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Shelf stability of milk protein gels created by pressure-assisted enzymatic gelation.

L. Wang

Abstract:

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Shelf stability of milk protein gels created by pressure-assisted enzymatic gelation.
L. Wang*, C. I. Moraru. Cornell University Ithaca, NY.

Recent studies showed that high-pressure processing (HPP) provides exciting opportunities for structure formation in high concentration protein foods, with minimal impact on their overall nutritional and sensory properties. In this work, a new concept of pressure-assisted enzymatic gelation of milk protein concentrates (MPC) was applied, with the goal of further enhancing the structure and stability of pressure-induced milk protein gels, facilitating their use for the manufacture of novel dairy products. MPC powder was reconstituted to form a 12.5% (wt/wt) protein solution. Calf chymosin (45 IMCU/1000g milk) was added to the samples. Immediately after chymosin addition, the samples were treated with HPP at 600 MPa at 5�C for 3 min, followed by a shelf life study of 28 d at 4 � 0.2�C. Textural analysis and water holding capacity measurements were carried out on d 0, 7, 14, 21, and 28. The processing trials and measurements were conducted in triplicate. Statistical analyses were performed by ANOVA at a 95% confidence level. Pressurization of MPCs led to extensive protein aggregation and gel formation, in a much shorter time (3min) compared with conventional enzymatic coagulation (around 30 min). The gel hardness of MPCs with added chymosin was 297 � 61g at the beginning of storage and remained at 410 � 19 g after 7 d. The water holding capacity remained at 91 � 1% during refrigerated storage. Without chymosin, HPP-created MPC gels had a lower gel hardness value, of 227 � 54g, which decreased by 5.9% to 213 � 10 g during refrigerated storage. However, the water holding capacity remained at 100% during 28 d of refrigerated storage. These results clearly show that enzymatic coagulation under pressure can create gel structures that are stable during 28 d of refrigeration. These findings demonstrate that controlled, fast structural modification of high concentration protein systems can be obtained by pressure-assisted enzymatic treatment. Overall, this study provides insights into the possibility of using HPP for the development of milk-protein based products with novel structures and extended shelf life.

Keywords: high-pressure processing (HPP), milk protein gels, shelf stability.

Biography: Linran Wang was born in Chengdu, China. She earned a B.S degree in Food Science with Honors in research from Cornell University, during which time she conducted a shelf life study on microfiltration treated milk under the supervision of Dr. Carmen I. Moraru. After completion of her B.S degree, Linran continued her research as a Ph.D. student in Dr. Moraru's lab. Linran studies applications of nonthermal processing technologies on traditional dairy foods. She hopes that her work can bridge together scientists from the dairy foods community and scientists working on nonthermal processing techniques, with HPP being one of them.