The incorporation of preheated whey protein isolate and pectin complexes as natural emulsifiers and stabilizers in processed cheddar cheese sauce
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Processed products that contain no artificial ingredients are becoming a new trend and there is a need to develop emulsifiers and stabilizers for clean label application. Whey protein isolate (WPI) has excellent emulsifying properties and has been a widely used natural emulsifier in food application. However, WPI does not provide long term stability and its functions are minimized when the pH is at or near its isoelectric point (pI). At pI, protein has no net charge and therefore, protein-stabilized emulsions become unstable. In order to improve the emulsification properties of WPI, the incorporation of additional ingredients such as polysaccharides are needed. Previous studies showed that heated WPI and pectin soluble complexes (HCPX) can be developed to have improved emulsification and stabilization properties in model emulsions. In this study, the effects of HCPX as emulsifier and stabilizer in cheese sauce were investigated. HCPX were made by heated 3% (w/w) WPI with 0.45% or 0.6% pectin at pH 5.5 or 6.2. All model cheese sauces were prepared from cheddar cheese (25% w/w), vegetable oil (7.7% w/w), and corn starch (3% w/w). The effects of HCPX (1.5% protein from HCPX in the final sauces) on cheese properties were compared with 0.3% pectin (PT), heated whey protein isolate (HWPI), HWPI with added 0.3% pectin (HWPI + PT), emulsifier (ES) (0.3% w/w), and the controlled formulation (CRT) with only starch. Cheese sauces were cooked using a multifunctional laboratory-scale cooker. Properties of the freshly made cheese sauces were characterized by dynamic rheology and fat droplet size analysis. Stability of the sauces was determined by measuring droplet size and syneresis after three-week storage. Five samples that showed a significant difference in storage stability were selected for freeze/thaw stability and microstructural analysis. As shown by the rheological properties results, cheese sauces containing HWPI and PT had increased solid-like behavior (e.g., elastic modulus or G']) compared to CRT while the sample with ES had decreased G'. Among samples with pectin, those made with HWPI + pectin (HWPI + PT) and HCPX were firmer (e.g., higher G') compared to HWPI or pectin alone. Sauces with the HCPX formed with 0.6% pectin at pH 6.2 exhibited the largest elastic property. Mean droplet particle sizes for CRT and PT were significantly larger (p<0.05) compared to the other treatments. After 3-week storage, CRT and ES samples had the largest syneresis. Adding pectin and/or HWPI alone led to reduced syneresis; however, samples with the mixtures at higher pectin concentration were most stable. When subjected to freeze/thaw cycle, all cheese sauces containing pectin were significantly more stable than CRT with the most stable samples being HCPX-0.6-6.2 and HWPI+PT. Finally, microstructural analysis revealed that sauces containing HCPX-0.6-5.5 and HCPX-0.6-6.2 had the smallest droplet sizes which were in agreement with other results. In conclusion, HCPX can be applied to foods such as cheese sauce and replace synthetic emulsifiers and stabilizers. Pectin concentration and pH during HCPX formation could affect the function of the HCPX in the resulting cheese sauces. HCPX can be utilized in various oil in water food emulsions.
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