Research On Storage And Processing Technology Of U.S. Pecan (Carya Illinoensisk Koch.)

Pecan is one of the important tree nuts oil resource in our country at present. The fat content of pecan kernel is more than 70%, and 90% of the fat is unsaturated fatty acid; protein content is up to 22.5%, which contains 18 kinds of amino acids. Therefore, pecan has a high nutritional value. Although the consumption of pecans has a long history in China, all aspects of their research are still in lacking. With the development of economic and the improvement of the people’s awareness of health care, the demand for pecans which contain higher nutritional value is increasing. So to research and utilize the pecan is necessary and urgent.In this study, the U.S. pecans were packed in polypropylene and nano packages, respectively, then placed at room temperature (20℃) and refrigerator (5℃), and stored for 180 days. The storage lasted 180 days and the economic characters and physiological index of pecans were measured every 30 days. The results showed that in the the same package, low temperature storage was helpful to delay the pecan kernel in the decline of soluble protein and fat, and inhibit the rancidity of fat. At the end of the cold storage, the pecan both in nano package and polypropylene package, still had the good eating quality. Under the same temperature condition, the effect of preservation of nano packaging was better than that of polypropylene packaging. Pecans with nano package and stored in low temperature kept the best quality of nuts.We investigated the effect of adding different contents of salt and vanilla on pecan quality to process pecans was investigated. To get good pepper salt taste, the adding content of salt was 10%, while the adding content of vanilla was 1.5% to process creamy pecans. Optimum condition of pecans food processing was that pecans were pre-cooked for 6 min under 80 ℃ and dried for 45 min under 80 ℃,then stir fried under 1500 W. The pecan products were dark red and crispy with roasted aromas. The moisture content of product was 3.4%, and protein content was 9.82%, fat content was 66.57%.Total number of bacteria was less than 79 cfu/g, coliform bacteria and pathogenic bacteria were not detected.We studied the effect of different concentrations of NaOH solution and heat time on removing walnut peel and the effect of citric acid and. sodium sulfite on walnut color protect. The optimum process conditions of the pecan oil was as follows:0.5% NaOH solution under 100℃ heat for 3 min and then rinse with tap water to remove skin; using 1.0 g/L citric acid+1.0 g/L sodium sulfite to color protect and then under 65 ℃ dry for 60 min; using secondary classification method to extract the pecan oil hydraulic press, squeezing pressure of 10-20 MPa for the first time, the second squeezing pressure ascension is 35-45 MPa. The pecan oil was up to national standard of edible oil.The walnut cake removed some oil after the hydraulic press method was processed into skim fat walnut powder by spray drying method. The powder was evenly distributed, also has high solubility and good dispersion, and less energy loss. The powder was obtained by the condition that the homogenization pressure was 40MPa, solid-liquid ratio was 1:9, and the inlet temperature was 180℃. Eventually the powder was up to national standards.