Document Type

Dissertation - Open Access

Award Date

2020

Degree Name

Doctor of Philosophy (PhD)

Department / School

Dairy Science

First Advisor

Lloyd Metzger

Keywords

Greek yogurt acid whey, Lactose crystallization, Nanofiltration, Permeate, Soluble soybean polysaccharide, Spray drying

Abstract

Growth of higher protein dairy products and ingredients such as cheese, Greek yogurt, whey protein concentrates, and milk protein concentrates is limited by the amount of co-product generated and the ability to process them into value added ingredients. Finding value for all the co-products will help dairy industry to meet the growing demand for dairy protein products and ingredients. Commercial scale evaluation of new technologies for improving lactose crystallization and drying ability of Greek yogurt acid whey will help dairy industry to better utilize different dairy co-products. Commercially, lactose is manufactured from concentrated permeate by cooling and separating α-lactose monohydrate crystals. Factors that impact crystallization of lactose during cooling will influence the yield of lactose. Caking and powder stickiness are major challenges during drying of Greek yogurt acid whey or Greek acid whey (GAW), because of high acidity, high mineral concentration, and relatively low protein content in it. The first objective of this study was to evaluate commercial feasibility of using Soluble Soybean Polysaccharide (SSPS) to improve lactose recovery during manufacture of lactose from permeate. Previous research has demonstrated that lactose crystallization could be modified by using SSPS in pure lactose solutions. However, commercial lactose is typically manufactured by crystallization of concentrated permeate (CP). A laboratory scale crystallization set up with parallel crystallizers was utilized to conduct control and treatment experiments simultaneously. Lactose recovery with 0.1% SSPS addition was significantly (P < 0.05) higher (76.31%) as compared to the control (71.33%). Out of the total SSPS added to the treatment solution, 79.82% was recovered into the wash water. The findings of this study suggest potential feasibility of SSPS for enhancing lactose crystallization during lactose manufacture from concentrated permeate. The objective of the second study was to evaluate commercial feasibility of using SSPS to improve the drying ability and powder characteristics of GAW. The composition of GAW is considerably different from that of cheese whey making it difficult to process into powder ingredients. The high lactic acid and mineral content in GAW delays lactose crystallization which causes stickiness during spray drying and caking during storage of the powder. The first study had shown that soluble soybean polysaccharide (SSPS) can enhance lactose crystallization in concentrated permeate. However, the effect of SSPS on the crystallization of lactose in concentrated GAW has not been evaluated. GAW obtained from a Greek yogurt manufacturer was vacuum concentrated to 56% total solids (30% Lactose) and crystallized using a laboratory scale crystallization tank. After crystallization, the concentrate was spray dried using a pilot scale NIRO dryer. GAW powder yield (51.87%) with 0.1% SSPS addition was significantly (P < 0.05) higher compared to that of GAW without SSPS (44.51%) and observed to be less sticky on the dryer surface. The findings of this study indicate that SSPS can enhance lactose crystallization in concentrated GAW during crystallization, reduce the sticking of the caking of the GAW powder. The objective of the third study was to evaluate the feasibility of partial demineralization and deacidification of GAW by nanofiltration (NF) to improve the drying ability and powder characteristics of GAW. Greek yogurt acid whey (GAW) contains high concentrations of lactic acid (LA) and minerals as compared to cheese whey. The LA and the minerals, particularly the Calcium (Ca) in GAW cause stickiness during spray drying, thus limiting the processing and utilization of GAW. Nanofiltration (NF) has been in use to for partial removal of minerals from cheese whey and milk to produce high value-added dairy ingredients. Similarly, NF can potentially be applied for partial demineralization and deacidification of GAW to improve spray drying and powder properties. By NF processing, the lactic acid and total ash concentrations were reduced significantly (P < 0.05) by 34.3±0.2 and 37.8±0.7, respectively. The reduction of monovalent ions, i.e., sodium and potassium were observed to be higher (66% and 62%) than that of calcium (41%). GAW-NFR powder yield (56.35%) was significantly (P < 0.05) higher compared to that of GAW (44.51%) and observed to be less sticky on the dryer surface. The findings of this study indicate that partial demineralization and deacidification of GAW using NF can improve the spray drying characteristics of the GAW powder. The objective of the final study was to evaluate the effect of addition of SSPS to NFR-GAW on the drying characteristics of the GAW. In this study, the yield, and drying characteristics of GAW with and without 0.1% SSPS were compared. There was no significant (P > 0.05) difference observed between the yields of GAW-NFR (56.35%) xvi and GAW-NFR with SSPS addition (58.24%). However, the yield of NFR-GAW (56.35%) was significantly (P < 0.05) higher than that of GAW with SSPS addition (51.87%). From this study it can be concluded that there may not be any additional advantage in addition of SSPS to NFR-GAW in improving the spray drying characteristics of GAW.

Library of Congress Subject Headings

Dairy processing -- By-products.
Whey.
Lactose.
Greek yogurt.
Spray drying.
Polysaccharides.

Format

application/pdf

Number of Pages

152

Publisher

South Dakota State University

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Rights Statement

In Copyright