Application of Ultrafiltration to Produce Sheep’s and Goat’s Whey-Based Synbiotic Kefir Products

Round 1

Reviewer 1 Report

This study focuses at the use of UF to concentrate liquid whey from ovine and caprine source, in order to develop kefir products. Overall, this is an interesting study where the main focus in on the use of different starters.  UF-concentration is performed using a 10 kDa membrane, up to a 20X volumic concentration factor. Therefore, 25L of concentrate is prepared, leaving behinf 475L of whey permeate.  This is an important environmental issue since it contains most of the lactose which is responsible for the high Biochemical Oxygen Demand (BOD) of whey (ca. 40-50 g/L).

The authors absolutely need to notify this drawback (or limitation) in their discussion/ conclusion:  UF-concentration of whey improves the use of whey proteins but it does not solve the environmental problem associated with cheese whey.

Author Response

Please see attached file.

Author Response File: Author Response.doc

Reviewer 2 Report

Title:

Application of ultrafiltration to produce sheep's and goat's whey based synbiotic kefir products.

General comments:

The paper still needs English revisions

Specific comments:

Abstract:

Why the abstract is divided into several sections? Is it the journal guidelines? Could you please make the abstract as one section with no subtitle for each part?

Background:  Membrane  filtration  technologies  are  the  best  available  tools  to  manage  dairy  13

byproducts such as cheese whey (CW) and buttermilk. These technologies allow for the selective  14

concentration of specific components of such products, namely proteins. Due to their acceptable  15

costs and ease of operation, these technologies can be applied by small/medium scale dairy plants.  16

Therefore, these companies can transform byproducts such as CW into value-added dairy products.  17

Methods:  In  the  present  work,  sheep’s and goat’s  CW were  concentrated  by  ultrafiltration  (UF)  18

envisaging  their  utilization  in  the  production  of  synbiotic  dairy  products  based  on  kefir  and  19

probiotic bacteria, with inulin. For each type of whey, four formulations based on a commercial kefir  20

starter or a traditional kefir, without or with the addition of a probiotic culture, were produced. All  21

samples were evaluated regarding their physicochemical, microbiological and sensory properties.  22

Results: The UF operation performed with a pilot plant allowed to conclude that this process can be  23

applied even in dairy plants processing ca.500 L/milk/day envisaging the production of liquid whey  24

concentrates  (LWCs)  that  can  be  used  as  the  main  ingredient  of  the  formulations.  The  25

physicochemical characteristics of the kefir samples produced reflect the composition of the LWCs.  26

Sheep’s and goat’s products presented high levels of protein (>15% for sheep’s and >7.5% for goat´s  27

products). The fat content of sheep’s products was significantly lower than that of goat’s products.  28

All samples presented counts of lactic acid bacteria higher than log 7 CFU/mL, indicating the good  29

adaptation of microorganisms to the matrixes. The sensory evaluation indicated that further work  30

must be undertaken in order to improve the acceptability of the products.  31

Conclusions: It could be concluded that small/medium scale dairy plants can use UF equipment  32

with the aim to valorize sheep´s and goat´s CW through the production of dairy formulations with  33

added prebiotics and probiotics, while reducing the environmental impact of their activities.

Could you please show more date in the abstract?

Introduction:

Please extend the second paragraph in the introduction to have more info about membrane filtration, UF, and the engineering behind that and studies who worked on that before!

Material and methods:

No number should start the sentence, e.g. 500 L

Results and discussions:

Why didn’t you standardize the composition of both whey before the UF?

Table 1 shows that the protein content was not standardized in the whey of sheep and goats that’s why you have different composition in the final concentrates.

Based on that you will find different characteristics!

There are many work done on UF that were not mentioned in the paper!!

The paper needs English revisions.

Author Response

Please see attached file.

Author Response File: Author Response.doc

Round 2

Reviewer 2 Report

Thanks to the authors for applying my comments. All the best!