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JOURNAL OF RESEARCH IN NATIONAL DEVELOPMENT VOLUME 8 NO 1, JUNE, 2010


QUALITY CHARACTERISTICS OF GARI PRODUCED IN SOME SELECTED CASSAVA PROCESSING CENTRES IN OWO, ONDO STATE, NIGERIA

E. A. Komolafe
Department of Food Science and Technology
E-mail: komodeji@yahoo.com
and
J. O. Arawande
Department of Science Laboratory Technology, Rufus Giwa Polytechnic, Owo
E-mail: jowande1@yahoo.com

 

Abstract
In this study, the quality characteristics of gari samples collected from ten cassava processing centres in Owo, Ondo State were determined. Freshly processed gari samples were randomly collected from six processors, bulked, packaged and labelled to obtain a representative sample in each centre. Parameters measured as an index of quality were proximate, residual hydrocyanic acid content, swelling capacity and bulk density. The results showed wide and significant variation in the measured indices from one processing centre to another as follows: Moisture content, 13.00% to 17.35%; Crude fibre, 1.50% to 3.74%; Hydrocyanic acid (HCN) content, 1.35mgHCN/100g to 3.32 mgHCN/100g; Swelling capacity, 245% to 340%; and bulk density, 0.50g/cm3 to 0.91g/cm3.Sixty percent of the processing centers produced gari with more than 2.00% fibre allowable in good quality gari. Higher level of cyanide (3.02mgHCN/100g, 3.21mgHCN/100g and 3.32mgHCN/100g) was detected in gari samples from Arupe village, Uselu and Idimepen respectively. Other centres produced gari with acceptable cyanide concentrations. Results also indicated that sixty percent of the centres produced gari with less than 300% minimum swelling capacity recommended for a good quality gari. Ijebu  Owo gari sample had the highest swelling capacity of 340% while idasen recorded the lowest value of 245% swelling capacity in its gari. The bulk density of 0.50g/cm3 to 0.91g/cm3 were recorded for gari produced from all the processing centres. All the gari samples from the various processing centres were acidic with a pH range 3.4 to 4.5.

Keywords: Cassava, gari, processing centres, quality characteristics


Introduction
Cassava (Manihot escullenta Crantz) is a staple food and an important source of calories to millions of people particularly in the tropics (Oyewole and Odunfa, 1989). However its use as a food source is limited by its perishability, low protein content and potential toxicity (Cooke and Coursey, 1981). Numerous processing methods have been devised including grating, fermentation followed by roasting to reduce the toxicity and at the same time convert the highly perishable fresh roots of cassava into stable products (Coursey, 1973; Oyewole, 1991). Gari is the most popular form in which cassava is consumed in Nigeria (Ikediobi etal; 1980; Odoemelam, 2005). Gari is a fermented, gritty, starchy food or free flowing dry granular product produced from cassava (IITA, 1990). It is processed by fermenting peeled and grated roots followed by dewatering, sieving and frying. Gari is consumed principally as a main meal (eba) or taken as a snack when soaked in cold water, sweetened with sugar and consumed with roasted groundnut, coconut and sometimes dry fish (UNICF/IITA, 1989). Gari features more frequently up to 3 times in the daily diet of most households in the producing areas (Adindu and Aprioku, 2006). However, the presence of cyanogens in the cassava variety used for processing gari in Nigeria, when not properly processed makes the product unsafe for consumption. The processing of cassava into gari is one of the major cottage industries in Owo. The gari processing centres are located in every nooks and cranny of the town. A good number of people, particularly the working class and urban dwellers obtain their gari from these centres for immediate consumption and storage at home.

The surplus gari produced at these centres are sent to other local markets for sales. However, field observations at these gari processing centres revealed a total lack of standardization in the gari production practices employed leading to different quality of gari being sold to the members of the public. Since the quality of the gari offered for sales or consumption is inextricably tied up with the processing operations and very little information is available on the quality characteristic of gari produced at these centres. This study was undertaken to determine the quality characteristics of gari produce at these centres which are of nutritional, economic, and health significance to consumers. Data generated from this study will be on immense benefits in formulating policy on good quality gari production practices in Owo and the Local Government Area at large.

Materials and methods
The freshly produced gari samples used for this study were collected from ten major gari processing centres located in Owo. The processing centres were located at Ehinogbe, Otapete, Aba housing, Arupe village, Police barrack, Isikaye, Idimepen, Ijebu Owo, Uselu and Idashen. The cassavas used for gari production in these centres were of mixed variety with a mean age of 15 months. In each of the centre visited, freshly produced gari samples were randomly collected from six processors and mixed together to obtain representative sample for each centre. Each lot was packaged and labelled in separate polythene for proper identification and until used for analysis.

Chemical analyses
The moisture, protein (10 x 6.25), fat, fibre, ash and Carbohydrate (by difference) contents were analyzed according to the AOAC (2000) method. The hydrogen cyanide was determined using Knowles and Wathins (1990) method of analysis. The pH and Total titratable acidity (TTA) were determined as described by Oyewole and  Odunfa (1989). pH meter (Model Jenway) was used.

Physical properties
The swelling capacity was determined according to the procedure described by Ukpabi and Ndimele (1990). Bulk density was determined according to the method described by Okaka and Potter (1979). A 50g sample was put into a 100ml graduated cylinder. The cylinder was tapped 40 times and the bulk density was calculated as weight per unit volume.

Results and discussion
The results of the proximate composition of gari samples produced at the various cassava processing centres are shown in Table 1. The moisture content of the samples varied from 13.00% to 17.35%. The gari produced at Ijebu Owo processing centre had the lowest moisture content of 13.00% while the gari produced at Idashen processing centre had the highest moisture content value of 17.35%, only the moisture content of Ijebu Owo gari sample fell within the range 12-13%  moisture level recommended by Okpugo et al., (1979) for locally processed good quality gari. However, the results indicated that the moisture content of the gari samples from all the processing centres under investigation were generally higher than the safe level for storage (below 12%) recommended for good quality gari (NSPRI, 1983). The moisture content is indicative of the level of processing (dewatering and roasting) as well as the shelf stability of the product. The gari samples from Aba housing, Isikaye, Idimenpen, Iselu, Arupe village and idasen had high moisture content (above 15%) values of 15.22%, 15.50%, 15.60%, 15.85%, 16.80% and 17.35% respectively, these may have enough free moisture to support microbial growth and hence spoilage. The shelf life was dependent on the final moisture content of the dried gari. Because of inefficient drying (roasting) the moisture content of gari from the six processing centre listed remained high (above 15%), two high for long storage. For this reason, any gari purchased from these centres had to be consumed within a very short period to avoid cakines, lumpiness and mouldiness of the product.

The crude fibre ranged 1.50% to 3.74% with seven centres producing gari having values less than or equal to 3%, the nutritionally maximum level recommended by Ibe (1981). However, the gari produced at Ijebu Owo, Isikaye and Idasen processing centres had a higher fibre content of 3.05%, 3.41% and 3.74% respectively. The cultivars of cassava used in gari production at these centres are presumably responsible for the high fibre content recorded. Furthermore, only gari produced at Otapete, Idimenpen, Aba housing and Ehinogbe processing centres had a fibre content of 1.50%, 1.66%, 1.85% and 2.00%, values equal to or less than the 2% recommended fibre value in a good quality gari by the Nigerian Industrial standard, NIS (1988). Low fibre content is among the preferred qualities of gari. The fat content of the gari produced in all the centres ranged from 0.15% to 0.70%, a value similar to those reported by other workers. The near zero fat content of the various gari samples is important for longer storage life, since there is less opportunity for hydrolysis of the fat or its oxidation. The crude protein content ranged between 0.85% for gari produced at Arupe village to 1.32% for Ijebu owo gari sample. Also, the ash content varied from 1.05% to 2.50% for Uselu and Arupe village gari samples respectively. The high carbohydrate content (76.60%-81.86%) of the gari samples from these centres makes it a good sources of energy in communities where it is consumed as a staple food. However, the significant variations which existed in the chemical composition of the gari samples between processing centres could be attributable to factors such as types of cultivars, method of cultivation and management practices, age of harvesting, type and length of fermentation. Others could also include method of processing, cultural practice, climatic and soil factors (Jackson et al., 1992).
           
From Table 2, it is evident that all the gari samples from the various processing centres were acidic with pH ranging from 3.4 to 4.5. The acidity of fermented cassava roots and its products has been found to be caused by the synthesis of lactates, acetates and some volatile organic acids (Oyewole and Odunfa, 1989). The acid contributes to the desirable sourness of gari. The total titratable acidity (TTA) expressed as percentage lactic acid of gari samples varied between 0.25% for Ehinogbe gari and 1.36% for Idimenpen gari. The values of 1.35% TTA and 1.36% TTA detected in gari produced at Ijebu Owo and Idimenpen processing centres respectively were not in agreement with NIS(1998) recommendation of less than 1.00% TTA for gari samples. This shows that the period of fermentation of these samples was inadequate.
 
Cyanide concentration in gari from the ten processing centres under investigation ranged from 1.35mgHCN/100g to 3,32mgHCN/100g only. The results show wide variations in the HCN contents of the gari produced at these centres. The variations can be attributed to the apparent lack of standardization in the processors methods of gari production and also to the type of cassava roots (bitter or sweet variety) used. Since properly processed gari should not contain more than 3.0 mgHCN/100g material, the suggested maximum concentration for safe human consumption (Akinrele, 1986; Ajibola et al., 1987). It therefore indicated that the gari produced at Arupe village, Uselu and Idimepen with cyanide conents of 3.02mgHCN/100g, 3.21mgHCN/100g and 3.32mgHCN/100g respectively were not properly processed and fermented. Odoemelam (2005) has shown in his work that the level of residual cyanide in gari decreased significantly (P<0.05) with length of the fermentation period. Therefore the high level of cyanide (3.02, 3.21 and 3.32 mg HCN/100g) recorded in the gari from three of the processing centres is an indication of a short fermentation period which does not allow for the complete breakdown  of the cyanorganic glucosides in cassava roots during fermentation.

Gari is one of the Cassava-based ready-to-eat products in Nigeria. Presence of cyanide above safe levels may pose health risks among consumers. Health problem referred to as Tropical Ataxic Neuropathy (TAN) reported in Nigeria (Osuntokun et al., 1968; Akintomiwa et al., 1994) was associated with consumption of high-level cyanide in cassava-based meals. TAN is produced by chronic cyanide intoxication and is common among older people (Bradbury, 2004).

The results of the swelling capacity of the gari samples from the processing centres ranged from 245% to 340% for gari produced at idasen and Ijebu Owo centres respectively. Swelling capacity is a function of the starch content and the degree of gelatinization of the gari is reflected in its swelling properties when in water. According to Ingram (1975),  good quality gari should have swelling capacity value between 300% and 500% volume increase. The result indicates that out of the ten centres, only four centres: Otapete, Police Barrack, Ehinogbe and Ijebu Owo produced gari with desirable and acceptable swelling capacity value of 310%, 320%, 325% and 340% respectively. However, the gari produced at remaining six centres gave swelling capacity ranging from 245% to 285%, which although lower than the acceptable level of 300%, is comparable to those (260% to 330%) quoted by Ajibola et al., (1987) for swelling capacities of gari samples in the market. The bulk density result of the gari produced at the various processing centres was desirable and fell within acceptable range of 0.50g/cm3 to 0.91g/cm3 and is within the limit reported by Adindu and Aprioku (2006). Bulk density (BD) is a reflection of the load the samples can carry if allowed to rest directly on one another. The gari produced at Ijebu Owo processing centre had the best BD value (0.50g/cm3). The lower the BD value, the higher the amount of gari that could be packaged in a given volume of container, thus saving space, packaging cots and a lower transportation cost too.

 Conclusion
The excessive high moisture contents detected in gari samples from all the centres coupled with high residual cyanide (more than 3mg HCN/100g) recorded in gari samples from three out of the ten centres is a clear indication that some processors may be using the “short cut” method in gari production. From field observation, prominent among the “short cut” methods employed are reduction in the fermentation period (to less than 72 hrs) to allow for rapid turn over of capital, and the fry-drying (inefficient roasting) given to the gari by some processors to avoid economic loss through loss in volume may not be adequate in removing residual cyanide as well as reducing the moisture content of the gari to safe level. Cyanide intoxication could arise from consumption of insufficiently processed gari and loss of revenue may results from storage of gari with high level of moisture due to mouldiness and other forms of spoilage. Since gari is a favourite ready-to-eat-cassava food in Nigeria, improved processing methods and measures to avoid “short cuts” in the production process should be developed and promoted as well. Finally, urgent intervention to educate all gari processors on better processing method and the standardization of the production process, couple with outright ban of any “short cut” method currently being used will enhance and ensure the production of good quality gari with low level moisture and residual cyanide contents with good swelling capacity.  Therefore the lack of quality control measures and the involvement of “short cut” methods in gari production may be responsible for the production of product with variable and poor quality in some of the centres studied.


References


Adindu, M. N. and Aprioku, A. B. I. (2006): Cyanogenic content of gari from some processing centres in River State, Nigeria. Nigeria Food Journal 24(1): 135-138.
Ajibola, O. O, Ige, M. T. and Makanjuola, G. A (1987). Preliminary studies of a New Techniques of cassava Mash Gelatin; Sation J. Agric Engineering Research 36: 97-100.
Akinrele, I. A. (1986). Hydrocyanic acid  Hazard during Large Scale cassava processing. Trop. Sc 26: 59-65.
Akintomiwa, Tunswashe, O. and Onifade, A. A (1994) Fatal and Non-fatal Acute poisoning attributed to cassava based meal. Acta Horticulture, 375: 285-288.
AOAC (200). Official methods of Analysis, Association of official Analytical Chemists. Processing of cassava to Reduce Cyanide content. Cassava Cyanide Diseases Network News (CCDN), Issue Number 3:3-4.
Cooker, R. O and Coursey, D. G (1981). A major Cyanide containing Food Crops in Cyanide Metabolism. Academic Press, London and New York. Pp 29-52
Coursey, D. G (1973). Cassava as food: Toxicity and Technology in Chronic cassava Toxicity (Nestle B. L. and Macintyre, R. Eds) IDRS Ottawa, Canada P 27-35
Ibe, D. C. (1981). Semi Mechanized Gari Processing for Rural Communities in Nigeria. In Tropical Root Crops: Research Strategies, for the 1980s. Terry, E. R., Oduro, K. A. and Cavebess, E. (Eds). International Society for Tropical Root Crops. African Branch, Ibadan pp 159.
IITA (1990). Cassava in Tropical Africa: A reference Manual, International Institute of Tropical Agriculture. Balding Mansell International, Wisbech U. K. pp173
Ikediobi, C. O., Onfia, G. O. C. and Eluwah, C. E. (1980). A Rapid and Inexpensive Enzymatic Assay for Total Cyanide in Cassava (Manichot Esculenta Crantz) and Cassava Products. Agric. Bio. Chem., 44: 2803-2809.
Ingram (1975). Standards, Specification and Quality Requirements for processed Cassava products. Reports G102. Tropical product Institute, London.
Jackson, F. L. C.; Jackson, R. T., Dehuman, B. I., Sio, S. F; Dinkins, L. and Muhammed, A. F. H. (1992). Cassava (Maniho esculenta) in Liberia: History, Geography, traditional processing, and cyanogenic glucoside levels. Ecol. Food Nutr, 28:227-242.
Knowles, T. and Wattins, M. (1990). Bitter and sweet Cassava Hydrocyanic Acid Content. Trinidad and Tobago. Bulletin, 14:52-56.
NIS (1998). Nigerian Industrial Standard, Standard for Gari. Standard Organization of Nigeria. Fed Ministry of Industries, Lagos.
NSPRI (1983). Nigerian Stored Products Research Institute. Storing your Produce. Advisory Leaflet. No3. Cassava and Gari. p2-12.
Odoemelam, S. A (2005). Studies on Research Hydrocyanic Acid in Gari Flour Made from Cassav (Manchot Spp) Pakistan J. Nutrition 4(b): 376-378.
Okaka, J. C and Potter, N. W. (1979). Physicochemical and Functional properties of cowpea powders processed to Reduce Beany Flavours. J. Food Sc., 44:1235-1240
Okpugo, T. I., Cornes, M. A and Adesuyi, S. A. (1979). Operation Feed the Nation: Storing your Produce. Advisory Leaflet No 3. Cassava and Gari. Nigeria Stored products Research Institute, Lagos 1-6pp.
Osuntokun, B. O., Durowoju, J. E., Mefarlare, H., and Wilson, J. (1968). Plasma Amino acids in the Nigeria Nutritional Ataxic Neuropathy. British Medical Journal, 2:647-649
Oyewole, O. B. (1991). Fermentation of Cassava for Lafun Production. Food Lab News 17(2): 29-31
Oyewole, O. B. and Odunfa, S. A. (1989). Microbiological Studies on Cassava Fermentation for Lafun production. Food Microbiology 5:125-133.
Ukpabi, U. J. and Ndimele, C. (1990). Evaluation of the Quality of Gari produced in Imo State. Nigerian Food Journal 8:105-109.
UNICEF/IITA (1989). In Praise of Cassava. IITA/UNICEF Household Food Security and Nutrition Program. International Institute of Tropical Agriculture, Ibadan pp 229.


Table 1: Proximate Composition of Gari Produced at Different Processing Centres in Owo, Ondo State Nigeria.


Sample Code

Location

Moisture (%)

Crude Protein (%)

Fat
(%)

Crude Fibre (%)

Ash
(%)

Carbohydrate
(%)

A

Ehinogbe

13.38 h

1.25a

0.38c

2.00ef

1.13d

81.86a

B

Otapete

14.65 f

1.04c

0.62b

1.50gc

1.25d

80.94c

C

Aba Housing

15.22 e

1.05c

0.25d

1.85f

1.10d

80.53d

D

Arupe Village

16.80b

0.85f

0.30d

2.58d

2.50a

76.97g

E

Police Barrack

13.95g

1.30a

0.26d

2.10e

1.07d

81.32b

F

Isikaye

15.50d

1.15b

0.40c

3.41b

1.55b

77.99f

G

Idimepen

15.60d

1.01cd

0.65ab

1.66g

1.61b

79.47e

H

Ijebu Owo

13.00i

1.32a

0.70a

3.05c

1.31a

80.67d

I

Uselu

15.85c

0.95de

0.23d

2.42e

1.05d

79.50e

J

Idasen

17.35a

0.88ef

0.15e

3.74a

1.28c

76.60h

 

LSD

0.219

0.07

6.079

0.15

0.12

0.24

Values with the same alphabet in with a column are not significantly different.


Table 2: Selected Chemical and Physical Properties of the Gari Produced at the Different Cassava Processing Centres Located in Owo, Ondo State Nigeria.


Sample Code

Location

PH

 

TTA
(%)

HCN mg/100g

Swelling Capacity

Bulk Density g/cm3

A

Ehinogbe

4.5a

0.25e

1.36f

325b

0.55ef

B

Otapete

3.9de

0.35cde

1.72e

310c

0.59de

C

Aba Housing

4.3dc

0.38cd

2.63d

275e

0.62cd

D

Arupe Village

4.4ab

0.26de

3.02b

260f

0.84b

E

Police Barrack

4.2c

0.40c

1.47f

320b

0.57de

F

Isikaye

3.8e

0.90b

2.82c

285d

0.64c

G

Idimepen

3.4f

1.36a

3.32a

280d

0.67c

H

Ijebu Owo

3.6g

1.35a

1.35f

340a

0.50f

I

Uselu

4.0d

0.41c

3.21a

270e

0.82b

J

Idasen

3.8e

0.91b

2.93bc

245g

0.91a

 

LSD

0.11

0.12

0.16

0.99

0.066

Values with the same alphabet in with a column are not significantly different.