Technical noTes Journal of Agricultural and Marine Sciences 2021, 26(1): 57–61 DOI: 10.24200/jams.vol26iss1pp57-61 Reveived 14 Oct 2020 Accepted 05 Dec 2020 Correlation between Sensory and Instrumental Textural Attributes of Date Palm (Phoenix dactylifera L.) fruits: Technical Note Vandita Singh1,*, Mohammad Shafiur Rahman2, Nejib Guizani2, Hakikulla Shah3 Vandita Singh1,*( ) vandita31@gmail.com, 1Department of Food Science and Human Nutrition, College of Applied and Health Sci- ences, A’Sharqiyah Universit y, P. O. Box 42, Ibra, Oman,2Depart- ment of Food Science and Nutrition, College of Agricultural and Marine Sciences, Sultan Qaboos Universit y, Muscat, Oman, 3De- partment of Biological Science and Chemistry, College of Arts and Sciences, Universit y of Nizwa, Post Box 33, PC 616, Nizwa, Oman, Introduction Texture, defined as the sensory manifestation of food structure and the way this structure reacts to the forces applied and it represents the junc- tion of all the mechanical, geometric, and superficial attributes of a product, sensed through mechanical, tac- tile, visual, and hearing receptors (Rahman, 2009; Rah- man et al., 2020). Assessment of textural attributes by either instrumental method (i.e. Textural Profile Anal- ysis, TPA) and or by sensory methods is of great inter- est in food technology (Rahman, 2019). The correlation obtained between sensory and instrumental texture measurements could be used to assess quality control parameters, consumers liking and their overall accept- ability for product development or improvement, and it is also useful to improve the instrumental method for better pairing with sensory results (Aguirre et al., 2018; Kurotobi et al., 2018). Date Fruits (DFs) are popular sta- ple food in the Middle East as well as, source of income for many families. The DFs are commercially import- ant and sold as fresh (i.e. Rutab) and dried (i.e. Tamar) (Chandrasekaran and Bahkali, 2013). Hence, there is a great amount of research in the field of DF including their phytochemical contents (Al-Hinai et al., 2013; Essa et al., 2019; Hossain et al., 2014; Singh et al., 2013; Singh et al., 2012). The growing food industry is also utilizing the DFs to produce variety of products (e.g. biscuits, fla- vored dairy products, and chocolate). Texture is a criti- cal property of the fruit that can dominate quality of the product. In the past decade few studies have focused on the instrumental texture of the DF (Al-Hinai et al. 2013). The growing date industries demands for assessing the sensory analysis of date fruits. The fruits quality is assessed based on texture, flavor, color, and nutritional properties (Ismail et al., 2008).The sensory textural characteristics are recognized as crit- ically important factors of food choice (Grunert, 2015; االرتباط بني السمات املقيمة حسيا و ابألجهزة لفاكهة شجرة النخيل )التمر( (.Phoenix dactylifera L): مالحظة فنية فانديتا سينغ1 ، * ، حممد شفيور الرمحن2 ، جنيب غيزاين2 ، حقيق هللا شاه3 Abstract. Food industries are constantly looking for optimum instrumental methods that can consistent- ly estimate sensory textural qualities of food products. Monitoring texture using instrumental methods is cheaper over time than maintaining a sensory quality panel. However, a good correlation between sensory and instrumental textural attributes is highly needed. In the present research, we aimed to report the cor- relation between instrumental and sensory textural attributes of date fruit varieties. Specifically, Instru- mental Texture Profile Analysis(TPA) and sensory textural attributes were correlated. We found significant correlations between sensory and instrumental TPA attributes of date fruit varieties and this suggests a great promise for developing quality control. Keywords: Date fruits, Sensory analysis, Instrumental texture, Phoenix dactylifera, Correlation املســتخلص:تبحث الصناعــات الغذائيــة ابســتمرار عــن األســاليب اآلليــة املثلــى اللــي متكنهــا مــن تقديــر جــودة صفــات الرتكيــب النســيجي احلســي للمنتجــات الغذائيــة. تعــد متابعــة النســيج ابســتخدام األجهــزة أرخــص مــع مــرور الوقــت مــن احلفــاظ علــى لوحــة ملقيمــي اجلــودة احلســية. ومــع ذلــك، مــن الضــرورة أن يوجــد ارتبــاط وعالقــة جيــدة بــن الســمات احملــددة حســيا و تلــك احملــددة ابألجهــزة. هدفنــا يف البحــث احلــايل هــو حتديــد االرتبــاط بــن الســمات املقيمــة حســيا و ابألجهــزة لنســيج أصنــاف مــن فاكهــة التمــر. و ابلتحديــد، كان هنــاك ارتبــاط بــن الســمات احملــددة حســيا و ابســتخدام اجلهــاز املخصــص لتحليــل النســيج )TPA( لفاكهــة التمــر و قــد كان هــذا االرتبــاط ذو أمهيــة إحصائيــة؛ ممــا يعــي أن هنــاك إمكانيــة لتطويــر مراقبــة اجلــودة ابســتخدام األجهــزة. الكلمات املفتاحية: مثار التمر، التحليل احلسي، النسيج اآليل، فينيكس داكتيليفريا (Phoenix dactylifera)، االرتباط 58 SQU Journal of Agricultural and Marine Sciences, 2021, Volume 26, Issue 1 Correlation between Sensory and Instrumental Textural Attributes of Date Palm (Phoenix dactylifera L.) fruits: Technical Note Rahman, 2019). Generally, sensory methods are more useful in developing new products and defining product standards in comparison with instrumental method (i.e. TPA). Although sensory analysis (i.e. descriptive meth- od) require a panel training and maintenance, however, it is not only time-consuming and expensive, but also demands proper reference standards for calibration (Joyner, 2018). Hence, attempt have been made to estab- lish the relationship or predictive model between sen- sory attributes and instrumental parameters (Li et al., 2020; Taniwaki et al., 2010). There is continuous industrial search for certain in- strumental techniques for forecasting the sensory tex- tural attributes of final processed products and/or even raw materials (Barbieri et al., 2018; Li et al., 2020; Rah- man et al., 2020; Taniwaki et al. 2010). Instrumental methods have advantage, as they tend to offer precise results (Rahman et al., 2020). Generally, instrumental results can be directly linked to chemical and physi- cal properties permitting the investigator to achieve a mechanistic understanding of experimental differences. Instruments are more sensitive to small alterations be- tween samples and capable to detect trends in quality loss before it can be detected by humans (Mestres et al., 2019; Rahman et al., 2020; Yu et al., 2017). Instruments can be used to yield large amounts of data without ob- jection, making them excellent screens in quality control operations (Yu et al., 2017). The data on the instrumen- tal and sensory textural attributes of 9 date fruit varieties as a function of their physicochemical characteristics were published earlier (Singh et al., 2013; Singh et al., 2015). Hence, we aimed in this paper to report the cor- relation between the instrumental and sensory textural attributes of date fruit varieties. Materials and methods Nine batches of DFs at Tamar stage (Figure 1) with dif- ferent quality levels were obtained from the local market at Muscat. All the samples were stored at -20˚C until used for the analysis (Singh et al., 2013). Instrumental Texture Profile Analysis (TPA) Different instrumental textural attributes (i.e. hardness; adhesiveness; springiness; cohesiveness; resilience; gumminess; chewiness; elasticity) of date fruits samples were measured earlier (Singh et al., 2013). Briefly, all ex- periments were conducted at room temperature (25 ± 2°C). One pitted date was divided into two halves and one side was placed over another. It was then pressed to prepare a flat slab. A typical force-time graph of two-cy- cle instrumental TPA for different date samples was an- alyzed (Singh et al., 2013). Textural Sensory Analysis The textural sensory attributes (i.e. hardness; adhesive- ness; springiness; cohesiveness; resilience; gumminess; chewiness; elasticity) of date fruits were assessed by 20 trained-panels (SQU students) using descriptive test. The panelists were trained on how to assess the defined attributes with respect to the provided references. The training proceeds with the actual samples. More details were presented in the earlier published work (Singh et al. 2015). Statistical Analysis Experimental data were analyzed using PAST Software. Multivariate Analysis (MVA) was performed to deter- mine the correlations between sensory and instrumen- tal textural characteristics of DFs (Hammer et al., 2001). MVA including Pearson’s (i.e. linear) and Spearman’s correlation matrix were run using all sensory and instru- mental textural attributes. Linear and Spearman’s cor- relations were used to determine the relationships be- tween each variable for the P values ≤ 0.05 and P≤ 0.10. Results and Discussion The instrumental forces for texture analysis were cor- related with sensory attributes. Correlation results showed that instrumental hardness were significantly correlated with sensory hardness, along with adhesive- Figure 1. Photos of date samples used for the textural studies 59Technical notes Singh, Shafiur, Guizani, Hakikulla Shah ness, springiness, cohesiveness, chewiness and elasticity (P<0.05) in both linear and spearman’s correlation, and with sensory resilience (P<0.1) linearly (Table 1). In the literature, often instrumental hardness are significant- ly correlated with the sensory hardness (Prakash et al., 2005; Tao et al. 2020). Similar correlation was report- ed for Instrumental hardness with sensory hardness in cooked rice (P<0.05) (Prakash et al., 2005). Significant correlations were also observed in the cases of instru- mental hardness and springiness with sensory hardness and springiness (P<0.001) when 21 different foods sam- ples, for examples caramel, egg white, cream cheese, corn muffin were considered (Meullenet et al. 1998). In the case of baked product, Young’s modulus correlated with sensory elasticity. Conversely, instrumental cohe- siveness and chewiness did not show correlations with sensory cohesiveness and chewiness (P>0.05). Howev- er, correlations of these two attributes were significant- ly improved when the variables were transformed with logarithmic function (i.e. non-linearity) (P<0.05) (Meul- lenet et al., 1998). We observed similar results for our in- strumental cohesiveness, which did not show any linear correlation however, correlation was improved in spear- man’s correlation with sensory cohesiveness (P<0.1), chewiness and resilience (P<0.05). Further, our results showed that instrumental resil- ience was correlated with sensory resilience (P>0.10) and with other sensory attributes, such as hardness, adhesiveness, springiness, cohesiveness, chewiness and elasticity in both Pearson’s and Spearman’s correlations. Instrumental adhesiveness and springiness did not show significant correlations (P>0.10) with the any of the sen- sory attributes in both Pearson’s and Spearman’s cor- relations. Similar results were reported in the case of cooked rice, where instrumental adhesiveness did not show any correlation with sensory stickiness (P>0.05) (Prakash et al., 2005). The poor correlation between sen- sory and TPA springiness was not surprising since simi- lar results were reported recently (Nishinari et al., 2019). Moreover, instrumental gumminess showed linear correlation with sensory hardness and elasticity (P<0.05) and with sensory adhesiveness, springiness, cohesive- ness and chewiness (P<0.10). Instrumental chewiness was significantly correlated with sensory chewiness (P<0.05) and with all others sensory attributes except gumminess. In the case of cereal snack bars, senso- ry attributes of chewiness, firmness, and crumbliness showed very high degrees of correlations (P<0.001) with the instrumental TPA (Kim et al., 2009). Similarly, Chi- nese moon cake showed instrumental hardness, chewi- ness, and stickiness highly correlated with the sensory data (Jia et al., 2008). Instrumental Elasticity 1 was correlated with senso- ry elasticity in both linear and spearman’s correlation. It was linearly correlated with sensory cohesiveness chew- iness (P<0.05), hardness, adhesiveness (P<0.1). Further, correlation with sensory hardness (P<0.05), springi- ness (P<0.1) was improved in Spearman’s. Instrumen- tal Elasticity 2 did not show any linear correlation with respective sensory attributes however, in spearman cor- relation, it was related to sensory gumminess (P<0.05), springiness (P<0.1). Out of eight sensory attributes studied, four were well predicted with their respective instrumental measurements, while others i.e. adhesive- ness, cohesiveness, springiness and gumminess were not correlated with their respective instrumental attributes. Table 1. Coefficients of Linear and Spearman correlation between sensory and instrumental texture measurements for nine varieties of Date fruits Instrumental Sensory attributes attributes Linear correlation Spearman’s correlation HA AD SP CO RE GU CH ES HA AD SP CO RE GU CH ES HA * * * * * * NS * * * * * * NS NS * * AD NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS SP NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS NS CO1 NS NS NS NS NS NS NS NS NS NS NS * * * NS * NS RE * * * * * * NS * * * * * * * * NS * * GU1 * * * * * * * NS NS * * * * * NS * NS NS NS NS * * CH1 * * * * * NS * * * * * * * NS * * E1 * * * * NS * NS NS * * * NS * * NS NS NS NS * E2 NS NS NS NS NS NS NS NS NS NS * * NS NS * NS NS * p<0.05; ** p<0.10; NS: No significant correlations Note: HA: hardness; AD: adhesiveness; SP: springiness; CO: cohesiveness; RE: resilience; GU: gumminess; CH: chewiness; E: elasticity 60 SQU Journal of Agricultural and Marine Sciences, 2021, Volume 26, Issue 1 Correlation between Sensory and Instrumental Textural Attributes of Date Palm (Phoenix dactylifera L.) fruits: Technical Note This may be due to the difference in compression plate size and test sample in TPA, which may lead to variance in major cutting or shearing of the sample (Kim et al., 2009). The lack of cutting or shearing may lower the cor- relation values between instrumental and sensory attri- butes (Battaglia et al., 2020; Paula and Conti-Silva, 2014). Conclusion In the current study, sensory and instrumental textur- al attributes were correlated. The evaluation of texture obtained by instrumental measurements of dates had a significant correlation with the sensory evaluation of textural parameters. Among the eight sensory attributes studied, four were well predicted with their respective instrumental measurements. These attributes were hardness, resilience, chewiness, and elasticity. The sig- nificant correlations between the sensory attributes and the instrumental measurements showed great promise for developing quality control during the selection of dates for commercial processing. Acknowledgement Authors acknowledge the Sultan Qaboos University for PhD Scholarship to Vandita Singh. 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