Compliance of Maize Flour Samples from the Industry to Food Safety Standards in Kenya

Oketch Francis Aila; Sila Daniel Ndaka; Maina John Mwai; Mokua Beatrice Nyanchama Kiage

Compliance of Maize Flour Samples from the Industry to Food Safety Standards in Kenya

Oketch Francis Aila^*, Sila Daniel Ndaka, Maina John Mwai and Mokua Beatrice Nyanchama Kiage: School of Food and Nutrition Sciences, Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000-00200 Nairobi, Kenya

^*Corresponding Author: Oketch Francis Aila, School of Food and Nutrition Sciences, Jomo Kenyatta University of Agriculture and Technology, P.O Box 62000-00200 Nairobi, Kenya, Tel: +254720361018, Email: francisaila08@gmail.com

Received: 01-May-2023 / Manuscript No. snt-23-98368 / Editor assigned: 04-May-2023 / PreQC No. snt-23-98368(PQ) / Reviewed: 18-May-2023 / QC No. snt-23-98368 / Revised: 23-May-2023 / Manuscript No. snt-23-98368(R) / Published Date: 30-May-2023

Abstract

Food safety is a major concern worldwide. Aflatoxins contamination is a public health concern affecting close to 5 billion people worldwide. Aflatoxins cause liver cancer, stunted growth in children and suppress the immune system especially in immunocompromised patients. This study determined the prevalence of aflatoxin contamination in maize flour obtained from maize milling industries in Kenya. One hundred and five (105) maize flour samples were collected from 8 regions across the country from various milling industries classified as small, medium or large scale depending on their production capacity. The samples were analysed in triplicates for total aflatoxin content using the Elisa method. The study findings indicate that 85.3% of the samples complied with the aflatoxin standards (≤10ppb) in maize flour in Kenya. Compliance with the aflatoxin’s standard varied across the regions with very high contamination being detected in Lower Eastern region (mean aflatoxin content of 68.7ppb) whereas no contamination was detected in North Rift, Nyanza and Coast regions. The mean aflatoxin levels in maize flour from the small, medium and large mills were 44.2, 17.2 and 3.1ppb, correspondingly. Maize flour from the large mills were safer compared to those from the small and medium size mills with compliance rates of 92.7%, 72.7% and 84.6%, respectively. Aflatoxin contamination is still prevalent in Kenya with the situation being of major concern at small scale level compared to large scale millers. There is need for targeted support to understand the root causes of these contaminations at small, medium and large-scale milling in order to define sustainable mitigation measures.

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Keywords

Food safety; Aflatoxin; Maize flour; Millers

Introduction

Food safety is a major concern worldwide [1] Aflatoxin, a type of mycotoxin produced by the fungus Aspergillus spp. is a threat to the safety of food consumed by both human beings and animals [2]. Worldwide, aflatoxins are of public health importance and have been reported to affect close to 5 billion people [3]. Among the effects of aflatoxin contamination on human health include acute toxicosis, stunting, and cancer [1]. Besides having effects on human health, aflatoxin contamination may also lead to major economic losses as a result of rejection of contaminated foods, compensation costs in case of claims by the population affected, treatment costs for the sick and costs associated with testing [4]. Aflatoxin contamination is majorly witnessed in Africa and Asia due to favourable weather conditions that promote the growth of aflatoxin producing fungi in both field and storage conditions.

In Kenya, aflatoxin contamination poses a major challenge to human health with cases of aflatoxin poisoning reported in several regions [5- 7] resulting in both morbidity and mortality. Foods commonly consumed in Kenya have been reported to be contaminated with aflatoxin an indication of how the population is exposed to aflatoxins in the food chain. Maize samples from National Cereals & Produce Board (NCPB) stores in the 5 counties of Meru, Embu, Machakos, Isiolo and Makueni showed high levels of contamination with aflatoxin with means of aflatoxin quantities ranging from 8.8ng/g in Embu County to 198.5ng/g in Makueni County. There was no single sample that was found to be aflatoxin free [8]. The aflatoxin contamination challenge is Kenya is further demonstrated by the various reports from different studies in different parts of the country. Studies following aflatoxicosis cases reported in Makueni county, showed that maize obtained from both the farms of the affected families and other markets were contaminated with aflatoxins an indication of continued exposure to aflatoxins [9, 10]. It is also reported that in Nandi and Makueni counties, children under 5 years were being exposed to aflatoxin from both breastmilk, maize and sorghum used during the introduction of complementary feeds [11]. Peanuts collected in markets from Kisii and Busia districts showed high levels of aflatoxin contamination with all the samples from Kisii being contaminated and 97% of the samples from Busia having aflatoxin [12].Children in Kisumu county were shown to be at risk of consuming aflatoxin contaminated foods commonly used for complementary feeds such as omena, sorghum, milk, rice groundnuts, cassava and maize [13]. Aflatoxin contamination in maize was observed to occur both after the short and long rains in Eastern Kenya [14] a pointer to the exposure of the population to aflatoxin throughout the rain cycle.

Maize is a staple food in Kenya with the population deriving most of their daily calories from either maize consumed directly or its products such as porridge or ugali [15]. In recent studies conducted in Kenya, maize flour from the Kenyan market was found to be contaminated with aflatoxin [16]. Noncompliance to the aflatoxins standard in maize flour was highest in Kiambu County (30%) while Mombasa County had the lowest contamination level (5%). The four types of aflatoxin B1, B2, G1, and G2 were detected in the samples across the different regions. The objective of this study was to determine the prevalence of aflatoxin contamination in maize flour obtained from maize milling industries in Kenya.

Methodology

Overview of industry surveillance study

The study was conducted throughout Kenya from maize meal millers. To work effectively while covering most parts of Kenya, the Country was divided into 8 regions as indicated below:

i. Nairobi & Kajiado

ii. Central Kenya (Kiambu, Nyeri, Laikipia, Kirinyaga)

iii. Lower Eastern (Machakos)

iv. Upper Eastern (Meru, Embu)

v. North Rift (Trans Nzoia, Uasin Gishu)

vi. South Rift (Nakuru, Bomet, Kericho)

vii. Coast (Mombasa, Kilifi)

viii. Western and Nyanza (Kisumu, Busia)

A total of 105 samples were collected and the regional distribution of the samples is indicated in Table 1 below.

S.No	Region for sampling	Maize flour samples
1	Nairobi	20
2	Central	25
3	Lower Eastern	12
4	Upper Eastern	12
5	North Rift	6
6	South Rift	25
7	Coast	4
8	Nyanza and Western	1
	Total	105

Classification of industries and data collection protocol

The samples collected were drawn from 102 industries which were classified into small, medium and large based on the milling capacity.

In each industry, a structured questionnaire was administered while observing the food processing practices on site. The questionnaire captured information on geographic location of the industry, date of establishment, milling capacity, personnel (number and capacity), record keeping, and quality control/assurance measures put in place among others.

This was followed by collection of 200g of samples (maize flour) every 15 minutes from the processing line for laboratory analysis as provided for by Kenya Bureau of Standards (KEBS) guidelines. The 4 samples collected were blended in the laboratory and an analytical sample drawn for analysis. The safety of maize flour samples was determined and evaluated against the aflatoxin standards in Kenya (< 10ppb of aflatoxin) as established by KEBS.

Determination of Prevalence and Content of Aflatoxin

a) Sample extraction

Twenty grams of each flour sample were weighed into clean disinfected bottles and labelled. Methanol solution (70%) was prepared by mixing 70 parts of absolute methanol (Analytical Grade) with 30 parts of distilled water. Samples were extracted with 100ml of the 70% methanol solution (ratio of sample to extraction solvent was 1:5). The samples were mixed by shaking and then filtered into clean centrifuge tubes using Whatman filter paper No.1. The residue on the filter paper was discarded and the filtrate retained in the tube for analysis.

b) Aflatoxin Testing

Two hundred micro litres (200μl) of aflatoxin-Horseradish Peroxidase (HRP) conjugate was transferred into the coloured premixing microtiter wells using a micropipette, and small aliquots of 100μl from each standard, sample filtrate and quality control material added and mixed by priming at least three times with a micropipette. One hundred micro litres (100μl) of the content from each mixing well was then transferred to a corresponding antibody coated microtiter well and then incubated for 15 minutes at room temperature. After incubation, the contents of the microtiter wells were discarded and the microtiter wells washed at least 5 times by filling each with Phosphate Buffered Saline (PBS)-Tween wash buffer, then decanting the buffer into a discard basin. The microwells facing down were tapped on a layer of absorbent towels to remove residual buffer. Approximately100 μl of the substrate reagent was added into each of the microtiter wells and incubated at room temperature for five (5) minutes. The reaction in this process resulted in a colour change from clear to blue colouration, depending on the aflatoxin content. A deeper colour indicated more reaction with the substrate and less aflatoxin concentration in the sample.

To stop the reaction from proceeding, 100 μl of acidic stop solution (Sulfuric acid) was added, which resulted in colour change from blue to yellow, with varying intensities depending on the aflatoxin content. The resultant solutions in the microtiter wells were fed into a microtiter plate reader (Robonik Read well strip Elisa analyser) where the optical density of each microtiter well was read using a 450nm filter, which gave the amount of total aflatoxin present in each sample quantitatively.

Data analysis

Statistical analysis was done using Excel for calculation of means, standard deviations and proportions. Means were calculated for the triplicate samples analysed for each maize flour brand and the pooled mean for aflatoxin content for samples based on mill size. Standard deviations were also determined for the triplicate analytical samples. Proportions were calculated for samples complying with the set standards for aflatoxin against the total number of samples collected.

Results and discussions

Prevalence of aflatoxin in small, medium and large-scale mills

Differences in the distribution of mills based on mill capacity were observed among the 102 mills visited with the large millers (40.2%) being the majority followed by the medium (38.2%) and small-scale millers (21.6%) in that order (Table 2).

Region	Total Industries(n)	Proportion of small size industries (%)	Proportion of medium size industries (%)	Proportion of large size industries (%)
Central	25	7 (28)	9 (36)	9 (36)
Coast	4	0 (0)	1 (25)	3 (75)
Lower Eastern	12	2 (16.7)	4 (33.3)	6 (50)
Nairobi	20	1 (5)	9 (45)	10 (50)
North Rift	6	0 (0)	0 (0)	6 (100)
Nyanza and Western	1	0 (0)	0 (0)	1 (100)
South Rift	22	10 (45.5)	11 (50)	1 (4.5)
Upper Eastern	12	2 (16.7)	5 (41.7)	5 (41.7)
Total	102	21.60%	38.20%	40.20%

Table 2: Industries distribution per region based on size.

The mean contamination levels of aflatoxins varied across the different mill sizes (Table 3). The smaller mills had the highest mean aflatoxin levels that were almost 15 times those of the larger mills and almost 3 times of the medium mills. Aflatoxin contamination was detected across all the mill sizes an indicator that potential sources of contamination to humans could occur from maize flour consumed from any level of mill size. Despite contamination being reported across all the mill sizes, compliance to the set aflatoxin standards were higher in the big mills at 92.7% a pointer to the fact that it is possible to have aflatoxin free maize flour in the market if all quality assurance systems were optimized.

Mill Size		Range of aflatoxin (ppb)	Mean levels of aflatoxin (ppb)	% Compliance to KEBS aflatoxin standards
Large	41	BDL-45.7	3.1	92.7
Medium	39	BDL-218.4	17.2	84.6
Small	22	BDL-700.8	44.2	72.7

Table 3: Aflatoxin compliance based on mill size.

BDL – Below Detectable Limit.

The sample with the highest levels of aflatoxin (700.8ppb) was from a small mill located in lower Eastern region. The small mills also had a higher mean of aflatoxin contamination (44.2ppb) compared to the large mills (3.1ppb) (Table 3). The range of contamination also increased as the mill size decreased. The level of compliance to aflatoxin standards was higher in the large mills (92.7%) compared to the medium (84.6%) and small-scale mills (72.7%). The inability of small and some medium mills to implement adequate quality control measures, could be a possible cause for the high contamination levels amongst samples from these millers [17]. From the study 86.2% of the large millers had undergone quality assurance (QA) training; 63% of the medium scale millers had QA training and only 50% of the smallscale millers had been trained on quality assurance (Figure 1) These results indicate that a lot of emphasis needs to be put in the medium and small-scale mills if exposure of consumers to aflatoxins is to be reduced in the country.

Figure 1: Millers undergoing quality assurance training.

There was a large variability in the aflatoxin content in the noncompliant samples (Figure 2) with 3 samples registering an aflatoxin content above 100ppb, one of which had an aflatoxin content of 700.8ppb. Similar high contamination levels were observed in maize flour samples from markets in Democratic Republic of Congo that had levels 100 times [18] the recommended upper limits for aflatoxins in maize flour. These high levels of aflatoxin contamination could be a potential cause for aflatoxicosis in both human beings and animals [19].

Figure 2: Aflatoxin content of maize flour from Kenyan industries.

Regional differences in aflatoxin contamination

There were regional disparities in compliance levels with Upper Eastern having the least compliance at 50% (Table 4) while Coast, North Rift and Nyanza had all the samples complying to the set standards for aflatoxin contamination in maize flour. The samples from these regions did not have any detectable levels of aflatoxin an indication of the stringent measures used by the industries in these regions while receiving their maize grains for milling. The disparity in compliance based on regions could also be attributed to the difference in aflatoxin contamination of maize from different regions in Kenya and across the East African region as a whole [20- 24]. In general, these results are similar to the previous market surveillance study that revealed compliance levels to the aflatoxin standard in maize flour in Kenya was at 85.6% [16].

Region	Number of samples collected (n)	Number of samples with aflatoxin levels above 10ppb	Mean aflatoxin levels (ppb)	Range of aflatoxin levels (ppb)	% samples complying with set standards
Central	25	3	5.6	BDL-71.7	88
Coast	4	0	0		100
Lower Eastern	12	2	68.7	BDL-700.8	83.3
Nairobi	20	1	4.5	BDL-76.4	95
North Rift	6	0	0		100
Nyanza	1	0	0		100
South Rift	25	3	12.2	BDL-218.4	88
Upper Eastern	12	6	34.3	BDL-199.7	50
Kenya	105	15	16.9	BDL-700.8	85.7

Table 4: Regional Aflatoxin contamination.

BDL – Below Detectable Limit.

Regions with no aflatoxins detected were majorly characterized by the availability of large mills (100% each for Nyanza and North Rift and 75% for Coast region – (Table 2). The large mills are known to have both the financial and technical capacity to implement robust quality assurance systems and this could have contributed to the low contamination levels in these mills [17]. The high level of contamination could be potential cause of acute aflatoxicoses [25]. An analysis of maize samples, soil samples and mill dust from Machakos showed high levels of contamination with aflatoxins an indication that the environmental factors play a key role in maize contamination in the region [26].

The distribution of the aflatoxin containing samples per region is illustrated in (Figure 3). The Eastern region had the highest number, followed by Central and South Rift regions. This is similar to other studies where the Eastern region has been reported as an aflatoxin hotspot region [26-28, 9, 10]. It is not clear whether the millers from those regions sourced their maize from their surroundings environments. However past aflatoxin poisoning in this region was attributed to maize from households in the Eastern region [9,10] an indication that the millers could have also sourced their maize from the same environment. This continuous detection of aflatoxin in the Eastern region is a cause for alarm as previous cases in the country have been detected from this region and long-term effects of aflatoxin contamination could be occurring in the region [29]. More efforts are therefore needed to understand the root cause of the aflatoxin contamination and mitigation measures put in place to limit the negative effects of aflatoxin contamination on human and animal life.

Figure 3: The distribution of aflatoxin containing samples by region.

A further scan into the aflatoxin containing samples reveals that, two samples from the Lower Eastern region had aflatoxin content above 100ppb (Figure 4). This is very worrying as it indicates that a large population of people are being exposed to high quantities of aflatoxin and a possibility of aflatoxicosis occurrence [30, 25]. The Upper Eastern region had 6 samples with aflatoxin content above the maximum limit set by KEBS (Figure 4). The exact quantities per brand is provided and it is in the range 20.3 - 199.7ppb. This calls for concerted efforts from government, industry and other relevant stakeholders to put in strategies for aflatoxin management.

Figure 4: Aflatoxin levels in Eastern region.

In more recent studies, aflatoxin contamination has been reported in up to 25% of samples collected from the Eastern part of Kenya [27, 28]. This demonstrates that enough measures are yet to be put in place to curb contamination of food sources given the long history of food contamination in the area [9, 10, 26].

Figure 5 indicates the regional distribution of the aflatoxin containing maize flour samples in Kenya.

Figure 5: Hot spots for aflatoxin contamination in Kenya.

Aflatoxin contamination was prevalent in many regions in the country [31]. Frequent exposure to aflatoxin even at low levels may still pose a health hazard [32] hence the need for systems to stem out aflatoxin contamination especially in foods that are eaten in relatively large quantities per day like maize and maize products. Previous reports indicate that maize consumption is high in Kenya with intake of between 355 to 400g per day per person [33]. These high intakes could lead to a cumulative effect of aflatoxin if measures are not put in place to ensure the safety of the food consumed [32, 17].

Studies conducted in Eastern Kenya encompassing, Makueni, Meru, Embu, Machakos, and Isiolo revealed high contamination levels of maize from NCPB stores, county markets, retail stores and farmers stores [34]. The contamination levels above the recommended levels allowable for human consumption was 93% indicative of the high levels of unsafe maize in the region. These high levels of contamination across the entire store chain in the region could also explain why the maize flour from the region is highly contaminated with aflatoxins.

Approximately 85.3% of maize samples were found to be compliant (Table 3). Regional disparities were observed with compliance levels ranging from 50% to 100%. Upper Eastern had the least compliance at 50% and was followed by Lower Eastern at 83.3%. South Rift, Central and Nairobi had compliance levels of 88%, 88% and 95% respectively. The proportion of non-compliant samples (15%) has not changed since the previous study conducted in 2020 on maize flour brands collected from the market [16].

Conclusion

The study revealed that 14.7% of maize flour brands are contaminated with aflatoxin above the maximum levels set by KEBS (10ppb). Most of these samples are from the Eastern region of Kenya with Central and South Rift following closely. The size of the mills also determined the level of contamination in the maize flour with the small mills being most affected. It is important to determine the root causes of these contaminations so that intelligent mitigation measures can be applied. The authors recommend an audit of the quality assurance systems in place in the maize milling industry to establish the root cause of contamination in the mills.

Ethical considerations

Informed consent was sought from all the industries that participated in the study.

Acknowledgements

The authors wish to acknowledge the financial support received from the European Union for conducting this study.

References

Kumar P, Mahato DK, Kamle M, Mohanta TK, Kang SG (2017) Aflatoxins: A global concern for food safety, human health and their management. In Frontiers in Microbiology 7.

Journal of Nutrition Science Research Open Access