| Shatangju is a kind of cold sensitivity fruit, and it’s easy to suffer from chilling injury which causes fruit decay and loses edibleness causing economic loss in transport and sale. In order to prevent and alleviate chilling injury, it’s necessary to buid a nondestructive, safe method to detect the chilling injury shatangju.The study used the shatangju to investigate the effects of chitosan coating and change temperature treatment of chilling injury under chilling injury temperature. In the same time, the study conducted a qualitative discrimination and quantitative analysis to chilling injury shatangju by the Vis/NIR spectra technology to provide basis and consult for controlling and nondestructive examining of shatangju chilling injury. The main results were showed as following:(1) The shatangju of CK group stored at 1℃ for 20 d around sunken water-soaked spots on the fruit began to appear, the fruit became soft, lighter skin color, yellow. The optimum chitosan concentration of shatangju was 1.0%.Compared with the CK, 1.0% of chitosan concentration treatment group could significantly improve the fresh rate of shatangju, inhibit the decrease of content of soluble solid, titratable acid and Vitamin C, maintain the low content of malonaldehyde (MDA), the high activity of peroxydase (POD), catalase (CAT) and superoxide dismutase (SOD),and also delay the shatangju chilling injury symptom development. The structure of shatangju epidermis was studied with scanning electron microscope (SEM). The results showed that shatangju epidermis turned shrinking for water losing, and cracking for chilling injury, while coating with chitosan could maintain the completeness of shatangju epidermis. What’s more, it could improve the metastasis, resistance and storage quality by controling the size of shatangju epidermal stoma.(2) Change temperature treatment could relieve the low temperature coerce of shatangju in varying degrees. It could not only effectively relieve the occurrence of chilling injury, but also increase the fresh rate and maintain the low content of MDA and improve the activity of POD, CAT and SOD when the shatangju were stored at 1℃ for 7 days and then stored at 6 ℃ condition. Change temperature treatment were not very obvious by comparing the change of different treatment aroma components during the storage, but it promoted the produce of alcohols and ketones that were positive to citrus aroma. At the same time, it inhibited the increase of ester. Aroma components like D-limonene, myrcene, (1R)-(+)-pinene, L-carvone that belonged to sugar orange characteristic were higher than the CK group in the process of storage, but decanal and acrylic bornyl acetate that had citrus aroma were lower than the CK group, so it had negative effects on the shatangju aroma components when the shatangju were storaged under the early chilling temperature.(3) The Near-Infrared model which were used to distinguish chilling injury fruits from normal fruits. The DPLS model using Savitzky-Golay (SG) convolution smoothing spectral in the range of 350-1100 nm could be best, that the discriminate accuracies of calibration was 100%, and the prediction was 89.7%. It can basically meet the requirement of non-destructive testing of chilling injury shatangju. These results could indicate that near infrared diffuse reflectance spectroscopy applied to chilling injury shatangju detection is feasible.(4) PLS modle of shatangju was established by eliminating abnormal samples of concentration and preprocessing spectrum and selecting band under the temperature of the chilling injury. The model about shatangju TSS, TA, Vc and water content, correlation coefficients of calibration were respectively 0.803,0.928,0.845 and 0.854, root mean square error of calibration (RMSEC) were 0.823,0.080, 2.251 and 0.842, correlation coefficients of prediction were respectively 0.783,0.732,0.765 and 0.714, root mean square error of prediction (RMSEP) were 1.033,0.202, 3.766 and 1.407. Using NIR technology analysis shatangju quality indicators TSS, TA, Vc, water content model is feasible, and shatangju chilling fruit qualitative discriminant model used in combination, for the actual testing chilling shatangju grading lay a good foundation. |
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