A Comparative Study of Physicochemical Attributes of Pigmented Landrace Maize Varieties

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Introduction
Biodiversity conservation in food crops is a backbone of food and nutrition security and maize is one of the food crops that has the largest diversity worldwide [1,2]. Constant production and utilization of diferent maize varieties have helped to improve the well-being of the people by supplying them with the required ingredients in their diet [2]. Production and utilization of PLMVs have to a large extent helped to boost small-scale businesses in diferent communities globally [3]. Maize is utilized as a staple food crop by many Sub-Saharan African countries, and it also serves as a source of livelihood for smallholder farmers in diferent niches of the globe [4,5]. Tere is an estimate of about 6,400 indigenous plant species that are useful in Africa and more have been discovered worldwide [1]. PLMVs contribute to a wide diversity of maize and their disuse would contribute to their extinction [1,6]. Over the past years, there has been high adoption of white hybrid maize which has reduced the production of PLMVs [6]. Not much information is available on PLMVs [7] and the efect of the production location on the physicochemical attributes of PLMVs grown in Malawi. Tis study was therefore conducted to compare the physicochemical attributes of PLMVs from diferent production locations.
Biased production of selected varieties promotes biodiversity loss in useful crop species which increases the danger of encountering food and nutritional insecurity [8,9]. Absolute promotion of one crop variety contributes to decreased production and access to another and it is unsustainable in today's world of pandemics [10,11]. Terefore, there is a need to intensify production systems that promote crop biodiversity conservation [12]. Understanding of the social, cultural, nutritive, culinary value, consumer acceptability, and the impact of production location on proximate compositions of PLMVs grown by smallholder farmers can help its increased production and utilization. Te physicochemical properties of diferent maize varieties give information on maize kernel quality and would help in making choices of which variety to cultivate [13]. Such information would also be very useful in determining which PLMVs to be included in the diet.
PLMVs grown by smallholder farmers globally greatly contribute to the health and well-being of the people in their respective locations [14][15][16][17]. A study in Malawi revealed that the orange maize crop plays a vital role in providing essential natural ingredients for micronutrient production [6]. It has sadly been observed that over 2 billion people worldwide are afected by micronutrient defciency which results in a high rate of morbidity and mortality [17]. Tis is due to a lack of knowledge and failure to harness the diversity of available food crops.
Micronutrient defciency which is also described as hidden hunger is highly prevalent among vulnerable populations such as children in Sub-Saharan Africa [18]. Tis is due to the lack of access and utilization of diferent kinds of nutritive foodstufs. Te potential increases in food production are far from being realized under feld conditions although there are many available technologies provided by science and diversifcation avenues [6]. One of the main problems, encountered by farmers and all stakeholders involved in maize production, is postharvest losses. Dent corn maize varieties are easily attacked by pests when compared to fint corn of PLMVs [6]. Climate change has aggravated the conditions of both biodiversity loss and food insecurity by increasing the risks of crop failure. Tere has been crop population extinction because of the higher frequency of extreme events and progressive change in key climate variables [12]. Worldwide food and nutrition insecurity are major and growing problems [19,20]. About 48% of underfve children in Malawi are said to be chronically malnourished and 5% have acute malnutrition while 22% are categorized as underweight [21]. Tis has been attributed to the displacement of a diversity of macronutrient and micronutrient-rich indigenous crops but also the choice and selection of food crops contributing to the diet of many modernized individuals [22].
Indigenous crops usually adapt and grow well in their production provenances [12]. Tis is mainly because they develop resistance to diseases as a result of developing together with their pests and disease-causing pathogens [6,23]. Tis ofers a diversity of food crops from which individuals can choose and achieve food and nutrition security [23]. Smallholder farmers continue to cultivate PLMVs due to their yield stability [24]. Te process of bufering in PLMVs enables the crop to possess diversity within and between crops [12,24], and this also contributes to yield stability under low input systems of crop production [12,14]. Due to these characteristics, PLMVs are therefore the best option for resource-poor smallholder farmers who cannot aford seed and other costly inputs annually. Less cost of maize production would give chance to resource-poor farmers to use their income to access other nutritious food crops which would enable them to deal with problems of food and nutrition insecurity [24,25].
Production locations experience diferent climatic factors and are associated with diferent parameters that contribute to food crop growth and development [26]. Mineral bioavailability is infuenced by diferent abiotic factors such as soil mineral content, nutrient solubility, and the capacity of the diferent crop varieties to absorb the available nutrients in their vicinity [26]. Soil quality needs to be monitored for quality food production [27]. Tis study was carried out in three districts having warm temperate climates and higher rainfall in summer compared to winter. For instance, Ntcheu (central region) has an average annual temperature of 20.3°C and receives about 986 mm of precipitation annually, it is located between latitude and longitude coordinates of 14°49′12.97″S, 34°39′9.1″E while Dedza (central region) has an average annual temperature and precipitation of 18.2°C and 1010 mm, respectively, and is located between latitude and longitude coordinates of 14°22′40.44″S, 34°19′59.59″E. Mzimba (northern region) on the other hand has an average annual temperature of 20.1°C and receives about 915 mm of precipitation annually and is located between latitude and longitude coordinates of 11°54′0´´S, 33°36′0´´E. Te observed diferences in climatic conditions in the study locations may have an impact on the nutritional and physicochemical attributes of PLMVs grown in Malawi. Looking at the value of PLMVs, it is advisable that individuals should continue to cultivate and utilize PLMVs in order to beneft from its attributes. Tis study was therefore conducted to compare PLMVs attributes such as ash, moisture, crude protein, fat, carbohydrate, and mineral content of orange, red, and purple maize varieties grown by smallholder farmers in Malawi.

Pigmented Landrace Maize Samples.
Fifty-four diferent farmers were involved in this study. Tree diferent pigmented landrace maize varieties (orange, red, and purple) were collected from them. Samples were collected and carried in ziplock plastic bags from specifc study locations, thus Mzimba (northern region), Ntcheu, and Dedza districts (central region). Orange, red, and purple maize samples were collected from six diferent farmers in each district. Samples were ground using a wooden mortar and pestle to uniform size (0.5 mm). Tereafter, extraction was conducted. Soils were also taken from the felds where the PLMVs were grown. Te samples were kept in ziplock plastic bags until mineral analysis time.

Moisture Determination.
Moisture determination was undertaken as described by Shaista et al. [2] with some modifcations. Triplicates of each sample (500 mg) were oven-dried at 60°C for 24 hours in pre-weighed aluminum dishes thereafter cooled in a desiccator for 30 min and weighed. Moisture was determined as follows: moisture (µgg −1 ) � (W 2 -W 3 )/(W 2 -W 1 ) × 100, where W 1 is the weight of the empty dish, W 2 is the weight of dish + sample before drying, and W 3 is the weight of dish + sample after drying.

Ash Determination.
Ash determination was undertaken as described by Shaista et al. [2] with some modifcations. Clean crucibles were incinerated in a furnace at 525°C for 1 hour and cooled in a desiccator at room temperature, for 30 min, and weighed on an analytical balance. Ten, 200 mg of each sample (in triplicates) was weighed in the crucibles, incinerated in the furnace at 525°C for 30 min, then cooled in a desiccator for 30 min, and reweighed. Ash was determined as follows: aAsh (µgg −1 ) � (W 3 -W 1 )/(W 2 -W 1 ) × 100, W 1 is the weight of crucible, W 2 is the weight of crucible + sample before incineration, and W 3 is the weight of crucible + sample after incineration.

Crude Protein Determination.
Crude protein determination was undertaken as described by Shaista et al. [2] with some modifcations. Digestion, steam distillation, and titration processes were followed, where: 100 mg powdered sample was weighed on flter paper and placed in Kjeldahl fask and mixed with 1.7 g of mixed catalysts (160 g of potassium sulfate, 10 g copper sulfate, and 3 g selenium powder). Tereafter, 2 mL of water and 20 mL of concentrated sulfuric acid were added. Te mixture was rested for 20 min and then heated on a hot plate in a fume hood while rotating the fask occasionally until the mixture cleared. A blank was prepared by mixing 1.7 g of mixed catalysts, 2 mL of water, and 20 mL of concentrated sulfuric acid in a Kjeldahl fask without the sample, and all the necessary treatments as done to the samples were also carried out on the blank.
Te cooled digest of the sample was quantitatively transferred into a 250 mL volumetric fask and diluted to the mark with distilled water. An aliquot (5 mL) of the diluted digest was placed in a reaction tube in the distillation unit and was mixed with NaOH (46%, 5 mL) and steam distilled to liberate ammonia. Te distilled sample was collected in a 250 mL Erlenmeyer fask containing boric acid (4% w/v, 10 mL) and the indicator (0.1% methyl red in 95% ethanol with 200 mL (0.25 M) bromocresol green in 95% ethanol) was added drop by drop until color changed from red to green. Te distillate was then titrated with standard acid HCl (1.0 M) solution and volumes were recorded.
Crude protein calculation equation: where S is the sample titrant volume (of HCl 1.0 M), B is the Blank titrant volume (of HCl 1.0 M), and VF is the volume factor (250/5).

Crude Fats Determination.
Crude fat determination was undertaken as described by Hwang et al. [28] with some modifcations. All the glassware were rinsed with distilled water and dried in an oven at 105°C for 30 min and cooled in a desiccator. Accurately, 100 mg of the milled sample was measured on a flter paper and put into the thimble that had a plug of cotton on its bottom; the sample was covered with another plug of cotton, on top of the extraction thimble. Ten, the thimble was placed in the Soxhlet liquid extractor. A clean dry 150 mL round bottom fask was weighed accurately and in it, 90 mL of petroleum ether was added, and the extraction unit was assembled on an electric heating mantle and heated until the solvent in the fask boiled. Ten, the heat source was adjusted so that the solvent dripped from the condenser into the sample chamber drop by drop until all the solvent was collected. Te extraction unit was then removed from the heat source and the extractor was detached from the condenser.
Te round bottled fask was then placed in a desiccator to cool down. Tereafter, the fask was weighed and the % crude fats were calculated as follows: % crude fat � ((W 2 -W 1 ) x 100/S), W 1 is the weight of the empty fask (g), W 2 is the weight of fask + extracted fats, and Sis the weight of the sample.

Mineral Determination in Pigmented Maize Grains and
Soil Samples. Mineral determination was done using Carpenter and Hendricks [29] method with modifcations. Here, 100 mg of the sample was weighed using an analytical balance and placed in a 150 mL conical fask, and then 5 mL of HNO 3 was added to the sample. Tis mixture was rested for 8 hours. Tereafter, 6.9 mL of HNO 3 and 3.1 mL of perchloric acid were added. Tis mixture was heated on a hot plate to about 180°C until the white fumes evolved and transparent white content was left in the fask. Ten, the transparent content was cooled down in a desiccator. After cooling, 25 mL of distilled water was added and the mixture was fltered into a 100 mL volumetric fask with 3-4 washing Journal of Food Quality of the conical fask, and then the mixture was made to 100 mL mark with distilled water. Te fltrate was used to determine the concentrations of the following minerals: calcium, magnesium, potassium, zinc, iron, and phosphorus.

Calcium (Ca) and Magnesium (Mg).
Aliquot samples of 5 mL in separate 100 mL volumetric fasks were mixed with lanthanum solution (5 mL) and the solutions were made to the mark with distilled water. Ten, intermediate standard stock solutions of 10 ppm for each of the minerals were prepared by diluting their standard stock solution of 1000 ppm, 10 mL to 1000 mL with distilled water. Ten, aliquots ranging from 0 to 16 mL of the intermediates standard solution were put in separate 100 mL volumetric fasks mixed with lanthanum solution (5 ml) and diluted to the mark with distilled water yielding a range of 0 to 0.16 ppm calcium and magnesium working standard solutions. Both the samples and the working standard solutions of each of the minerals were aspirated on an Atomic Absorbance Spectrophotometry (AAS) (Agilent tech.200 series, Mumbai, India) to obtain absorbance for each working standard solution. Sample concentration was calculated from the calibrated curve obtained from the concentrations and absorbance of the working standard solutions [29].

Zinc (Zn) and Iron (Fe).
Te working standard solutions were made by diluting the standard stock solutions of each of the minerals (1000 ppm, 10 mL) to 1000 mL with distilled water. Te resulting solutions ranging from 0 to 15 mL were further diluted to 100 mL mark with HCl (0.1 M) in a separate volumetric fask to obtain the working standard solutions ranging from 0 to 0.05 ppm of zinc and 0 to 0.15 ppm of iron. Ten absorbance was obtained by aspirating the working standard solution on AAS. Te calibration curve was plotted from the absorbance and concentrations of the working standard solutions. Samples were then aspirated on an AAS to obtain their absorbance, and concentrations were calculated from the calibration curve [29].

Potassium (K) and Phosphorus (P).
Te working standard solutions ranging from 0 to 2 ppm of potassium were prepared from the standard stock solution of (1000 ppm, 10 mL) which was diluted to 1000 mL with distilled water to obtain a range of 0 to 20 ppm. Ten, aliquots of resulting solutions were diluted further to 100 mL with HCl (0.1 M) in separate volumetric fasks to obtain the working standard solutions ranging from 0 to 2 ppm of potassium. Absorbance was obtained by aspirating the working standard solutions on the AAS. Te calibration curve was plotted from the absorbance and the concentrations of the working standard solutions of potassium. Ten, an aliquot sample (2 mL) was diluted with distilled water to the mark in a 100 mL volumetric fask and was aspirated on the AAS to obtain absorbance. Te concentrations of the samples were calculated against the calibration curve. Phosphorus was determined by taking aliquots of phosphorus standard stock solution (2.00 mg P/ mL, 50 mL) which was diluted to 1000 mL to produce an intermediate standard stock solution of (0.1 mg P/mL). Ten, a range of 0 to 10 mL aliquots of the intermediate stock solutions were put in separate 100 mL volumetric fasks. And aliquots of the samples (5 mL) were put in freshly rinsed 100 mL volumetric fasks. To each of the fasks containing working standard solutions and samples, molybdovanadate solution (20 mL) was added. Ten, the mixture was diluted to the mark with distilled water, mixed thoroughly, and allowed to stand for about 10 min for 8 full-color development, and the absorbance was determined on the atomic absorbance spectrophotometer (AAS). A curve of absorbance against concentration for the working standard solutions was plotted and was used to determine the concentrations of the samples [29]. P (mgg −1 ) � (conc. × DF V)/mass × 100, where Conc. is the concentration reading of samples read of from the standard curve, DF is the dilution factor, V is the volume, 100 is the 100 g of the dried sample (100 mL of mother liquor), and mass is the mass (g) of the sample incinerated (mL, mother liquor incinerated).

Statistical Analysis.
Results are presented as mean-± standards deviation (SD) of triplicate analysis. On analysis of variance (ANOVA) by Turkey's Honestly Signifcant Diferences (HSD), the method was used to compare the means of composition attributes in the three production locations. All analyses were performed at a 95% confdence level (p < 0.05) using IBM SPSS version 26.

Results and Discussion
Moisture content refers to the number of water molecules that become incorporated into a food product. Moisture content is an important attribute of food crops that afects not only storability but also the enzyme activities within the maize grains [30]. Te humidity in the storage environment should be low because when dried foods pick up moisture from the storage area, molds and bacteria can grow. Moisture can also lead to the breakdown of some packaging materials (paper degradation and metal rusting). Product quality and shelf life decrease if dry foods are exposed to moisture. Te resulting mold and bacterial growth can lead to spoilage and food-borne illnesses. Moisture content highly contributes to postharvest losses of maize by promoting the rotting of the grains either in the feld or in the storage facilities [31,32]. A moisture reading of 0-15% is quite normal and gives no cause for concern. However, moisture readings over 15% indicate the need for further inspection. Levels between 25% and 30% indicate that there may be water ingress; hence, remedial work is required. Research has shown that 90% of the human population world over is food insecure not because of lack of food production but because three-quarters of the realized food is lost through rotting due to moisture mismanagement [31,32]. Food preservation methods such as drying, freezing, and adding salt or sugar work by lowering the available moisture in foods. Moisture in foods occurs in two forms: (1) water bound to ingredients in the food (proteins, salt, and sugars) and (2) free or unbound water that is available for microbial growth. Knowledge and management of moisture content in maize grains may help in saving food crops from damage and improve the food security of the people and the nation at large [33].
Determination of the physicochemical characteristics of maize such as moisture helps to understand important information about the maize grains' quality and nutritional composition [13]. Te physicochemical and proximate content of the sampled PLMVs grown by smallholder farmers in three districts of Malawi are not the same ( Table 1). Most of these characteristics appeared to difer signifcantly (p < 0.05). Te moisture range of the orange, red, and purple maize was between 13.05 and 17.30%. Te minimum value was slightly lower and the maximum value was slightly higher than the range of the International Life Sciences Institute (ILSI) Crop database with an expected mean value of 14.5% moisture content in feld maize [16]. At harvest, maize usually has a moisture content ranging from 18 to 24% but desirable moisture which is safe for storage is 14% [16]. In the present study, purple maize from Mzimba (13.05%) had the lowest mean value of moisture content while orange maize from Dedza (17.30%) had the highest value. Farmers sun dry maize after harvesting to lower the moisture content for easy storage [16]. It is recommended that moisture content should be regulated because it afects the yield quantity and quality of food crops. Damage to the kernel (usually during the shelling operation) is related to moisture content at harvest; the lower the moisture content, the less the damage [30]. Results from the present study have revealed that farmers who would wish to produce orange, red, and purple maize would have little problems in managing moisture content due to its manageable levels ( Table 1). Less damage after harvest would result in achieving food security for the community and the nation as a whole.
Ashing is the frst step in preparing a food sample for specifc elemental analysis. Ash content measures the total mineral content of the food crops under study [34]. Minerals are generally important in the maintenance of the health of plants and animals [19]. Ash is a source of the macronutrients such as Ca, C, K, Mg, P, S, and N. Higher ash content for maize varieties indicates that the four contains more of the germ, bran, and outer endosperm. Lower ash content means that the four is more highly refned. Ash content observed in our study was within the levels reported in the local and composite maize but slightly higher in some cases [34]. Orange maize from Dedza (2.28%) displayed the highest ash content and the lowest was discovered in purple maize from Mzimba (1.10%). Tis is similar to what Murayama et al. [35] reported. Diferences in ash content in PLMVs were attributed to diferences in maize varieties and genetic make up but also environmental diferences in mineral composition. Te varieties in this study were different and were also grown in diferent production locations. Tis would have contributed to the diferences in their ash content (Table 1).
In terms of proteins, results in this study mirror the fndings of Villa et al. [12], who reported the presence of proteins and fats in pigmented maize varieties but his fndings were lower as compared to the fndings of the present study. Our fndings revealed that red maize from Dedza (12.57%) had the highest protein content than what Shaista et al. [2] reported (12.45%) and Mzimba (10.16%) orange maize reported the lowest. Te fndings are in line with what Murayama et al. [35] reported in a study that was also done in Malawi on orange maize. Te diferences in protein content observed in this study would be a result of the interaction between environmental factors and the genetic makeup of the varieties which infuences protein metabolic processes within the plants [26]. Maize is probably the major source of protein in the diet of many Malawians because maize is considered a staple food [4]. Nevertheless, the insufcient quantity of lysine and tryptophan, which are among the eight essential amino acids, makes maize's nutritional quality poor [19,34,36,37]. Te fat content of corn ranges from 5% to 6%, making it a low-fat food but higher and lower levels have been reported [38,39]. However, corn germ, an abundant side-product of corn milling, is rich in fat and used to make corn oil, which is a common cooking product. Tis study revealed high average fat content in Dedza (10.73%) red maize and purple maize from Mzimba (3.30%) had the lowest. Te high content of specifc attributes has been reported in some corn grains [2,40]. Tis study, therefore, revealed that red maize from Dedza is one of the best suppliers of proteins and fats, as reported in other pigmented maize varieties [2,40]. Utilization of red maize from Dedza would solve the problem of lack of fats in the diet of Malawian people.

Journal of Food Quality 5
About 50% of the Caloric intake of Malawians comes from diferent varieties of maize [16]. Maize has a characteristic quality of about 85.3% digestibility and is one of the major sources of carbohydrates [4]. In this study, the average carbohydrate content of orange, red, and purple pigmentedlandrace maize varieties ranged from 58.73% to 65.52%. Te highest value in this study was within the range as reported by Shaista et al. [2] in white maize (65.38% to 78.74%) but was higher than in yellow maize (60.23%) as reported by the same author. Diferent values of carbohydrates have been reported by diferent authors, and the highest content range is between 76% and 84% [2,41]. In this study, the highest value was reported in purple maize from Dedza (65.52%) and is within the published ranges [2,39,42]. It has been reported that traditional maize varieties have strong photosensitivity which is linked to their ability to convert energy from the sun into carbohydrates stored in grains which is the consumable part of the crop [16]. Te diferences in carbohydrate content might be attributed to diferences in the light absorption capacities at the flling stage of grain formation by diferent maize varieties in diferent environmental conditions [26]. Purple maize inclusion in the diet would ensure an energetic population which would contribute to the development of Malawi.
Phenotypic variations for grain color have been used by farmers to distinguish and maintain diversity within landraces that are underutilized but preferred for specifc traditional uses [3,43,44]. Ambuye angafe and Mthikinya are orange pigmented maize varieties cultivated by smallholder farmers in Ntcheu district. Local farmers continue to cultivate Ambuye angafe mainly because it matures earlier than Mthikinya and it saves communities of people from hunger; hence, it is named "Ambuye angafe," meaning it matures faster so that elders should not die.
Physicochemical analysis of these two phenotypically diferent maize varieties revealed that Ambuye angafe had higher protein (12.26%) and fat (8.35%) content than Mthikinya which had 10.99% protein and 5.58% fat, respectively. In terms of carbohydrates, Mthikinya had a signifcantly higher content (68.76%) than Ambuye angafe (63.76%) (Figure 1). Tis study has therefore revealed that Ntcheu provenance infuenced the increased protein and fat content in "Ambuye angafe" orange maize than Mnthikinya orange maize. Ntcheu farmers would be advised to produce Ambuye angafe if they were to beneft from its high protein and fat content. Diversifcation of these maize varieties would help to attain the benefts of both varieties. Te noted variations in physicochemical attributes in pigmentedlandrace maize cultivars may be due to diferences in the variety's genetic makeup and not the environment. Tis is because they were grown in the same location and the environmental efects; they received were the same. Nevertheless, the interaction between the environmental factors and the crop's genetic makeup may have contributed to the observed diferences [4,26,41].
Cereal grains, such as wheat (Triticum aestivum), fnger millet (Eleusine coracana), and tef (Eragrostis tef), are relatively high in calcium but not as high as dairy sources [26,45]. Te best sources of calcium are dairy products, including milk, yogurt, cheese, and calcium-fortifed beverages such as almond and soy milk. Calcium is also found in dark-green leafy vegetables, dried peas and beans, fsh with bones, and calcium-fortifed juices and cereals. Most whole grains are a good source of magnesium [2]. Phosphorus is an essential nutrient required for bone health and many other bodily functions. Although it can be found in many food grains, maize whole grains provide a substantial amount of phosphorus compared to high levels supplied by animal proteins, dairy products, nuts and seeds, and legumes [38,39]. Murayama et al. [35] reported concentration ranges of calcium, magnesium, and phosphorus which were higher in orange maize than in hybrid maize. Te high levels of minerals revealed in the present study in PLMVs can be an option for those vying for natural sources and would augment the diversity of readily available sources of these minerals to smallholder farmers and rural communities as a whole.
Red maize from Dedza provenance showed a signifcantly high content of iron (59.80 ± 0.26 mg·kg −1 ) while purple maize from Dedza and Ntcheu revealed a signifcantly high content of zinc (54.61 ± 0.43 mg·kg −1 ) and potassium (808.58 ± 0.27 mg·kg −1 ), respectively ( Table 2). Iron is a major component of hemoglobin, a type of protein in red blood cells that carries oxygen from our lungs to all parts of the body. Without enough iron, there cannot be enough red blood cells to transport oxygen in the body. Iron is an essential micronutrient for plant growth and development. It plays a key role as it is involved in the synthesis of chlorophyll and other enzymatic and metabolic processes [41]. Gopalan et al. [46] reported high iron content in pigmented maize than in white hybrid maize cereal grains which is in line with what was found in the current study. Malawi would, therefore, beneft from these maize varieties as it is  reported that iron defciency is prevalent in 22% of preschool children, 5% of school-aged children, 15% of nonpregnant women of reproductive age, and in 1% of men [47].
Whole grains are zinc-rich foods for vegetarians. Zinc is one of the important components of various enzymes responsible for running diferent metabolic processes in crops [41]. Growth and development would not continue if specifc enzymes were not present in plants. Carbohydrate, protein and chlorophyll formation is signifcantly reduced in zinc-defcient plants [48]. Zinc is an important mineral in the context of malnutrition, and this mineral also has signifcant variability in maize. Zinc is necessary for the activity of over 300 enzymes that aid in metabolism, digestion, nerve function, and many other processes [41,48]. In addition, it is critical for the development and function of immune cells. Tis mineral is also fundamental to skin health, DNA synthesis, and protein production [41]. Te average zinc content of maize kernels is 20 mg·kg −1 , and 30% of these are located in the endosperm. Te lowest value of zinc content revealed in this study was higher and lower in some cases than the reported average maize kernel content [19,41]. Dedza purple maize would therefore be utilized in the diet of all requiring high supplements of zinc ( Table 2).
Potassium is one of the major nutrients in maize which has signifcance because an average human diet lacks it [34]. Potassium is found naturally in many foods and as a supplement. Its main role in the body is to help maintain normal levels of fuid inside our cells. Sodium, its counterpart, maintains normal fuid levels outside of cells. Potassium is associated with the movement of water, nutrients, and carbohydrates in plant tissue. It is involved with enzyme activation within the plant, which afects protein, starch, and adenosine triphosphate (ATP) production. Te production of ATP can regulate the rate of photosynthesis in plants [19]. Potassium also helps muscles to contract and supports normal blood pressure. Te present study's mineral content in PLMVs was higher in some cases than what was reported by Murayama et al. [35] and Rouf-Shah et al. [42] (Table 2). Tis might be due to variety and environmental interactions which infuences diferent attributes of PLMVs [6]. Te revealed signifcantly high content of iron, zinc, and potassium in red maize from Dedza, purple maize from Dedza, and Ntcheu, respectively, would contribute to solving some of the defciencies of national concern.
Plant growth and development highly depend on the combination but also concentration of mineral nutrients present in the soil where the plants are grown [6]. Plants often face signifcant challenges in obtaining adequate nutrients to meet the demands of diferent cellular processes due to their immobility [48]. Soils from Ntcheu and Mzimba grown with orange maize had a signifcantly higher content of magnesium (925.32 ± 0.24 mg·kg −1 ) and phosphorus (3225.40 ± 0.12 mg·kg −1 ), respectively. Tis resulted in more than 50% bioavailability of these minerals in orange maize grains; thus, (502.59 ± 0.25 mg·kg −1 ∼54.32%) for magnesium and (1920.28 ± 0.11 mg·kg −1 ∼59.54%) for phosphorus. Te mineral bioavailability trend was not uniform in all production areas (Tables 2 and 3). Some provenances had high mineral availability which resulted in high bioavailability while in other provenances though high mineral availability was observed, PLMVs revealed low content. For instance, soils from Dedza and Mzimba grown with red maize had a signifcantly higher content of iron (67.42 ± 0.23 mg·kg −1 ) and zinc (78.56 ± 0.15 mg·kg −1 ) but only the maize grains from Dedza had high percentage bioavailability of iron (59.80 ± 0.26 mg·kg −1 ∼88.70%) than zinc (38.93 ± 0.19 mg·kg −1 ∼50%). Purple maize soils from Ntcheu and Dedza had signifcantly high content of calcium (87.43 ± 0.31 mg·kg −1 ) and potassium (988.98 ± 0.24 mg·kg −1 ), respectively, but comparing the bioavailability of these two minerals, it was revealed that only (45.07 ± 0.33 mg·kg −1 ∼51.55%) of calcium was available in purple maize grains from Ntcheu while (724.37 ± 0.25 mg·kg −1 ∼73.24%) potassium was available in purple maize grains from Dedza (Tables 2 and 3). Mineral availability in the soil afects its presence both in the food crops and in individual human beings who utilize a particular food crop [25].
Mineral intake difers in individuals due to diferences in dietary preferences and levels of mineral content in the soils on which plants grow [49]. Te solubility of the minerals determines their presence in the soil and their potential availability to crops grown on such soils [50]. Environmental factors like pH and parent rock from where soils originate have an infuence on mineral availability in the soil [25]. Mineral availability in the crops is therefore infuenced by the interactions that exist between the diferent crop varieties and the environmental factors found in diferent locations of crop production [26]. Many other factors afect the availability of soil nutrients including leaching, soil erosion, soil de-nitrifcation, volatilization, nitrogen immobilization, and crop nutrient uptake [27]. Soil pH afects nutrient availability for plant growth in that in highly acidic soils, minerals such as manganese can become more available to plants while calcium, magnesium, and phosphorus are less available; hence, environmental factors have a bearing on mineral presence in the soil [6,48]. In highly alkaline soils, most micronutrients and other macronutrients such as phosphorus become less available. Varietal diferences have a great impact on mineral absorption from soils but the temperature is a key factor afecting the rate of nutrient uptake [41]. Low temperature reduces nutrient uptake by decreasing plant growth rate [48]. PLMVs in this study were grown in diferent locations with diferent temperature ranges which may have afected cation exchange capacity (CEC) in the soils. As CEC increases, more nutrients are attached to soil particles, while fewer remain in the soil solution. Few nutrients in soil solutions result in few being available to crops. Parent rock has a direct infuence on the mineral contents of the soil which has a bearing on the bioavailability of the minerals in the crops [6]. It can therefore be concluded that nutrient availability in both soil and plants is infuenced by many interrelated factors hence the diferences encountered in the present study. It is very important to know which crop does better in which production area so that its quality attributes such as mineral bioavailability are highly utilized in the diet.

Conclusion
Tis study has revealed that there are signifcant diferences in the physicochemical attributes of pigmented landrace maize varieties in their areas of production. Te study has also demonstrated that pigmented landrace maize varieties are a good source of minerals such as Mg, K, P, Fe, Zn, and Ca. Tese substances are very important in the promotion of healthy living of the people. For instance, minerals such as zinc and iron present in pigmented landrace maize play a great role in solving the problem of micronutrient defciencies of national concern in many communities in Malawi. Utilization of PLMVs having signifcantly high content of the revealed minerals in their areas of production would help solve diferent defciency diseases.
Te signifcant diferences in the proximate composition of PLMVs are attributed to the genetic makeup and the interaction that exist with the environmental factors in their respective areas of production. Enhancing the production and consumption of grains that best suit a particular area of production has a big potential in improving the health status of smallholder farmers and those who directly and indirectly access and utilize the products of these grains. Looking at physicochemical attributes and the value of PLMVs, it can be concluded that biodiversity conservation ensures access to nutritious food crops. Terefore, Farmers are encouraged to produce and utilize PLMVs that have a high content of the diferent attributes in their localities to beneft from these attributes.

Data Availability
All data are included in the manuscript.

Conflicts of Interest
Te authors declare that there are no conficts of interest as the research was not conducted for commercial or fnancial purposes.