Assessment of elemental profiling combined with chemometrics for authenticating the geographical origins of Pacific white shrimp (Litopenaeus vannamei)

Highlights

• 24 elements in shrimp were different between north and south China.

• Only Cd and Tb in feeds were related to elements in shrimp.

• KNN and RF obtained higher discrimination rates than LDA.

• The highest discrimination rate was over 98.75%.

Abstract

Pacific white shrimp (Litopenaeus vannamei) is an important aquaculture species worldwide, and there is a growing concern over misdescribed shrimp products, particularly over their geographical origins. Shrimp samples were collected from 12 locations in northern and southern China to develop traceability methods in identifying their geographic origins. In one of the sampling sites, shrimp were collected from five farms using the same water source but feeding with different brands of feed to investigate the effect of feed on the elemental compositions of shrimp. Totally 35 elements (Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, Y, U, Li, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, As, Rb, Sr, Ag, Cd, Cs, Ba, and Pb) were detected in both shrimp and feed. Only Cd and Tb in shrimp were positively correlated with those in the feed. Moreover, 24 elements (Li, Al, V, Fe, As, Rb, Sr, Cd, Pb, Ce, Nd, Pr, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu, Th, and Y) in shrimp were significantly different between northern and southern China. Elements As, Fe, Pb, Rb, Cs, and U, selected by stepwise discriminant analysis (SDA), were used to create a new dataset (SSDAs dataset) to compare with the entire dataset (ATEs dataset) in discrimination analyses. Classification tools, including linear discriminant analysis (LDA), k-nearest neighbor (KNN), and random forest (RF) were used to create a discrimination model to authenticate shrimp provenance based on the ATEs and SSDAs datasets. The highest discrimination rate was achieved with RF using the SSDAs dataset, which achieved an overall correct discrimination rate of 100%, a cross-validation rate of 98.78%, and a predictive discrimination rate of 100%. Therefore, elemental profiling combined with chemometrics is a promising method which can be used to identify shrimp provenance.

Introduction

Authenticating aquatic food is increasingly important due to the globalization of the aquatic products trade and recurring food safety alerts (Leal, Pimentel, Ricardo, Rosa, & Calado, 2015; Li, Boyd, & Sun, 2016; Sheikha & Xu, 2017). Aquatic products are more susceptible to fraud than other food products (Hassoun et al., 2020). Consequently, consumers have become keenly interested in the authenticity of aquatic food, particularly its geographical origin. Despite that regulations have been implemented against food fraud worldwide to protect public health and consumer’ interest (Ortea & Gallardo, 2015; Zhang et al., 2019), fraud or mislabeling remains a widespread issue in aquatic products of animal origin (Delpiani, Delpiani, Antoni, Ale, & Research, 2020; Donna-Mareè, Charles, & Stefano, 2018). A variety of analytical techniques, including elemental profiling, stable isotope fingerprinting, fatty acid composition, and spectroscopic analyses have been used to successfully determine the geographical origin of aquatic food (Gopi et al., 2019b, 2019a; Han et al., 2020; Li, Boyd, & Odom, 2014; Richter, Gurk, Wagner, Bockmayr, & Fischer, 2019; Zhang et al., 2019; Zhao, Liu, Li, Zhang, & Qi, 2018). Among them, elemental profiling is widely used.

Elemental profiling has been used to authenticate the geographical origin of shrimp, clam, sea cucumber, seabass, and other fish species (Liu et al., 2012; Iguchi, Isshiki, Takashima, Yamashita, & Yamashita, 2013; Chaguri et al., 2015; Gopi et al., 2019a, 2019b). Trace elements, such as Li, V, Mn, Co, As, Rb, Mo, Ba, Pb, U, Al, Mn, Fe, Ni, Cu, Se, Cd and Hg, are commonly used to identify the geographical origins of aquatic food (Iguchi, Takashima, Namikoshi, Yamashita, & Yamashita, 2013; Liu et al., 2012). Subsequently, some studies have suggested that rare earth elemental profiling can be used to authenticate the provenance of food products (Danezis et al., 2017; Drivelos, Danezis, Haroutounian, & Georgiou, 2016). Furthermore, the combination of trace elements and rare earth elements performs well for identifying the geographical origin of black tiger prawn (Penaeus monodon) with 100% discrimination rate (Gopi et al., 2019a).

Nevertheless, aquatic animals can directly absorb elements from the diet (Kalantzi et al., 2013); thus, feed is an important factor affecting the elemental composition of aquatic animals. Some essential elements are often added to commercial aquaculture diets to improve growth performance (Bussel, Schroeder, Mahlmann, & Schulz, 2014; Musharraf & Khan, 2018). For example, Co is a constituent mineral of vitamin B₁₂ (VB₁₂) and is added to the aquatic diet to satisfy the VB₁₂ requirement of aquatic animals (Yoshimatsu et al., 2006). Dietary Co concentration can significantly affect Co concentration in the whole-body of rainbow trout (Bussel et al., 2014). In addition, large differences in elemental concentrations of commercial feeds are contributed by differences in the raw ingredients or contamination (Li et al., 2016; Tacon & De Silva, 1983), resulting in the variations in the elemental composition of aquatic animals (Fei & Wang, 2009; Kamunde, Grosell, Higgs, & Wood, 2002; Chowdhury et al., 2005; Musharraf & Khan, 2018). Furthermore, Li et al. (2016) suggested that feed must be seriously considered when conducting an elemental analysis of aquaculture products, as mineral concentrations vary widely in fish feeds. However, few studies have evaluated whether the diet affects the discrimination rate of discriminating the geographical origin of an aquatic product based on elemental profiling.

Pacific white shrimp (Litopenaeus vannamei) is the most economically important shrimp species farmed worldwide. According to statistics from the Food and Agriculture Organization of the United Nations, global production of L. vannamei was 4,980,281 metric tons in 2018 (FAO, 2020). In China, the production of L. vannamei was more than 1,760,341 metric tons in 2018, constituting 35.35% of the global L. vannamei production and 43.04% of total shrimp production in China (China Fisheries Yearbook, 2019). L. vannamei in China are mainly cultured in coastal areas covering eight provinces, and these locations have been divided into northern and southern China due to the differences in climate. Consumers expect to be told the origin of shrimp. Moreover, regulations, such as EU Regulation No. 1379/2013, Management plan for protect food against intentional adulteration (2019–2021) of China, emphasize that aquatic products sold in markets must be labelled with their geographical origin information, because shrimp are often traded across a wide geographic area. Therefore, there is a pressing need to develop a method to differentiate shrimp provenance to protect consumer confidence for shrimp products and ensure enforcement of regulations.

In this study, L. vannamei samples were collected from northern and southern China. The concentrations of trace elements and rare earth elements were determined in the shrimp to develop a method for identifying the geographical origin. In addition, shrimp cultured in the same water and fed different brands of feed were collected to investigate the effects of feed on the elemental composition of the shrimp and the efficiency of the discrimination models based on elemental profiling.