1035
Effect of storage temperature on the physio-chemical properties of skim milk powders treated with chelators

Wednesday, July 23, 2014
Exhibit Hall AB (Kansas City Convention Center)
Vandna Sikand , Dept. of Dairy Science, California Polytechnic State University, San Luis Obispo, CA
Phillip S Tong , Dept. of Dairy Science, California Polytechnic State University, San Luis Obispo, CA
Sean Vink , Dept. of Dairy Science, California Polytechnic State University, San Luis Obispo, CA
Soma Roy , Dept. of Statistics, California Polytechnic State University, San Luis Obispo, CA
Abstract Text:

The objectives of this study were to determine the impact of storage temperature on functional properties – solubility, opacity and heat stability compared to freshly manufactured skim milk powder (SMP) samples treated with mineral chelators. This study was conducted by adding 5, 15 and 25mM sodium citrate dihydrate (SCD), sodium polyphosphate (SPP) and disodium EDTA (DSE) to skim milk concentrate (30% total solids) and adjusting the concentrate to 6.65 pH before spray drying. One set of sample bags were stored at room temperature (22oC). The second sets of bags were kept at 37oC for three months.  The experiment was repeated twice.

Samples were tested for solubility index (SI) and reconstituted to contain 9% TS and tested for opacity by using a Hunter Lab Colorimeter. Heat stability was determined by measuring the heat coagulation time (HCT) at 140oC as the time required for visible flocculation for samples.

SI indicated high solubility of all SMP samples. However, lower values for SI were observed for samples treated with 5mM SPP and DSE (0.13 mL) as compared to samples treated with SCD (0.3mL). Furthermore, low SI values were observed with an increasing level of chelating agents regardless of chelator type. No significant difference was observed in SI of samples stored at 37oC as compared to SI tested for freshly manufactured samples. A decreased opacity (L* value) or an increase in the lightness of samples was found with increasing levels of mineral chelating salt treatment (P < 0.001).  Furthermore, lower L* values were observed in samples stored at 37oC (P < 0.001) as compared to freshly manufactured samples.  Heat stability studies showed that SMP (pH 7.0) treated with 5mM DSE or SCD chelators had higher HS (> 30 minutes) as compared to the SPP (16 minutes). Samples treated with 15mM SPP showed significantly higher HS (20 minutes) as compared to SCD or DSE treated samples. Samples showed poor HS (< 5 minutes) chelator type at 25mM concentration level. Slightly lower HCT values were observed for samples stored at 37oC (P< 0.001) as compared to freshly manufactured samples, regardless of any concentration level. The results from this study showed that storage temperature may impact the functional properties.

Keywords: SMP, Chelators, Solubility, Heat Stability

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