## 5 Food Safety and Quality Applications  
Over the past 15 years, line-scan hyperspectral imaging techniques have been intensively researched and developed for measuring physical, chemical, and biological properties of a broad range of food and biological materials. The application scope has been expanded rapidly into many food and agricultural areas such as food safety and quality evaluation, plant maturity and disease monitoring, raw material screening, food processing assessment, and equipment sanitation inspection. Table 1 lists many such line-scan hyperspectral imaging applications. The selected applications, which are representative rather than exhaustive, were categorized based on the underlying spectroscopy techniques used in the line-scan hyperspectral imaging measurements. It should be noted that these applications are generally under indoor-controlled lighting conditions (e.g., laboratory and food processing plant). Outdoor and field applications of the hyperspectral imaging techniques (e.g., plant cultivation and phenotyping) [22; 23] are beyond the scope of this review. Food and agricultural products are complicated systems that can be considered mixtures of different types of molecules. The interesting molecules in a food matrix can be investigated based on different types of spectral information. Reflectance, transmittance, fluorescence, and Raman spectroscopy and imaging techniques can be used to analyze many intrinsic compositions (e.g., proteins, fats, carbohydrates, carotenoids, fatty acid, and inorganics) and extrinsic components (e.g., bacteria, adulterants, and contaminants) of the food and biological samples. As shown in Table 1, one main application area is food surface inspection. Reflectance imaging in the visible and near-infrared region, fluorescence imaging in the visible region, and Raman imaging in the near-infrared region can all be utilized to inspect exterior characteristics of different types of food and agricultural products, such as inspecting bruises on apples using reflectance [24], detecting fecal contamination on apples using fluorescence [6], and screening for chemical adulterants in food powders using Raman [25]. Transmittance imaging in the visible and near-infrared region using high-intensity light sources is suitable to assess overall interior attributes of small or thin food samples, such as detecting insect damage in soybean [26] and mapping fat distribution in pork belly and salmon fillet [27]. Integration of different spectroscopy techniques into hyperspectral imaging measurements can provide more detection capacities and achieve more accurate results than those using a single imaging mode, such as evaluating both external and internal quality of pickling cucumbers using integrated reflectance and transmittance imaging [28] and detecting aflat in corn kernels using combined reflectance and fluorescence image data [29]. Besides imaging, spatially resolved spectroscopy techniques based on line-scan hyperspectral acquisition methods can be used for obtaining internal or subsurface information from heterogeneous or layered food samples, such as firmness assessment of peach fruit using spatially resolved diffuse reflectance spectroscopy [30] and through-plastic-package inspection of cane sugar using spatially offset Raman spectroscopy [21]. In addition, line-scan imaging systems working in both hyperspectral and multispectral modes have been developed, in which the number of bands, central wavelengths, and bandwidths can be controlled via software in the multispectral mode [31; 32]. Such systems can scan hundreds of lines per second using CCD exposure times at the millisecond level, making them particularly useful to inspect fast-moving food items on the processing lines in real time. Figure 11 shows an example of using line-scan hyperspectral/multispectral reflectance imaging for online wholesomenesis inspection of freshly slaughtered poultry carcasses on a high-speed commercial chicken processing line [32].