Effect of Water Content and Pectin on the Viscoelastic Improvement of Water-in-Canola Oil Emulsions

Round 1

Reviewer 1 Report

This paper is well written. The paper investigates the rheological properties of a concentrated water in oil emulsion. I disagree with the statement that this is the first to show a viscosity increase with increase in the water drop content. All water in oil emulsions show increased viscosity, especially as the water drop volume fraction exceeds the level required for close packing, causing deformations between adjoining drops. The authors need to remove this statement, but they should replace it with a statement that more clearly states the purpose of the work. While the paper provides interesting data sets, I would like to see a clearer message on the advance that the paper brings.

Author Response

Reviewer 1

This paper is well written. The paper investigates the rheological properties of a concentrated water in oil emulsion. I disagree with the statement that this is the first to show a viscosity increase with increase in the water drop content. All water in oil emulsions show increased viscosity, especially as the water drop volume fraction exceeds the level required for close packing, causing deformations between adjoining drops. The authors need to remove this statement, but they should replace it with a statement that more clearly states the purpose of the work. While the paper provides interesting data sets, I would like to see a clearer message on the advance that the paper brings.

Authors’ response: It was modified in lines 105-108 (section 1) and 710-715 (section 4), giving the emphasis to LMP in the enhancement of gel strength, combined with the increase of water content.

Line 105-108: “This study significantly advances the knowledge on the incorporation of hydroxyl group donating agent (such as LMP) in the aqueous phase in combination with an increase in water content to strengthen the gelation behaviour of W/CO emulsion”.

Line 710-715: “Such highly concentrated water-in-vegetable oil emulsion stabilized with GMO with high stability and gel strength at a lower saturated fat concentration is a difficult system to stabilize. The role of aqueous phase LMP in stabilizing the GMO-coated water droplets is one of the most critical aspects in developing such systems with close-packed water droplets, which could be used in the development of low-fat tablespreads.”

Reviewer 2 Report

This paper concerns the studies of gelation in water-in-canola oil emulsions stabilized with glycerol monooleate and varying water content and concentration of low methoxyl pectin. Improvement of freeze-thaw stability of emulsions was investigated by using differential scanning calorimetry technique.

This manuscript that reports important results deserve publication. However, I have several questions and comments listed below.

What was used as the reference sample to sequester the measurement signal originating from the sample in the DSC measurements?

Did the respected authors try to estimate the yield strength of the emulsions? Can the dependencies of viscosity on water content be approximated with some semi-empirical models, for example, equations of Mooney, Krieger, and Dougherty, or Richardson?

In my opinion, frequency dependencies of viscoelastic moduli should be included in the manuscript for a better understanding of the rheological behavior of the emulsions.

The authors mentioned that the crystallization temperature of water droplets depends on droplet size. Unfortunately, the authors did not give any quantitative information about the size of aqueous droplets in emulsions, for example, average droplet size or droplet size distribution.

I consider that this paper can be published after some modification.

Author Response

Reviewer 2

Comments and Suggestions for Authors

This paper concerns the studies of gelation in water-in-canola oil emulsions stabilized with glycerol monooleate and varying water content and concentration of low methoxyl pectin. Improvement of freeze-thaw stability of emulsions was investigated by using differential scanning calorimetry technique. This manuscript that reports important results deserve publication. However, I have several questions and comments listed below.

What was used as the reference sample to sequester the measurement signal originating from the sample in the DSC measurements?

Authors’ response: Added in Section 2.7. in line 188. It reads: “An empty T-zero pan was utilized as a reference”.

Did the respected authors try to estimate the yield strength of the emulsions?

Authors’ response: Thanks for the suggestion. We did not calculate yield strength. Rather we have data for gel strength under linear viscoelastic region and cross-over strain for gel break down. We believe that this viscoelastic information will be useful to understand our emulsion rheology.

Can the dependencies of viscosity on water content be approximated with some semi-empirical models, for example, equations of Mooney, Krieger, and Dougherty, or Richardson?

Authors’ response: We have now addressed the modelling part of the work using a more generalized Pal model. See new section 3.2.3.

In my opinion, frequency dependencies of viscoelastic moduli should be included in the manuscript for a better understanding of the rheological behavior of the emulsions.

Authors’ response: At this time, it is not possible for us to do frequency sweep measurement. However, we have done a detailed analysis of strain sweep viscoelasticity including G’, crossover stain and tan delta. We believe it would provide a good understanding of the rheological behaviour.

The authors mentioned that the crystallization temperature of water droplets depends on droplet size. Unfortunately, the authors did not give any quantitative information about the size of aqueous droplets in emulsions, for example, average droplet size or droplet size distribution.

Authors’ response: It was not possible to measure the water droplets due to the extensive aggregation of water droplets using light scattering or image analysis. We do not have access to an NMR restricted diffusion-based droplet size determination.