Identifying natural products for improving shelf life of mayonnaise

Abstract

Mayonnaise, is susceptible to oxidation resulting in quality deterioration and the formation of undesirable components such as free radicals and reactive aldehydes. A better understanding of the factors affecting lipid oxidation and ways of retarding oxidation in mayonnaise is essential to improve the shelf life of mayonnaise.Eliminating possible factors, which will reduce the induction period and hasten rancidity, can increase the shelf life of mayonnaise but one of the most effective means of retarding lipid oxidation in mayonnaise is to incorporate antioxidants. Due to the negative effects and perceptions of synthetic antioxidants, there has been a growing interest in using natural antioxidants in food products. Recent studies showed that incorporation of natural antioxidants in mayonnaise could increase its oxidative stability. However, natural antioxidants may exert a negative effect on sensory properties and further studies are needed to identify and overcome this problem.The aim of this project was to study the efficacy of natural antioxidants in inhibiting lipid oxidation in mayonnaise.The evolution of volatile oxidation compounds (VOxCs) in mayonnaise stored at varying temperatures for 92 days was investigated using static headspace extraction and separation by two-dimensional gas chromatography/time-of-flight mass spectrometry. Considerable differences in the headspace composition of samples stored at 4, 25 and 38 °C were found due to the different oxidation levels reached. The content of hexanal in mayonnaise at 1-5 days of storage at 38 °C could be used to predict the corresponding compound in mayonnaise at 1-62 days of storage at 25 °C. Some volatile compounds were identified that could be a useful indicator of lipid oxidation of the sunflower oil in the mayonnaise, and by using an antioxidant to reduce these compounds a good oxidative stability could be reached.Interpreting the activity of antioxidants has been difficult due to the complex effect of lipid oxidation conditions and systems. Lipid oxidation process and effect of Butylated hydroxy anisole (BHA) was evaluated in sunflower oil and mayonnaise. The rate of lipid oxidation was higher in mayonnaise compared to bulk oil that could be due to the high surface area of oil that increases lipid interactions with aqueous phase pro-oxidants. BHA, a non-polar antioxidant was more effective in mayonnaise than oil. Differences seen in the efficacy of BHA in oil and mayonnaise could be explained by its affinity towards oil-water interface in mayonnaise. Therefore, the matrix plays an important role on the antioxidant efficacy.The antioxidant capacity of five natural antioxidants (green tea extract (GTE), tocopherols (TOCs), rosemary extract containing 2.7% carnosic acid (CA, REW), oil-soluble rosemary extract containing 5.2% CA (REO) and lemon myrtle (LEM)) was evaluated in vitro and in situ and compared to BHA. The antioxidant capacity was determined by measuring ferric reducing antioxidant power (FRAP) and free radical scavenging activity (ABTS). BHA showed the highest antioxidant capacity and was stable during storage of mayonnaise. GTE and TOCs had the highest antioxidant capacity among natural antioxidants but their activity decreased during storage of mayonnaise. Although REO had higher CA, it exhibited similar ABTS and FRAP activity to REW.The antioxidative efficiency of hydrophilic GTE (500 mg/kg oil), lipophilic TOC 500 (mg/kg oil), and a green tea/tocopherol mixture (GTT) in mayonnaise was investigated by measuring hydroperoxide concentration, VOxCs, colour and sensory properties, during 60 days of storage at 38 °C. Although, GTE and TOC had high antioxidant capacity in vitro and in situ they acted as pro-oxidants in mayonnaise. The pro-oxidative effect of GTE could be due to partitioning of hydrophilic tea catechins in the water phase of the emulsion and becoming less protective and/or reducing transition metals to their catalytically active state. The combination of GTE with TOC improved the antioxidant activity compared to the individual extracts that could be due to reduction of the TOC radicals by the water-soluble reductant in GTE or reduction of the lipophilic radicals. Sensory properties showed that GTE promoted the development of unpleasant fishy and rancid aroma. Partial least square analysis elucidated the predictive ability of VOxCs for sensory terms.The antioxidant effects of TOC, LEM, REW, REO, BHA and the combination of TOC with LEM (L+T) and water-soluble rosemary extract (R+T) during storage of mayonnaise at 38 °C for 60 days were assessed. The hydroperoxides and VOxCs, colour and sensory properties were measured, and the results were compared to samples without any additive (CON). All the natural antioxidants inhibited lipid oxidation as well as BHA except REO. However, the sensory properties of LEM and REW were inferior compared to TOC and BHA. Irrespective of CA content and solubility, REW showed significantly higher antioxidant activity compared to REO in mayonnaise. A combination of TOC with LEM and REW did not exert a tendency for improving the activity of each individual antioxidant. Thus, TOC (1000 mg/kg oil) can be recommended for the food industry as a substitute for the synthetic antioxidant usually used in mayonnaise