Document Type

Thesis - Open Access

Award Date

2019

Degree Name

Master of Science (MS)

Department / School

Dairy Science

First Advisor

Lloyd E. Metzger

Keywords

Functional characteristics, High concentrated micellar casein, Process cheese products, Shelf-life

Abstract

Micellar casein is a high-protein ingredient that can be used in process cheese products (PCP) formulations. PCP is a dairy food prepared by blending dairy ingredients (such as natural cheese, protein concentrates, butter, non-fat dry milk NFDM, whey powder, and permeate) with nondairy ingredients (such as sodium chloride, water, emulsifying salts, color, and flavors) and then heating the mixture with a continuous agitation to produce a homogeneous product with an extended shelf-life. The first objective of this study was to produce a highly concentrated micellar casein (HC-MC) and evaluate its storage stability. Skim milk was pasteurized at 76°C for 16 sec and kept at ≤4°C until the following day. The skim milk was heated to 50°C using a plate heat exchanger and microfiltered (MF) with graded permeability (GP) ceramic MF membrane system (0.1μm) in a continuous feed-and-bleed mode (flux of 71.43 L/m2 per hour) using a 3× concentration factor (CF). Subsequently, the retentate of the first stage was diluted 2× with soft-water (2 kg of water: 1kg of retentate) and again MF at 50°C using a 3× CF. The retentate of the second stage was then cooled to 4°C and stored overnight. The following day, the retentate was heated to 63°C and MF in recirculationmode (retentate recirculated to system balance tank) until total solid (TS) was approximately 22% (wt/wt). Consequently, the MF system temperature was increased to 74°C and MF continued until permeate flux reached less than 3 L/m2 per hour. The HCMC was then divided into three aliquots of approximately 10 kg each. The first portion was a control, while 1% sodium chloride added to the second portion (T1) and 1% sodium chloride + 1% sodium citrate was added to the third portion (T2). Treated HCMC retentates were transferred at 74°C to sterilized vials and stored at 4°C to study the storage stability every 30 d. This trial was repeated three times using separate lots of skim milk. The HC-MC at d = 0 (immediately after manufacturing) contained average 25.41% TS, 21.65% true protein (TP), 0.09% nonprotein nitrogen (NPN), and 0.55% noncasein nitrogen (NCN). No difference (P > 0.05) was detected in the composition of control, T1, and T2 HC-MC during the 60 d of storage at 4°C. However, the NCN content increased significantly (P < 0.05) from 0.55 to 0.76%, 0.55 to 0.82% and 0.55 to 0.94% in control, T1, and T2, respectively, during the 60 d of storage at 4°C. Mean aerobic bacterial count in control, T1, and T2 at 0 d was 2.6, 2.5 and 2.8 log cfu/mL, respectively, and increased significantly (P < 0.05) to 4.3, 4.06 and 5.3 log cfu/mL, respectively, after 60 d storage at 4°C. Coliform, yeast, and mold were not detected during the 60 d of storage. This study determined that HC-MC with > 25%TS and > 95% casein as % of TP can be manufactured using ceramic MF membranes and could be stored up to 60 d at 4°C with no significant changes in the composition. The second objective of this study was to utilize the high concentrated micellar casein (HC-MC) as an ingredient in making PCP and examine the effect of its storage on the functionality of PCP. The functionality of PCP was measured by determining the cooked apparent viscosity by using the rapid visco analyzer (RVA), hardness by using texture profile analysis (TPA), and melting temperature by using dynamic stress rheometer (DSR). Three treatments of HC-MC (Control= HC-MC; T1= HC-MC + 1% sodium chloride; T2= HC-MC+ 1% sodium chloride and 1% sodium citrate) were examined for the shelf-life at 0, 30, and 60 d. A 300 gm batch of each formula was prepared by mixing all ingredients (aged Cheddar cheese, HC-MC, water, unsalted Butter, deproteinized whey, sodium phosphate dibasic, salt, and sodium citrate) in a kitechenaid at room temperature for 30 min to get a homogenous paste. A 25gm sample of the paste was then weighed in a canister and tempered at 38°C for 15min. The PCP canisters were cooked in the RVA for 4 min at 90°C. The stirring speed was 1000 rpm for the first 2 min and 160 rpm for the last 2 min. Once the PCP was cooked, it was filled in molds and kept to the next day for further analysis. This trial was repeated three times using three separate batches of HC-MC at 0, 30, and 60 d of storage. Significant differences (P< 0.05) were detected between treatments in the pH and moisture content of PCP. Also, the functionality of PCP was affected (P0.05) was found in the functionality of PCP during the shelf-life of HC-MC at 0, 30, and 60 d. Overall, the addition of sodium chloride and sodium citrate to HC-MC during the shelf-life improved the melt characteristics of PCP.

Library of Congress Subject Headings

Process cheese -- Analysis.
Process cheese -- Storage.
Casein.
Micelles.
Milk proteins.

Format

application/pdf

Number of Pages

140

Publisher

South Dakota State University

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Rights Statement

In Copyright