冬枣（Ziziphus jujuba cv. Dongzao）是中国优良的晚熟鲜食枣品种。质地是水果的重要感官品质指标。为探究冬枣质地指标间的关系，建立冬枣质地品质评价体系，采用TMS-Touch质地多面分析法（TPA）对采自中国三大主产区的1150个冬枣果实进行8项质地指标测定，包括胶粘性、咀嚼性、内聚性、粘附性、破裂力、弹性、硬度和最大粘附力，其最佳拟合分布分别为弹性—Beta General分布，咀嚼性、胶粘性和硬度—Inv Gauss分布，粘附性和内聚性—Log Logistic分布，破裂力—Pearson分布，最大粘附力—Weibull分布。每项冬枣质地指标均可基于最佳拟合分布，用第10、30、70和90百分位点值划分为极低、低、中、高和极高五个等级。相关分析显示，冬枣质地指标间的28个相关系数中，82%的相关系数达到极显著（p<0.01）。其中，咀嚼性与弹性和胶粘性均呈极显著正相关，相关系数分别达0.8692和0.8096；粘附性与最大粘附力呈极显著负相关，相关系数为-0.7569。在胶粘性、咀嚼性、内聚性、弹性、硬度等5项冬枣质地指标中，各指标均存在关于其余4项指标的多元线性回归方程，决定系数均在0.94以上，平均拟合误差和平均预测误差均小于10%。基于因子分析建立了冬枣质地综合评价模型：Q = 0.370C₁ + 0.251C₂ + 0.241C₃ + 0.138C₄，综合得分较高的冬枣果实表现为较高的弹性和咀嚼性，以及较低的最大粘附力和粘附性。通过因子分析和聚类分析，可将8项冬枣质地指标分为4组（内聚因子、粘附因子、梗硬因子和酥脆因子），其代表性指标分别为弹性、粘附性、硬度和破裂力。本研究探讨了冬枣果实8项质地指标及其相互关系，筛选出了代表性指标，并建立了冬枣果实质地评价体系。研究结果可为冬枣质地评价提供方法依据和技术支撑。

In order to establish grading standards of evaluation indices for sour flavor of apples, 10 indices of samples from 106 apple cultivars were tested, including: malic acid (Mal), oxalic acid (Oxa), citric acid (Cit), lactic acid (Lac), succinic acid (Suc), fumaric acid (Fum), total organic acids (ToA, the sum of the six organic acids tested), titratable acid (TiA), acidity value (AcV), and pH value.  For most of the cultivars studied (85.8%), the order of the organic acid contents in apples was Mal>Oxa>Cit>Lac>Suc>Fum.  Mal was the dominant organic acid, on average, accounting for 94.5% of ToA.  Among the 10 indices, the dispersion of pH value was the smallest with a coefficient of variation of only 8.2%, while the coefficients of variation of the other nine indices were larger, ranging between 31 and 66%.  There were significant linear relationships between Mal and two indices (ToA and AcV) as well as between ToA and AcV.  There were significant logarithmic relationships between pH value and four indices: Mal, TiA, ToA, and AcV.  All the equations had very high fitting accuracy and can be used to accurately predict related indices.  According to this study, Mal, ToA, and AcV of apple were normally distributed, TiA was close to normally distributed, whereas pH value had a skewed distribution.  Using the fitted normal distribution curves, the grading standards of Mal, TiA, ToA, and AcV were established.  The grading node values of pH value were obtained using the logarithmic relationship between pH value and Mal.  The grading standards of these five indices can be used to evaluate the sour flavor of apple.  This study provides a scientific basis for evaluating apple flavor and selecting apple cultivars.

To assess levels of contamination and human health risk, we analyzed the concentrations of the heavy metals lead (Pb), cadmium (Cd), chromium (Cr), and nickel (Ni) in China’s main deciduous fruits - apple, pear, peach, grape, and jujube. The concentration order of the heavy metals was Ni>Cr>Pb>Cd. In 97.5% of the samples, heavy metal concentrations were within the maximum permissible limits. Among the fruits studied, the heavy metal concentrations in jujube and peach proved to be the highest, and those in grape proved to be the lowest. Only 2.2% of the samples were polluted by Ni, only 0.4% of the samples were polluted by Pb, and no samples were polluted by Cd or Cr. Compared with the other fruits, the combined heavy metal pollution was significantly higher (P<0.05) in peach and significantly lower (P<0.05) in grape. For the combined heavy metal pollution, 96.9% of the samples were at safe level, 2.32% at warning level, 0.65% at light level, and 0.13% at moderate level. In the fruits studied, the contribution of heavy metals to the daily intake rates (DIR) followed the order of Ni>Cr>Pb>Cd. The highest DIR came from apple, while the lowest DIR came from grape. For each of the heavy metals, the total DIR from five studied fruits corresponded to no more than 1.1% of the tolerable daily intake, indicating that no significant adverse health effects are expected from the heavy metals and the fruits studied. The target hazard quotients and the total target hazard quotients demonstrated that none of the analyzed heavy metals may pose risk to consumers through the fruits studied. The highest risk was posed by apple, followed in decreasing order by peach and pear, jujube, and grape. We suggest that the main deciduous fruits (apple, pear, peach, grape, and jujube) of China’s main producing areas are safe to eat.

The presence of pesticide residues in pears is a serious health concern. This study presents the results from a 2-year investigation (2013–2014) that used gas chromatography, GS/MS and UPLC/MS-MS to measure the levels of 104 pesticides in 310 pear samples. In 93.2% of the samples, 43 pesticides were detected, of which the maximum residue levels (MRLs) were exceeded in 2.6% of the samples. Multiple residues (two to eight compounds) were present in 69.7% of the samples; one sample contained nine pesticides and one sample contained 10. Only 6.8% of the samples did not contain residues. To assess the health risks, the pesticide residue data have been combined with daily pear consumption data for children and adult populations. A deterministic model was used to assess the chronic and acute exposures based on the Joint Meeting on Pesticide Residues (JMPR) method. A potential acute risk was demonstrated for children in the case of bifenthrin, which was found to be present at 105.36% of the acute reference dose (ARfD) value. The longterm exposure of the Chinese consumer to pesticide residues through the consumption of raw pears was far below the acceptable daily intake (ADI) criterion. Additionally, the matrix ranking scheme was used to classify risk subgroups of pesticides and pear samples. In general, 95.5% of samples were deemed to be safe and nine pesticides were classified as being of a relatively high risk. The findings indicated that the occurrence of pesticide residues in pears should not be considered a serious public health problem. Nevertheless, a more detailed study is required for vulnerable consumer groups, especially children. Continuous monitoring of pesticides in pears and tighter regulation of pesticide residue standards are recommended.