Analysis and evaluation of fruit mastication of mandarins in Hubei Province

Abstract:【Objective】Mastication quality is one of the important qualities of citrus fruits, which significantly affects the consumer’s taste experience. However, previous researches of citrus fruit qualities mainly focus on the sugar and acid. The researches of citrus fruit mastication are still very limited. Thus, the objective of this study is to explore the differences in mastication quality among mandarins in Hubei Province and its main influencing factors.【Methods】Samples of early-maturing and mid-early maturing mandarins were selected from different orchards in Hubei Province. Fully ripe fruits were collected at the appropriate harvest time, and 45 healthy fruit of medium size from different parts of the tree were selected for the experiment. The fruit samples were transported to the laboratory on the day of harvest for the determination of physiological and biochemical indicators. The samples were separated into peel and pulp, with a portion of the pulp frozen in liquid nitrogen and stored at -80 ℃ for the determination of cellulose and pectin. The remaining pulp samples were dried in an oven at 120 ℃ to a con-stant weight, ground, and then sieved through a 60- mesh screen. The sieved samples were placed in sealed bags and stored at room temperature in a desiccator for later determination of lignin content. A comprehensive evaluation of the mastication quality of mandarins was conducted through sensory assessment and texture analysis instruments. Furthermore, the main factors influencing the mastication quality of mandarin fruits were preliminarily analyzed through correlation analysis, multiple linear regression analysis, and principal component analysis.【Results】The individual fruit weight of early-maturing mandarins from different production areas varied significantly, ranging from 54.00 to 129.33 g, with peel thickness ranging from 2.15 to 4.32 mm. The transverse diameter ranged from 5.03 to 7.03 cm, and the longitudinal diameter from 3.73 to 5.82 cm. The internal quality differences were pronounced, with soluble solids content ranging between 8.63% and 13.7%, averaging 10.56%; titratable acidity between 0.33% and 0.84%; vitamin C content between 15.92% and 39.81 mg·100 g-1 , and the sugar to acid ratio between 10.33 and 31.31, with an average value of 16.40. The individual fruit mass of mid-early maturing mandarins from different production areas ranged from 68.17 to 169.67 g, with peel thickness ranging from 0.83 to 4.14 mm. The transverse diameter ranged from 5.56 to 8.1 cm, and the longitudinal diameter from 4.18 to 6.64 cm. The content of soluble solids in the fruits of mid-early maturing mandarins ranged from 8.47% to 14.3% , with an average of 11.53% ; titratable acidity ranged from 0.3% to 1.09%, vitamin C content from 17.5 to 46.23 mg·100 g-1 , and the sugar to acid ratio from 10.33 to 31.31, with an average value of 18.30. There were significant differences in the quality of mandarins from different production areas in Hubei, with the mid-early maturing mandarins generally exhibiting better quality than the early-maturing mandarins. The mid- early maturing varieties in 2022 exhibited characteristics of high sugar and high acidity. The mastication score of early- maturing mandarins ranged from 4.6 to 8.55, with an average score of 6.38. Puncture force ranged from 97.09 to 302.5 g; shear force from 896.43 to 2 683.33 g; lignin content from 37.05 to 209.18 mg · g^{- 1} ; cellulose content from 10.1 to 20.15 mg · g^{- 1} ; and pectin content from 7.54 to 24.79 mg · g^{- 1} . Specifically, sample No. 9 had the lowest mastication score at 4.6 but the highest puncture and shear forces, as well as the highest lignin content. The mastication score of mid-early maturing mandarins ranged from 3.38 to 8.24, with an average of 6.01. Puncture force ranged between 78.45 and 239.38 g; shear force between 848.58 and 3 926.24 g; lignin content from 66.48 to 208.9 mg·g^-1 ; cellulose content from 10.1 to 20.15 mg·g^-1 ; and pectin content from 7.54 to 24.79 mg · g^{- 1} . Specifically, sample No. 55 had the highest in mastication score at 8.24; sample No. 29 had the lowest score at 3.38, but the highest puncture and shear forces. Correlation analysis indicated that the transverse diameter, longitudinal diameter, and individual fruit weight were significantly positively correlated with each other and negatively correlated with total soluble solids and vitamin C content, but positively correlated with shear force and lignin content. The mastication score was significantly negatively correlated with titratable acidity, shear force, and puncture force, while shear force was significantly positively correlated with puncture force. Lignin content was significantly positively correlated with peel thickness and shear force, and negatively correlated with sugar to acid ratio. Pectin content showed a significant positive correlation with transverse diameter, titratable acidity, and cellulose content. A predictive model for the sensory comprehensive evaluation was constructed using multiple linear regression analysis with variables including total soluble solids, puncture force, lignin content, and pectin content. The regressed function was Y (mastication score) = 5.875+ 0.108X (TSS content)-0.007X (puncture force) -0.007X (lignin content) + 0.044X (pectin content). The comprehensive taste prediction score based on this model was essentially consistent with the actual comprehensive taste score.【Conclusion】The comprehensive score prediction model established basedon regression analysis facilitates the comprehensive evaluation of the sensory quality of mandarin fruits. The indices of texture characteristics and physicochemical components, serving as objective methods, can effectively compensate for the subjective shortcomings in sensory analysis and can be applied to the quality evaluation of mandarins in Hubei Province.