Physicochemical and sensory properties of oil cake enriched with cinnamon extract

Cakes are one of the most consumed foods in the world, and their health-oriented product is of great importance. Due to the high amount of sugar and fat in these products, efforts have always been made to produce these products with less fat and sugar (Lebesi and Tzia 2011). Due to the undesirable side effects of synthetic antioxidants such as butylated hydroxyl anisole (BHA) and butylated hydroxy toluene (BHT), natural antioxidant have recently received attention as a source of bioactive compounds such as anti-cancer and anti-mutagenic. Consumers are gradually becoming more aware of natural ingredients (Kallel et al., 2014), which has critical implications for the food industry. Many types of aromatic plants as suitable alternatives are used in food products (Kordsardouei et al., 2013). In addition to the health benefits, it has been shown that the unique functional properties of these materials can lead to improved texture, consistency, and stability in food production and storage (Jahanbakhshi and Ansari 2020). Therefore, researchers are always looking to identify, extract and purify plant compounds for their use in the food industry (Ashfaq et al., 2021). One of these medicinal plants, which is used as a spice in food worldwide, is cinnamon. It is a valuable substance with high therapeutic potential and various medicinal and industrial applications (Jumbo et al., 2014). Many studies have shown the therapeutic effects of cinnamon including its antioxidant, anti-microbial, anti-bacterial, anti-viral, anti-fungal, anti-tumor, anti-diabetic, anti-hypertensive, anti-lipemic, gastroprotective, and immune modulators effects) Hajimonfarednejad et al., 2019; Singletary 2019). In different types of food products, cinnamon is used as a flavoring agent, coloring agent, and food preservative (Saleem et al., 2015). It seems that its bioactive compounds can be suitable for use in food products, such as oil cakes. The purpose of this study was to investigate the physicochemical and sensory properties of oil cake enriched with different percentages of cinnamon extract for applications in the food industry.

Numerous researches have been done to identify suitable extraction methods with high efficiency and environment friendly. Aqueous extraction is a cheap, non-toxic, green extraction technique and a highly acceptable method for consumers (Kallel et al., 2014; González-Centeno et al., 2015). Therefore, an aqueous extraction method was used in this study. The cake samples were prepared with the sugar-dough according to the Peyghambardoust method (2010). The drying of samples was done in an oven at 45ºC for 12 hours. Then, the dried cake samples were powdered and pH, protein, fat, and carbohydrate were measured for each sample. The pH of the dried cake samples was measured by Benchtop pH Meter. The moisture content of fresh cake samples was measured by the weight method. The water activity of the cake samples was measured at 25°C using a Water Activity Meter. Protein, fat, and carbohydrate contents were determined using the Kjeldahl method, the Soxhlet extraction method, and the Lane-Eynon method, respectively. The total ash content was determined by burning the samples in a furnace at 550º C. The content of acid-insoluble was also obtained by adding 25 ml of hydrochloric acid 5N to the raw ash. Sensory evaluation of food products is necessary to test the acceptability of foods (Nakov et al., 2020). Due to the high importance of sensory evaluation in the food industry, the sensory properties of oil cake enriched with different concentrations of cinnamon extract were also investigated in this research. In the current study, a completely random design was used with five different concentrations of extract cinnamon (0.05, 0.10, 0.15, 0.20, and 0.25 % W/V) and the control sample, each with three replications. SPSS 21.0 software was used for statistical analysis, and the one-way ANOVA and Fisher's LSD post hoc test were applied to compare samples. The data were reported as mean ± standard deviation, and the significance level of the tests was p<0.05.

According to the measured variables, there was no significant difference in the pH of different samples, and this value varied from 7.41 to 7.49. The measured moisture content of the cake samples was higher than the control sample, and the results showed a significant difference between the control samples with 0.15 % and 0.25 % (p<0.05). The obtained water activity values showed that with the increase in the extract concentration, the water activity value decreased compared to the control sample. So that the highest amount of water activity belonged to the control sample. The sample containing 0.25% of the extract showed a significant difference in protein values compared to the control samples, 0.05 and 0.01 % (p<0.05). The fat percentage has decreased compared to the control sample for all samples, except for the 0.05% sample. So, this value was obtained at 13.46% and 13.03% for the control sample and the sample 0.25% extract, respectively. Also, carbohydrates decreased from 42.65 % in the control sample to 39.82 % in the 0.25 % sample. No significant difference was found in the total ash content of the samples. On the other hand, the extract percentage was directly related to the increase of acid-insoluble ash in the cake; this value increased from 0.16% for the control sample to 1.18% for the sample containing 0.25% extract. The results of the sensory evaluation showed that the color of the samples improved with the increase in the extract percentage. There was a significant difference between the control and other samples in the odor score. The highest and lowest taste scores were observed in samples containing 0.20% and 0.05% of the extract, respectively. All of the samples, compared to the control cake, had higher scores in the texture. The overall acceptability for the control sample showed a significant difference (p<0.05) compared to the 0.15, 0.20, and 0.25 % samples, so the best scores were related to the samples of 0.20%, and 0.25% extracts. In general, adding cinnamon extract improved the sensory characteristics of the oil cake.

Based on the investigated physicochemical and sensory properties, it seems that there is a possibility of enriching aqueous cinnamon extract into oil cake as a functional food ingredient in the food industry.