Abstract

Chia has been reported to have wide nutrient and health benefits. Its nutrient composition has however been reported to be affected by genotype and environment in which it has been grown. This study therefore aimed at assessing the nutrient composition of the genotypes that are currently being grown in Malawi and the effects of environment on nutrient composition. Results showed that there were no significant differences (p > 0.05) among the genotypes within the trial site, however, the significant differences (p < .001) were observed across the environments. This affirms what other studies have reported.

1. Introduction

Sufficient nutrition to human body is fundamental key to healthful living and prevention of most of the lifestyle-related diseases such as cardiovascular diseases, diabetes and obesity. Nutritional recommendations which may help to protect human health, inhibiting the rise of some diseases and alleviating the symptoms and effects have been issued worldwide in both governmental and non-governmental institutions ¹. However, the current and future challenge is to provide people with enough, safe and health food which is able to address the body nutrient requirements while addressing health challenges, since animal and fish based foods which provide essential nutrient elements are becoming dangerous to consume ². For this reason, there has been an increasing demand for grain foods that will help to prevent and control the non-communicable diseases which have currently hit the human race ^{3, 4}.

Chia (Salvia hispanica L.), has emerged to be one of such important crop with wide acclaimed nutrient and health benefits. Chia seeds have been reported to be rich in proteins (18-24%), fats (30-40%) which are dominated by PUFAs (Omega 3 and Omega 6), dietary fiber (30-34%), essential mineral elements, vitamins and bioactive compounds ^{2, 5, 7}. The nutrient composition of Chia however varies with the environments in which it has been produced ⁸, ⁹. This study was therefore carried out in Central Malawi under rain-fed cropping system of 2021/2022 to determine the nutrient composition of Chia genotypes under different environments.

2. Materials and Methods

Field trials were conducted the 2021/22 rain-fed cropping season, in four sites which represented the main three agro-ecological zones in Malawi. The sites were Lisasadzi in Kasungu district, which is 13.1928S and 33.5356E, with an elevation of 1,104.12m above sea level, Bunda college student farm in Lilongwe district located at 14.1851S and 33.7719E at an altitude of 1,185.42m above sea level, Kamona EPA in Salima district located at the 13.4726 S and 34.2477E with an elevation of 531.76m above sea level and Bembeke in Dedza district located at 14.3510S and 34.4311E with an elevation of 1,601.87m above sea level. Bembeke represented high altitude, wet and cool plateau zones, Bunda and Lisasadzi represented middle altitude warm plain zones while Kamona represented low altitude and hot agro ecological zones ¹⁰

On soil type, Bembeke reported to have Sandy loam lithosols soil type, Bunda had sand clay loam lithosols soil type, while Kamona Loamy sand lixisols soil and Lisasadzi sandy luvisols soil type. Whereas Rainfall amounted to 815mm, 896mm, 1071mm and 1295mm the whole season for Lisasadzi, Bunda, Kamona and Bembeke respectively. The rainfall data was collected from the stations close to the experimental sites. Chia in Salima and Bembeke experienced heavy rains in the early weeks of germination and seedling establishment, which led to death and wiping out of seedlings for the two sites, however, the mild rainfall for Bunda and Lisasadzi led to proper seedling establishment.

Seed samples were collected from the three genotypes of Chia (CGF03C, CGL01C and CGL02C) which were harvested from the four environments (Bembeke in Dedza district, Bunda in Lilongwe district, Kamona in Salima district and Lisasadzi in Kasungu district). These genotypes were sourced from farmers within Malawi who are currently producing Chia. The farmers got the seeds from different sources, Bunda College Crop and Soil Sciences research farm sourced CGF03C from Food lovers, Namitete farmers, sourced CGL01C from a Ghana and Beatrice Mwangonde sourced CGL02C from a Uganda.

Seed samples of 5g were taken from each genotype from all the four environments, amounting to a total of 12 samples. They were then packed into well labelled plastic packaging bags and brought to the laboratory. The samples were then oven dried at 100^oC for 24 hours to remove excess moisture and standardize the moisture content of the seeds. The dried samples were later ground in a blender to achieve fine and even particles which were used for different nutrient element analyses. The ground samples were then repacked in plastic bags ready for analyses.

Crude protein determination was done using Kjedahl method (Official method 92.87), determination of crude fat was done using SoxhJet method (Official method 920.85), while minerals such as potassium, magnesium, iron and zinc determination were done using Atomic Absorption Spectrometry (AAS), however firstly the samples underwent dry ashing method before conducting AAS ^{11, 12}.

Data analysis was conducted using general linear model (GLM) and analysis of variance (ANOVA) in Genstat statistical software 21st edition. The data was firstly subjected to exploratory analysis to make sure it meets the analysis of variance (ANOVA) assumptions such as normal distribution. The following model was fit to different traits of data which was collected per seed samples; crude protein, crude fat, potassium, magnesium, iron and zinc.

Where Y_ijk is the jth observation associated with ith genotype on jth environment

µ is the overall mean

g_i is the genotypic treatment effects in the ith level

s_j is the environmental treatment effects in the jth level

(gs)_ij refers to the effects due to the interaction of genotypes and environments tested

β_ij means the effects of jth block in the ith location

ε_ijk refers to the random error.

Multiple comparisons were done using Bonferroni test at 95% confidence interval and Least Significant Difference (LSD) at 5% level of significance. Parameter correlations were done using Pearson’s correlation model.

3. Results and Discussion

Results on protein and fat content in Chia seed are presented in Table 1 and Table 2 respectively. From the results, it is evident that both protein and fat content were significantly affected by the environment from which it was grown.

The results showed that Chia seeds from Bembeke had higher values of protein whereas Kamona higher in fat compared to the other environments. Additionally, results further showed that Chia seeds from Lisasadzi had lower values of protein and fat compared to the other environments. Results from other researchers reported that environment significantly affected fatty acid content of Chia genotypes ¹³. It has been further reported that cooler temperatures increase the level of unsaturated acids in Chia seeds just as other oilseed crops ¹⁴.

The average crude protein content of Chia cultivated in Malawi was found to be around 20% (Table 1) which is within the range reported by other researchers ^{15, 16} and ¹⁷. ¹⁷ reported that Chia seeds contain protein content in the range of 17.0 to 23.0%. The high protein content in Chia seeds grown in Bembeke in Dedza district is in agreement with findings by ¹⁴, who reported that Chia protein content tends to increase with decreased temperature and increased elevation ¹⁸. Dedza district in Malawi usually has low temperatures and high altitude compared to the other areas. The decrease in temperature offer a long period enough for the accumulation and build-up of protein molecules compared to warmer areas which offers shorter period for seed setting and maturity process ^{19, 20}. While other studies have shown that increase in soil nutrients affect seed nutrient composition, some studies have reported that excess phosphorus leads to depressed protein and oil composition in some oilseed crops ²¹. This might be the reason why Bembeke and Bunda had higher protein and fat contents than Lisasadzi which had higher phosphorus as per soil analysis results.

Total fat content from this study varied from 24.47% to 38.97% (Table 2) which agrees with findings by ²² who previously reported the crude oil content in Chia seed to be ranging from 24% to 40%. The high fat content of Chia seeds from Bembeke in Dedza district could be attributed to the low temperature as well, as it offers long time for assimilation before maturity and dryness of the seeds. However, ¹⁵ and ²³ have also reported that oil content is very much dependent on various factors such as extraction method, soil nutrition and climatic conditions.

The environmental effects on amount of fats in Chia seeds vary from one study to another and one region to another such that it is difficult to make conclusion ^{8, 24, 25, 26}. This further explains why there is also inconsistency in fat content trends between low altitudes cultivated Chia and mid altitude cultivated Chia, which are exhibiting similar fat contents despite variations in the ecological parameters. Nonetheless, it has been reported in other studies that extreme heat and temperature lowers the oil concentration in seeds up to 30% ²⁷. It was further reported that heat not only lowers the oil content but also alters the composition of the oil content by lowering the concentration of polyunsaturated fatty acids (PUFAs), a case observed in quinoa. In a study conducted to evaluate the climatic effects on Flax seed oil concentration, ²⁸, reported that there is but little effects of temperatures on oil concentration which would not be substantiated to the changes they observed ²⁸. This therefore suggests that oil seed have varied responses to varied temperature regimes.

Results on mineral content of Chia seeds grown in Central Malawi are presented in Tables 3, 4, 5 and 6. The results showed that there were no significant differences in mineral content among the genotypes within the environments, however the differences were observed across the environments. Chia seeds from Bembeke had high values of potassium compared to the other environments. Furthermore, results showed that potassium content was lowest at Kamona (Table 3). However, there were significant differences among the genotypes which were used across the environments.

With respect magnesium, results (Table 4) showed that chia seeds grown at Bunda had the highest magnesium content while the lowest magnesium content was registered in chia seeds grown at Kamona whereas Bembeke and Lisasadzi were intermediate.

Results on iron content showed minor differences with chia seeds grown at Bembeke having the highest content seconded by Bunda, Lisasadzi and Kamona had the least iron content (Table 5). There were however no significant differences observed in iron content among the genotypes within the environment.

In terms of zinc content, the results in Table 6 shows that there were no significant differences for chia seeds grown in the four environments with chia seeds grown at Bunda having slightly high zinc content compared to the other environments.

The mineral content of Chia seed cultivated in Central Malawi is in agreement with what other researchers in other regions found ^{5, 22}. Potassium content reported by ²² was 407mg/100g of Chia seeds, whereas on average the K content in Chia seeds cultivated in Malawi is 445.10mg/100g (Table 4.3), with chia seeds grown in Bembeke having the highest content (over 500mg/100g) while chia seeds grown at Kamona registered the lowest value which was below the average value reported by other researchers ^{25, 29, 30}. However, the values reported for magnesium, iron and zinc in chia seeds were lower compared to values reported by other researchers ⁵.

The accumulation of nutrient elements in seed is dependent on how much of that particular element is in the soils and how much is assimilated to the plant ³¹. The abundance of these elements in the soil determines how much will be absorbed, however, pH and salinity of the soils also plays a role on how much of the elements may be absorbed by the plant as well as the mobility of the elements ³². Further, other studies have also shown that accumulation of some elements in the soils such as phosphorus tend to affect the uptake of other mineral elements such as iron and zinc in oilseed crops ²¹. This suggests that the variations in mineral content of Chia seeds from the four environments might be mainly due to differences in soil composition.

4. Conclusions

The study has proved that climatic conditions significantly affect protein and fat content of Chia seed. High altitude areas with cooler and wet environments increase the protein and oil content in Chia compared to hot and dry environments since quick shading of leaves deters oil accumulation in seeds during maturation of seeds.

The study has also proved that there is a relationship between soil nutrient and accumulation of mineral elements in seeds, hence it should be given enough attention. The amount of nutrients in the soil substrate is directly correlated to amount of the same nutrient the plant absorbs and utilizes.

5. Recommendations

There should be further studies on effects of environment on fat quality in Chia and also other nutrient analyses to be done which would help in promoting the use of Chia in the country.

Further studies are also needed to evaluate the effects of soil salinity and accumulation of other mineral elements in nutrient composition. It has been reported in other oilseed crops that soil salinity affects the quality of fats in oilseeds and also that excess phosphorus in the soil lowers the levels of protein, fats and other mineral elements such as iron and zinc.

ACKNOWLEDGEMENTS

We would like to acknowledge the Norwegian University of life Sciences (NBMU) in collaboration with Lilongwe University of Agriculture and Natural Resources (LUANAR) for the support and materials they provided for the successfulness of the study.

References