Assessment of heavy metals and microbial contamination of gari from Liberia

Abstract Cassava is a staple mostly eaten in the form of gari, after rice in Liberia. The local method of gari processing often leads to product contamination, thus, a study was done to assess the heavy metals and microbial contamination of gari in eight counties of the country. A total of sixty‐one gari samples were collected and packaged in an airtight polyethylene bag for analyses, using standard methods. Results depict that the mean of the heavy metals in the gari samples is iron (Fe) 43.87 ppm, copper (Cu) 0.94 ppm, zinc (Zn) 5.49 ppm and aluminum (Al) 257.45 ppm. Yellow gari had the highest Fe (64.90 ppm), Cu (1.25 ppm) and Zn (7.85 ppm) content, but with the least Al content (87.15 ppm). The Fe content was lower in groundnut‐fortified gari (42.93 ppm), and the Cu (0.70 ppm) and Zn (3.50 ppm) content were lower in groundnut‐moringa‐fortified gari. The samples and counties have no significant statistical effect (p > .05) on the heavy metals composition of the products. No microbial growth was observed in groundnut‐fortified and groundnut‐moringa‐fortified gari but with coconut‐fortified gari having the highest total fungi count of 800 CFU/g. The major fungi identified in the gari samples are Penicillium and Aspergillus spps., but with their counts within the regulated level. Therefore, the gari consumed in Liberia are safe except for the high Fe and Al content, which needs to be addressed with the use of unpainted stainless steel materials as food contact surfaces.


| Collection of gari samples in Liberia
Sixty-one gari samples (white gari-45, yellow gari-1, Coconut-fortified gari-4, Groundnut-fortified gari-10, and Groundnut-moringa-fortified gari-1) were collected from the processors and marketers in eight counties; Rivercess, Grand Bassa, Bomi, Margibi, Sinoe, Gbarpolu, Montserrado, and Grand Capemount, for assessment. The yellow gari and groundnut-moringa-fortified gari were collected from just a point in Montserrado County. Each of the gari samples collected is a representative of the sampling frame, thus, the unequal sampling size.
Samples were packaged in hermetically sealed polyethylene bags for laboratory analyses. The processing methods for the different types of gari are described in Table 1.

| Analysis of heavy metal contamination
The iron, zinc, copper, and aluminum content of the samples were determined, using the method described by Jones, Benton, and Vernon (1990). The samples were ashed at 550°C. The ash was dissolved in 5 ml water and 15 ml HNO 3 /HCl (1:3) for heavy metal determination, using Atomic Absorption Spectrophotometer (Buck 205 model; Back Scientific, USA).

| Analysis of microbial contamination
Analysis of microbial contamination by total plate count of fungi was done following the method described by Amankwah, Barimah, Acheampong, Addai, and Nnaji (2009). Fungal isolates were identified and characterized under a light microscope (Leica Galen III) based on morphological and cultural features as described by Harrigan and McCance (1976).

| Statistical analysis
Analysis of variance (ANOVA), separation of the mean values (using Duncan's Multiple Range Test at p < .05), and frequency distributions were calculated, using Statistical Package for Social Scientists (SPSS) software (version 21.0). Dix (1981) reported that human exposure to heavy metals causes serious adverse health effects, including reduced growth and development, cancer, organ damage, and in extreme cases-death. Nevertheless, iron (Fe), copper (Cu), and zinc (Zn) are also referred to as trace metals, which are naturally present in foodstuff and confer some nutritional benefits to human, but toxic when consumed in excess (Magomya, Yebpella, Udiba, Amos, & Latayo, 2013). The means of the heavy metal composition of the gari samples were 43.87 ppm, 0.94 ppm, 5.49 ppm and 257.45 ppm for Fe, Cu, Zn, and Al, respectively (Table 2).

| Heavy metal composition of gari products in Liberia
Although there were no statistically significant differences (p > 0.05) in the heavy metal composition of the products (Table 2), yellow gari had the highest Fe (64.90 ppm), Cu (1.25 ppm), and Zn (7.85 ppm) content, but the least Al content (87.15 ppm). The Fe content was lower in groundnut-fortified gari (42.93 ppm), and the Cu (0.70 ppm) and Zn (3.50 ppm) content were lower in groundnutmoringa-fortified gari. Additionally, groundnut-fortified gari had the highest Al content (180.52 ppm).
T A B L E 1 Processing methods for gari from fresh cassava roots in Liberia

Type of gari
Processing method White gari Peeling, washing, grating, bagging and dewatering, granulation, and roasting in earthenware pots.
Yellow gari Same processing steps as above with mixing of palm oil to the granules before roasting

Coconut-fortified gari
Grating and roasting of matured coconut pulp before mixing with white gari

Groundnut-fortified gari
Roasting and milling of groundnuts before mixing with white gari Groundnut-moringafortified gari Drying of fresh moringa leaves, milling, and mixing with groundnut-fortified gari Considering the Counties, there were no statistically significant differences (p > .05) in the heavy metal compositions of the products apart from Zn ( Metals such as Fe, Cu, and Zn have been observed to be essential components of many alloys, wires, and vehicle tyres and, which are usually released into the roadside environment because of mechanical abrasion and normal wear and tear (Harrison, Laxen, & Wilson, 1981). This implied that yellow gari with the highest values of these metals might have been roasted closer to a roadside or a market where heavy vehicular movement exist. However, the values for Zn and Cu in the yellow gari were below the recom-

| Microbial identification in gari products
The total fungi count (TFC) of the gari samples revealed that no microbial growth was observed in groundnut-fortified and groundnutmoringa-fortified gari, but with coconut-fortified gari having the highest TFC of 800 CFU/g (Table 3). Additionally, gari from Bomi and Grand Cape mount counties have no fungi growth, but with gari from Rivercess county having the highest TFC (1500 CFU/g) (

| CONCLUSION
The gari produced in Liberia may be safe for consumption since the zinc and copper content were below the recommended maximum limit stipulated by the FAO/WHO. However, there is a need for caution in the use of mild or galvanized steel instead of stainless steel materials as food contact surfaces, as well as painting of processing machine surfaces with metallic polish because of the high iron and aluminum content in the gari. Although the average total fungi count value of the gari samples is less than the International Commission on Microbiological Specifications for Foods levels, there is need to reduce the presence of Aspergillus and Penicillium spps. in the gari samples by following strictly good manufacturing/hygienic practices, as these microorganisms are known to produce harmful mycotoxins under favorable conditions.

CONFLICT OF INTEREST
No conflict of interest.

ACKNOWLEDGMENTS
The gari analyses were done in the Food and Nutrition Sciences labo-