Ph.D. Dissertation:

extraction of antimicrobial compounds from apple waste by novel extraction methods and evaluation of extract effect on the spoilage micro organisms and the shelf life on cakes

The present study was conducted with the aim of optimal use of apple peppers as agricultural residues and apple juice factories and extraction of bioactive compounds (antioxidant and antimicrobial) in three stages. In order to solve environmental problems caused by the use of organic solvents, new extraction methods based on ultrasound and infrared water were used in this research. To obtain optimal conditions for extraction of biologically active apple pods with the infra-critical water of the surface-response method using a central axial compaction scheme. In the first stage, the optimal conditions for extracting the effective compounds of the ethanolic extract of apple pulp using the ultrasonic process (sound intensity: 20, 60 and 100%; and the time of applying ultrasound: 15, 35 and 55 minutes; and temperature: 35.50 and 65 degrees Centigrade) and response surface method (central center composite design) were evaluated. The conditions of the extraction process were subcritical water method including temperature (110, 140 and 170 ° C) and process time (20, 30 and 40 min). The amount of polyphenolic compounds, DPPH free radical inhibitory activity and the extraction efficiency of dependent variables were measured. In the ultrasonic method, the amount of phenolic compounds was 74.55 mg gallic acid, the free radical gravity was 83.86%, and the extraction efficiency was 17.73 per 5 g of the initial powder. In general, the optimum conditions for extraction of ethanolic extract of apple pepper were determined by ultrasonic process on the responses by numerical and graphical optimization, ultrasound intensity of 82.38% for 35 minutes and temperature of 51.49 ° C. The optimum extraction conditions were determined in the water-infra-crystalline method to obtain an extract with maximum antioxidant strength of 170 ° C and 40 minutes. Under these conditions, the content of polyphenols, DPPH free radical inhibitory power and extraction efficiency is 487.054 mg, based on acid gallic acid, 96.56%, and 18.66% efficiency per 5 g of initial powder. In the second phase of this study, the antimicrobial effect of optimum extracts from the subcritical water process by microdilution method was evaluated on two bacteria of Staphylococcus aureus and Escherichia coli and Aspergillus niger fungus. The results of this study showed that the extract had the most effect on Staphylococcus aureus bacteria and also affected Asheria clai and Aspergillus niger. In the last step of this research, the effect of extract of apple pulp (20, 40 and 60%) was studied as a natural additive to improve the physicochemical and sensory properties of oatmeal cake compared to 0.1% potassium sulfate synthetic preservative. Based on the results, it was determined that the extract was able to control the growth of mold and yeast by retaining sensory properties in cake. The lowest mold and yeast growth after 9 days of storage in environmental conditions was observed in a sample containing 60% of the aqueous extract which was equivalent to the effect of the preservative The chemical was potassium sorbate. The results confirm the use of infrared water as a suitable method for extracting biological materials from apple pepper. Also, the results showed that instead of synthetic enhancers and preservatives, apple pulp extract can be used, which in addition to increasing the shelf-life of the product improves the physical and sensory properties of cake.

Keywords: sub critical water, ultrasound, apple, mic, cake, sensory properties, physicochemical properties