Sweetpotato-based infant foods produce porridge with lower viscosity and aflatoxin level than cereal-based complementary blends.

The viscosity, protein, and total aflatoxins contents in orange-fleshed sweetpotato (OFSP) and cereal-based commercial complementary formulations and the effect of dilution on the protein content of the formulations were investigated. Standard procedures were used for the determination of these parameters. Over 80% of the formulations had a viscosity above the recommended consistency of 1000-3000 cP for feeding young children. The consistency of OFSP-legume porridge was significantly (2392.5 cP; p < 0.001) lower, about 1.7 and 3.4 times than cereal-only and cereal-legume blends, respectively. All the complementary flours, except the cereal-only, met the proposed protein requirement of 6 to 11 g per 100 g for feeding children aged 6 to 23 months on an as-is basis. However, the protein content in the porridges on an as-would-be-eaten basis was about 6% lower than the as-is basis value. About 38% of the complementary foods had total aflatoxin level above the acceptable limit of 10 ppb, mainly in blends containing peanuts, maize, or both. Adding more water to meet the required thickness of cereal-only and cereal-legume porridges diluted the protein content. More efforts are needed from regulatory bodies and all stakeholders to ensure complementary foods are safe in terms of mycotoxin levels, particularly those containing maize, peanut, or both as ingredients.

1. Introduction

Malnutrition remains the leading cause of child mortality in developing countries. For example, according to the World Health Organization, sub-Saharan Africa still has the highest global mortality rate of children under the age of 5; treatment and preventable efforts to curb this includes adequate nutrition and access to safe foods [1].

Complementary feeding in low-income countries in sub-Saharan Africa depends mainly on cereals [2, 3]. Due to the high dietary bulk, complementary foods require excess dilution with water during preparation to achieve a suitable consistency [4]. Excessive addition of water leads to a reduction in energy and nutrient density [5]. Thus, children are fed porridges with low nutrient- or energy-density [6, 7]. The low energy and nutrient density of complementary foods are critical contributors to childhood malnutrition and growth faltering [8]. This can be prevented through optimal complementary feeding (i.e., timely, adequate, appropriate, and safe) [8].

Complementary foods augment breast milk and should ideally have the consistency of yoghurt in a tub, be energy- and nutrient-dense, and be free of microbial contamination (live organisms, toxins, or by-products). Walker [9] proposed that porridge viscosity is a significant factor in protein-energy malnutrition. A porridge viscosity between 1000–3000 cP has been reported to be of appropriate consistency for the first solid foods for infants [7]. However, such viscosity required for complementary foods is difficult to achieve in cereals if they are fermented, roasted or blended with legumes unless germinated [10-Agric Biol J North Am. 2011 ">12]. Ideally, cereals used as feed ingredients should be pre-digested by α-amylase to partially digest the starch and reduce the viscosity of the porridge [13].

Lutter & Dewey [14] proposed a protein content of 6 to 11 g per 100 g in complementary food flours for the diet of children aged 6 to 23 months. It should be noted that the nutrient content of the flour for porridge may not be the same as the porridge served. The nutrient level could be diluted by the quantity of water added to obtain a suitable consistency.

Complementary foods are also expected to be microbially safe, either by being free from microbial contamination (live organisms, toxins, or by-products) or having a contamination level below nationally and internationally acceptable limits. However, from a two-week, cross-sectional survey in most regions of Ghana, where 48 commercial complementary samples were sourced and analysed for total aflatoxins, about a third of the samples exceeded the acceptable limit of 20 ppb [15]. Thus, there should be a greater interest in finding alternative non-cereal-based complementary foods. In addition, it has been reported that cereal-legume blends, mainly made from maize and peanuts, usually have higher total aflatoxin loads [15, 16]. When fed to infants and young children, these toxin-infested foods expose them to aflatoxin and its related adverse effects. This is evidenced in a longitudinal study conducted in Benin, West Africa, among children aged 16 to 37 months, where a strong association was found between aflatoxin exposure and impaired growth, with possible effects on immunity and susceptibility to infections [17]. For this reason, countries such as Switzerland and the Netherlands have set 0.18 ppb and 0.21–0.39 ppb, respectively, as the maximum allowable limit for aflatoxin (B1) in foods for infants and young children, with the European Union value of 0.10 ppb being stricter [18]. To curb the negative effect of aflatoxin, its ingestion from food should be kept as low as possible [19]. If possible, food for infants and young children should be kept under 1.0 ppb aflatoxin contamination [18].

There is no standard for non-cereal-based complementary foods, only cereal-based [20], implying that cereals should be the base ingredient for complementary foods. This may have contributed to the over-dependency on cereals, even though other crops can be used for complementary foods, particularly in low-income countries where complementary foods for the resource-poor are prepared from locally available ingredients and are not enriched with micronutrients [21]. Therefore, there is a need to utilise other climatic-smart crops. For example, the ability of sweetpotato to be cultivated in most ecologies, being drought-tolerant once established with a relatively short maturity period of three (3) to five (5) months, makes it a climatic-smart crop [22]. In addition, an earlier study has shown that sweetpotato requires less use of energy for cooking and the addition of water than cereals in preparing complementary food recipes at the household level [23].

Complementary foods have been formulated using sweetpotato, including orange-fleshed sweetpotato (OFSP), as a base ingredient [24-27]. The reported advantages of these formulations over household-level cereal-based blends included a higher concentration of provitamin A (plant dietary source of vitamin A), simple sugars (imparting natural sweetness), and forming less viscous porridge (less reduction of nutrient and energy density) [28]. The levels of simple sugars, especially sucrose, increase during root storage [29-31]. Additionally, maltose is formed from starch when the roots are cooked at a temperature of 65 °C and above [29, 31–33]. The conversion of starch to these simple sugars during storage and cooking imparts a natural sweetness to the porridge. Also, it contributes to the lower viscosity of sweet potato formulations for infants compared with cereal-based types [5].

In a review of the efficacy and effectiveness of nutrition interventions, provitamin A from sweetpotato roots was found to have better bioavailability than that from other leafy vegetables [34]. Also, OFSP complementary foods meet WHO recommendations for daily consumption of fruits and vegetables for older infants and young children [35].

This study aimed to assess the viscosity, protein and aflatoxin contents (on an as-would-be-eaten basis) in sweetpotato- and cereal-based commercial formulations sourced from Ghana and Uganda. It is hypothesised that the sweetpotato-based formulations would have lower viscosity, less protein dilution and lower total aflatoxins than cereal-based blends.

2. Materials and methods

2.1 Study design & sampling

A completely randomised design was employed in this study. Different brands (n = 23) of commercial complementary foods were obtained from open markets and supermarkets in Ghana and Uganda. In addition, the OFSP-based formulations were obtained from a product exhibition at a workshop organised by International Potato Centre in 2019 in Kampala, Uganda. One (1) household-level maize-only dough was prepared from orange maize for this work. To prepare the orange maize dough, 500 g of whole orange maize grain was steeped for 74 h, wet-milled and sieved using a 630 μm mesh size. A commercial maize-based complementary food in Ghana was used as the control. The ingredients of the control formulation included whole-corn flour, skimmed milk, sucrose, palm olein, acidity regulator, calcium carbonate, vitamins, ferrous fumarate, vanillin, zinc sulphate, Bifidus culture and potassium iodide. The cereal used in the control formulation was pre-digested, denoted as CHE (cereal hydrolysed enzymatically). For ethical reasons, none of the proprietary products is referred to by brand name in this manuscript; instead, identification is based on the ingredients listed on the package.

2.2 Laboratory analysis

The moisture, crude protein and total aflatoxin content of the complementary flour and the orange maize dough samples were determined. The viscosity and protein levels of the prepared porridges were also measured.

2.2.1 Moisture determination

The analytical procedure for moisture (AOAC 925.10) published by AOAC International was slightly modified; drying was done at 108°C overnight using a Thermo Scientific Heratherm oven [36]. The moisture determination was to correct the weights for the viscosity measurement and express the total content of aflatoxin on a dry matter basis.

2.2.2 Crude protein determination

The total nitrogen content was determined using the AOAC 960.52 [36], and crude protein was calculated using 6.25 as the conversion factor.

2.2.3 Total aflatoxins determination

Total aflatoxins in all the complementary flours were quantified using a tablet-assisted aflatoxin mobile assay (mReader) that uses Reveal Q+ test strips (Neogen Corporation) as previously published [15].

2.2.4 Viscosity measurement

The weight of each flour or dough equivalent to 100 g dry matter was determined (Table 1) and used to prepare the porridge according to the manufacturer’s instructions or as it is conventionally done for the orange-maize dough in Ghana. For ease of handling, apart from the product with maize, maltodextrin, skimmed milk powder, micronutrients or CHE printed on the package, the weight used for all the others was equivalent to 50 g dry matter. To minimise the effect of temperature on viscosity measurement using a DVE digital viscometer (Ametek Brookfield, Korea) at 100 rpm, the prepared porridges were carefully transferred to a 600-mL glass beaker in a water bath with intermittent stirring to avoid the formation of air bubbles at the bottom until the temperature was 40°C. The initial viscosity was measured with an average torque of 47% and varying spindle numbers (2 to 5) depending on the consistency of the porridge.

Table 1

Moisture and weights taken equivalent to 100 g dry matter content.

Constituent of complementary food (number of blends)	Moisture as-is (g/100 g)	Weight equivalent to 100 g dry matter content (g)	Total volume of water used to attain suitable viscosity (ml)
Maize+Maltodextrin+Skimmed milk powder+Micronutrients	3.67 e-g (2.39, 4.95)	103.81 c,d (101.64, 105.99)	300.00 g,h (280.60, 319.40)
Maize+Millet+Soy	3.02 f,g (1.75, 4.31)	103.14 c,d (100.96, 105.31)	335.67 e-h (316.27, 355.06)
Maize+Millet+Soy+Micronutrients	3.98 d-g (2.70, 5.26)	104.14 c,d (101.97, 106.32)	403.00 b,c (383.60, 422.40)
Maize+Millet+Soy+Peanut	4.23 c-g (2.95, 5.51)	104.42 b-d (102.25, 106.60)	387.30 b-d (367.90, 406.70)
Maize+Millet+Wheat+Rice+Soy+Peanut	4.88 d-g (3.60, 6.16)	105.14 b-d (102.96, 107.31)	337.33 d-h (317.94, 356.73)
Maize+Soy a	3.98 d-g (3.08, 4.89)	104.16 c,d (102.62, 105.70)	409.20 b (395.50, 422.90)
Maize+Soy+Amaranth+Beetroot	7.70 b,c (6.42, 8.98)	108.35 b,c (106.17, 110.52)	347.00 d-g (327.60, 366.40)
Maize+Soy+Peanut b	4.34 d-g (3.61, 5.08)	104.56 b-d (103.30, 105.82)	364.42 c-e (353.22, 375.62)
Millet+Soy a	6.85 b-d (5.95, 7.76)	107.39 b,c (105.85, 108.93)	350.02 d-f (336.30, 363.73)
OFSP+Maize+Pea	9.01 b (7.73, 10.29)	109.91 b (107.73, 112.08)	300.00 g,h (280.60, 319.40)
OFSP+Rice+Soy	7.29 b-d (6.01, 8.57)	107.87 b,c (105.69, 110.04)	310.40 f-h (291.00, 329.80)
OFSP+Sorghum+Soy	6.45 b-e (5.17, 7.73)	106.89 b-d (104.72, 109.07)	345.67 d-g (326.27, 365.06)
OFSP+Soy+Yellow maize	6.72 b-e (5.44, 8.00)	107.21 b-d (105.03, 109.38)	300.00 g,h (280.60, 319.40)
Fermented orange maize	48.97 a (47.69, 50.25)	196.18 a (194.01, 198.36)	482.00 a (462.60, 501.40)
Rice+Soy	7.66 b,c (6.38, 8.94)	108.31 b,c (106.14, 110.49)	361.60 c-e (342.20, 381.00)
Rice+Wheat+Soy	4.88 c-g (3.60, 6.16)	105.14 b-d (102.96, 107.31)	383.83 b-e (364.44, 403.23)
Wheat+Maltodextrin+Skimmed milk powder+Micronutrients a	2.82 g (1.91, 3.72)	102.90 d (101.37, 104.44)	300.00 g,h (286.30, 313.70)
Wheat+Soy	6.08 b-f (4.80, 7.36)	106.47 b-d (104.30, 108.65)	371.67 b-e (352.27, 391.06)
Yellow maize+Wheat+Millet+Soy+Coconut	5.02 c-g (3.74, 6.30)	105.28 b-d (103.11, 107.46)	369.33 b-e (349.94, 388.73)
P-value	<0.0001	<0.0001	<0.0001

Values are means of triplicate measurement per number of sample (95% confidence interval for the mean). Means that do not share a letter are significantly different.

aWheat + Maltodextrin + Skimmed milk powder+Micronutrients; Millet + Soy; and Maize + Soy: Two (2) different brands.

bMaize + Soy + Peanut: Three (3) different brands.

All others were one (1) brand.

After the first viscosity measurement, the porridges were diluted with water to a viscosity of 1000 to 3000 cP, which corresponded to the range of consistency of the control samples. Spindle number 2 at a rotational speed of 100 rpm and an average torque of 62% was used during dilution to adjust the viscosity of the porridges to the suitable consistency. The volume of water used to achieve the right consistency of the porridges required for complementary feeding was measured by the difference between the initial and final volumes of water used for the dilution. Triplicate readings were taken for each aliquot sampled for the porridge preparation.

2.3 Statistical analysis

One-way analysis of the variance procedure in Minitab®16.2.2 (Minitab Inc., State College, PA, USA) was used to compare the means for each parameter assayed. In addition, Tukey’s studentised range test was employed when the mean comparison test was significant (p < 0.05) to ascertain which treatment means differed.

3. Results and discussion

3.1 Viscosity of prepared porridge and after dilution

Nearly 80% of the samples had viscosities exceeding the drinking consistency of 1000–3000 cP before dilution (Fig 1A). The viscosity of the sweetpotato-legume porridge was significantly (p < 0.001; 2392.5 cP) lower than that of cereal-only and cereal-legume porridges. The consistency in sweetpotato-legume porridge was respectively about 1.7 and 3.4 times lower than cereal-only and cereal-legume porridges but 1.1 times higher than the control. The viscosity of the OFSP-based porridges obtained in this study was in the range reported by Araro et al. [37]. The viscosity trend for the ready-to-consume cereal-based porridges confirms previous work on complementary foods [38].

Fig 1

(A) Viscosity of commercial complementary blends before dilution and (B) the viscosity of commercial complementary blends after dilution.

The lower viscosity values recorded for the OFSP-legume blends were in line with those reported by Jemberu et al. [39] for similar OFSP-legume mixtures. In their study, they observed a reduction in viscosity values of formulated porridges as the proportion of OFSP flour was increased. This observation was likely due to the high content of simple sugars in the sweetpotato flour [5, 39].

According to Copeland et al. [40], high viscosity is attributed to the characteristic swelling of starch during cooking, which causes it to gelatinise. This limits the food intake of the child. Therefore, it is desirable to reduce the viscosity of ready-to-consume porridge. This is achieved by adding a certain amount of diluent (usually water), which results in reduced energy and protein density.

The cereal-based porridges with similar viscosity as the OFSP-based samples contained cereal in the form of CHE. The α-amylase hydrolyses starch to dextrin and maltose during the pre-digestion, reducing the consistency of the thick cereal porridges and enhancing their energy and nutrient density [41]. Interestingly, the OFSP-based products produced by small-scale manufacturers that did not use CHE as an ingredient had comparable viscosity to CHE-containing products. The relatively low viscosity of OFSP-based porridges confirms previous reports by Ridley et al. [31] and Nabubuya et al. [42]. The endogenous β-amylase in OFSP led to self-viscosity thinning. The thinner the porridge at preparation, the more "food" will be added to obtain a suitable porridge viscosity, which invariably increases nutrient density.

The viscosity values of the porridges after dilution (Fig 1B) showed no significant difference (p = 0.273) since the goal was to achieve the desired consistency of the control sample. It could be argued that amylolytic flour (produced from germinated cereals) produces a less viscous porridge when made at the household level. Previous researchers have shown that it is not effective when added before cooking the slurry for porridge, as the enzyme will be denatured by heat. Although it can be added to porridge, microbial safety concerns have been highlighted [7]. Furthermore, the porridge prepared from fermented orange-maize has a higher tendency for the starch to associate and retrograde, forming a thick paste upon cooling. This is not desirable as such products require additional water to obtain a viscosity suitable for feeding, which further reduces the energy and nutrient density.

3.2 Protein content of complementary flours and dough on as-received and as-would-be-eaten bases

The protein content (g/100 g) on an as-is basis of fermented orange-maize dough was significantly lower (3.85; 95% CI = 1.19, 6.52) than that of the other complementary flours investigated (Fig 2). Apart from the cereal-only (fermented orange-maize) flour, all other complementary flours met the suggested protein content of 6 to 11 g for feeding children 6 to 23 months of age [14]. As expected, protein content in the porridges on as-would-be-eaten basis was almost 1.6-times lower than on as-received basis (7.9 vs. 12.8; p < 0.001). The protein content of orange-maize porridge is similar to that observed by Alamu et al. [43], who also reported lower (1–3.7%) protein content of traditional maize-based complementary foods in Zambia.

Fig 2

The protein content of commercial complementary blends.

Therefore, future research efforts should focus on how best to meet the energy and nutrient requirements, but also take into account factors that affect energy intake, such as the energy density and viscosity of complementary foods.

3.3 Volume of water used for dilution to get appropriate consistency for complementary feeding

All but the control sample and those containing maltodextrins were wet-cooked into porridge before serving. The quantity of water used to obtain the appropriate consistency of 1000–3000 cP [7] for the same amount of complementary food is presented in Table 1. The amount of water needed to dilute the complementary blends to obtain the proper drinking consistency varied significantly (p < 0.0001) among the mixtures, with the cereal-only porridge recording the largest volume (482 ml). The water required to dilute the OFSP-based complementary blends to a drinking consistency ranged from 300–345 ml, which was lower than the cereal-based complementary blends. The volume of water added to attain the suitable viscosity is crucial because more water means lower energy and nutrient density, which is the case with most cereal-based complementary foods in Africa. This finding supports Amagloh & Andrade [23], who reported that less water was required in the preparation of the OFSP-based porridge than for Weanimix, a maize-based complementary food in Ghana.

Therefore, OFSP could be regarded as a climate-smart food ingredient for complementary foods because it cooks quickly [44] and requires less water during cooking [23].

3.4 Total aflatoxins contamination

The level of aflatoxin contamination in the complementary foods sampled is shown in Fig 3. Generally, about 38% of the foods had aflatoxin levels above 10 ppb, while 21% contained aflatoxins above20 ppb. All samples with contamination above the U.S. tolerable limit of 20 ppb were cereal-legume mixtures containing either peanuts, maize or both, as reported in a previous study by van Egmond et al. [45]. Using the African median permissible limit of 10 ppb for processed foods [45], as in the case of many international jurisdictions, 63% of the commercial baby foods examined in this study are still not considered wholesome even for adult consumption. It is particularly worrying that 25% of the proprietary complementary foods examined in this study had contamination levels above 20 ppb.

Fig 3

Aflatoxin concentration of commercial complementary blends.

However, these results are not surprising, as in a similar study [15], about 60% of 48 complementary foods in the Ghanaian market had aflatoxin contamination above 20 ppb. Unfortunately, parents/caregivers may purchase these foods on the market, often with limited resources to support children’s growth and overall health, only to inadvertently expose them to aflatoxins that could be detrimental to their health. These high levels of aflatoxin contamination in complementary foods underscore the importance of enhanced regulatory measures. It is reasonable to assume that either the raw materials used for these foods are highly contaminated with the toxin, or the toxin multiplies in the product due to favourable storage conditions [46]. It is also noteworthy that the complementary foods sampled were all above more stringent maximum allowable limits for aflatoxin (B1) in infant foods in Switzerland (0.18 ppb), the Netherlands (0.21–0.39 ppb) and the European Union (0.10 ppb) [18]. This is a grave public health concern that needs urgent attention from regulatory bodies in the sub-region.

The effect of dilution on other nutritional properties (apart from protein content), though expected to be reduced during the dilution, was not included in this study due to financial constraints and is recognised as a study limitation.

4. Conclusions

The OFSP-containing blends made porridge with appropriate viscosity that did not require further dilution with water as was required for most of the cereal-legume combinations. Apart from the cereal-only porridge, the complementary foods had sufficient protein content to meet the recommendation for 6 to 23 months children The complementary foods, with the exception of the OFSP-legume blend, had consistencies that greatly exceeded the recommended range for young children. Adding more water to produce the required viscosity will likely reduce energy and nutrient density significantly. Furthermore, the high aflatoxin contamination in the complementary food blends containing maize, peanuts or both underscores the importance of enhanced regulatory measures to address this public health concern. Based on the present findings, OFSP could be a better alternative ingredient for complementary foods, particularly for resource-poor households, as it requires less dilution with water, has an appropriate viscosity when prepared as a porridge and is associated with lower total aflatoxin content. However, more efforts are needed from regulatory bodies and all stakeholders to ensure that complementary foods, especially those containing maize, peanuts, or both as ingredients, meet local and international standards for aflatoxin contamination.

4 Aug 2022

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Reviewer #1: Although the aims of the study are good, it was planned and carried out very superficially. It has been seen that the written language, sample, analyzes and methods of construction are not sufficient. Samples are not well explained, not understandable. It is thought that measuring each of the samples in the viscosity study by bringing them to the same dry matter significantly affects the difference between the samples. It is thought that the evaluation made in this way will not give correct results.

Reviewer #2: PONE-D-22-17748-peer-review-v1.comments

Sweetpotato-based infant food as an alternative complementary formulation

Comment 1: The research is quite innovative and interesting, with clearly established objectives and conclusions.

Comment 2: Abstract: The following line is little bit confusing, it is recommended to rephrase it to make it more clear and easily understandable: ‘However, the protein content in the porridges on an as-would-be-eaten basis was about 6% lower.’

Comment 3: Abstract: Have you mentioned the amount and the desirable water content for proper mixing of the blends?

Comment 4: 62: Is not 10 ppb really high even to be marked as maximum level for infant cereals, when we are talking about the acceptable levels as 0.18-0.39 ppb?

Comment 5: Line No. 109: Did you measures moisture and protein content only in nutritional parameters? If so, what about the determination of other nutritional contents like minerals, fiber and vitamins?

Comment 6: Line No. 150: Have you mentioned anywhere about total number of samples or treatments that you have used?

Comment 7: Line No. 223: In my opinion this level of alfatoxin as reported from the results here are high for infant consumption. Please add justification.

Comment 8: Line No. Conclusion: Overall the study is good, but in this type of study a small animal based efficacy investigation should also be included as to ensure pros and cons of the product developed. Without having its safety confirmation we are unable to recommend such innovative idea.

Reviewer #3: The research article “Sweetpotato-based infant food as an alternative complementary formulation” by Francis seeks to describe the combination of different ingredients and their properties and product studies (protein and viscosity).

The article needs extensive corrections.

I think the author should change the title it did not match with the content.

Comment 1: First, the English language has to be corrected, the authors use too much every-day spoken English, too much for a scientific publication.

Comment 2: Authors should add the descriptive sensory analysis or 9-point hedonic scale and shelf life of porridge.

Comment 3: The author should add the physico-chemical properties of multigrain porridge such as fat, crude fiber, ash, and carbohydrates

Comment 4: Author should check the dough's rheological properties which are prepared from orange maize.

Comment 3: The abbreviation CHE have no sense in line number 104-105, the abbreviation details should be added in line number 101-104 (The ingredients of the control formulation included whole corn flour (CHE indicated on the package), skimmed milk, sucrose, palm olein, acidity regulator, calcium carbonate, vitamins, ferrous fumarate, vanillin, zinc sulphate, Bifidus culture, and potassium iodide.)

Comment 6: In line number 114 the author should clearly add which type of dry process and instrument were used for drying at 108°C overnight.

Comment 7: Rewrite the viscosity measurement protocol from line number 124-142.

Comment 8: In Table 1 no need for the repetition of (n=1), you can add it at end of the table

Example: Data are presented as mean ± SD (n = 3)

a-nMeans with the same superscript in a column do not vary significantly (p<0.05) from each other

In table 1 author adds the value please justify then and explain in paragraph also. Or the author removes those values.

Comment 9: The author checks the result discussion and conclusion part.

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10 Aug 2022

Response to queries in italics: Reference to revised manuscript with track changes

Reviewer reports:

Reviewer #1:

Although the aims of the study are good, it was planned and carried out very superficially. It has been seen that the written language, sample, analyzes and methods of construction are not sufficient. Samples are not well explained, not understandable. It is thought that measuring each of the samples in the viscosity study by bringing them to the same dry matter significantly affects the difference between the samples. It is thought that the evaluation made in this way will not give correct results.

Your comments are very much appreciated. However, the samples were existing proprietary products (lines 107 – 108); thus, their brand names were undisclosed for ethical reasons. Therefore, the best way to describe these samples without disclosing brand names was to indicate their constituent ingredients, as captured in lines 107 – 108. Regarding analyses and methods, some revisions have been made (lines 103, 105 – 106, 131 – 135).

Although what you have suggested is right for getting the actual viscosities of the samples. It is required, in rheological analyses such as visco-analysis, that samples are corrected to the same dry matter to avoid wrong comparisons as a result of varied initial moisture contents. With the same dry matter content, the viscosity of the samples can best be compared, hence the reason to correct the samples to the same dry matter content in this study.

Reviewer #2: PONE-D-22-17748-peer-review-v1.comments

Comment 1: The research is quite innovative and interesting, with clearly established objectives and conclusions.

Thank you very much for your kind remarks.

Comment 2: Abstract: The following line is little bit confusing, it is recommended to rephrase it to make it more clear and easily understandable: 'However, the protein content in the porridges on an as-would-be-eaten basis was about 6% lower.'

Thank you for your comment. The statement has been rephrased: ' However, the protein content in the porridges on an as-would-be-eaten basis was about 6% lower than the as-is basis value.'

Comment 3: Abstract: Have you mentioned the amount and the desirable water content for proper mixing of the blends?

No, please, reason being the word limit for the abstract. However, it has been stated in the materials and methods section (lines 139 – 142).

Comment 4: 62: Is not 10 ppb really high even to be marked as maximum level for infant cereals, when we are talking about the acceptable levels as 0.18-0.39 ppb?

Yes, you are very right. The statement has been revised as "To curb the negative effect of aflatoxin, its ingestion from food should be kept as low as possible (19)."

Comment 5: Line No. 109: Did you measures moisture and protein content only in nutritional parameters? If so, what about the determination of other nutritional contents like minerals, fiber and vitamins?

Yes, please. Moisture and protein contents were the only parameters measured. The study did not include other nutritional properties due to financial constraints, which was captured as a limitation (lines 248 – 250).

Comment 6: Line No. 150: Have you mentioned anywhere about total number of samples or treatments that you have used?

Yes, please. The total number of samples (24) was mentioned in line 97.

Comment 7: Line No. 223: In my opinion this level of alfatoxin as reported from the results here are high for infant consumption. Please add justification.

You are right. The aflatoxin level reported is for infant consumption. Lines 243 – 247 underscores the importance that the complementary blends assessed were not safe for infant consumption as all of them had toxin level above the permissible limit for infants as per Switzerland, Netherlands, and European standards and the need for stricter regulatory measures.

Comment 8: Line No. Conclusion: Overall the study is good, but in this type of study a small animal based efficacy investigation should also be included as to ensure pros and cons of the product developed. Without having its safety confirmation we are unable to recommend such innovative idea.

Your comment is highly appreciated. However, the products used for this study were on the market, and were not developed by the author. Thus, the study could not include any animal-based investigations.

Reviewer #3:

The research article "Sweetpotato-based infant food as an alternative complementary formulation" by Francis seeks to describe the combination of different ingredients and their properties and product studies (protein and viscosity).

The article needs extensive corrections.

Your comment is greatly appreciated. Some revisions have been made to that effect.

I think the author should change the title it did not match with the content.

Thank you very much. The title has been changed as suggested to "Sweetpotato-based infant foods have lower viscous porridge and total aflatoxins level than cereal-based complementary blends" in lines 1 – 2.

Comment 1: First, the English language has to be corrected, the authors use too much every-day spoken English, too much for a scientific publication.

Thank you for your comment. The safety and quality of complementary foods are critical; thus, there is the need to present it in such a way that the general populace can read and understand the manuscript. I am also finding it difficult where the "every-day spoken English" phrases are in the manuscript.

Comment 2: Authors should add the descriptive sensory analysis or 9-point hedonic scale and shelf life of porridge.

The author appreciates your comment. However, the samples used in this study were existing products on the market and not developed by the author. Hence, sensory analysis and shelf-life studies were not relevant. These are done during the product development phase.

Comment 3: The author should add the physico-chemical properties of multigrain porridge such as fat, crude fiber, ash, and carbohydrates.

Thank you. The author would have loved to determine the aforementioned physico-chemical properties. However, the study did not include these properties due to financial constraints, as indicated in lines 248 – 250. Moreover, being proprietary products, the nutritional information was on the package. The cereal-only sample, particularly from white-coloured maize, has been reported in previous work to be nutritionally inappropriate for complementary feeding.

Amagloh, F. K., Weber, J. L., Brough, L., Hardacre, A., Mutukumira, A. N., & Coad, J. (2012). Complementary food blends and malnutrition among infants in Ghana–A review and a proposed solution. Scientific Research and Essays, 7(9), 972-988. doi:10.5897/SRE11.1362

Comment 4: Author should check the dough's rheological properties which are prepared from orange maize.

The viscosity measured for the (fermented) orange maize is one of the rheological properties.

Comment 3: The abbreviation CHE have no sense in line number 104-105, the abbreviation details should be added in line number 101-104 (The ingredients of the control formulation included whole corn flour (CHE indicated on the package), skimmed milk, sucrose, palm olein, acidity regulator, calcium carbonate, vitamins, ferrous fumarate, vanillin, zinc sulphate, Bifidus culture, and potassium iodide.)

Comment well noted and the revision has been done appropriately. Lines 103, 105 & 106.

Comment 6: In line number 114 the author should clearly add which type of dry process and instrument were used for drying at 108°C overnight.

Thank you. The instrument used was a Thermo Scientific Heratherm oven. This has now been added to the revised manuscript (lines 115 – 116) as suggested.

Comment 7: Rewrite the viscosity measurement protocol from line number 124-142.

Thank you. Please, some revisions have been made as suggested, as captured in lines 131 – 135, 138 – 139.

Comment 8: In Table 1 no need for the repetition of (n=1), you can add it at end of the table

Example: Data are presented as mean ± SD (n = 3)

a-nMeans with the same superscript in a column do not vary significantly (p<0.05) from each other

In table 1 author adds the value please justify then and explain in paragraph also. Or the author removes those values.

Your comments are well noted. Please, revisions have been made to that effect. Lines 223-225.

Comment 9: The author checks the result discussion and conclusion part.

Thank you very much. The author has re-checked the abovementioned areas as suggested.

Submitted filename: Rebuttal.docx

Click here for additional data file.

31 Aug 2022

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We look forward to receiving your revised manuscript.

Kind regards,

Fatih Oz, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments:

Dear Authors,

Please take into consideration the comments raised by Reviewer 1. The language has to be checked by a native speaker. This will be the last option for revision.

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Reviewers' comments:

Reviewer's Responses to Questions

Comments to the Author

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Reviewer #1: (No Response)

Reviewer #2: All comments have been addressed

Reviewer #3: All comments have been addressed

**********

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Reviewer #1: Partly

Reviewer #2: Yes

Reviewer #3: Partly

**********

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Reviewer #1: Yes

Reviewer #2: Yes

Reviewer #3: Yes

**********

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Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

**********

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Reviewer #1: No

Reviewer #2: Yes

Reviewer #3: Yes

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6. Review Comments to the Author

Please use the space provided to explain your answers to the questions above. You may also include additional comments for the author, including concerns about dual publication, research ethics, or publication ethics. (Please upload your review as an attachment if it exceeds 20,000 characters)

Reviewer #1: Unfortunately, my views on the study before the revision have not changed. The study was planned and carried out very superficially. It has been seen that the written language, sample, analyzes and methods of construction are not

sufficient. Samples are not well explained, not understandable. The author made few changes in the article and could not give adequate answers to the comments and suggestions of other referees due to various reasons.

Reviewer #2: You have revised this paper in a very good way. Thanks a lot for your great work. Wish you all the best.

Reviewer #3: The author addresses all comments. But the author should take the comments in a positive way which helps their manuscript to make more effective.

**********

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Reviewer #1: No

Reviewer #2: Yes: Rana Muhammad Aadil

Reviewer #3: No

**********

[NOTE: If reviewer comments were submitted as an attachment file, they will be attached to this email and accessible via the submission site. Please log into your account, locate the manuscript record, and check for the action link "View Attachments". If this link does not appear, there are no attachment files.]

While revising your submission, please upload your figure files to the Preflight Analysis and Conversion Engine (PACE) digital diagnostic tool, https://pacev2.apexcovantage.com/. PACE helps ensure that figures meet PLOS requirements. To use PACE, you must first register as a user. Registration is free. Then, login and navigate to the UPLOAD tab, where you will find detailed instructions on how to use the tool. If you encounter any issues or have any questions when using PACE, please email PLOS at figures@plos.org. Please note that Supporting Information files do not need this step.

9 Sep 2022

Response to queries in italics

Reviewer reports:

Reviewer #1:

Unfortunately, my views on the study before the revision have not changed. The study was planned and carried out very superficially. It has been seen that the written language, sample, analyzes and methods of construction are not sufficient. Samples are not well explained, not understandable. The author made few changes in the article and could not give adequate answers to the comments and suggestions of other referees due to various reasons.

The author appreciates your comments and has made some revisions to that effect in track changes. I have attached comments from a commercial proofreader for your perusal.

I also got Prof Jane Coad, a British, who made some comments I have used to revise the manuscripts.

I also made other comments and can be seen as track changes

However, regarding the correction of the samples to the same dry matter, attached are some published articles that also used a similar approach for viscosity determination (Boulemkahel et al., 2021; Iwe et al., 2016; Nawaz et al., 2016; Wang et al., 2013). The author hopes these revisions and references meet your expectation and kind consideration.

The author has shared pictures of the complementary blends from which the author selected some for this study. However, this should not be made public as the author did not obtain approval or consent from the companies.

Reviewer #2: PONE-D-22-17748-peer-review-v1.comments

Comment: You have revised this paper in a very good way. Thanks a lot for your great work. Wish you all the best.

Thank you very much for your great remarks.

Reviewer #3:

Comment: The author addresses all comments. But the author should take the comments in a positive way which helps their manuscript to make more effective.

Thank you very much for your constructive comments. Your advice is well taken.

References

Boulemkahel, S., Betoret, E., Benatallah, L., & Rosell, C. M. (2021). Effect of low pressures homogenization on the physico-chemical and functional properties of rice flour. Food Hydrocolloids, 112, 106373.

Iwe, M. O, U. Onyeukwu, U, & A.N. Agiriga, A. N | Yildiz, F. (2016). Proximate, functional and pasting properties of FARO 44 rice, African yam bean and brown cowpea seeds composite flour, Cogent Food & Agriculture, 2:1, DOI: 10.1080/23311932.2016.1142409

Nawaz, M. A, Fukai, S., & Bhandari, B. (2016). Effect of Different Cooking Conditions on the Pasting Properties of Flours of Glutinous Rice Varieties from Lao People’s Democratic Republic, International Journal of Food Properties, 19:9, 2026-2040, DOI: 10.1080/10942912.2015.1092163

Wang L, Deng F, Ren WJ, Yang WY. (2013). Effects of shading on starch pasting characteristics of indica hybrid rice (Oryza sativa L.). PLoS One. Jul 5;8(7):e68220. doi: 10.1371/journal.pone.0068220. PMID: 23861872; PMCID: PMC3702574

20 Sep 2022

Sweetpotato-based infant foods produce porridge with lower viscosity and aflatoxin level than cereal-based complementary blends

PONE-D-22-17748R2

Dear Dr. Amagloh,

We’re pleased to inform you that your manuscript has been judged scientifically suitable for publication and will be formally accepted for publication once it meets all outstanding technical requirements.

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Kind regards,

Fatih Oz, Ph.D.

Academic Editor

PLOS ONE

Additional Editor Comments (optional):

Reviewers' comments:

4 Oct 2022

PONE-D-22-17748R2

Sweetpotato-based infant foods produce porridge with lower viscosity and aflatoxin level than cereal-based complementary blends

Dear Dr. Amagloh:

I'm pleased to inform you that your manuscript has been deemed suitable for publication in PLOS ONE. Congratulations! Your manuscript is now with our production department.

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