Flux Behaviour, Rejection and Concentration Factors, and Energy Demand during Ultrafiltration of Sweet Buttermilk

Round 1

Reviewer 1 Report

This work aimed to study the flux behaviour, selectivity, concentration factor, and energy demand in order to establish the optimal conditions during ultrafiltration of sweet buttermilk to produce ice cream. The overall experiments were well presented. I have minor comments as following:

1 What does "selectivity" mean in the abstract? Is it the composition of protein, fat, starch etc.? Probably use other words to replace "selectivity" to make it more clear to the readers. 

2. What does the "biologically active substances" mean in the abstract and conclusion? Please specify these substances. 

3. Why do the authors select the polyacrylonitrile membrane UF25-PAN? Is there specific reason? Could the authors compare this membrane with other membranes in the discussion section since this membrane is not available world widely. 

 

Author Response

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Author Response File: Author Response.pdf

Reviewer 2 Report

Utilization of buttermilk has high relevance for the dairy industry. As authors established, milk fat globule membrane has several beneficial effects on human health. In the MFGM utilization the separation and mild concentration steps have crucial importance.

For the separation/concentration of bioactive components, membrane technology is considered as a suitable technology. As authors mentioned, among the pressure driven membrane operations - considering the pressure need, rejection/separation efficiency etc.- the ultrafiltration has the highest relevance for practical use in the industry (microfiltration has lower separation efficiency, NF has high pressure demand, for instance).

The separation efficiency is determined by membrane fouling that has effect on flux behaviour and, therefore on the economy of membrane separation, and the life-time of membranes (membrane modules). Detailed analysis of permeate flux behaviour, fouling mechanisms and optimisation of process parameters of membrane separation has high relevance not just for the science, but also for the practice. Therefore, the topic of the manuscript can be interesting for the readers of Applied Sciences journal.

The manuscript has a logic structure. Key words are well defined. Introduction section summarizes well the relevance of the study. The applied methods (characterization of UF efficiency, analytical methods) are adequate and, in general, described well in the methodology section (see my comments). The manuscript contains interesting results that have practical relevances. Results are discussed with relevant references.

 

 

Comments, suggestions:

Abstract should be an ‘essence’ of the study. In my opinion, the abstract of the present manuscript is too general. Please give some more concrete establishments.

Please define clearly and highlight the novelties of the present study in the Introduction section (compared to published papers, and/or give the ‘gap in the knowledge’ clearly and in more details).

In my opinion, it should be refer to the role and effects fouling on the capacity of membrane separation (permeate flux) and energy demand in more details in the Introduction section, as well (not just in discussion part).

Please give how was the temperature of membrane filtration test selected/determined. If pasteurization is followed by UF step, it can be use higher temperature-to increase permeate flux/reduce energy demand, for example (or the operating temperature is limited by the specifics/characteristics of UF25-PAN membrane, for instance?)

It should be give the main characteristics of sweet buttermilk (section 2.1).

Please unify the units in the manuscript (see ‘330 dm3/h’ for feed flow rate in line 93, but ‘L/(m2.h)’ for permeate flux in line 17, for instance).

The permeate fluxes are very low (see Fig.2, initial permeate flux is approx.. between 10-12 litre per 1m2 membrane surface, hourly). Is it possible to use the UF process for MFGM separation/concentration in the industry?

A 'real’ optimization of process parameters of UF is missing.

Author Response

Please see the attachment

Author Response File: Author Response.pdf

Round 2

Reviewer 2 Report

The authors have revised the manuscript thoroughly according to reviewers comments and suggestions and provided detailed answers for reviewers questions. Amendments, rephrasings and corrections made the manuscript more complete and clear. The overall scientific quality of the manuscript has been improved suignificantly due to the revision. I agree and accept all modifications made by the authors.