Physicochemical Characteristics, Microstructure and Health Promoting Properties of Green Banana Flour

Round 1

Reviewer 1 Report

A study is carried out to characterise the main components in general terms of the flours of the banana species studied, as well as some technological and antioxidant properties. The article is well organised although there are some aspects that need to be improved:

Line 12. It must be specified which method has been used for the determination of the antioxidant activity.
On line 17 and 20, the acronyms SEM and RS must be defined.
Line 47, define f.w and d.w, and put TSS in brackets instead of "total soluble solids".
Line 76, how was neutralisation performed?
Line 89, according to the calculation of the total amount of carbohydrates, compounds such as phenols or saponins are included in the total carbohydrates.
Line 111, 30 seconds instead of 30s, or put 30 s with a space in between.
Line 112, the units of ºC should be put on all temperatures and not only on the last one.
Line 147, although a kit has been used, a brief description of the method or a reference is necessary, indicating the apparatus used, and the units used. Same in section 2.7.3.
Line 231. To say that a lower fat concentration creates an environment in which oxidation is not suitable is not correct, it is more correct to say that a lower fat content decreases the risk of lipid oxidation in general.  It may be another type of oxidation, or it may be that even though there is less fat, it is richer in polyunsaturated fat and therefore more easily oxidisable.
Line 313. Define what retrogradation means.
Table 4. The unit of ºC is missing for the temperature of 90 in the swelling power.
Section 3.4.1. It would be interesting if the authors could explain whether the type of milling influences the particle size of the flour and how it can be improved.
In general in the tables it should be explained well what the units are referring to, in table 4 explain g/g dry or fresh matter, in table 3 and 5 if the % is referring to dry or fresh matter, and in table 6 the acronyms d.w. should be explained.
Put in vitro in italics throughout the text.

Author Response

Point 1: Line 12; “it must be specified which method has been used for the determination of the antioxidant activity.”

Response 1: Line 12; the sentence has been rephrased to: “(TFC) and antioxidant activity (DPPH, FRAP) of green banana flour (GBF) cultivars”

Point 2: Line 17 and 20; “the acronyms SEM and RS must be defined.”

Response 2: Line 17; authors agree with the reviewer and the acronyms have been defined: “Scanning electron microscopy (SEM)”. Line 20; “The resistant starch (RS)” 

Point 3: Line 47; “define f.w and d.w, and put TSS in brackets instead of "total soluble solids".

Response 3: Line 47; the statement has been revised as suggested and now reads as: “52.7-54.2% Resistant starch (RS); 1.81% Total Soluble Solids (TSS), 76.77% Total Starch and 14-17% non-starch polysaccharides.”

The acronyms f.w and d.w have been defined as fresh weight and dry weight in the document.

Point 4: Line 76; “how was neutralisation performed?”

Response 4: Line 75-77; the following has been added in the Materials and Methods: “The starch sediment was suspended in water, stirred for 5 min and allowed to stand for 2 h. The supernatant was discarded and the sediment was re-suspended in water, stirred and allowed to settle, and re-suspended in water again until the wash water reached a neutral pH 6.68.”  

Point 5: Line 111; “30 seconds instead of 30s, or put 30 s with a space in between.”

Response 5: Line 109; “and mixed for 30 s using a vortex mixer.”

Point 6: Line 112; “the units of ºC should be put on all temperatures and not only on the last one.”

Response 6: Line 110; the units of °C have been added on all temperatures: “bath at 50 °C, 70 °C, 90 °C for 20 minutes”

Point 7: Line 147; “although a kit has been used, a brief description of the method or a reference is necessary, indicating the apparatus used, and the units used. Same in section 2.7.3.”

Response 7: Line 143- 146 &155; “banana flour sample (80 mg)was incubated with a mixture of pancreatic α-amylase and amyloglucosidase (PAA/AMG) in maleate buffer, pH 6.0,  according to the procedure used for measurement of dietry fiber at 37 °C for up to 4 h with continual stirring (K-RNTDF; AOAC Method 2017.16)”  

Line 153; a reference has been inserted: “described by Jiung et al. (16).”

Point 8: Line 231; “to say that a lower fat concentration creates an environment in which oxidation is not suitable is not correct, it is more correct to say that a lower fat content decreases the risk of lipid oxidation in general.  It may be another type of oxidation, or it may be that even though there is less fat, it is richer in polyunsaturated fat and therefore more easily oxidisable.”

Response 8: Line 230; Thank you for pointing this out. The statement has been corrected to: “The low fat content of banana flour creates an environment which is not suitable for oxidation reactions, resulting in extended shelf life. In fact, it reportedly decreases the risk of lipid oxidation which may result in extended shelf life.”

Point 9: Line 313; “define what retrogradation means.”

Response 9: Line 312; Retrogradation has been defined: “  a process a reaction that takes place in gelatinised starch, when disaggregated amylopectin and amylose chains reassociate to form more ordered structures)”

Point 10: Line 322; “table 4. The unit of ºC is missing for the temperature of 90 in the swelling power.”

Response 10: Line 322; the units of °C have been added on table 4.

Point 11: Line 322; Section 3.4.1. It would be interesting if the authors could explain whether the type of milling influences the particle size of the flour and how it can be improved.

Response 11: Line 340; The study did not investigate the influence of milling on the particle size. Only one type of milling was used in the study.

Point 12: Line 322 & line 462; “in general in the tables it should be explained well what the units are referring to, in table 4 explain g/g dry or fresh matter, in table 3 and 5 if the % is referring to dry or fresh matter, and in table 6 the acronyms d.w. should be explained. Put in vitro in italics throughout the text.”

Response 12: Line 322 & line 462; the authors have explained the units on the tables in line 322 & line 462 and in other tables of the paper. The term in vitro has been written in italics throughout the text.”

Reviewer 2 Report

The manuscript is well designed in general and informative. However I would suggest that the authors request a scientific editor to look through the work so as to correct mistakes in the English formatting of sentences. This will help the manuscript to be easier to read.

I would also suggest adding a couple of recent papers looking at the effect of including banana flour and starch material on the glycaemic effect of foods. Also possibly looking at the diversity of phenolic compounds and quality attributes in banana, as well as the potential benefits or opportunities in this field of research. This would allow deeper evaluation of how the results of the researchers contribute to our grater understanding. 

One of the interesting point in relation to TPC and phenolic content in fruits is that they are dependent on maturity and also storage conditions. I would suggest that the authors should put more information on the maturity of the bananas used and how that this may have impacted the research findings. 

This is also important in relation to the resistant starch content and the amylose content of the starch.  Maturity and ripeness would affect these values (potentially). Could the authors increase their discussion with regards to this and how variations in amylose content may impact on the glycaemic load of flours and products?

Have the authors evaluated whether these trends occur season to season. Does location and season contribute more to this variation rather than genetics? Please discuss in more detail.

1. Ramírez-Bolaños, S., Pérez-Jiménez, J., Díaz, S. and Robaina, L. (2021), A potential of banana flower and pseudo-stem as novel ingredients rich in phenolic compounds. Int J Food Sci Technol. https://doi-org./10.1111/ijfs.15072
2. Scott, G.J. (2021), A review of root, tuber and banana crops in developing countries: past, present and future. Int. J. Food Sci. Technol., 56: 1093-1114. https://doi-org.10.1111/ijfs.14778

Author Response

Point 1: Line 390 – 425; “I would also suggest adding a couple of recent papers looking at the effect of including banana flour and starch material on the glycaemic effect of foods. Also possibly looking at the diversity of phenolic compounds and quality attributes in banana, as well as the potential benefits or opportunities in this field of research. This would allow deeper evaluation of how the results of the researchers contribute to our greater understanding.”

Response 1: Line 390-396; thank you for pointing this out. The statement has been added: “It is widely acknowledged the GI and RS content are two significant indicators of starch digestibility (12,54). In a study by Soto-Maldonado et al. (55) on the glycaemic index of banana flour developed from whole banana and  overripe banana, it was observed that the GI in increased with food maturation, which associated with a decrease in in starch content., which was associated with a decrease in in starch content.”

Line 429- 431 “phenolic compounds are essential secondary metabolites, they are found in high level in banana compared to other fruits (61). They have been linked with health benefits such as prevention of diebetes, obesity and cardiovascular diseases (23, 61, 62).

Line 436- 439; “Anyani et.al. Reported the presence of gallic acid, catechin, epicatechin and myricetin3-O-rhamnosyl-glucoside in ripe and unripe banana flour cultivars. Furthermore, phenolic compounds are as food additives in food industry applications, to prevent lipid oxidations reactions in food formulations.”

Point 2: Line 429- 438; “one of the interesting point in relation to TPC and phenolic content in fruits is that they are dependent on maturity and also storage conditions. I would suggest that the authors should put more information on the maturity of the bananas used and how that this may have impacted the research findings.” 

Response 2: Line 429- 438; the following statement has been added: “moreover, maturity has been reported to significantly affect the total phenolic content green banana flour (1,24,63) Passo et al.(64) found that over ripened banana flour had 52 % less phenolic contents, while ripe banana flour had 15-45 % less phenolic content in green banana flour. Banana flour contain phenolic compounds such as catecholamines, phenolic acids and flavonoids (51,62). With its high TPC content Grand Naine has potential for use in the food industry as a raw material for generating functional ingredients. Therefore, maturation must be considered when selecting banana flour as a raw material, based on the findings in the present study the use of “unripe”/green banana flour is recommended for food industry applications.  The variation in total phenolic content observed in the present results may be attributed to genetic differences amongst different banana flours.

Point 3: Line 390- 414; This is also important in relation to the resistant starch content and the amylose content of the starch.  Maturity and ripeness would affect these values (potentially). Could the authors increase their discussion with regards to this and how variations in amylose content may impact on the glycaemic load of flours and products?

Response 3: Line 390-391; the following statement has been added: “It is widely acknowledged that the GI and RS content are two significant indicators of starch digestibility (12,54).”

 Line 394-398; the following statement has been added: “It is however worth noting that the GI of green banana flour may vary based on protein content, fat content and particle size and the maturity and ripeness (54). In a study by Soto-Maldonado et al. (55) on the GI of banana flour developed from whole banana and  overripe banana, it was observed that the GI in increased with banana maturation, which was associated with a decrease in starch content.”

Line 403-404; the following statement has been added: “furthermore, RS can regulate the high release of glucose from starchy foods thus lowering the risk of obesity.”

Line 413-414; the following statement has been added: “previous studies (61–63) suggest that a high amylose content of foods generally tends to give rise to a lower GI.”

Author Response File: Author Response.docx