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Detection of Corn and Whole Wheat Adulteration in White Pepper Powder by Near Infrared Spectroscopy

Xin-wei Li , Rui Lu, Zhe-xuan Wang, Pei Wang, Li Zhang, Peng-xiao Jia
American Journal of Food Science and Technology. 2018, 6(3), 114-117. DOI: 10.12691/ajfst-6-3-5
Published online: March 19, 2018

Abstract

White pepper is a high-value commodity that is a target for adulteration, leading to loss of quality and encroachment on the rights and interests of consumers. Therefore, it is imperative to develop fast and reliable methods for detecting white pepper powder adulteration. The present paper investigated the feasibility of using near infrared (NIR) spectroscopy for quantifying adulteration (including whole wheat flour and corn flour) in white pepper powder. Partial least squares (PLS) calibration models were developed. Results showed that the standard error of calibration (SEC) and prediction (SEP) were 0.788% and 0.920%, respectively.

1. Introduction

Pepper is a member of the spice family. In addition to the main component of pepper piperine, it also contains of aromatic oils, starch, crude protein and soluble nitrogen 1, 2, 3. Since being introduced to China in 1947, pepper has become one of the most popular spices in China, and is widely planted in the southeast provinces of Hainan (over 80% of the total output), Guangdong, Yunnan and Guangxi 2, 3. In recent years, a wide number of varieties of pepper are available in the market, and white pepper takes a large part of the market. White pepper powder is made of nearly mature pepper plant by peeling, soaking and blanching. It is one kind of spice that has high nutritional and medical values 4, 5, 6 (such as having certain curative effect on vitiligo and myocardial ischemia), therefore, white pepper powder owns a broad market prospect.

Nowadays, food adulteration has become a common and serious problem in many countries, and adulteration of white pepper powder with lower value materials such as corn and wheat being used as adulterants. Because adulteration of white pepper powder in these forms may be difficult to distinguish by sense due to the similar colour and small particle size, it has become a problem that affects both the quality and potentially the safety of the product, as well as encroaching on the rights and interests of consumers. Besides, there are no relevant national standards for the rank of pepper in China 3, a real-time, low-cost and convenient detection method is in need.

Currently, chemical methods such as supercritical fluid extraction can be used to detect the adulteration of peppers 7, 8, 9, 10. However, these analytical methods may not be convenient for routine sample analysis or require a certain degree of expertise. In some cases, chemical standards may be rare or expensive or lack identifiable markers. Thus, there is still a need to develop a fast, chemical-free, and cost-effective method for the detection of adulteration of white pepper powder. Near infrared (NIR) spectroscopy primarily reflects absorption of overtones and combination of vibrations of X-H functional groups (such as C-H, O-H, and N-H). Because of weak absorption strength, most of samples can be measured directly without pre-processing, moreover, NIR analysis has the advantage of rapid determination, non-pollution, low cost and being non-destructive, and is commonly used in many areas, including agriculture, food, environment, bio-medicine and pharmaceuticals 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22. It was shown that satisfactory results were achieved in food adulteration detection carried out by NIR spectroscopy in such foods as milk, oil, onion 11, 17, 19. However, white pepper powder adulteration detection using NIR is a novel application.

The aim of this study was to show the possibility to apply NIR to determine the adulteration in white pepper powder. Whole wheat flour and corn flour were used as adulterants according to the actual situation. Partial least squares (PLS) regression combined with NIR spectroscopy was employed for the quantitative detection of white pepper powder adulteration.

2. Materials and Methods

2.1. Instrument

A laboratory NIR spectrometer (NIR B603, Boer instrument (Tianjin) CO., LTD, China) was employed throughout. The instrument operates in the 1300-2600nm range, with a spectral resolution of 8nm. The instrument uses tungstem radiation source to illuminate samples for diffuse reflectance measurements, and adopts an InGaAs sensor for detection. The lamp was allowed to warm up for 30min before use. A rotary sample cell with 6.5cm diameter was used for sample presentation. Self-calibration was undertaken before measurements, and spectral data acquisition was an average of 30 scans.

2.2. Samples

As this paper was a confirmatory study of using NIR to detect the adulteration percentage of white pepper powder, only one sample of pure white pepper powder was used to obtain adulterated samples. The pepper powder was produced in Lingshui Li Autonomous County, Hainan, China. And the adulterants including whole wheat flour and corn flour were produced in Shandong, China.

In order to present the diversity of pepper adulteration in the market, adulterants were made in five categories, respectively: corn flour, whole-wheat flour and the mixture of corn flour and whole-wheat flour in three kinds of proportions (1:1, 1:2 and 2:1). Then adulterated samples were obtained with pure white pepper and each adulterant, and the adulteration concentration ranged from 1% to 50% with step size 1%. Finally, a total of 250 adulterated samples were used for this study, as shown in Table 1.

All samples were sealed in sample bottles and allowed to stabilise to room temperature (22°C±2°C) before NIR spectra were recorded.

2.3. Data Analysis

The raw spectra data were imported into the MATLAB software (version R2014a) for data treatment and modelling. In order to achieve high instrument performance, both edges of wavelength band were discarded, and the 1400-2500nm range was used to build PLS models. Leave-one-out cross validation method was used to find out singular points, and 6 outliers were removed from sample set. The Kennard-Stone (K-S) algorithm was used and samples were divided into calibration (163 samples) and validation (81 samples). The statistics of samples involved in modelling was shown in Table 2. Detrending was used and several other mathematical pretreatments were tested to improve the PLS models. Correlation coefficient method was tested to select appropriate wavelength combinations. And this method calculated the correlation between spectral absorbance at each wavelengths and adulteration concentration, and picked up characteristic wavelengths by a proper threshold of correlation coefficient. The calculation formula of correlation coefficient was shown in Eqn. (1), where X is the spectral absorbance matrix, Y is the concentration matrix, Cov(X,Y) is the covariance between X and Y, D(X) is the variance of X, and D(Y) is the variance of Y. The correlation between actual and predicted constituent values (R2), standard error of both calibration (SEC) and validation (SEP), average of difference between actual and NIR predicted values (bias) and ratio of standard deviation to SEP (RPD) were used to test the performance of calibrations.

(1)

3. Results and Discussion

The detrending spectral data of three pure materials including whole wheat flour, corn flour and white pepper powder were recorded and shown in Fig 1. It can be seen that the spectra of three materials were closely, and they shared similar trends and peaks. The main absorbance peaks can be found at 1457nm, 1705nm, 1927nm, 2077nm, 2296nm and 2466nm.

Several spectral pretreatment methods such as multiple scatter correction, derivative, standard normal variable and Savitzky-Golay convolutions were tested, and it was indicated that none of the mathematical pretreatments tested improved the prediction accuracy of the PLS models. Similar results had been reported in models developed for the prediction of chemical components in food such as olive fruits 23.

Correlation coefficient method was tested to select characteristic wavelengths. The threshold of correlation coefficient was optimized based on SEC and SEP, as shown in Figure 2, and the correlation coefficient at each wavelength points was shown in Figure 3. It was indicated that the accuracy of PLS models barely changed when threshold of correlation coefficient (Th) was below 0.85, and it decreased rapidly in other range. The lowest values of SEC and SEP occurred when threshold equalled to 0.19, as shown in Table 3, where F was the number of factors. It can be obtained that when threshold equalled to 0.19, a total of 1046 wavelength points were selected, including [1400,1406]∪ [1413,1501]∪[1512,1869]∪[1874,2043]∪[2050,2313]∪[2321,2397]∪[2420,2500]nm, and the prediction of corresponding PLS model was shown in Figure 5. When threshold equalled to 0.85 (Figure 4), a total of 569 wavelength points were selected, including [1537,1636]∪[1748,1838]∪[1883,2034]∪[2060,2185] ∪ [2203,2215]∪[2441,2500]nm, and the prediction of corresponding PLS model was shown in Fig 6. In comparation, the PLS model was good enough for practical application when threshold was 0.85, meanwhile, its compute was reduced largely.

4. Conclusion

White pepper powder is one of the most popular flavorings, and owns a broad market prospect in China. The identification of adulteration is of great significance for white pepper powder food safety and the interests of consumers. In the present study, a fast-screening approach for detecting adulteration such as whole wheat flour and corn flour in white pepper powder with NIR spectroscopy was developed. Quantitative PLS models were constructed and showed satisfactory performance with a RPD of 15.2.

More samples of pure white pepper and adulterants will be used to build quantitative model combined with handheld NIR spectroscopy, which will be the direction of the future researches.

Acknowledgements

The authors would like to acknowledge Boer instrument (Tianjin) CO., LTD for providing NIR instrument and useful advices. This work was supported by the fundamental research funds for the central universities (No. BLX201610).

References

[1]  Eva María Toledo-Martín, María Carmen García-García, Rafael Font, José Manuel Moreno-Rojas, Pedro Gómez, María Salinas-Navarro, and Mercedes Del Río-Celestino, “Application of visible/near-infrared reflectance spectroscopy for predicting internal and external quality in pepper”, Journal of the Science of Food and Agriculture, 96(9). 3114-3125. Oct.2015.
In article      View Article  PubMed
 
[2]  Liu Yang, Xue Wang, Jia Wang, Jiaojiao Xu and Shengan Tang, “Research on constituents of pipernigrus L.”, Journal of Tianjin Medical University, 22(04). 300-301. Apr.2016.
In article      
 
[3]  Huasong Wu, Jianfeng Yang and Liyun Lin, “A summary of pepper research in China”, Scientia Agricultura Sinica, 42(7). 2469-2480. Jul.2009.
In article      View Article
 
[4]  Yinfu Bai and Hong Xu, “Protective action of piperine against experimental gastric ulcer”, Acta Pharmacologica Sinica, 21(4). 357-359. Apr.2000.
In article      PubMed
 
[5]  ES Sunila and G Kuttan, “Immunomodulatory and antitumor activity of Piper longum Linn. and piperine”, Journal of Ethnopharmacology, 90(2-3). 339-346. Feb.2004.
In article      View Article  PubMed
 
[6]  Huasong Wu, Jianfeng Yang and Liyun Lin, “Piperine suppresses tumor growth and metastasis in vitro and in vivo in a 4T1 murine breast cancer model”, Scientia Agricultura Sinica, 33(4). 523-530. Mar.2012.
In article      View Article
 
[7]  Paramita Bhattacharjee, Rekha S Singhal, and Achyut S Gholap, “Supercritical carbon dioxide extraction for identification of adulteration of black pepper with papaya seeds”, Journal of the Science of Food and Agriculture, 83(8). 783-786. Jun.2003.
In article      View Article
 
[8]  D.R.R.P. Dissanayake, H.M.P.D. Herath, M.D.M.I.M. Dissanayake, M.D.M. Chamikara, M.M. Jayakody, S.S.C. Amaresekara, K.W.T.R. Kularathna, N.N.H. Karannagoda, M. Ishan, and S.D.S.S. Sooriyapathirana, “The length polymorphism of the locus psbA-trnH is idyllic to detect the adulterations of black pepper with papaya seeds and chili”, Journal of Agricultural Sciences, 11(2). 74-87. May.2016.
In article      View Article
 
[9]  P Bhattacharjee, RS Singhal and AS Gholap, “Identification of black pepper adulteration”, Journal of the Science of Food & Agriculture. 83(3). 783-786(4). Jun.2003.
In article      View Article
 
[10]  K. Dhanya, S. Syamkumar and B. Sasikumar, “Development and application of SCAR marker for the detection of papaya seed adulteration in traded black pepper powder”, Food Biotechnology, 23(2). 97-106. May.2009.
In article      View Article
 
[11]  C. Lu, B. Xiang, G. Hao, J. Xu, Z. Wang, and C. Chen, “Rapid detection of melamine in milk powder by near infrared spectroscopy”, Journal of Near Infrared Spectroscopy, 17(2). 59-67. Jan.2009.
In article      View Article
 
[12]  Jill K. Winkler-Moser, Mukti Singh, Kathy A. Rennick, Erica L. Bakota, Gulab Jham, Sean X. Liu, and Steven F. Vaughn, “Detection of corn adulteration in brazilian coffee (coffea arabica) by tocopherol profiling and near-Infrared (NIR) spectroscopy”, Journal of Agricultural and Food Chemistry, 63(49). 10662-10668. Nov.2015.
In article      View Article  PubMed
 
[13]  Santosh Lohumi, Sangdae Lee, Wang-Hee Lee, Moon S. Kim, Changyeun Mo, Hanhong Bae, and Byoung-Kwan Cho, “Detection of starch adulteration in onion powder by FT-NIR and FTIR spectroscopy”, Journal of Agricultural and Food Chemistry, 62(38). 9246-9251. Sep.2014.
In article      View Article  PubMed
 
[14]  H. B. Ding, and R. J. Xu, “Near-Infrared spectroscopic technique for detection of beef hamburger adulteration”, Journal of Agricultural and Food Chemistry, 48(6). 2193-2198. Jun.2000.
In article      View Article  PubMed
 
[15]  Banu F. Ozen, and Lisa J. Mauer, “Detection of hazelnut oil adulteration using FT-IR spectroscopy”, Journal of Agricultural and Food Chemistry. 50(14). 3898-3901. Jul.2002.
In article      View Article  PubMed
 
[16]  Simon A. Haughey, Stewart F. Graham, Emmanuelle Cancouët, and Christopher T. Elliott, “The application of Near-Infrared reflectance spectroscopy (NIRS) to detect melamine adulteration of soya bean meal”, Food Chemistry, 136(3-4). 1557-1561. Feb.2013.
In article      View Article  PubMed
 
[17]  Amrita Poonia, Alok Jha, Rajan Sharma, Harikesh BahadurSingh, Ashwini Kumar Rai and Nitya Sharma, “Detection of adulteration in milk: A review”, International Journal of Dairy Technology, 69. 1-20. Nov.2016.
In article      View Article
 
[18]  P Pathompong, B Els, V Berte, N Bartm and S Wouter, “Non-destructive measurement of firmness and soluble solids content in bell pepper using NIR spectroscopy”, Journal of Food Engineering, 94(3-4). 267-273. Oct.2009.
In article      View Article
 
[19]  Enrico Valli, Alessandra Bendini, Annachiara Berardinelli, Luigi Ragni, Bruno Riccò, Marco Grossi, and Tullia Gallina Toschi, “Rapid and innovative instrumental approaches for quality and authenticity of olive oils”, European Journal of Lipid Science and Technology, 118(11). 1601-1619. Oct.2016.
In article      View Article
 
[20]  L.P.D. Ribeiro, A.P. Monteiro da Silva, A.A. de Lima, E. de Oliveira Silva, Å. Rinnan and C. Pasquini, “Nondestructive determination of quality traits of cashew apples (Anacardium occidentale, L.) using a portable near infrared spectrophotometer”, Journal of Near Infrared Spectroscopy, 24(1). 77-82. Jan.2016.
In article      View Article
 
[21]  R.E. Masithoh, R. Haff and S. Kawano, “Determination of soluble solids content and titratable acidity of intact fruit and juice of satsuma mandarin using a hand-held near infrared instrument in transmittance mode”, Journal of Near Infrared Spectroscopy, 24(1). 83-88. Feb.2016.
In article      View Article
 
[22]  MT Sánchez, K Floresrojas, JE Guerrero, A Garridovaro and D Pérezmarín, “Measurement of pesticide residues in peppers by near-infrared reflectance spectroscopy”, Pest Management Science, 66(6). 580-586. Jun.2010.
In article      View Article  PubMed
 
[23]  A. Gracia and L. León, “Non-destructive assessment of olive fruit ripening by portable near infrared spectroscopy”, Grasas Y Aceites, 62(3). 268-274. Nov.2011.
In article      View Article
 

Published with license by Science and Education Publishing, Copyright © 2018 Xin-wei Li, Rui Lu, Zhe-xuan Wang, Pei Wang, Li Zhang and Peng-xiao Jia

Creative CommonsThis work is licensed under a Creative Commons Attribution 4.0 International License. To view a copy of this license, visit http://creativecommons.org/licenses/by/4.0/

Cite this article:

Normal Style
Xin-wei Li, Rui Lu, Zhe-xuan Wang, Pei Wang, Li Zhang, Peng-xiao Jia. Detection of Corn and Whole Wheat Adulteration in White Pepper Powder by Near Infrared Spectroscopy. American Journal of Food Science and Technology. Vol. 6, No. 3, 2018, pp 114-117. http://pubs.sciepub.com/ajfst/6/3/5
MLA Style
Li, Xin-wei, et al. "Detection of Corn and Whole Wheat Adulteration in White Pepper Powder by Near Infrared Spectroscopy." American Journal of Food Science and Technology 6.3 (2018): 114-117.
APA Style
Li, X. , Lu, R. , Wang, Z. , Wang, P. , Zhang, L. , & Jia, P. (2018). Detection of Corn and Whole Wheat Adulteration in White Pepper Powder by Near Infrared Spectroscopy. American Journal of Food Science and Technology, 6(3), 114-117.
Chicago Style
Li, Xin-wei, Rui Lu, Zhe-xuan Wang, Pei Wang, Li Zhang, and Peng-xiao Jia. "Detection of Corn and Whole Wheat Adulteration in White Pepper Powder by Near Infrared Spectroscopy." American Journal of Food Science and Technology 6, no. 3 (2018): 114-117.
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[1]  Eva María Toledo-Martín, María Carmen García-García, Rafael Font, José Manuel Moreno-Rojas, Pedro Gómez, María Salinas-Navarro, and Mercedes Del Río-Celestino, “Application of visible/near-infrared reflectance spectroscopy for predicting internal and external quality in pepper”, Journal of the Science of Food and Agriculture, 96(9). 3114-3125. Oct.2015.
In article      View Article  PubMed
 
[2]  Liu Yang, Xue Wang, Jia Wang, Jiaojiao Xu and Shengan Tang, “Research on constituents of pipernigrus L.”, Journal of Tianjin Medical University, 22(04). 300-301. Apr.2016.
In article      
 
[3]  Huasong Wu, Jianfeng Yang and Liyun Lin, “A summary of pepper research in China”, Scientia Agricultura Sinica, 42(7). 2469-2480. Jul.2009.
In article      View Article
 
[4]  Yinfu Bai and Hong Xu, “Protective action of piperine against experimental gastric ulcer”, Acta Pharmacologica Sinica, 21(4). 357-359. Apr.2000.
In article      PubMed
 
[5]  ES Sunila and G Kuttan, “Immunomodulatory and antitumor activity of Piper longum Linn. and piperine”, Journal of Ethnopharmacology, 90(2-3). 339-346. Feb.2004.
In article      View Article  PubMed
 
[6]  Huasong Wu, Jianfeng Yang and Liyun Lin, “Piperine suppresses tumor growth and metastasis in vitro and in vivo in a 4T1 murine breast cancer model”, Scientia Agricultura Sinica, 33(4). 523-530. Mar.2012.
In article      View Article
 
[7]  Paramita Bhattacharjee, Rekha S Singhal, and Achyut S Gholap, “Supercritical carbon dioxide extraction for identification of adulteration of black pepper with papaya seeds”, Journal of the Science of Food and Agriculture, 83(8). 783-786. Jun.2003.
In article      View Article
 
[8]  D.R.R.P. Dissanayake, H.M.P.D. Herath, M.D.M.I.M. Dissanayake, M.D.M. Chamikara, M.M. Jayakody, S.S.C. Amaresekara, K.W.T.R. Kularathna, N.N.H. Karannagoda, M. Ishan, and S.D.S.S. Sooriyapathirana, “The length polymorphism of the locus psbA-trnH is idyllic to detect the adulterations of black pepper with papaya seeds and chili”, Journal of Agricultural Sciences, 11(2). 74-87. May.2016.
In article      View Article
 
[9]  P Bhattacharjee, RS Singhal and AS Gholap, “Identification of black pepper adulteration”, Journal of the Science of Food & Agriculture. 83(3). 783-786(4). Jun.2003.
In article      View Article
 
[10]  K. Dhanya, S. Syamkumar and B. Sasikumar, “Development and application of SCAR marker for the detection of papaya seed adulteration in traded black pepper powder”, Food Biotechnology, 23(2). 97-106. May.2009.
In article      View Article
 
[11]  C. Lu, B. Xiang, G. Hao, J. Xu, Z. Wang, and C. Chen, “Rapid detection of melamine in milk powder by near infrared spectroscopy”, Journal of Near Infrared Spectroscopy, 17(2). 59-67. Jan.2009.
In article      View Article
 
[12]  Jill K. Winkler-Moser, Mukti Singh, Kathy A. Rennick, Erica L. Bakota, Gulab Jham, Sean X. Liu, and Steven F. Vaughn, “Detection of corn adulteration in brazilian coffee (coffea arabica) by tocopherol profiling and near-Infrared (NIR) spectroscopy”, Journal of Agricultural and Food Chemistry, 63(49). 10662-10668. Nov.2015.
In article      View Article  PubMed
 
[13]  Santosh Lohumi, Sangdae Lee, Wang-Hee Lee, Moon S. Kim, Changyeun Mo, Hanhong Bae, and Byoung-Kwan Cho, “Detection of starch adulteration in onion powder by FT-NIR and FTIR spectroscopy”, Journal of Agricultural and Food Chemistry, 62(38). 9246-9251. Sep.2014.
In article      View Article  PubMed
 
[14]  H. B. Ding, and R. J. Xu, “Near-Infrared spectroscopic technique for detection of beef hamburger adulteration”, Journal of Agricultural and Food Chemistry, 48(6). 2193-2198. Jun.2000.
In article      View Article  PubMed
 
[15]  Banu F. Ozen, and Lisa J. Mauer, “Detection of hazelnut oil adulteration using FT-IR spectroscopy”, Journal of Agricultural and Food Chemistry. 50(14). 3898-3901. Jul.2002.
In article      View Article  PubMed
 
[16]  Simon A. Haughey, Stewart F. Graham, Emmanuelle Cancouët, and Christopher T. Elliott, “The application of Near-Infrared reflectance spectroscopy (NIRS) to detect melamine adulteration of soya bean meal”, Food Chemistry, 136(3-4). 1557-1561. Feb.2013.
In article      View Article  PubMed
 
[17]  Amrita Poonia, Alok Jha, Rajan Sharma, Harikesh BahadurSingh, Ashwini Kumar Rai and Nitya Sharma, “Detection of adulteration in milk: A review”, International Journal of Dairy Technology, 69. 1-20. Nov.2016.
In article      View Article
 
[18]  P Pathompong, B Els, V Berte, N Bartm and S Wouter, “Non-destructive measurement of firmness and soluble solids content in bell pepper using NIR spectroscopy”, Journal of Food Engineering, 94(3-4). 267-273. Oct.2009.
In article      View Article
 
[19]  Enrico Valli, Alessandra Bendini, Annachiara Berardinelli, Luigi Ragni, Bruno Riccò, Marco Grossi, and Tullia Gallina Toschi, “Rapid and innovative instrumental approaches for quality and authenticity of olive oils”, European Journal of Lipid Science and Technology, 118(11). 1601-1619. Oct.2016.
In article      View Article
 
[20]  L.P.D. Ribeiro, A.P. Monteiro da Silva, A.A. de Lima, E. de Oliveira Silva, Å. Rinnan and C. Pasquini, “Nondestructive determination of quality traits of cashew apples (Anacardium occidentale, L.) using a portable near infrared spectrophotometer”, Journal of Near Infrared Spectroscopy, 24(1). 77-82. Jan.2016.
In article      View Article
 
[21]  R.E. Masithoh, R. Haff and S. Kawano, “Determination of soluble solids content and titratable acidity of intact fruit and juice of satsuma mandarin using a hand-held near infrared instrument in transmittance mode”, Journal of Near Infrared Spectroscopy, 24(1). 83-88. Feb.2016.
In article      View Article
 
[22]  MT Sánchez, K Floresrojas, JE Guerrero, A Garridovaro and D Pérezmarín, “Measurement of pesticide residues in peppers by near-infrared reflectance spectroscopy”, Pest Management Science, 66(6). 580-586. Jun.2010.
In article      View Article  PubMed
 
[23]  A. Gracia and L. León, “Non-destructive assessment of olive fruit ripening by portable near infrared spectroscopy”, Grasas Y Aceites, 62(3). 268-274. Nov.2011.
In article      View Article