Xin-An Zeng

Recent Advances in Wavelength Selection Techniques for Hyperspectral Image Processing in the Food Industry

During the past decade, hyperspectral imaging (HSI) has been rapidly developing and widely applied in the food industry by virtue of the use of chemometric techniques in which wavelength selection methods play an important role. This paper is a review of such variable selection methods and their limitations, describing the basic taxonomy of the methods and their respective advantages and disadvantages. Special attention is paid to recent developments in wavelength selection techniques for HSI in the field of food quality and safety evaluations. Typical and commonly used methods in HSI, such as partial least squares regression, stepwise regression and spectrum analysis, are described in detail. Some sophisticated methods, such as successive projections algorithm, uninformative variable elimination, simulated annealing, artificial neural network and genetic algorithm methods, are also discussed. Finally, new methods not currently used but that could have substantial impact on the field are presented. In short, this review provides an overview of wavelength selection methods in food-related areas and offers a thoughtful perspective on future potentials and challenges in the development of HSI systems.

Effects of ultrasound treatments on quality of grapefruit juice

Sonication is recognised as a potential technique for improvement in the quality of fruit juices. This study was initiated with the objective of evaluating the effect of sonication treatments on some important quality parameters of grapefruit juice such as physico-chemical (pH, acidity and °Brix), Hunter colour values (L(*), a(*) and b(*)), cloud value, electrical conductivity, total antioxidant capacity, DPPH (2,2-diphenyl-1-picrylhydrazyl) free radical scavenging activity, ascorbic acid, total phenolics, flavonoids and flavonols. Sonication of grapefruit juice was done in a bath type sonicator at a frequency of 28 kHz by maintaining a constant temperature of 20 °C. Results showed that there was significant improvement in the cloud value, total antioxidant capacity, DPPH free radical scavenging activity, ascorbic acid, total phenolics, flavonoids and flavonols in all the juice samples sonicated for 30, 60 and 90 min but no changes occurred in the pH, acidity and °Brix value as compared to control. Some differences in all the colour values were also observed but overall quality of grapefruit juice was improved, suggesting that sonication technique may successfully be implemented an industrial scale for the processing of grapefruit juice.

Texture and Structure Measurements and Analyses for Evaluation of Fish and Fillet Freshness Quality: A Review

 Recently, food safety and quality have become critical issues of great concern throughout the world. Fish is one of the most vulnerable and perishable aquatic products. The evaluation of fish and fillet freshness is therefore very significant in research and development for providing premium and supreme quality for human health and acceptance by consumers, as well as for international trade. The texture and structure of fish muscle are important freshness quality attributes that depend on several parameters such as hardness, cohesiveness, springiness, chewiness, resilience, and adhesiveness, as well as the internal cross-linking of connective tissue and the detachment of fibers. This review aims to present recent advances of texture and structure measurements and analyses, including sensory evaluation and instrumental methods, for indicating and evaluating fish freshness quality. Factors affecting these measurements are detailed and correlations between texture and structure are discussed. Moreover, the limitations and challenges of fish texture and structure measurements are described and some viewpoints about current work and future trends are also presented.

Combination of spectra and texture data of hyperspectral imaging for prediction of pH in salted meat

This study was carried out to investigate the feasibility of combining spectral with texture features in order to improve pH prediction for salted pork. Average spectra were extracted from the region of interest (ROI) of hyperspectral images over the wavelength region of 400-1000 nm and 9 characteristic spectral variables were then selected by principal components analysis (PCA). Meanwhile, gray-level gradient cooccurrence matrix (GLGCM) analysis was implemented on the first PC image (accounted for 96% of the total variance) to extract 13 textural feature variables. Partial least-squares regression (PLSR) was developed for predicting pH based on spectral, textural or combined data. Coefficient of determination (R(2)P) of 0.794 for the prediction samples based on data fusion was achieved, which was superior to the results based on spectra (R(2)P=0.783) or texture (R(2)P=0.593) alone. Hence, methods of combining spectral with texture analyses are effective for improving meat quality prediction.

Feasibility of using hyperspectral imaging to predict moisture content of porcine meat during salting process.

The feasibility of using hyperspectral imaging technique (1000-2500 nm) for predicting moisture content (MC) during the salting process of porcine meat was assessed. Different spectral profiles including reflectance spectra (RS), absorbance spectra (AS) and Kubelka-Munk spectra (KMS) were examined to investigate the influence of spectroscopic transformations on predicting moisture content of salted pork slice. The best full-wavelength partial least squares regression (PLSR) models were acquired based on reflectance spectra (Rc(2)=0.969, RMSEC=0.921%; Rc(2)=0.941, RMSEP=1.23%). On the basis of the optimal wavelengths identified using the regression coefficient, two calibration models of PLSR and multiple linear regression (MLR) were compared. The optimal RS-MLR model was considered to be the best for determining the moisture content of salted pork, with a Rc(2) of 0.917 and RMSEP of 1.48%. Visualisation of moisture distribution in each pixel of the hyperspectral image using the prediction model display moisture evolution and migration in pork slices.

Effect of pulsed electric fields assisted acetylation on morphological, structural and functional characteristics of potato starch

Pulsed electric fields (PEF)-assisted acetylation of potato starch with different degree of substitution (DS) was prepared and effects of PEF strength, reaction time, starch concentration on DS were studied by response surface methodology. Results showed DS was increased from 0.054 (reaction time of 15 min) to 0.130 (reaction time of 60 min) as PEF strength increased from 3 to 5 kV/cm. External morphology revealed that acetylated starch with higher DS was aggravated more bulges and asperities. Fourier-transformed infrared spectroscopy confirmed the introduction of acetyl group through a band at 1730 cm(-1). The optimum sample (DS =0 .13) had lower retrogradation (39.1%), breakdown (155 BU) and setback value (149BU), while pasting temperature (62.2 °C) was slightly higher than non-PEF-assisted samples. These results demonstrated PEF treatment can be a potential and beneficial method for acetylation and achieve higher DS with shorter reaction time.

Recent Advances in Methods and Techniques for Freshness Quality Determination and Evaluation of Fish and Fish Fillets: A Review

The freshness quality of fish plays an important role in human health and the acceptance of consumers as well as in international fishery trade. Recently, with food safety becoming a critical issue of great concern in the world, determination and evaluation of fish freshness is much more significant in research and development. This review renovates and concentrates recent advances of evaluating methods for fish freshness as affected by preharvest and postharvest factors and highlights the determination methods for fish freshness including sensory evaluation, microbial inspection, chemical measurements of moisture content, volatile compounds, protein changes, lipid oxidation, and adenosine triphosphate (ATP) decomposition (K value), physical measurements, and foreign material contamination detection. Moreover, the advantages and disadvantages of these methods and techniques are compared and discussed and some viewpoints about the current work and future trends are also presented.

Effects of pulsed electric field treatments on some properties of tapioca starch.

Tapioca starch-water dispersions (8.0%, w/w) were subject to pulsed electric fields (PEF) at 30, 40 and 50 kV cm(-1), respectively. The effect of the intense energy input (Q) of PEF treatment (over 28.85 J g(-1)) on the functionality of tapioca starch was investigated. Scanning electron microscopy analysis revealed the dissociation and damage of PEF treated tapioca starch granules. X-ray diffraction analysis demonstrated that tapioca starch tended to transform from crystalline to amorphous structure after PEF treatments. It was found that higher energy input (>49.36 J g(-1)) could destroy the crystal region of tapioca starch. Meanwhile, with increasing electric field strengths, the gelatinization temperature, the gelatinization enthalpy, the peak viscosity and the breakdown viscosity of PEF-treated samples showed a remarkable decrease. These results suggest that PEF treatments would be a promising physical method to modify the properties of starch in order to obtain desired products in food industry.

Recent Developments and Applications of Hyperspectral Imaging for Quality Evaluation of Agricultural Products: A Review

Food quality and safety is the foremost issue for consumers, retailers as well as regulatory authorities. Most quality parameters are assessed by traditional methods, which are time consuming, laborious, and associated with inconsistency and variability. Non-destructive methods have been developed to objectively measure quality attributes for various kinds of food. In recent years, hyperspectral imaging (HSI) has matured into one of the most powerful tools for quality evaluation of agricultural and food products. HSI allows characterization of a samples chemical composition (spectroscopic component) and external features (imaging component) in each point of the image with full spectral information. In order to track the latest research developments of this technology, this paper gives a detailed overview of the theory and fundamentals behind this technology and discusses its applications in the field of quality evaluation of agricultural products. Additionally, future potentials of HSI are also reported.

NIR Spectroscopy and Imaging Techniques for Evaluation of Fish Quality—A Review

Abstract Fish is a highly perishable product and it is particularly important to pay attention to its quality changes. Maintenance of the high quality of fish and fishery products necessitates development of means for precise and rapid quality evaluation. Near-infrared (NIR) spectroscopy and imaging techniques are proven technologies that can provide useful information for the estimation of quality attributes in fish and fishery products due to fast speed, noninvasiveness, ease of use, and minimal sample preparation. The aim of this review is to communicate perspectives and aspects relating to NIR spectroscopy and imaging techniques with regard to evaluation of chemical composition (fat, protein, and moisture), microbiological (freshness, spoilage, and nematodes), and sensory (flavor, texture, and color) attributes of fish and fishery products. Moreover, the usefulness of NIR spectroscopy and imaging techniques for fish authentication and classification are presented. Finally, some viewpoints on the current situation and suggestions for future research directions are proposed.