Isolation And Identification Of Bacterial Flora From Garri Sold At Ogige Market, Nsukka, Enugu State

Cassava (Manihot spp) is an important crop widely cultivated in Sub-Saharan Africa. Although, the crop is grown virtually in all parts of the sub-continent, production is specific in the humid tropics (Okereke, Dosso and Salau, 2001).

Cassava plays a major role in efforts to alleviate Nigeria’s food crisis because of its efficient production of food energy, all year round availability, and tolerance to extreme stress conditions and suitability to various farming and food systems (Awah and Tumanteh, 2001). Cassava is capable of providing food energy much more than maize, sorghum and rice (Achinihu and Onuamanam, 2001). Garri, a product from cassava, constitutes more than 70% of total cassava consumption in Nigeria (Dorosh, 1989).

Garri is the most popular fermented food product made from cassava (Manihot esculenta Crantz) and is widely consumed as processed by millions of people in West Africa where it forms a significant part of their diet (Edem et al., 2001; Kostinek et al., 2005; Oduro et al., 2000; Ogiehor et al., 2007). It is preferred by urban consumers irrespective of ethnicity and socio-economic class as it is a pre-cooked food product with good flavour (Jekayinfa and Olajide, 2007). The dry form of post processed garri as obtained in markets is commonly consumed without further cooking (soaked in water) with sugar, smoked fish, roasted groundnuts, cooked cowpea and coconut, and sometimes with milk and beverages as complements.

It can also be prepared into a stiff paste called ‘Eba’ by adding the granules into hot water and stirring to make a paste of varied consistency which can be consumed with local soups or stews various types by chewing or swallowing in morsels (Asegbeloyin and Onyimonyi, 2007).

Thus, garri is one of the staple food items consumed in Nigeria. It therefore implies that garri is eaten by every family irrespective of their socio-economic status and religious background. Thus, garri commands much interest and hence gets a considerable preference on the household daily budget. This means that there will be across the board high demand for the product.

Evidence had shown that food production in Nigeria has not kept pace with the increasing population. The annual growth rate of the food sub-sector is 2.0 percent while the annual population growth rate is 3.3 percent (National Bureau of Statistics, 2002). This presupposes that a wide gap existed between food supply and the demand for food by the nation’s populace.

The seasonality of agricultural products causes price instability. Evidence has shown that periods of surpluses are usually supplanted by periods of scarcity. This vagary in the price variable cause unpredictable fluctuations in the demand and supply factors. In addition, there are other factors that influence the purchase decision of consumers such as organoleptic features as colour, taste, aroma, texture, physio-chemical and hydrogen cyanide (HCN) residues. Ezedinma and Oti, stated that the traditional methods of cassava processing into garri are often contaminated with undesirable extraneous matters that make them unhygienic thereby affecting demand and consumption (Ezedinma and Oti, 2001).

 Types of cassava

There are two types of cassava

1. Sweet cassava
2. Bitter cassava

Like other roots and tubers, both bitter and sweet varieties of cassava contain anti nutritional factors and toxins, with the bitter varieties containing much larger amounts.

Cynaide

Manihot  belongs  to  the  same  sub-family  as  rubber  (Hevea  brasiliensis)  and  like  rubber contains both cyanogenic  glucosides  and latex  (Jorgensen  et  al.,  2005). A  food  safety  problem  with  cassava  is  that  cassava  roots  contain  considerable  quantities of  cyanide  which  occurs  in  the  form  of  cyanogenic  glycosides,  primarily  linamarin  and  a small  amount  of  lotaustralin  (Uyoh  et  al.,  2007). 

These  cyanogenic  glycosides  break down  to  release  toxic  hydrogen  cyanide  gas  during  digestion  (Poulton,  1988).  The consumption  of  cassava  can  therefore  be  harmful  to  human  health.     Despite  the  presence of  these  naturally  occurring  toxins,  millions  of  people  all  over  the  world  have  been  safely consuming  cassava  for  hundreds  of  years.  The  on-going    challenge  is  to  ensure  that  the presence  of these  cyanogenic  glycosides are  minimized through proper  understanding  and possibly  control  of  factors  that  affect  cyanogenic  glycoside  content  of  cassava.  Roots  and leaves contain the highest amount of linamarin (Cereda  and Mattos, 1996).

There are factors that affect cyanide content:

Cultivar:

Thousands  of  cassava  cultivars  have  been  developed  that  are  adapted  to  local  conditions and  differ  in  their  ability  to  tolerate  pest  and  diseases,  yield,  nutritional  and  cooking qualities  of  food  products.  Cassava  is  propagated  clonally  from  stem  cuttings  so  there  is minimal  variation  between  individuals  of  one  cultivar  when  grown  under  the  same environmental  conditions.  All  cassava  cultivars  contain  cyanogenic  glucosides  however  a wide  variation  in  the  concentration  of  cyanogens  exists  among  different  cultivars.  This can  range  from  1  to  2,000  mg/kg  (Cardoso  et  al.,  2005,  CIAT  2007).

Climatic conditions:

Temperature  is  important,  as  all  growth  stops  at about  10ºC.   The  plant  produces  best  when  rainfall  is  fairly  abundant,  but  it  can  be  grown  where annual  rainfall  is  as  low  as  500  mm  or  where  it  is  as  high  as  5,000  mm.    The  plant  can stand  prolonged  periods  of  drought  in  which  most  other  food  crops  would  perish.    This makes  it  valuable  in  regions  where  annual  rainfall  is  low  or  where  seasonal  distribution  is irregular.    In  tropical  climates  the  dry  season  has  about  the  same  effect  on  Cassava  as  low temperature  has  on  deciduous  perennials  in  other  parts  of  the  world.    The  period  of dormancy  lasts  two  to  three  months  and  growth  resumes  when  the  rains  begin again. 

Cassava  is drought  resistant and  grows well  in poor soil (Java  Cassava, 2007). The  problem  however  is  that  cyanide  content  of  cassava  tends  to  increase  during  periods of  droughts  and  or  prolonged  dry  weather  due  to  water  stress  on  the  plant  (Bokanga  et  al., 1994)

Age of cassava at harvesting:

A  study  by  Hidayat  et  al.  (2002)  on  ninety  nine  variety  of  cassava  showed  that  there  is  a significant  correlation  between  cyanide  potential  of  roots  and  leaves.  The  cyanide  content was higher in  younger leaves  compared  to older  ones, suggesting  that  cyanide potential of roots  drops  as  plant  ages.  This  seems  to  agree  with  investigations  by  Chotineeranati,  et  al (2006).  Cooke  and  Elba,(1982  )  reported  that  the  root  parenchymal  tissue  and  root  cortex were  not  significantly  different  between  6  and  14  months;  both  tissues  displayed  peak concentrations at 6 and 14 months.

Post harvest practices:

Post-harvest  deterioration  (PHD)  is  the  most  important  cause  of  loss  in  cassava production  and  this  is  mainly  as  a  result  of  microbial  invasion  of  the  tuber  (Okigbo  et  al 2009).  PHD  can  render  cassava  unpalatable  and  un-marketable  within  24-72  h  (Rielly  et al. 2004). Cassava  must  also be processed before  being  eaten.   The  Amerindians,  who  first  cultivated  cassava,  over  the  years,  have  devised  numerous processing  techniques  not  only  to  increase  palatability  and  extend  shelf  life,  but  also  to decrease  its  cyanogenic  potential.  Today,  a  great  diversity  of  processing  methods  are found  in  the  various  parts  of  the  world  where  cassava  is  consumed  (Lancaster  et  al.,1982). These  methods  consist  of  different  combinations  of  peeling,  chopping,  grating,  soaking, drying  frying,  boiling  and  fermenting.  In  Africa  where  cassava  flour  is  a  major  product, wetting  (Bradbury  2006;  Cumbana  et  al.  2007)  is  an  effective  method  of  cyanide  removal.