Study On Chemical Ingredients, Juice Processing Technology And Volatile Profile Of Pyrus Pyrifolia

Ingredients of nutrition of five cultivars of pear from Lanshan country, Hunan, were studied. Seven kinds of mineral element were analysed by atomic absorption spectrometry. And amino acid was determined by HPLC ACCQ. Tag, others were carried out by national standards analytical methods. The results showed that: the range of water content, 86. 2⁹0.4 %; the total sugar content, 5.00⁷.49%; protein, 0.11⁰.22%; Vc, 4.4⁷.2 (mg/100g) and the total acid content, 0. 14⁰. 34%. With respect to the macro-element of content, Kalium (Fengshui pear, 239.1mg/100g) ranks first, Magnesium (cuiguan pear, 21.88mg/100g) ranks second. As to the trace elements, the higher of those are zinc (11. 5mg/100g, Cuiguan pear), iron (2.75 mg/lOOg, Qingxiang pear). The 16¹7 kinds of amino acid were found in the samples. Among of them, 6⁷ kinds were essential amino acids.The technology of clarification and protect color of clear Pyrus pyrifolia juice and the stability of the turbid juice were studied. The results showed that 0. 4g · kg^-1 Vc could keep the color of clarified juice as straw yellow; juice extraction was improved from 72.6% to 80. 7% under the incubation of pectinase at the condition of 50°C, 2. 5,g. kg"1, 90min. The dosage of pectinase is the key factor of juice extraction. In the processing of the turbid juice extraction, the color of the pear juice was preserved and the loss of Vc was reduced by using vacuum degassing before homogenization. Stabilizer and homogenization could improve stability of the turbid pear juice. The optimum concentration of stabilizer was 0.20% (CMC-Na), or the mixture of xanthan gum and CMC-Na was 0. 05% and 0. 15%, respectively. Homogenization was carried out at 24000 r/min for 4 min. The sterilization was performed at 121℃ for 30s.The volatile profile of pear juices was determined by using solid phase microextraction (SPME) coupled with GC-MS. The optimum experiment parameters for SPME were: amount of juice 7 mL, extraction time 45min, extraction temperature 50°C, NaCl concentration 25g/dL. A total of 30 volatile components were identified from the four juice samples. Esters were the dominant constituents in all of the samples. The important compounds which contribute to pear aroma were: ethyl hexanoate, ethyl butanoate, hexyl acetate, hexyl alcohol, hexanone, d- limonene, α — terpinolene.