Effect of Various Antioxidants on the Oxidative Stability of Acid and Alkali Solubilized Muscle Protein Isolates

Abstract

Protein isolates prepared from cod (Gadus morhua) myofibrillar proteins using acid or alkali solubilization are susceptible to oxidative rancidity. Oxidation could be delayed by the exogenous addition of antioxidants. The objective of this research was to compare the efficacy of antioxidants such as d-tocopherol, butylated hydroxyanisole (BHA) and propyl gallate, to inhibit oxidation in acid-and alkali-solubilized cod protein isolates. Oxidation was catalyzed using cod hemolysate. Oxidation of lipids was monitored by the measurement of thiobarbituric acid reactive substances and painty odor. Results showed that protein isolates prepared using the acid process was significantly (P < 0.05) more susceptible to lipid oxidation than alkalisolubilized protein isolates. Regardless of pH treatments, the efficacy of various antioxidants decreased in the order propyl gallate > BHA > d-tocopherol. PRACTICAL APPLICATIONSResearch has shown that seafood available for human consumption is rapidly getting depleted and that many fish species may become extinct in the next half-century or so. Acid and alkali solubilization methods are recent but well-known techniques used for preparing protein isolates from under-utilized aquatic species and the by-products of seafood industry. Although numerous researchers have studied the use of acid and alkali processes on several sources * Corresponding author. S. Raghavan, 163 of seafood, almost no research has been done on the use of antioxidants to protect protein isolates from lipid oxidation. In our research, we have studied the effect of various antioxidants on the oxidative stability of acid-and alkalisolubilized fish myofibrillar proteins. The results from this work will enable the seafood industry to properly identify the process and the type of antioxidants required for making muscle food products with increased oxidative stability. 164 S. RAGHAVAN and H.O. HULTIN 165 ACID-AND ALKALI-SOLUBILIZED MUSCLE PROTEIN ISOLATES

Structural, functional, and sensorial properties of protein isolate produced from salmon, cod, and herring by-products

“…However, herring protein powder showed high intensity of lipid oxidation related odor and flavor and the highest intensities of dried fish and fish oil. The lipid oxidation odor and flavor could result from oxidation taking place in the herring samples during the actual protein isolation (Undeland et al, 2005) because of the substantially higher amount of heme-protiens, wellknown pro-oxidants which can even be further activated during the pH-shift process (Raghavan and Hultin 2009). Extra precautions are thus required to prevent lipid oxidation during pH-shift processing of byproducts from dark muscle and fatty fish-like herring.…”

The Acid and Alkaline Solubilization Process for the Isolation of Muscle Proteins: State of the Art

“…In a recent study by Raghavan and Hultin (2008), the oxidative stability of acid-and alkali-produced cod proteins in the presence of exogenously added Hb (6 μM) was studied during ice storage. Attempts to inhibit such oxidation with 300 ppm δ-tocopherol, 200 ppm BHA, and 200 ppm propyl gallate were also done.…”

Enzymatic propyl gallate synthesis in solvent-free system: Optimization by response surface methodology

“…Several studies have demonstrated the benefits of PG as an antioxidant [6,9,10], as a chemopreventive agent [11,12] and as an anti-inflammatory agent [13]. For instance, PG is an efficient protector of liver cells from lipid peroxidation by oxygen radicals [6].…”