Sirinnapa Saranwong

System design for non-destructive near nfrared analyses of chemical components and total aerobic bacteria count of raw milk

In order to develop a system for quality and safety evaluation of non-homogenised raw milk using near infrared (NIR) spectroscopy, two stages of research have been conducted. The first stage was the development of a compact NIR system for measuring the major constituents such as fat and protein in an aseptic environment. The second stage was the measurement of the total aerobic bacteria count (TBC). In the first stage, two compact sample holders for commercially-available capped test tube were designed. One system was equipped with an NIRSystem6500 research-type NIR spectrophotometer, hereafter referred to as MilkSpec-2. The other was equipped with a hand-held NIR spectrophotometer, the FT20, hereafter referred to as MilkSpec-3. For MilkSpec-2, the highly satisfactory results were obtained with the multiple determination coefficients of determination (R2) = 0.99 and 0.96, and standard errors of prediction (SEP) = 0.03% and 0.07% for fat and protein, respectively. The results for MilkSpec-3 were also satisfactory but inferior compared with MilkSpec-2; the results were R2 = 0.99 and 0.91 and SEP=0.06% and 0.08% for fat and protein, respectively. In the following stage, MilkSpec-2 was used for the measurement of TBC in terms of log colony forming units (CFU) mL−1. In the case of TBC measurements, where the concentration of bacteria itself or its by-products were very low, three kinds of commercial test tube made of the same kind of glass but differing in diameter were used to identify the appropriate physical pathlength. It was found that the medium sized test tube with an external diameter of 20 mm provided the best calibration results with R2 = 0.83, SEP = 0.55 log (CFU) mL−1 and the ratio of standard deviation of reference data in the validation set to SEP (RPD) = 2.33. The analysis of the calibration structure indicated that the information related to absorptions by bacteria metabolites such as lactic acid, urea and those of the carbon sources such as lactose and protein in milk might play substantial roles in the NIR-TBC determination.

Interpretation of near Infrared Calibration Structure for Determining the Total Aerobic Bacteria Count in Raw Milk: Interaction between Bacterial Metabolites and Water Absorptions

The objective of this work is to clarify the structure of the near infrared (NIR) calibration equation for predicting the total aerobic bacteria count (TBC) of raw milk which was developed in a previous article. First, an experiment on the monitoring of chemical changes in stored raw milk having different levels of TBC was conducted. Then the relation between the regression coefficient plots of the TBC calibration equation and the absorption bands of the constituents related to bacterial metabolism was investigated. Finally, the meaning of each factor used in the calibration equation was interpreted through the study of its loading weight plots. It was found that lactic acid and urea–nitrogen, the waste from lactose and from protein catabolism of bacteria, increased with the increase of TBC value. On the other hand, the decreases in lactose and protein content, the energy sources of many bacteria, were observed. The results from the investigations on the regression coefficient and the loading weight plots indicated that the TBC calibration equation utilised the information from both the absorptions of the four chemicals and the absorptions of water species. It is believed that the changes in the metabolites and energy sources influenced the species and the NIR absorptivity of water. In addition, the band assignments in the regression coefficient plots have been performed. For example, the peak at 988 nm was linked to lactic acid absorption, the peak at 1008 nm peak was identified as due to urea–nitrogen absorption, and the 1026 nm and 1032 nm peaks were identified as being due to casein–protein absorptions. As for water, the 952 nm, 962 nm, 976 nm and 998 nm were likely to represent the fluctuation of water species with 0, 1, 2 and 3 hydrogen bonds, respectively.

The reliability of pesticide determinations using near infrared spectroscopy and the dry-extract system for infrared (DESIR) technique

In a previous article, a pesticide determination system using near infrared (NIR) spectroscopy and the dry-extract system for infrared (DESIR) technique had been developed. In order to evaluate system reliability, a number of tests had been conducted. To reduce time and labour needed for pesticide assays by gas chromatography, artificial solutions of each pesticide in acetone were used in place of sample extract that was used in the previous article. Effects of several factors, such as chemical structure, interference of another reagent in the solution and sample presentation, on the system accuracy were evaluated. A tentative collaborative study was conducted to evaluate the possibility of large scale utilisation. To test the influence of chemical structure, three pesticides— acephate, dichlofluanid and tetrachloro-isophthalonitrile (TPN)—having different numbers of functional groups with strong dipole moment were used. From the range of 0 ppm to 50 ppm active ingredient in acetone, the SEPs obtained were 2.1, 5.3 and 9.3 ppm for acephate, dichlofluanid and TPN, respectively. These results corresponded to the number of strong dipole moment groups in the chemical structure which were four for acephate, two for dichlofluanid and none for TPN. In the case where two kinds of pesticide were presented in the system, the SEP became larger compared to the single pesticide results. The degree of interference differed depending on the relative absorptivity between the target pesticide and the interference. Using the system developed and acephate solution, a tentative collaborative study was conducted using three laboratories and four technicians. The almost similar SEPs of 2.8, 2.8, 3.0 and 2.5 ppm were obtained by the four technicians, indicating that even if the NIR instruments used and the degree of professional skill differed between technicians, satisfactory results could be obtained after a few hours of training and a proper bias correction. Finally, to simplify the system, three kinds of sample presentation were used to develop a calibration equation for acephate. The SEPs obtained differed only minutely. It could be concluded that when using NIR analysis the operator may choose between the highly precise system which requires more time and labour because of the sample preparation involved or a slightly less precise system with simple sample presentation. Based on the Japanese pesticide control level, the developed system could be used for the monitoring of some pesticides in fruits and vegetables.

Short communication: A feasibility study using simplified near infrared imaging to detect fruit fly larvae in intact fruit

The potential for near infrared (NIR) imaging technology to yield improved sensitivity for detecting oriental fruit flies infested in intact mangoes was investigated. Hyperspectral data from 400 nm to 1000 nm were acquired from eight infested mangoes and eight control mangoes at Oh, 24 h and 48 h after infestation. Sixteen pores were created on each mango. Four mangoes from each class were set aside as independent test samples. From each of the eight remaining fruit, nine spectra (3 × 3 pixel) from the area of each pore were extracted. Each spectrum was considered to be an individual, multiple-feature sample. The features were input into an iterative Bayesian discriminant analysis routine for the classification. Using the three selected wavelengths for spectra measured at 48 h after infestation, classification results were 0.9% false negatives (infested fruit misclassified) (range of fruit fly larvae: 8–57) and 5.7% false positives (control fruit misclassified). Grey-scale images of the area (4 × 4 cm) containing the pores for each fruit were generated based on the Mahalanobis distance calculated from the pretreated 48 h absorbance values at each of the three wavelengths selected. Clear distinction between infested areas were observed with few false positive results in the control fruit, indicating the feasibility of using NIR imaging as the basis for a low-cost, high-speed device for the detection of the oriental fruit fly in mangoes.

An Evaluating Technique for Variety Compatibility of Fruit Applied to a near Infrared Brix Calibration System: A Case Study Using Brix Calibration for Nectarines:

In a practical near infrared (NIR) sweetness sorting facility, there is a high possibility that the variety of incoming fruit will be different from the one(s) used to develop a calibration model. In this kind of situation, significant bias could occur and result in a high price difference. In this work, a method to identify whether the pre-installed calibration models could be used to predict Brix values of the unknown samples or not was established. Two kinds of calibration model for Brix determination of nectarines were examined, one developed from spectra of the single nectarine variety called Big Bang Maillarà (BB), the other developed from spectra of two nectarine varieties, BB and Nectaross (NT). Another variety called Sweet Red (SR) was used to demonstrate the situation of an unknown sample or a different variety. For the general biases evaluation, significant biases occurred in the SR samples whether the prediction was done using the BB calibration (bias = −6.74°Brix) or the BB+NT calibration (bias = −3.09°Brix). A survey using score plots of principle component analysis (PCA) indicated that the characteristics of the BB and the SR samples were quite different from each other, while the NT samples were located in between. Even though the trend of differences between the PCA scores of the three varieties could be observed, a clear classification result could not be obtained. Another classification attempt was made using soft independent model for classification analogy (SIMCA). For each calibration (BB and BB+NT), a SIMCA model was developed using the samples used to develop the calibration model. A calculation was performed to evaluate whether the unknown samples (BB, NT and SR) were in the same class as the calibration sample or not. It was found that, in the case of the single variety calibration where the SIMCA model was also developed from the single variety (BB), clear identification of unfitted samples could be obtained with classification accuracy more than 95% (false negative 0%). However, in the case of the two varieties calibration, the use of a SIMCA box developed from two varieties would make the in-class distance become too wide and this reduced the classification accuracy of unfitted samples (false negatives = 74%). The solution was to develop two SIMCA boxes, one for BB and one for NT, then examine the compatibility of unknown samples twice. Using this technique, satisfactory classification results with false negatives of 10% could be obtained.

Applying near infrared spectroscopy to the detection of fruit fly eggs and larvae in intact fruit.

The objective of this work was to investigate the potential use of near infrared (NIR) spectroscopy for non-destructive detection of fruit fly eggs and larvae in intact fruit. Mangoes, the major export fruit of Thailand, were used as model samples. The NIR spectra acquired under interactance mode in the short wavelength region of 700 nm to 1100 nm provided the best classification results, compared with spectra taken under the reflectance mode in the long wavelength region from 1100 nm to 2500 nm. The dominant factor in correct classification was the incubation period after infestation. The best classification was achieved using spectra of green mangoes obtained 48 h after infestation, with an error rate of 4.2% (two out of 48) for infested fruit and 0% for the 48 control fruit. Comparing regression coefficient plots of various partial least squares discriminant analysis (PLS-DA) models, it was determined that the most important classification wavelength was near 730 nm, coinciding with a unique peak previously observed in the spectra of dried fruit fly larvae. A universal calibration developed from two mango cultivars produced similar error rates. The results justify development of an automatic classification and sorting system based on NIR imaging technology.

A simple method of instrument standardisation for a near infrared sorting machine: the utilisation of average spectra as input vectors

A new concept of spectral adjustment was examined to solve the problem of calibration transfer in a near infrared (NIR) sweetness sorting machine. Instead of pairing the absorbance values of each sample measured by master and slave instrument, the average spectrum of each instrument was used. Two identical NIR instruments, equipped with interactance fibre optics, were used as model instruments and a calibration equation for Brix determination of apples was developed as a model calibration. For each instrument, master and slave, each average spectrum was calculated from the spectra of an identical group of apples and then spectral matching of the slave instrument to the master was performed. The curve fitting method, either linear regression or polynomial, could not work well. However, by adding the difference spectrum, the differences of average absorbance values at wavelength i between the master and slave instruments, the spectrum of each sample measured by the slave instrument could successfully standardise the slave instrument. The matching was successfully done by adding the difference spectrum between the two average spectra to the slave instruments spectra. It was found that the method could be used to compensate for both the wavelength shift and photometric change and it also proved that the method was applicable for both multiple linear regression and partial least squares equations.

A noninvasive near infrared system for detection of platelet components contaminated with bacteria.

BACKGROUND: Platelet (PLT) transfusion–associated bacterial sepsis has remained a substantial patient risk, primarily due to lacking effective and point‐of‐issue measures to detect bacterial contamination. This study describes near infrared (NIR) spectroscopy to examine inoculated PLTs without sampling within a few seconds.

Commercial portable NIR instruments in Japan

At the present time, when most human-interfaced hardware such as the cellular phone and the computer are becoming smaller and smaller, the near infrared (NIR) spectrophotometer is another of the objects ripe for this size reduction. Around the world, scientists and engineers have tried both to invent and to utilise new portable or hand-held types of NIR instruments. Fred McClure was probably the first person to sell this dream by introducing the hand-held chlorophyll meter for tobacco. This year, at the New Zealand Conference, he stepped forward with manure evaluation using his in-house portable NIR instrument, the so-called “Mmeter”. For the commercial instrument, many researchers around the world are utilising the multipurpose spectrophotometers manufactured by Zeiss, either the MMS1 or the Corona. For example, Christian Paul from Germany attached the Corona to a harvester to perform real-time forage compositional analysis. This year, Kerry Walsh from Australia presented a stand-alone NIR instrument for detecting Brix value of peaches. The instrument has an overall weight of only 2 kg, and is equipped with the MMS1 as the detector. On the other side of the world, Veronique Bellon from France has also shown the possibility of using the MMS1 for predicting the acidity of grapes still on-the-vine. The results showed that further progress is still required but there is very clear potential. Beside these, there are still many more works related to portable NIR instruments that would take many pages to describe. In Japan, many researchers both from the private sector and governmental institutions, have been putting their greatest efforts into the development of hand-held or portable NIR instruments. The most interesting one is for measuring blood glucose in the human forearm. This is a result of the joint-research between Matsushita Electronics Company and Yukihiro Ozaki’s group at Kwansei–Gakuin University. A stream of papers have been produced from the approach of the hardware design to the chemometrics and medical viewpoints. The instrument is not yet on the market but probably will be released in the near future. From the latest paper, the group tested the system by measuring blood glucose content every five minutes after allowing five patients to drink 225 mL of a glucose solution. With the use of special chemometrics, an RMSEP of 2.68 mg dL was reported. The next instruments to be considered are designed to meet the needs of both growers and consumers for achieving high quality fruit. The competition between the Kubota and FANTEC companies is intense and this results in less expensive, high-performance and multi-add-on instruments. The Kubota company used to provide two types of instruments with the same name “Fruit Selector”, one for the supermarket shopper and the other for packing house and farm use. However, at present, the company is probably focusing on the farm use market with the new model “K-BA100R”. If you can read enough Japanese, there are many web pages providing suggestions from the Japanese Agricultural (JA) Cooperation that their members should employ this instrument before harvesting. The instrument employs a diode array detector in the wavelength region of 600–1000 nm. Using an interactance probe, Brix determination can be done within 2 s. The Company can provide Brix calibration equations for oranges, apples, tomatoes, peaches, pears, grapes, persimmons, strawberry, melons and small watermelon. Calibrations are also available for acidity in oranges, apples and tomatoes. Figure 1 shows the small size of the instrument. With a size of 240(H) × 00(L) × 118(W) mm and a weight of 5 kg (including battery), the instrument can be taken into the green house for on-tree measurement. Kubota does not sell an on-line type NIR sweetness sorting machine, but it can add the K-BA next to the sorting conveyer. This low-cost system can sort up to 500 fruits per hour. For FANTEC, the first portable NIR instrument was the “Fruit Tester 20 (FT20)” which the authors used for several experiments concerning on-tree maturity evaluation of mangoes. Even with a weight of only kg and a size almost similar to the K-BA, prolonged use, say –4 hours, of this not-handheld but portable NIR instrument could cause a surprising lot of fatigue. About three years ago, FANTEC made an improvement by reducing both the size and cost of the FT20 to become the “FQA-NIR Gun” (Figure 2). The function of the instrument is quite similar to the FT20 as it can measure an NIR spectrum in the region of 600–1100 nm (2 nm intervals) within a few seconds. The gun weight is only 750 g and its size is 220(H) × 225(L) × 85(W) mm. The reader may not appreciate the difference in size compared with the K-BA and the FT20, however, the gun is much smaller as its design is based on an Lshape rather than a square cross-section. For flexibility, the gun can work in both stand-alone mode (no computer) and computer-connected mode. A disadvantage of the system may be that you cannot see the spectra if the gun is not connected to a computer. An advantage is the ease of data transfer from Portable NIR in Japan

Detection of Fruit Fly Eggs and Larvae in Intact Mango by near Infrared Spectroscopy and Imaging

F or several decades, fruit flies have been one of the major fruit and vegetable pests worldwide, creating huge damage to these crops and industries. In countries or areas that are declared to be fruit fly free zones, such as South Australia or Japan, very strict precautions have been taken to protect against invasion by this insect; preventive measures put in place have mostly involved vapour heat treatment (VHT) or radiation. While radiation in this context has been accepted in many countries due to its less marked effect on fruit quality, public awareness and acceptance have been the major obstacles. In a country like Japan, all fruit from fruit fly infected zones, such as those in South East Asia, are required to be subjected to a VHT process that heats fruit until its core temperature reaches 50–55°C for 15 minutes. To comply with such a condition, the fruit often needs to be heated in a vapour heat chamber (Figure 1) for approximately three hours, resulting in significant damage to enzymes involving in the ripening mechanism and therefore a lowering of ripening quality indices such as sweetness, firmness etc. Since 2006, Kasetsart University (KU) Thailand and The National Food Research Institute (NFRI) of Japan have obtained funding for a bilateral research project from research agencies in each country to investigate whether near infrared (NIR) spectroscopy could be used to screen mango fruit infested with fruit fly eggs and larvae. The first stage of this project was to identify the proper wavelength region(s) and stage of infestation for which NIR showed potential for detecting infestation. Then, at a later stage, NIR imaging was employed for the actual detection of infestation. Image analysis was performed with the additional collaboration of the Western Region Research Center, United State Department of Agriculture (WRRC, USDA-ARS).