Antioxidant Characteristics Evaluation of Ziziphus Jujuba Fruit Extract Obtained by Ohmic Heating Method in Confectionery Cream

One of the most common problems in dairy products, which are rich in unsaturated fatty acids is lipid oxidation. This phenomenon can occur during processing, distribution and storage steps and leads to loss of valuable nutrients, discoloration and unpleasant flavor. Many medical studies confirmed harms and side effects of synthetic additives on human health. Accordingly, extracts and essential oils obtained from medicinal plants have received more attention as natural antioxidants in recent years. The use of phenols in these products has long been supported not only as natural antioxidants but also to produce new tasty and colorful natural products. Therefore, evaluating the function of jujube extract in a dairy emulsion system which is susceptible to oxidation could prove the ability of this fruit to help in processing and enhance the oxidative stability of food products.

At the beginning of this research, ohmic heating system equipped with a temperature regulator was designed and made. This system (a new and green heating technology) was applied in optimal conditions in order to obtain Jujube extract as a rich source of bioactive compounds and in the following, this extract was added to confectionery cream as a natural antioxidant. Confectionery cream samples were produced at the industrial pilot scale according to optimized formulation in the research and development unit of Zarrin Ghazal company. Formulations were contained of jujube extract at the level of 0.5 and 2.5%, synthetic antioxidant butyl hydroxytoluene (BHT) and BHT-extract combination. Assessment of oxidative stability was conducted by measuring peroxide, p-anisidine and total oxidation values during the storage period under different conditions such as darkness and ultraviolet light radiation.

The results showed that cream formulations containing BHT-extract and Jujube extract at the level of 2.5% had the lowest values of total oxidation which represented the highest free radicals inhibitory effect. Evaluation of anisidine number in the absence of ultraviolet light revealed that the growth rate of secondary products oxidation in samples containing jujube extract and BHT separately was significantly lower than the growth rate in control sample. While in the presence of ultraviolet light, only the growth rate of anisidine number of cream containing Jujube extract sample at the level of 0.5% was significantly different in comparison to control sample. However, It was observed that antioxidants in different concentrations and environmental conditions can act as proxidants. The inhibitory mechanism of antioxidants against photo-oxidation was similar to that in samples which were not exposed to light. Therefore, Jujube extract can act as an antioxidant against spontaneous and photo-oxidation. It also demonstrated antioxidant properties in confectionery cream emulsion and BHT-extract combination was affirmed to has synergistic effects against oxidation, due to different functions of polar and non-polar antioxidants. According to the sensory evaluation results, the highest general acceptance score was related to the cream sample containing 0.5% of Jujube extract. The positive effect of this extract on flavor, aroma, texture and desired mouthfeel was determined with a significant difference compared to other samples.

Jujube extract could be used as a natural alternative to synthetic antioxidants in the food and pharmaceutical industries. However, according to the results of sensory evaluation, by increasing the percentage of these compounds a negative impact on overall product acceptance was observed. On the other hand, due to the synergistic effects of polar and non-polar antioxidants and reducing the total oxidation, partial replacement of synthetic antioxidant with natural phenolic compounds is suggested as the optimal option. .Furthermore, fortified cream prepared in the present study could be introduced as a functional food because of health-promoting properties of Jujube extract.