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

AIM OF THE STUDY

Garri is a popular commodity in Nsukka and Nigeria as a whole, since students are part of the populace in Nsukka, the consumption rate of garri is higher, hence, it is urgent to study the bacterial content of the garri consumed in the town, so as to be able to enlighten the public on the possible health issues associated with garri consumption.

1.3 OBJECTIVES OF THE STUDY

This study is aimed at assessing the microbial quality of garri sold within the Nsukka metropolis with an intention to enlighten the public on the importance of proper food handling in food safety which will help in reducing or eliminating potential health hazards that could arise as a result of consumption of contaminated garri.

1.4 LITERATURE REVIEW

1.4.1 GARRI

Cassava for garri production is harvested manually in the farm with the aid of a cutlass, hoe and flat iron sheet (digger), which occasionally inflicts various degrees of injuries on the root tubers. After harvesting, the root tubers are hauled to the market where they are heaped in 20s, 40s, 50s, or 100s for sales under humid and warm topical conditions. These practices predispose the root tubers to contamination and infestation by various groups of microorganisms (especially moulds), mites and insects which potentiates biodeterioration  (Adeyemi and Balogh, 1985; Kayode,. Lombim and Owonubi, 1988).

The fermentation of cassava to produce garri provides an enormous scope for value addition and preserves this starchy food in a wide diversity of flavors, aromas and textures that enrich the human diet (Ray and Sivakumar,2009; Steinkraus, 1997), and helps to ensure distribution and storage of the product without the need for refrigeration. However, post-process problems of garri still persist and include loss of microbial stability and spoilage during storage, distribution and marketing.

Following processing, garri is spread on the bare floor or on a mat to allow it to cool before final sieving and packaging for marketing. In the open market, garri is displayed in open basins, bowls, bags and mats. These practices potentiate contamination by various groups of microorganisms and may predispose public health hazards (Ogiehor, 2002).

Various groups of moulds have reported to be associated with garri during storage and distribution(Adeyemi, 1976;  Oyeniran, 1978; Ekundayo). Moulds, if present can grow and affect the nutritional and sensory properties of garri , and species if toxigenic may produce mycotoxins. The cancerous and neurological associations of these toxins reinforce the need for continuous and regular search for their presence in foods (Beatriz, and Eliana, 2000)

Furthermore, the presence of aflatoxins in market food items such as yam flour, plantain flour, corn flour and others destined for consumption in Nigeria has been reported in previous studies((Beatriz, and Eliana, 2000)

 In Nigeria, the sale and distribution of garri in local markets is associated with practices such as display of product in open buckets, bowls and mats at points of sale and the use of bare hands during handling and sales. These unhygienic practices, which may lead to microbial contamination due to deposition of bioaerosols on exposed products, transfer of microbes from dirty hands and utensils and frequent visits by animals and fomites (which may carry infectious agents), can contribute to the post-process problems of this product.

Previous reports have revealed high bioload and a vast array of microorganisms in market samples of garri (Amadi and Adebola, 2008; Ijabadeniyi, 2007;Ogiehor et al., 2007).

 Most garri producers are yet to comply with the garri standards that exist at the level of the Codex Alimentarius Commission. (Ogugbue et al., 2011) observed that the current method of selling garri in most local markets may pose potential risks to public health. Air-borne contaminants in the market areas were found to contribute to the microbial burden of garri sold in the market. Some bacteria and molds have been reported to be present in garri (Ogiehor, Ikenebomeh, and Ekundayo, 2007; Jonathan, Abdul-Lateef, and Ayansina, 2013), but their pathogenicity is yet to be gauged. Other hazards such as aflatoxins and cyanide have been detected in garri (Jonathan, Abdul-Lateef, and Ayansina, 2013; Adebayo, B.A., Nanam, T.D., Bamidele, E.A., and Braima, D.J. (2012). Also, some studies highlighted the hazards and health problems of local garri processors in Nigeria (Bamidele, Adeomi, Adeoye, and Oladele, 2014; Koledoye, Deji, Owomb, and Toromade, 2012). There is yet to be any report focusing on consumers’ perception. It has been noted that consumer food safety knowledge and awareness of hazards in foods is vital in meeting food safety goals (Ajayi, and Salaudeen, 2014). Young adults are known to engage in food mishandling practices that keep them at risk for food borne diseases (Byrd-Bredbenner, Abbot, Wheatley, Schaffner, Bruhn, and Blalock, 2008).

Most University students are inadvertently exposed to microbial hazards from several sources (Okafor, Igwesi, David, Okolo, and Agu, 2016), which can cause diseases that go unreported, because their symptoms are mistaken for other ailments such as malaria (Ajayi, and Salaudeen, 2014). Personnel of the Guidance and Counseling unit have expressed concerns that students lose study and lecture periods due to illnesses which turn out to affect their academic performance and emotional wellbeing (Personal communication). The issue is further exacerbated by the fact that most students lack knowledge on the specific food vehicles that transmit common food borne pathogens (Garayoa, Cordoba, Garcia-Jalon, Sanchez-Villegas, and Vitas, 2005).

Process of garri processing

Garri  is made by peeling fresh cassava roots, then washing and grating, fermenting, dewatering or pressing, breaking of the cake, sifting, roasting, sieving or grading, and packaging. The quality of  garri  depends mostly on the quality of the cassava variety and how adequate the processing steps were taken. The descriptions of the processing steps are as follows:

Peeling:  Freshly harvested cassava roots are peeled immediately after harvesting or at  most, a day after  harvesting. Peeling must be thorough to avoid the presence of peel fragments in the final product. Manual peeling with knife is most common but mechanical peelers have recently become available in a few countries such as  Nigeria and Ghana. The practical significance of peeling is the removal of brown peel which might affect the color of the  gari  and increase fiber  content.

 Washing:  Peeled roots are washed thoroughly in potable water to remove all sand particles and dirt, which could mar the quality of the final product.

 Grating:  Clean  roots  are  grated to  obtain  a  mash. Grating is carried out  by  means  of  a  motorized cassava  grater  but hand  graters, made  by  fastening the  perforated grating sheets on wooden planks, are  still  used  in  some  rural villages  in some  countries.  A grating plate  is made  of  a  perforated metal  sheet  and with  a  sharp extruding face  as  the  grating  zone.  The  sharpness of  the  extruding zone  affects the  efficiency of subsequent operations such as fermentation and detoxification, and some  quality characteristics of the  final product  such  as fineness  (Oguntimein  et  al. 1995). Grating  disintegrates the  cassava  tissue  and frees  up the  moisture so that  mechanical dewatering  can  be  done  easily. Cassava  starch granules are  also partially  released due  to  grating. In addition, the  total surface  area  of  the  cassava  tissue  increases  significantly, the  endogenous linamarase  enzyme  is  released  and  initiates the rapid  enzymatic hydrolysis  of  the  bound  cyanogenic  glucosides into their intermediate  compounds. During grating of  freshly  harvested cassava,  and  before  fermentation sets in,  the  pH  is conducive for  a  spontaneous release  of hydrocyanic acid (HCN) from the intermediate  compounds, thereby detoxifying  the  cassava.

Fermentation: Grated cassava mash is loaded either into a polypropylene bag or basket (lined with polypropylene sack) and left for between 1 and 5 days to ferment, depending on the taste preferences of the targeted consumer. Fermentation of cassava is an important operation in terms of taste, aroma, safety, and general quality of  gari. The acceptability of  gari  is influenced by its sourness, which is related to the amount of lactic acid or length of fermentation.

Consumers in the south-east of Nigeria and most parts of Ghana accept a mild, sour taste while in the south-west of Nigeria they prefer an acidic taste. In order to get the acidic taste, the cassava mash is fermented longer (3-5 days) than in south-east Nigeria (1−2 days). Cassava fermentation for  gari  production occurs through the activities of endogenous microorganisms, mostly lactic acid bacteria, producing lactic acid that reduces the pH of the fermenting mash. The following lactic acid bacteria have been suggested as being responsible for the acidification process:  Lactobacillus spp.,  Streptococcus,  Corynebaterium, and  Leuconostoc  (Meraz et al. 1992). Heat is produced in the fermenting mash and pH decreases from near neutral (6.9) to 4.0 or less in 3-5 days of fermentation.

The longer the fermentation period the lower the pH of the mash or more sour the  garri  becomes. In addition to the acids, some other flavor compounds (pyrazines, aldehydes, esters, aldehydes, ketones, alcohols, etc) are produced by the fermenting bacteria and fungi. These compounds contribute to the aroma developed during  gari  roasting. Therefore the characteristic flavor of garri  is mostly due to the combination of fermentation and roasting.

Recent increased scientific knowledge about  the precise mechanism of  the hydrolysis  and  removal of  cyanogenic glucosides  in cassava has enabled scientists  to determine  the best procedures  for enhancing the  safety of  gari  and other cassava products.  The earlier belief  that  fermentation action was responsible for removal  of  cyanogens in  gari  has  been  replaced with more accurate  knowledge.

Cassava detoxification during  gari processing may  occur from grating  and  continue  simultaneously with fermentation until  after  roasting,  it  is  not necessarily caused by fermentation. Detoxification is  mainly as a  result of the  hydrolysis of  linamarase  (endogenous cassava  enzyme)  on cyanogenic  glucosides  (linamarin  and  lotaustralin)  when  the cassava tissue cellular  structure is damaged through grating. Cyanohydrins produced from  the hydrolysis  further  break  down automatically  at  neutral  pH. The  cyanohydrins and the smaller compounds are either removed  during pressing or  they  volatilize continuously  even  after  roasting.  Gari  processing  operations, especially  grating, fermentation, dewatering,  and  roasting, if properly  done will  ensure that the  cyanogens  are  removed to safe levels irrespective of  the  variety of  cassava  used.

Dewatering:  The fermented mash is dewatered inside a polypropylene sack by pressing with a manual screw or hydraulic press. Pressing is done principally to reduce the moisture content of the grated mash to 40-50%. Dewatering could be completed within a short time, 15−20 minutes, when  high capacity hydraulic systems are used. Simultaneous fermentation and gradual dewatering of cassava mash in a polypropylene bag is also done in some communities.

The dewatering operation contributes to cassava detoxification through the elimination of cyanogens, cyanohydrins in particular, with the waste liquor. Dewatering has to be done to the optimum moisture content for proper dextrinization during roasting.

Disintegration and Sieving:  The cake formed after dewatering is disintegrated or  granulated by a  hand-held  motorized cassava grater.  The  cake could also  be  broken up  by hand and sieved with a  manual  woven sieve or  rotary sieve, to  remove  the  fiber and lumps (pieces of improperly  grated cassava). The improperly grated cassava  pieces  could be returned to  the  grater for proper grating or  processed further into  other  types of  cassava  products. Sieving  reduces the  formation of  lumps during roasting.

Roasting:  The roasting process,  otherwise known as “garification” is done immediately after sieving. An earthenware stove and a frying pan made of molded aluminum or stainless steel are used, often on a wood fire. In some communities, the roasting pan is smeared with a small amount of shea fat or palm oil prior to roasting. The granules are fed in bits into the hot pan and stirred until an adequate quantity has been fed in. The use of mechanical fryers has become very common in Nigeria. Roasting is understood to be a two-step operation.

The first stage is partial gelatinization or dextrinization, followed by drying. The stirring of  gari, during roasting is continuous but with intermittent short breaks which allow proper gelatinization to occur. The  garri  is collected when it is dry and the color becomes creamy. A small amount is often left in the pan to facilitate the roasting of the next batch.  Gari  flavor develops and become very strong during the roasting or gelatinization stage. The gelatinization improves the digestibility of  garri  while the extent of dryness determines the crispiness of  gari  and the storability. The final moisture content of  gari  is 8−10%.

Cooling:  Roasted  gari  is allowed to cool for 4-6 hrs in clean containers. As the  gari  cools, it loses more moisture so becoming drier and more crisp.

Sieving  (Grading):  Depending on the preference of  consumers, the  roasted  gari  may  be sieved to  remove big lumps and obtain uniform  particle  sizes.  The  coarse  granules  or  lumps  are  sometimes milled to  smaller  particle  sizes  which are either used separately or mixed with  the main batch  depending  on  the  fineness after  milling.

Packaging:  The final product is packaged in unit packages of 1, 5, 10, 25, and 50 kg depending on the distribution outlet. The packaging material is either polyethylene bags for small unit packaging or polyethylene-lined polypropylene sacks for the larger sized packages. Packing is done soon after the  gari  has sufficiently cooled. Packing in moisture impermeable bags before adequate cooling (and moisture loss) or too late after the  gari has re-absorbed moisture will significantly reduce the shelf life of gari. 

Gari  that is properly packaged under the above conditions can be stored for at least a year, as long as the polyethylene lining in the package is not broken. Without the polyethylene lining the product absorbs moisture, loses its crispiness, and is prone to mold growth. Packaged  gari  should be stored in wellventilated rooms on pallets.