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Abstract [Objectives]This study was carried out to determine texture parameters for texture profile analysis （TPA）， and optimize the texture determination of ‘Yali’ by texture analyzer.
[Methods]The traditional varieties of ‘Yali’ were taken as the materials， and texture parameters were determined at different compression rates and deformations at target.
[Results]In the process of the TPA， the deformation at target had an extremely significant influence on 8 TPA texture parameters， namely， the hardness， cohesiveness， springiness， adhesiveness， gumminess， resilience， fracturability， and chewiness （P≤0.01）， while the compression rate had significant influence on the hardness and gumminess （P≤0.05）， had an extremely significant influence on fracturability （P≤0.01）， and had no significant influence on other 5 TPA parameters.
[Conclusions]Taking the compression rate of 1 mm/s and 20% deformation at target as the experimental conditions for TPA could avoid the impact load of high speed on the tissue and objectively reflect the textural characteristics of ‘Yali’ pulp tissue.
Key words Texture profile analysis （TPA）； ‘Yali’； Texture parameters； Optimization of texture determination
The Texture Profile Analysis （TPA） model is a new testing method developed in recent years for testing food textural properties using a mechanical texture analyzer. It uses mechanical method to simulate the food texture mainly through simulating the chewing movement of the human oral cavity. For setting of evaluation parameters， TPA is more objective and can fully reflect the hardness， adhesiveness， springiness， cohesiveness， and chewiness， and it can reduce the differences brought about by the subjective evaluation of the human oral cavity[1]. In foreign countries， TPA test is widely applied in the evaluation of quality of foods and fruits[2-5]. In China， TPA test is still in its infancy and mainly applied in foods[6]but seldom applied in fruits[7-11].
Pyrus bretschneideri Rehd. ‘Yali’ is an ancient local variety of pear in Hebei Province. It is one of the fine varieties of Rosaceae. It has strong adaptability， high yield， fine pulp， crisp and juicy， and moderate sweet and sour taste， known as "inborn sweet dew"， so it is deeply favored by people. At present， studies about the texture characteristics of ‘Yali’ fruits mostly depend on subjective evaluation of the oral cavity.
In view of texture parameters of ‘Yali’ pear， this experiment is aimed at elaborating specific meaning of texture parameters of TPA test， determine the effects of test conditions on the text parameters of ‘Yali’ pear， optimize the test conditions of TPA texture evaluation， and provide certain references for study of texture characteristics and quality changes of Pyrus bretschneideri Rehd through more comprehensive and accurate application of the texture analyzer. Materials and Methods
Experimental materials
The test ‘Yali’ pears were harvested from the pear orchard in Changli Institute of Pomology， Hebei Academy of Agriculture and Forestry Sciences in October 2015. The pears with the same size and consistent maturity but without diseases， insects， or damage were selected and measured.
Experiment methods
We adopted CT34500 Texture Analyzer （CID， USA）， and made an improvement with reference to the method of Gao Haisheng et al.[9]. We selected the fruit crest （as shown in Fig. 1） and used the TPA mode of Texture Analyzer， and made the profile get perpendicular to the probe， and the other side is cut into a flat plane and placed on the fixture table （in a flat manner）. Besides， we used TA41 probe （diameter of 6 mm）， set the compression rate at three levels （1.0， 2.5， 5.0 mm/s）， and set the deformation at target at seven levels （5%， 10%， 15%， 20%， 25%， 30%， and 35%）， and other conditions were the same. Each pear was measured 2 times， and 5 pears were selected for determination each time， and 10 replicates in total. We selected 8 texture parameters： hardness， cohesiveness， springiness， adhesiveness， gumminess， resilience， fracturability， and chewiness.
Fig. 2 is the TPA test chromatogram. The test conditions were as follows： test speed of 1.0 mm/s， prediction speed of 2.0 mm/s， return speed of 1.0 mm/s， and load at trigger point 10 g. The time at which the first compression reached the peak was denoted as t1， the time from the beginning of the second compression to the peak was denoted by t2， and the positive area （area 1 + area 2） of the first compression curve was denoted by S1 and S2， respectively； the negative area 3 of the curve from the first compression curve reaching the zero to the beginning of the second compression curve was denoted as S3； the positive area 4 of the second compression curve was denoted as S4， and the maximum value of the first curve of the double peak curve was denoted as P1， and the first significant fracture force during the test was denoted as F1. The hardness = P1； adhesiveness = S3； fracturability = F1； springiness = t2/t1； cohesiveness = S4/（S1 + S2）； resilience = S2/（S1 + S2）； gumminess = P1 × S4/（S1 + S2）； chewiness = P1× t2/t1 × S4/（S1 + S2）. The above parameters could be directly calculated by the computer analysis software of the texture analyzer.
Data processing
For statistical analysis of experimental data， we used Excel 2003 and SPSS 20.0 software， and used Pearson correlation to conduct the correlation analysis. Results and Analyses
TPA curve for ‘Yali’ fruits under different test conditions
Fig. 3 is the TPA test curve with a compression rate of 1 mm/s and deformation at target of 5% to 35%. The TPA curve at compression rate of 2.5 mm/s and 5 mm/s showed different time of peak from the TPA curve at the compression rate of 1 mm/s， the curve shape was similar， so it was not shown Fig. 3.
From Fig. 3， when the deformation at target was 5%-15%， the peak area of the two compressions was different， but the peak shape was basically the same， and both were singlepeak curves， indicating that the springiness of samples were within the range of resilience； when the deformation at target was 20%-25%， the peak shape of the first compression had an obvious single peak， but there were many miscellaneous peaks in the right， the peak shape of two compressions were not consistent with each other， indicating that there was certain degree of damage in the internal structure of the tissue； when the deformation at target was above 30%， the first compression had two obvious single peaks， but there were many miscellaneous peaks in the middle， and the single compression present a single peak curve， indicating that there was unrecoverable deformation in the structure of internal tissue， the resistance of the tissue declined， and the damage of internal tissue structure was serious.
Changes in parameters of ‘Yali’ under different test conditions
Changes in the hardness
The hardness is the force required for deformation of the pulp under the action of external force. From Fig. 4A， it can be known that when the deformation at target was consistent， the higher the compression rate， the higher the hardness is； when the compression rate was consistent， with the increase in the deformation at target， the harness gradually declined； when the deformation at target was above 25%， there was no significant change in the hardness， possibly because the internal tissue structure of the pulp was compacted. From Table 1， it also can be seen that the compression rate significantly affected the changes in the hardness of ‘Yali’ （P ≤0.05）， while the deformation at target extremely significantly affected the hardness of ‘Yali’ （P ≤0.01）.
Changes in the gumminess
The gumminess is the product of hardness and cohesiveness， and is used as an indicator of the viscous properties of a semisolid test sample. Like the hardness， the gumminess was significantly influenced by the compression rate and the deformation at target. From Fig. 4B， it can be seen that the higher the compression rate， the bigger the gumminess is. At the same compression rate， the gumminess increased with the increase of the deformation at target； when the deformation at target was 20%-25%， the gumminess was relatively stable or even declined； when the deformation at target was above 25%， the gumminess showed an increasing trend， possibly associated with high sugar content of ‘Yali’. From Table 1， it also can be seen that the compression rate significantly affected the changes in the gumminess of ‘Yali’ （P ≤0.05）， while the deformation at target extremely significantly affected the gumminess of ‘Yali’ （P≤0.01）. Changes in the springiness
The springiness is the ability of the fruit to restore its original shape when the compression is removed. From Fig. 4C， it can be seen that the springiness gradually increased with the increase in the deformation at target， and it showed a sharp rise trend. When the deformation at target was 25%-30%， the changes of springiness was gentle； when the deformation at target was above 30%， the springiness gradually declined possibly because the internal tissue structure was gradually compacted and the ability of restoration was weakened. From Table 1， it can be seen that the deformation at target extremely significantly affected the springiness （P≤0.01）， while the effect of compression rate on the springiness was not significant.
Changes in the fracturability
Fracturability is the fracture strength that the fruit surface can withstand under a certain level of deformation （the force of the first obvious fracture during the test）. From Fig. 4D， it can be seen that when the deformation at target was 20%， the fracturability tended towards consistency； when the deformation at target was above 20%， the fracturability slowly declined， possibly because the internal tissue structure was gradually compacted. From Table 1， it can be seen that the fracturability was greatly affected by the compression rate and deformation at target， and there was extremely significant correlation between them （P≤0.01）.
Changes in the cohesiveness
Cohesiveness is the size of the intercellular binding force and it is the trait of keeping the fruit intact when the pulp is chewed. The cohesiveness is slightly affected by the compression rate， but greatly affected by the deformation at target. From Fig. 4E， it can be seen that at the same compression rate， the cohesiveness increased with the increase in the deformation at target； when the deformation at target was 20%-25%， the cohesiveness was relatively stable； when the deformation at target was above 25%， the cohesiveness showed a rise trend. From Table 1， it can be seen that the cohesiveness was extremely significantly correlated with the deformation at target， but not significantly correlated with the compression rate.
Changes in the resilience
Resilience is the height of a sample to recover after removing the pressure， or the displacement from target force or displacement value dropping to zero force. From Fig. 4E， it can be seen that when the deformation at target was 5%-20%， the resilience difference was little； when the deformation at target was 20%， the resilience was consistent； when the deformation at target was above 25%， the resilience increased with the increase in the deformation at target； when the deformation at target was 30%， the resilience reached the peak and then gradually declined， possibly the internal tissue structure was gradually compacted and the ability of resilience lost. From Table 1， it can be seen that the resilience was extremely significantly correlated with the deformation at target （P≤0.01）， but not significantly correlated with the compression rate. Changes in the adhesiveness
Adhesiveness is the energy needed for overcoming the pulp surface attraction when chewing the pulp. From Fig. 4F， it can be seen that the adhesiveness increased with the increase in the deformation at target； when the deformation at target was 15%-25%， the increase of adhesiveness was slow， indicating that the energy needed for overcoming the pulp surface attraction when chewing the pulp was constant； when deformation at target was above 25%， the adhesiveness gradually increased， possibly because the some water in pulp was squeezed out and the juice became viscous. From Table 1， it can be seen that the resilience was slightly affected by the compression rate， but greatly affected by the deformation at target （P≤0.01）.
Changes in the chewiness
Chewiness is the continued resistance ability of fruit to chewing. From Fig. 4H， it can be seen that when the deformation at target was 5%-20%， the chewiness gradually increased； when the deformation at target was 20%-25%， the chewiness was relatively stable； when the deformation at target was above 30%， the chewiness firstly reached the peak then gradually declined. From Table 1， it can be seen that the chewiness was greatly affected by the deformation at target （P≤0.01）， but slightly affected by the compression rate.
Jintao XU et al. Optimization of Texture Determination of ‘Yali’ by Texture Analyzer
Conclusions and Discussions
The experiment results indicated that different compression rates had significant effects on the hardness， gumminess， and fracturability， but all eight parameters showed similar trends at three compression rates. In order to avoid the impact load， we adopted 1 mm/s as the compression rate for TPA test. The deformation at target had significant effects on these eight parameters. When the deformation at target was 5%-20%， the pulp tissue structure was relatively intact， and the fruit hardness was high. The effects on the hardness， cohesiveness， springiness， adhesiveness， gumminess， resilience， and chewiness were little because the deformation at target had not reached certain level. When the deformation at target was 20%-25%， the pulp tissue was stressed to a certain extent， and the tissue structure was gradually damaged. When the deformation at target was above 30%， the pulp tissue structure was greatly deformed， and the tissue structure was greatly damaged and accordingly declined. Considering the above factors， we selected 20% deformation at target as the reference value of ‘Yali’ TPA model test， because at this time the pulp tissue structure was relatively intact and not damaged， the decline in fruit hardness， springiness， chewiness， and cohesiveness due to structural damage was little. In summary， changes in each test condition will have a certain effect on the results. Considering changes in the overall factors， we took 1 mm/s compression rate and 20% deformation at target as the test conditions for TPA test. This experiment adopted main pear cultivar ‘Yali’ in northern area of China as research object. In future， it is necessary to conduct extensive and indepth research， combine with the sensory evaluation， to further improve the accuracy of TPA test of pears， and provide certain references for study of texture characteristics and quality changes of the pear fruit through more comprehensive and accurate application of the texture analyzer.
References
[1]YUAN CL， DONG XY， LI PH， et al. Changes in texture properties of crisp peach during postharvest storage by texture profile analysis[J]. Food Science， 2013 （20）： 273-276. （in Chinese）
[2]Lucey J A， Johnson M E， Horne D S. Perspectives on the basis of the rheology and texture properties of cheese[J]. Journal of Dairy Science， 2003， 86 （9）： 2725-2743.
[3]Sullivan P， Oflaherty J， Brunton N， et al. Fundamental rheological and textural properties of doughs and breads produced from milled pearled barley flour[J]. European Food Research and Technology， 2010， 231： 441-453.
[4]Golias J， Bejcek L， Gratz P， et al. Mechanical resonance method for evaluation of peach fruit firmness[J]. Hortscience， 2003， 30 （1）： 1-6.
[5]Zdunek A， Bednarczyk J. Effect of mannitol treatment on ultrasound emission during texture profile analysis of potato and apple tissue[J]. Journal of Texture Studies， 2006， 37 （3）： 339-359.
[6]LIANG H， DAI ZY. Application of texture analyzer in the assessment for food texture[J]. Food Research and Development， 2006， 27 （4）： 119-121， 118. （in Chinese）
[7]GAO HS， JIA YR， WEI JM， et al. Studies on the postharvested fruit texture changes of ‘Yali’ and ‘Jingbaili’ pears by using texture analyzer[J]. Acta Horticulturae Sinica， 2012， 39 （7）： 1359-1364. （in Chinese）
[8]PAN XJ， TU K. Comparison of texture properties of postharvested apples using texture profile analysis[J]. Transactions of the Chinese Society of Agricultural Engineering， 2005， 21 （3）： 166-170. （in Chinese）
[9]REN ZH， ZHANG KM， LI ZW， et al. Study on the evaluation of texture parameters of grape berry during storage by using texture profile analysis[J]. Science and Technology of Food Industry， 2011， 32 （7）： 375-378. （in Chinese）
[10]CAI C， GONG MJ， LI X， et al. Texture changes and regulation of postharvest loquat fruit[J]. Acta Horticulturae Sinica， 2006， 33（4）： 731-636. （in Chinese）
[11]LI JR. Study on key technologies of freshness and deep processing of red bayberry[D]. Hangzhou： Zhejiang University， 2001： 25-33. （in Chinese）
Editor： Huadong GUO Proofreader： Xinxiu ZHU
[Methods]The traditional varieties of ‘Yali’ were taken as the materials， and texture parameters were determined at different compression rates and deformations at target.
[Results]In the process of the TPA， the deformation at target had an extremely significant influence on 8 TPA texture parameters， namely， the hardness， cohesiveness， springiness， adhesiveness， gumminess， resilience， fracturability， and chewiness （P≤0.01）， while the compression rate had significant influence on the hardness and gumminess （P≤0.05）， had an extremely significant influence on fracturability （P≤0.01）， and had no significant influence on other 5 TPA parameters.
[Conclusions]Taking the compression rate of 1 mm/s and 20% deformation at target as the experimental conditions for TPA could avoid the impact load of high speed on the tissue and objectively reflect the textural characteristics of ‘Yali’ pulp tissue.
Key words Texture profile analysis （TPA）； ‘Yali’； Texture parameters； Optimization of texture determination
The Texture Profile Analysis （TPA） model is a new testing method developed in recent years for testing food textural properties using a mechanical texture analyzer. It uses mechanical method to simulate the food texture mainly through simulating the chewing movement of the human oral cavity. For setting of evaluation parameters， TPA is more objective and can fully reflect the hardness， adhesiveness， springiness， cohesiveness， and chewiness， and it can reduce the differences brought about by the subjective evaluation of the human oral cavity[1]. In foreign countries， TPA test is widely applied in the evaluation of quality of foods and fruits[2-5]. In China， TPA test is still in its infancy and mainly applied in foods[6]but seldom applied in fruits[7-11].
Pyrus bretschneideri Rehd. ‘Yali’ is an ancient local variety of pear in Hebei Province. It is one of the fine varieties of Rosaceae. It has strong adaptability， high yield， fine pulp， crisp and juicy， and moderate sweet and sour taste， known as "inborn sweet dew"， so it is deeply favored by people. At present， studies about the texture characteristics of ‘Yali’ fruits mostly depend on subjective evaluation of the oral cavity.
In view of texture parameters of ‘Yali’ pear， this experiment is aimed at elaborating specific meaning of texture parameters of TPA test， determine the effects of test conditions on the text parameters of ‘Yali’ pear， optimize the test conditions of TPA texture evaluation， and provide certain references for study of texture characteristics and quality changes of Pyrus bretschneideri Rehd through more comprehensive and accurate application of the texture analyzer. Materials and Methods
Experimental materials
The test ‘Yali’ pears were harvested from the pear orchard in Changli Institute of Pomology， Hebei Academy of Agriculture and Forestry Sciences in October 2015. The pears with the same size and consistent maturity but without diseases， insects， or damage were selected and measured.
Experiment methods
We adopted CT34500 Texture Analyzer （CID， USA）， and made an improvement with reference to the method of Gao Haisheng et al.[9]. We selected the fruit crest （as shown in Fig. 1） and used the TPA mode of Texture Analyzer， and made the profile get perpendicular to the probe， and the other side is cut into a flat plane and placed on the fixture table （in a flat manner）. Besides， we used TA41 probe （diameter of 6 mm）， set the compression rate at three levels （1.0， 2.5， 5.0 mm/s）， and set the deformation at target at seven levels （5%， 10%， 15%， 20%， 25%， 30%， and 35%）， and other conditions were the same. Each pear was measured 2 times， and 5 pears were selected for determination each time， and 10 replicates in total. We selected 8 texture parameters： hardness， cohesiveness， springiness， adhesiveness， gumminess， resilience， fracturability， and chewiness.
Fig. 2 is the TPA test chromatogram. The test conditions were as follows： test speed of 1.0 mm/s， prediction speed of 2.0 mm/s， return speed of 1.0 mm/s， and load at trigger point 10 g. The time at which the first compression reached the peak was denoted as t1， the time from the beginning of the second compression to the peak was denoted by t2， and the positive area （area 1 + area 2） of the first compression curve was denoted by S1 and S2， respectively； the negative area 3 of the curve from the first compression curve reaching the zero to the beginning of the second compression curve was denoted as S3； the positive area 4 of the second compression curve was denoted as S4， and the maximum value of the first curve of the double peak curve was denoted as P1， and the first significant fracture force during the test was denoted as F1. The hardness = P1； adhesiveness = S3； fracturability = F1； springiness = t2/t1； cohesiveness = S4/（S1 + S2）； resilience = S2/（S1 + S2）； gumminess = P1 × S4/（S1 + S2）； chewiness = P1× t2/t1 × S4/（S1 + S2）. The above parameters could be directly calculated by the computer analysis software of the texture analyzer.
Data processing
For statistical analysis of experimental data， we used Excel 2003 and SPSS 20.0 software， and used Pearson correlation to conduct the correlation analysis. Results and Analyses
TPA curve for ‘Yali’ fruits under different test conditions
Fig. 3 is the TPA test curve with a compression rate of 1 mm/s and deformation at target of 5% to 35%. The TPA curve at compression rate of 2.5 mm/s and 5 mm/s showed different time of peak from the TPA curve at the compression rate of 1 mm/s， the curve shape was similar， so it was not shown Fig. 3.
From Fig. 3， when the deformation at target was 5%-15%， the peak area of the two compressions was different， but the peak shape was basically the same， and both were singlepeak curves， indicating that the springiness of samples were within the range of resilience； when the deformation at target was 20%-25%， the peak shape of the first compression had an obvious single peak， but there were many miscellaneous peaks in the right， the peak shape of two compressions were not consistent with each other， indicating that there was certain degree of damage in the internal structure of the tissue； when the deformation at target was above 30%， the first compression had two obvious single peaks， but there were many miscellaneous peaks in the middle， and the single compression present a single peak curve， indicating that there was unrecoverable deformation in the structure of internal tissue， the resistance of the tissue declined， and the damage of internal tissue structure was serious.
Changes in parameters of ‘Yali’ under different test conditions
Changes in the hardness
The hardness is the force required for deformation of the pulp under the action of external force. From Fig. 4A， it can be known that when the deformation at target was consistent， the higher the compression rate， the higher the hardness is； when the compression rate was consistent， with the increase in the deformation at target， the harness gradually declined； when the deformation at target was above 25%， there was no significant change in the hardness， possibly because the internal tissue structure of the pulp was compacted. From Table 1， it also can be seen that the compression rate significantly affected the changes in the hardness of ‘Yali’ （P ≤0.05）， while the deformation at target extremely significantly affected the hardness of ‘Yali’ （P ≤0.01）.
Changes in the gumminess
The gumminess is the product of hardness and cohesiveness， and is used as an indicator of the viscous properties of a semisolid test sample. Like the hardness， the gumminess was significantly influenced by the compression rate and the deformation at target. From Fig. 4B， it can be seen that the higher the compression rate， the bigger the gumminess is. At the same compression rate， the gumminess increased with the increase of the deformation at target； when the deformation at target was 20%-25%， the gumminess was relatively stable or even declined； when the deformation at target was above 25%， the gumminess showed an increasing trend， possibly associated with high sugar content of ‘Yali’. From Table 1， it also can be seen that the compression rate significantly affected the changes in the gumminess of ‘Yali’ （P ≤0.05）， while the deformation at target extremely significantly affected the gumminess of ‘Yali’ （P≤0.01）. Changes in the springiness
The springiness is the ability of the fruit to restore its original shape when the compression is removed. From Fig. 4C， it can be seen that the springiness gradually increased with the increase in the deformation at target， and it showed a sharp rise trend. When the deformation at target was 25%-30%， the changes of springiness was gentle； when the deformation at target was above 30%， the springiness gradually declined possibly because the internal tissue structure was gradually compacted and the ability of restoration was weakened. From Table 1， it can be seen that the deformation at target extremely significantly affected the springiness （P≤0.01）， while the effect of compression rate on the springiness was not significant.
Changes in the fracturability
Fracturability is the fracture strength that the fruit surface can withstand under a certain level of deformation （the force of the first obvious fracture during the test）. From Fig. 4D， it can be seen that when the deformation at target was 20%， the fracturability tended towards consistency； when the deformation at target was above 20%， the fracturability slowly declined， possibly because the internal tissue structure was gradually compacted. From Table 1， it can be seen that the fracturability was greatly affected by the compression rate and deformation at target， and there was extremely significant correlation between them （P≤0.01）.
Changes in the cohesiveness
Cohesiveness is the size of the intercellular binding force and it is the trait of keeping the fruit intact when the pulp is chewed. The cohesiveness is slightly affected by the compression rate， but greatly affected by the deformation at target. From Fig. 4E， it can be seen that at the same compression rate， the cohesiveness increased with the increase in the deformation at target； when the deformation at target was 20%-25%， the cohesiveness was relatively stable； when the deformation at target was above 25%， the cohesiveness showed a rise trend. From Table 1， it can be seen that the cohesiveness was extremely significantly correlated with the deformation at target， but not significantly correlated with the compression rate.
Changes in the resilience
Resilience is the height of a sample to recover after removing the pressure， or the displacement from target force or displacement value dropping to zero force. From Fig. 4E， it can be seen that when the deformation at target was 5%-20%， the resilience difference was little； when the deformation at target was 20%， the resilience was consistent； when the deformation at target was above 25%， the resilience increased with the increase in the deformation at target； when the deformation at target was 30%， the resilience reached the peak and then gradually declined， possibly the internal tissue structure was gradually compacted and the ability of resilience lost. From Table 1， it can be seen that the resilience was extremely significantly correlated with the deformation at target （P≤0.01）， but not significantly correlated with the compression rate. Changes in the adhesiveness
Adhesiveness is the energy needed for overcoming the pulp surface attraction when chewing the pulp. From Fig. 4F， it can be seen that the adhesiveness increased with the increase in the deformation at target； when the deformation at target was 15%-25%， the increase of adhesiveness was slow， indicating that the energy needed for overcoming the pulp surface attraction when chewing the pulp was constant； when deformation at target was above 25%， the adhesiveness gradually increased， possibly because the some water in pulp was squeezed out and the juice became viscous. From Table 1， it can be seen that the resilience was slightly affected by the compression rate， but greatly affected by the deformation at target （P≤0.01）.
Changes in the chewiness
Chewiness is the continued resistance ability of fruit to chewing. From Fig. 4H， it can be seen that when the deformation at target was 5%-20%， the chewiness gradually increased； when the deformation at target was 20%-25%， the chewiness was relatively stable； when the deformation at target was above 30%， the chewiness firstly reached the peak then gradually declined. From Table 1， it can be seen that the chewiness was greatly affected by the deformation at target （P≤0.01）， but slightly affected by the compression rate.
Jintao XU et al. Optimization of Texture Determination of ‘Yali’ by Texture Analyzer
Conclusions and Discussions
The experiment results indicated that different compression rates had significant effects on the hardness， gumminess， and fracturability， but all eight parameters showed similar trends at three compression rates. In order to avoid the impact load， we adopted 1 mm/s as the compression rate for TPA test. The deformation at target had significant effects on these eight parameters. When the deformation at target was 5%-20%， the pulp tissue structure was relatively intact， and the fruit hardness was high. The effects on the hardness， cohesiveness， springiness， adhesiveness， gumminess， resilience， and chewiness were little because the deformation at target had not reached certain level. When the deformation at target was 20%-25%， the pulp tissue was stressed to a certain extent， and the tissue structure was gradually damaged. When the deformation at target was above 30%， the pulp tissue structure was greatly deformed， and the tissue structure was greatly damaged and accordingly declined. Considering the above factors， we selected 20% deformation at target as the reference value of ‘Yali’ TPA model test， because at this time the pulp tissue structure was relatively intact and not damaged， the decline in fruit hardness， springiness， chewiness， and cohesiveness due to structural damage was little. In summary， changes in each test condition will have a certain effect on the results. Considering changes in the overall factors， we took 1 mm/s compression rate and 20% deformation at target as the test conditions for TPA test. This experiment adopted main pear cultivar ‘Yali’ in northern area of China as research object. In future， it is necessary to conduct extensive and indepth research， combine with the sensory evaluation， to further improve the accuracy of TPA test of pears， and provide certain references for study of texture characteristics and quality changes of the pear fruit through more comprehensive and accurate application of the texture analyzer.
References
[1]YUAN CL， DONG XY， LI PH， et al. Changes in texture properties of crisp peach during postharvest storage by texture profile analysis[J]. Food Science， 2013 （20）： 273-276. （in Chinese）
[2]Lucey J A， Johnson M E， Horne D S. Perspectives on the basis of the rheology and texture properties of cheese[J]. Journal of Dairy Science， 2003， 86 （9）： 2725-2743.
[3]Sullivan P， Oflaherty J， Brunton N， et al. Fundamental rheological and textural properties of doughs and breads produced from milled pearled barley flour[J]. European Food Research and Technology， 2010， 231： 441-453.
[4]Golias J， Bejcek L， Gratz P， et al. Mechanical resonance method for evaluation of peach fruit firmness[J]. Hortscience， 2003， 30 （1）： 1-6.
[5]Zdunek A， Bednarczyk J. Effect of mannitol treatment on ultrasound emission during texture profile analysis of potato and apple tissue[J]. Journal of Texture Studies， 2006， 37 （3）： 339-359.
[6]LIANG H， DAI ZY. Application of texture analyzer in the assessment for food texture[J]. Food Research and Development， 2006， 27 （4）： 119-121， 118. （in Chinese）
[7]GAO HS， JIA YR， WEI JM， et al. Studies on the postharvested fruit texture changes of ‘Yali’ and ‘Jingbaili’ pears by using texture analyzer[J]. Acta Horticulturae Sinica， 2012， 39 （7）： 1359-1364. （in Chinese）
[8]PAN XJ， TU K. Comparison of texture properties of postharvested apples using texture profile analysis[J]. Transactions of the Chinese Society of Agricultural Engineering， 2005， 21 （3）： 166-170. （in Chinese）
[9]REN ZH， ZHANG KM， LI ZW， et al. Study on the evaluation of texture parameters of grape berry during storage by using texture profile analysis[J]. Science and Technology of Food Industry， 2011， 32 （7）： 375-378. （in Chinese）
[10]CAI C， GONG MJ， LI X， et al. Texture changes and regulation of postharvest loquat fruit[J]. Acta Horticulturae Sinica， 2006， 33（4）： 731-636. （in Chinese）
[11]LI JR. Study on key technologies of freshness and deep processing of red bayberry[D]. Hangzhou： Zhejiang University， 2001： 25-33. （in Chinese）
Editor： Huadong GUO Proofreader： Xinxiu ZHU