.5

741B

87.1

1.6

33.5

5.6

27.2

20.5

10.0

O.C.B

87.1

1.9

26.5

5.1

21.6

32.8

11.0

O.C.G

88.6

1.5

27.0

5.6

22.4

40.6

12.6

74112B

87.5

1.4

33.3

5.9

25.8

18.5

12.7

74112G

87.5

1.5

33.4

5.0

29.0

18.9

10.5

74158G

85.2

2.2

30.2

4.4

25.1

27.2

10.4

74165G

87.7

1.6

30.4

5.0

26.3

25.1

11.8

Mean

87.3

1.7

29.5

5.6

25.7

24.6

11.5

S.D.

0.88

0.21

3.24

1.54

2.52

6.40

1.88

Table 6. Effect of altitude on pulp composition.

Constituent

1200 mts

1800 mts

NDF

29.1 ± 2.7

26.7 ± 3.5

ADF

25.8 ± 2.4

25.7 ± 2.8

Lignin

5.9 ± 1.5

5.4 ± 1.8

Soluble phenolics

24.9 ± 5.0

25.2 ± 8.1

Insoluble proanthocyanidins

11.1 ± 1.8

12.9 ± 2.0

Cultivars with a high content of NDF seem to have a low to moderate content of soluble phenolics. This relationship led to a negative correlation between NDF and soluble phenolics (Table 7). However the correlation between NDF and insoluble proanthocyanidins was positive. Correlation of soluble phenolics and insoluble proanthocyanidins with other fibre components had the same sign as correlations with NDF and ADF. Large quantities of soluble phenolics if absorbed and excreted in the urine may lead to an over estimation of energy value (Reed, 1986). Soluble phenolics form indigestible protein and carbohydrate complexes in the digestive tract that increase fibre and lignin excretion in the faeces (Osbourn et al, 1971). Thus prediction of digestibility based on fibre components need to be adjusted for the content of soluble phenolics. Moreover the assumption that NDF represents cell wall carbohydrate and lignin in such residues is incorrect as NDF is associated with insoluble proanthocyanidins and may contain tannin-protein complexes.

Table 7. Correlation between NDF, ADF, Lignin (LIG), soluble phenolics and insoluble proanthocyanidins (A550/g NDF) in pulp of 15 Ethiopian coffee cultivar.


Soluble phenolics

Insoluble Proanthocyanidins A550/g NDF

NDF

ADF

A550/NDF

-.28




NDF

-.76**

.32



ADF

-.41

.48

.52*


LIG

-.40

.65**

.21

.61*

* p<0. 05
** p<0.01

Utilisation of the research results

This work was conducted as a basic study to look into some of the inherent constraints of the material and possible improvement by chemical treatment. Past studies of coffee pulp have suggested that coffee pulp has potential as livestock feed even though problems in its utilisation were encountered (Squibbo, 1950; Colborn and Hoxey, 1974, and Abate, 1986). Urea treatment, therefore was tested to asses its effect on the nutritive value of coffee pulp. Moreover the study on the relationship between coffee varieties and chemical composition was conducted to shed some light on the possible effects of plant genetic factors on the concentration of certain anti-nutritive factors in the pulp. The salient features of this research results were:

(a) Coffee pulp, depending on the methods of processing employed on the cherries, showed variations in nutritive value (Table 2). Effort, therefore, need to be made in adopting the method of processing (wet) that gives a better coffee grain yield and also a by-product with a better nutrient concentration for livestock feed.

(b) Weak alkalis like urea in water do not have significant effect in improving the energy status of coffee pulp in view of the effect of alkalis on the ligno-cellulose complex. However the urea may impart nitrogen and thus improve rumen fermentation.

(c) Due to high moisture content and bulkiness, coffee pulp cannot be utilised in areas far away from the processing site. Drying of coffee pulp at the site of production is not practical because of the use of the drying patios for the coffee grains. Ensiling coffee pulp without additives is practical. The coffee pulp ensiled for 5 months did not spoil except the top layer that showed mouldiness.

(d) The feeding value of coffee pulp in relation to the cultivars of the coffee tree is a point that could open further research into the investigation of the genetic factors associated with the coffee tree as they affect nutrient concentration. This enables one to develop plant-specific screening methods to determine the nutritive value of byproduct of various coffee cultivars. Coffee cultivars resulting from the joint selection for the feed value of the coffee pulp as well as coffee bean yield and quality will result is substantial economic gain.

Problems concerned with full utilisation of the research results - Extension and research linkage

In putting research into practice, research, development, extension and farming are equally important and interrelated. The limited attention and priority often given to extension does not allow feed-back mechanisms to function properly and thus the time attention given to solving problems which limit production may be long passed.

With very little effort made in understanding the system, it will be difficult to develop interest in utilising the research results. Lack of a viable national extension programme has resulted in the shelving of research results in research institutions and in poor integration of research scientists into the local community. The development of the peasant cooperatives in Ethiopia is a welcome trend that would allow the recognition of the importance of extension, and of course, research institutions have a lot to offer in this respect. Strengthening the weakest link in the chain i.e. extension, would allow researchers to work on feed-back mechanisms that follow the understanding of the constraints and development options of the current feeding system.

Conclusion

It may therefore be concluded that the availability of certain by-products like coffee pulp, per se does not warrant their immediate inclusion in livestock feeding. This calls upon the characterization of the material so that the inherent nutritional problems are defined. Further understanding of the nature of the complexing of nitrogen with the polyphenols and simple and cheaper methods of splitting this complex may allow efficient use of coffee pulp. The wet method of processing the coffee cherries could provide a by-product that has a better nutritive value and help in realizing the integration of livestock production with the crop production and allied processing industries.

References

AOAC (Association of Official Agricultural Chemists). 1980. Official methods of Analysis (13th edition). Assoc. Off. Anal. Chem., Washington, D.C.

Arnason, J. and Mo, M. 1977. Ammonia treatment of straw. Report on straw utilisation conference, Oxford, 24-25 Feb. Ministry of Agric. Fisheries and food, Oslo, Norway.

Bate-Smith, E.C. 1973. Tannins of herbaceous Leguminosae. Phytochem. 12:1809-1812.

Calborn, L.N. and Hoxey, M.J. 1974. Animal Nutrition: Some tropical by-products for compounded feeds. Span. 17, No 3:111.

Coxworth, E., Kernan, J., Nicholson, H., Chaplin, R. and Manns, J. 1976. A report on a search for economical farm scale methods of improving the feeding value of straw of Canadian prairies use of ammonia and other bases. Proc. 12th Annual Nutr. Con. for Feed manufacturers. Toronto, Canada.

Goering, H.K. and van Soest, p.J. 1970. Forage fibre analysis. Agricultural handbook No. 379. USDA, Washington, D.C.

Jayasuriya, M.C.N. 1984. Potential for the better utilisation of crop residues and agro-industrial by-products in animal feeding in the Indian sub-continent. Paper presented at the FAO/ILCA expert consultation on guidelines for research on the better use of by-products and crop residues in animal feeding in developing countries. Addis Ababa, Ethiopia, 5-9 March, 1984. FAO, Rome.

Mason, V.C. and Owen, E. 1986. Urea versus ammonia for upgrading graminaceous materials. In towards optimal feeding of agricultural by-products to livestock in Africa. Proc. workshop at University of Alexandria, Egypt. October, 1985.

Murillo, B., Cabezas, T., Jarquin, R. and Bressani,. 1977. Effect of bisulfite addition on the chemical composition and cellular content fractions of dehydrated coffee pulp digestibility. J. Agric. Food Chem. 25(5):1090-1092.

Osbourn, D.E., Terry, R.A., Cammel, S.B. and Outen, G.E. 1971. The effect of leuco-anthocyanins in sainfoin (Onobrychis vicifolia) on the availability of protein to sheep and upon the determination of the acid detergent fibre and lignin fractions. Proc. Nutr. Soc. 30:13A-14A.

Reed, J.D., McDowell, R.E., van Soest, P.J. and Horvath, P.J. 1982. Condensed tannins: a factor limiting the use of cassava forage. J. Sci. Feed Agric. 33:213-220.

Reed, J.D., Horvath, P.J., Allen, M.S. and van Soest, P.J. 1985. Gravimetric determination of soluble phenolics including tannins from leaves by precipitation with trivalent ytterbium. J. Sci. Food Agric. 36:255-261.

Reed, J.D. 1986. Relationship among soluble phenolics, insoluble proanthocyanidins and fibre in East African browse species. Journal of Range Management. 39 (1):5-7

Squibbo, R.L. 1950. Present status of dried coffee pulp and coffee pulp silage as animal feedstuff. Instituto Agropecuario Nacional, Guatemala. p. 10.

Sundstol, F. 1981. Methods for treatment of low quality roughages. In J.A. Kategile, A.N. Said and F. Sundstol (eds): Utilisation of low quality roughages in Africa. Agricultural University of Norway, Agricultural Report No.1.

van Soest, P.J. and Robertson, J.B. 1980. System of analysis for evaluating fibrous feeds, p. 49-60. In: W.J. Pigden, C.C. Balch and M. Graham (eds), Standardization of analytical methodology for feeds. Proc. workshop held in Ottawa, Canada, 12-14 March 1979. IDRC, Ottawa, Canada.


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