Progress 10/01/05 to 09/30/08
Outputs
OUTPUTS: The technical knowledge developed in this phase of the project to date in this project was incorporated in a presentation at a national conference and a research paper that has been submitted for publication. This will help disseminate the results of the project widely, both to academic researchers and to the Food Industry. This project had also an educational impact, since a graduate student is pursuing his PhD degree as part of the project, another one finalized her MS degree, and an undergraduate student gained significant research experience as part of a Summer Scholars Program. PARTICIPANTS: Carmen I. Moraru - PI, Mila Wihodo - MS student, Cosmin M. Beliciu - PhD student, Kellie Grant - summer scholar TARGET AUDIENCES: The results of this work are expected to directly impact the Food Industry, by providing technical information that would allow the development which will be able to design casein and / or soy protein films with unique characteristics and functionality. Such films could be primarily used for the manufacture of biodegradable and even edible packaging materials. PROJECT MODIFICATIONS: Not relevant to this project.
Impacts
Based on preliminary observations from the previous phases of the project, in the past year we focused on exploring the ability of soy proteins, casein and their mixtures to form edible biofilms that could have a wide range of applications in the food industry. Native micellar casein (MCN) and soy protein (SP) powders were used to prepare both individual protein solutions and mixtures with 1:1 SP:MCN ratio. In order to select the conditions for preparing the film-forming solution, the film properties of films prepared from un-heated solution, as well as protein solutions heated at 40, 80 and 90 deg C for 15 min were compared. Films were prepared by casting and their mechanical properties (tensile strength and % elongation), microstructure and moisture barrier properties were evaluated. For soy proteins, tensile strength increased with increasing temperature up to 80 deg C, but at 90 deg C smooth films could not be obtained because of the extensive foaming that occurred in the soy proteins solution. These results indicate the formation of covalent bonds in the soy protein solutions during heating up to 80 deg C. For the casein films, films made from protein solutions heated at higher temperatures became weaker. The partial disruption of the native micellar structure is probably responsible for the weakening of casein films after high temperature treatments. Based on these results, it was decided that films will be made from protein solutions heat treated at 40 deg C. In order to increase their mechanical strength by inducing cross-linking of the structure, the films were treated with Pulsed Light (PL). PL treatment with 15 pulses per side increased the tensile strength and percent elongation of soy protein films, although the effects were not statistically significant. PL treatment with 15 pulses per side significantly increased the percent elongation of casein films, while the effect of PL on tensile strength was not statistically significant. The higher amount of aromatic amino acids in casein as compared to soy proteins may have caused more cross-links being formed in the casein as a result of PL treatment, hence the more significant improvement of their mechanical properties. Subsequent work was performed on casein films, which exhibited higher mechanical resistance. Casein films were prepared with 5% glycerol added as a plasticizer, as well as with the addition of UV Polyethylene glycol (PEG) (200) diacrylate and PEG (400) diacrylate. PL treatment on casein films with up to 12 pulses increased surface smoothness and homogeneity, while higher levels of treatment caused some structural cracking. PL treatment did not affect water vapor permeability of the films. For casein films with PEG (400) diacrylate, a significant increase in tensile strength was observed after PL treatment. The incorporation of PEG (200) diacrylate resulted in films with a porous microstructure, with interesting photo-patterning effects observed at high level of PL treatment. The results of this work indicate the potential of PL in developing films with unique characteristics and functionality.
Publications
- Wihodo M. and Moraru C. I. 2008. Use of Pulsed Light curing to enhance the physical properties of protein films. Annual Meeting of IFT, New Orleans, July 2008
- Wihodo M. and Moraru C.I. 2008. Effect of Pulsed Light treatment on the physical properties of casein films. Submitted to Journal of Food Engineering
|
Progress 10/01/06 to 09/30/07
Outputs
OUTPUTS: The technical knowledge developed to date in this project was incorporated in a poster presentation at a national conference, and is expected to also be incorporated in minimum two research papers that will be soon submitted for publication. This will help disseminate the results of the project widely, both to academic researchers and to the Food Industry. This project had also an educational impact, since a graduate student is pursuing his PhD as part of the project, and an undergraduate student gained significant research experience as part of a Summer Scholar Program.
PARTICIPANTS: Carmen I. Moraru - Principal Investigator Cosmin M. Beliciu - PhD student Stephanie Sajuti - Senior, Summer Scholar
TARGET AUDIENCES: The results of this work are expected to directly impact the Food Industry, which will be able to design of new foods or ingredients based on the understanding of the intermolecular interactions between milk and soy proteins. The knowledge developed in this work can be used as a base for the development of soy/dairy products with unique textural properties and a healthy image, which is expected to ultimately benefit all consumers.
Impacts
This phase of the project focused on elucidating the occurrence and nature of heat-induced interactions between casein and soy proteins. Native micellar casein (MCN) and soy protein (SP) powders were used to prepare both individual protein solutions and mixtures with 1:1 SP:MCN ratio. The protein solutions were heat treated for 15min, both under denaturing and non-denaturing conditions for the SP (40C, 60C and 95C), cooled to 25C and their rheological properties determined using an ARES rheometer. The nature of intermolecular interactions was assessed with a differential solubilization method, using three buffers: B1 (0.35 M phosphate); B2 (B1 + 8M urea); B3 (B2 + 0.1M sodium sulphite). B1 dissolves readily soluble protein molecules, B2 dissociates physical interactions, while B3 cleaves covalent bonds. Buffer solutions were adjusted to 1ug/mL protein and centrifuged 1h at 5000g. The protein in the supernatant was analyzed using the BIORAD-RCDC assay. The higher amount
of casein solubilized in B2 relative to B1 and upon heating is justified by the role of hydrophobic bonds in the casein micelle's structure. Less SP was solubilized in B2 and B3 than in B1, at all temperatures, which requires further investigation. Both covalent bonds (prevalent) and physical interactions were identified in the mixtures, especially at higher temperatures, which explains the significant increase in heat treated mixtures' yield stress. The results of the study suggest that although covalent bonding is induced by high temperature treatments in the concentrated MCN-SP mixtures, they do not occur between soy proteins and casein micelles, but only between SP fractions. From a rheological point of view, the semi-dilute mixtures proved to be the most interesting, since heat treatments largely impacted the flow properties, covering a range of behaviors from a non-Newtonian "physical gel" (below 70C) to a Newtonian fluid (above 80C). The knowledge developed in this work can be
used as a base for the development of soy/dairy products with unique textural properties and a healthy image. These results advance the understanding of the intermolecular interactions between two important classes of food proteins, facilitating the design of new foods or ingredients.
Publications
- Beliciu C. M., Sajuti S., and Moraru C.I. 2007. Physical and chemical characterization of heat-induced interactions between micellar casein and soy proteins. Book of abstracts of the Annual Meeting of the Institute of Food Technologists, Chicago, IL, July 2007
|
Progress 01/01/06 to 12/31/06
Outputs
Combining milk and soy proteins could result in mixtures of unique functionality and health properties. The objective of this work was to study the compatibility between casein and soy proteins and the functionality of their mixtures. In this stage of the project, we have examined the behavior of casein, soy proteins and their mixtures as a function of temperature and concentration. Native micellar casein and soy protein isolates obtained by membrane separation were used to prepare mixtures of up to 12.5 percent concentration. The behavior of the protein mixtures during heating was evaluated using rheological analysis and particle size measurements. The apparent viscosity of soy proteins was higher than of casein, at all concentrations. The apparent viscosity of the casein dispersions was minimally affected by temperature, but increased with concentration. For soy proteins, apparent viscosity increased with concentration, but temperature had only a significant effect
for the concentrated systems. Above 7.5 percent concentration, a sudden increase in viscosity of soy protein systems occurred above 80 deg. C, which was attributed to covalent interaction by disulfide bond formation. The casein-soy protein mixtures revealed a very interesting and complex behavior. For dilute mixtures (less than 5 percent concentration) treated at temperatures below 50 deg. C, the mixtures behaved as mixed dispersions, with apparent viscosities below the values predicted based on the components' mass fraction. For the higher temperature treatments (50-80 deg. C), the dilute mixtures' apparent viscosity exceeded that of either component. The most notable aspect of the concentrated mixtures' rheological behavior was the much higher viscosity of the 10 percent concentration mixtures as compared to any of the individual or mixed systems. This was explained by the formation of a physical gel, due to the intermolecular interactions between casein and soy proteins. The
decrease in apparent viscosity with temperature indicates that hydrogen bonds play a significant role in these interactions. The flow behavior of all protein systems was also characterized. Most solutions manifested yield stress and shear thinning, but the occasional viscosity minima and dilatant behavior observed for 10 percent soy protein solution and mixture indicated a concentrated dispersion behavior. Yield stress, which is an indicator of the initial physical structure of a material, increased significantly with temperature. The sudden increase in yield stress that occurred for the mixtures treated at 90 deg. C indicated the possibility of covalent bond formation in the casein-soy protein mixtures, which needs to be further confirmed. The complex rheological behavior of the protein mixtures observed in this study could be useful in designing foods of desired texture and mouthfeel. Particularly interesting is the fact that, under given conditions, the protein mixtures did exhibit
higher viscosities than the individual components at the same concentration, which has potential practical applications for the development of soy/dairy products with unique textural properties.
Impacts
This project will generate significant information that will facilitate the development of novel highly nutritious food products based on milk proteins - soy proteins mixtures. The main outcome of the research will be represented by qualitative and quantitative rules of miscibility between milk and soy proteins, and identification of the conditions that lead to the formation of palatable milk-soy protein mixtures. In the long run, this is expected to have a positive impact on the nutrition and health of American consumers in general and NY State consumers in particular, due to the creation of new high protein-low fat foods, which have a 'clean' and healthy image and are also palatable. The NY dairy industry will benefit by potentially attracting consumers who are not big dairy consumers but will be captured by the enhanced healthy image of the newly created products. An overall increase in soy protein consumption will benefit soy producers and processors. The results
of this work are also expected to have economic impact, by helping the local and national food industry develop products that are not currently present on the market.
Publications
- Beliciu C.M. and Moraru C.I. 2006. Heat induced interactions between native micellar casein and soy proteins. Book of abstracts of the Annual Meeting of the Institute of Food Technologists, Orlando FL, June 2006
|
|