Absorbance Meter Research Articles

Regional Variation in the Index of Absorbance Difference as an Indicator of Maturity and Predictor of Storage Disorders in Apples

We evaluated regional variation in the Delta Absorbance Meter® index of absorbance difference (IAD) as a measure of harvest maturity and for predicting the occurrence of storage disorders in ‘McIntosh’ apples [Malus ×sylvestris (L.) var. domestica (Borkh.) Mansf.] in 2016 and ‘Honeycrisp’ apples in 2016 and 2017. Apples were grown in Maine (ME), Minnesota (MN), and Ontario (ON), and they were harvested from one orchard in each region, and two to three times each year, followed by cold storage at 0.5 °C for 2 months in 2016 and 4 months in 2017. In 2016, ‘Honeycrisp’ IAD values were similar in ME and ON, but lower than in MN. In 2017, IAD was greater in ME than in the other two regions during the first harvest, and it similar to MN in the latter two harvests and lower in ON than in the other regions. In ‘Honeycrisp’ apples, IAD was more strongly related to starch pattern index (SPI), internal ethylene concentration, and fruit peel blush than to chlorophyll or soluble solids concentration. Soft scald incidence (SSI) of ‘Honeycrisp’ fruit was greater in ME than in MN and ON in both years. In ME, SSI was related to IAD at harvest in both years, but with an inverse relationship with the first harvest and a positive relationship in the second harvest. A positive relationship also occurred in ON in 2017. SSI was not related to IAD at harvest in MN in both years and ON in 2016. Regional similarities in patterns of change in ‘Honeycrisp’ fruit IAD were not consistent from year to year, and this indicates that a single IAD standard should not be used to assess fruit maturity in different regions. In ‘McIntosh’, IAD values were variable among the three regions and were not related to other maturity indicators. IAD was not useful for measuring maturity in ‘McIntosh’ apples, but it was weakly related to core browning incidence.

Flow-through optical device based on silicone optical technology (SOT) for determination of iron in drinkable tap water

We propose a new concept “silicone optical technology (SOT)”, with low noise and simple integration of all optical components, and use a common matrix of polydimethylsiloxane (PDMS) as a prototype for rapid digital fabrication. This work involves the rapid design and fabrication of SOT optical modules designed to be coupled with a flow injection analysis system (SOT-FIA module), and their use in combination with a handheld photo absorbance meter “picoExplorer™” is also demonstrated. A digital fabrication method, by casting PDMS on the three-dimensional printed mold/frame, is developed. A simple structure of transparent PDMS mixed with the white pigment of titanium dioxide (TiO2) rutile particle (W-PDMS) optical core with a cladding of carbon black dispersed PDMS (K-PDMS) is fabricated. This structure performs as a tiny and straightforward optical filter and shows the ability to trap tilted incident light. The addition of the white pigment into PDMS results in a special enhancement of the optical sensitivity by increasing the amount of scattered light. This module is directly mounted on a white light emitting diode (LED) and the red-green-blue (RGB) sensor device from the picoExplorer at 45° to the flow channel to increase the detection length. The optical properties of the SOT-FIA module, which arise from the presence of white PDMS (W-PDMS) and the effect of the detection length, are investigated and show a dramatically enhanced sensitivity (30–45 times) of the optical detection compared with the calculation using Beer-Lambert's law. Moreover, lower than 1% of crosstalk is observed, which indicates the low noise level detection of the proposed SOT-FIA optical device. This proposed SOT-FIA module integrated with an LED detection system is developed to be combined with a flow injection analysis system for the colorimetric detection of iron in drinkable tap water samples. The results show excellent linearity, the ability for a wide range of chemical analysis, low detection limit, high percentage recovery, high precision and good agreement with the conventional spectrophotometric method. Furthermore, the tilted and tilt-shifted coupling alignments are newly developed and evaluated.

An optimal harvest maturity model for ‘Minneiska’ apple fruit based on the delta-absorbance meter

ABSTRACT A hand-held, chlorophyll content meter [the delta absorbance (DA) meter] was used to develop an optimal harvest maturity model for ‘Minneiska’ apples (Malus domestica Borkh). Fruit from four commercial orchards in the Annapolis Valley, Nova Scotia, Canada, were sampled weekly (25 fruit per location) over eight consecutive harvests during the 2011–2013 growing seasons. At each harvest, 60 fruit were measured for their DA value (IAD ), mass, firmness, titratable acidity (TA), soluble solids content (SSC), red skin colouration, starch-to-sugar conversion and internal core ethylene concentration. Following 3–3.5 months of refrigerated air storage at 3.5°C, samples were removed and assessed for fruit bruising, skin greasiness, rot and physiological disorders. Peel chlorophyll content was strongly and positively correlated with epidermal IAD measurements. IAD values declined significantly during fruit ripening and were negatively related to harvest week. The optimal harvest period was identified by aligning ‘at harvest’ IAD , fruit quality and ‘post-storage’ disorder data with the corresponding harvest week. IAD averages associated with harvests having high commercial fruit quality demarcated the optimal harvest boundaries. As the IAD values declined during fruit maturity, the upper boundary value of 0.26 was defined as ‘when to begin harvest’, while the lower boundary value of 0.12 was deemed ‘when to end harvest’ for longer-term storage.

Non-destructive quality assessment of tomato fruit using differential absorbance technique

A rapid and non-destructive assessment of quality parameters in tomatoes was evaluated using a portable differential absorbance (DA) meter in order to accurately establish optimum harvest maturity. A commercial tomato variety cv. ‘BARI Tomato-8’ grown in the summer season of Bangladesh was used in this study. Different quality parameters including fruit skin colour, tissue firmness, chlorophyll contents, ascorbic acid, total soluble solids (TSS), titratable acidity and pH of tomatoes were determined using standard reference methods. Correlation analysis was performed to determine the relationship between the difference in absorbance index (IDA) and fruit quality parameters. The correlation coefficients showed good ability in estimating the hue angle, chlorophyll contents, titratable acidity and firmness of tomatoes showing ‘r’ values of 0.93, 0.91, 0.91 and 0.92-0.94, respectively. However, the changes of ascorbic acid contents and TSS of tomatoes did not follow the linear model during fruit maturation. Thus, the DA meter could most accurately predict the major quality attributes and may be used as an efficient technique for in-plant non-destructive assessment of tomato fruit qualities.
 Int. J. Agril. Res. Innov. Tech. 9(2): 42-50, December 2019

Acetaldehyde and Ethanol Metabolism during Conditioning and Air Storage of ‘Honeycrisp’ Apples

‘Honeycrisp’ apples are susceptible to the physiological disorder soft scald, especially when stored at temperatures close to 0 °C. The disorder can be reduced by a conditioning treatment of 10 °C for 7 days before storage, but little is known about the underlying physiology of disorder development. The effects of storing ‘Honeycrisp’ apples in air at 0.5 °C for a total of 140 days, without and with conditioning, on internal ethylene concentration (IEC), ethanol and acetaldehyde concentrations, and activities of alcohol dehydrogenase (ADH) and pyruvate decarboxylase (PDC) were investigated in relation to soft scald incidence. Fruit were selected on the basis of background color (chlorophyll concentration) using a nondestructive delta absorbance (DA) meter to minimize variability of fruit maturation. Conditioning reduced soft scald incidence to 1% compared with 28% in unconditioned fruit. During the conditioning period, IECs were usually greatest in the conditioned fruit, with no effect on ethanol and acetaldehyde concentrations. During subsequent storage, IEC was greatest in conditioned fruit, whereas ethanol and acetaldehyde concentrations were generally less. However, ADH and PDC activities were unaffected consistently by conditioning or during storage.

Comparative study of transform-based image texture analysis for the evaluation of banana quality using an optical backscattering system

In this study, the application of a backscattering imaging system with different approaches of transform-based image texture analysis for the evaluation of banana quality at different ripening stages was investigated with Wavelet, Gabor and Tamura transforms. The attenuated images of the fruits were acquired using Laser Light Backscattering Imaging (LLBI) with laser diodes emitting light at three wavelengths viz 532, 660, and 830 nm. The elasticity, chlorophyll index and soluble solids content (SSC) of each sample were measured as reference parameters by using a texture analyser, a Delta Absorbance (DA) meter, and a refractometer, respectively. The performance of the extracted features from the selected transform-based image texture analysis for analysing the quality parameters of the fruit was evaluated by means of an artificial neural network (ANN) and a support vector machine (SVM). The results indicated that there were significant changes of elasticity, chlorophyll index and SSC as the ripening stages increased. Prediction model analysis showed that the Wavelet transform exhibited the most reliable results for all of the reference parameters followed by Tamura and the Gabor transform. The results also revealed that analysis using an ANN approach recorded better performance than SVM as reflected by higher coefficient of determination (R2) values. Thus, this study indicated that an LLBI system with transform-based image texture analysis coupled with computational intelligence techniques can be used for the evaluation of the quality of bananas.

Nondestructive Apple Ripening Stage Determination Using the Delta Absorbance Meter at Harvest and after Storage

The delta absorbance (DA) meter is a handheld instrument which noninvasively measures the chlorophyll content in fruits. In the present work, it was used to monitor the ripening process linked to the climacteric phase in apple (Malus ×domestica). The results [index of absorbance difference (IAD)] were correlated to quality attributes at harvest and after commercial scale storage at different conditions. Two cultivars (Red Delicious, Golden Delicious) were analyzed in two different seasons, whereas Morgenduft and Gala were analyzed only in the first and second seasons, respectively. In general, a linear reduction of the IAD values was observed in all apple cultivars along with the progression of ripening and ethylene biosynthesis. When ethylene production was inhibited by 1-methylcyclopropene (1-MCP) treatment, the decrease of IAD values was markedly reduced. IAD threshold values for each cultivar were identified, delineating the central phase of the ethylene climacteric rise. Predictive models were built by correlating IAD index to the soluble solids concentration (SSC), titratable acidity (TA), and firmness measured at harvest and after removal from different storage regimes. The best model was developed for SSC prediction on ‘Red Delicious’ apple [ratio performance deviation (RPD) = 1.88] and for firmess evaluation in ‘Golden Delicious’ apple (RPD = 1.84). Moreover, IAD values were consistently associated with the differences in fruit quality as affected by optimal and suboptimal storage conditions. The IAD, due to its acceptable accuracy and speed of assessment, can be a promising tool for assisting in sorting apples before and after storage in warehouses or commercial packing lines. IAD cannot totally replace standard ripening indices, but can effectively supplement data for these parameters.

‘Rough guide’ evanescent wave optrode for colorimetric metalloporphyrine sensors

When films of zinc 5-(4-carboxyphenyl),10,15,20-triphenyl porphyrin (ZnTPP) are exposed to waterborne amine in pH- neutral or alkaline media, both Q- band and Soret band respond with a change of absorbance due to the donation of amine ‘lone pair’ electrons to the metalloprophyrin π orbital. However, this is difficult to reveal with a conventional spectrometer even under high amine concentration. We therefore introduce optical fibres coated with ZnTPP into a bespoke ‘light balance’ evanescent wave absorbance meter [doi:10.1016/j.snb.2016.05.065]. The light balance makes absorbance changes clearly visible under only 5μM aqueous amine, making PVC membranes redundant. We find sensitivity is higher, and limit- of- detection lower, in the Soret band rather than the Q- band, reflecting the stronger Soret band absorbance. Also, we find that sensitivity is higher, and limit- of- detection approximately two times lower, when rough rather than smooth fibres are used. We believe the rough fibre surface leads to enhanced evanescence, and therefore better overlap of the wave propagating in the fibre with the ZnTPP fibre cladding. We find a limit of detection to waterborne amines below 1μM, which compares well to other sensors for waterborne amines [Korent, S.M. et.al. Anal. Bioanal. Chem. 387 (2007) 2863–2870; Algarni, S. A. et.al. Talanta 153 (2016) 107–110]. We therefore recommend ‘rough guide’ evanescent wave optrodes, in combination with sensitive ‘light balance’ detector, to succeed membrane- embedding of colorimetric sensitisers such as metalloporphyrines.

Non-destructive maturity assessment of ‘Empire’ apples treated with preharvest inhibitors of ethylene perception and production with a delta absorbance (DA) meter

Non-destructive maturity assessment of ‘Empire’ apples treated with preharvest inhibitors of ethylene perception and production with a delta absorbance (DA) meter

Fibre optic absorbance meter with low limit of detection for waterborne cations

We report an evanescent wave based fibre optic absorbance meter that enables the colorimetric detection of waterborne cations with water insoluble chromoionophoric sensitisers. This establishes an alternative to the PVC membrane based transducers that are conventionally used for this purpose. Here, a water insoluble sensitiser is coated as a thin film on an unclad section of a multimode optical fibre to overlap with the evanescent field of a light beam propagating along the fibre core. The colorimetric response of the sensitiser when in contact with waterborne cation leads to increased absorption of virtual photons associated with the evanescent field. The resulting intensity loss of the propagating beam is detected by a bespoke self-referenced evanescent wave absorbance meter with beam intensity modulation and Lock-in amplification. We validate our transducer with the well characterised water insoluble sensitizer, 1-(2-pyridylazo)-2-naphthol (PAN), for the detection of aqueous Zn2+ cations. We find a limit of detection (LoD) of 54nM Zn2+, 28 times lower compared to a PVC membrane based sensor using same sensitiser for same cation (Albero et al., Journal of Pharmaceutical and Biomedical Analysis 29 (2002), 779). Our evanescent wave absorbance meter can easily be adapted to other colorimetric sensitisers, including chromoionophoric complex forming macrocycles.

Determination of optimal harvest boundaries for ‘Ambrosia’ apple fruit using a delta-absorbance meter

ABSTRACTIn this study, a new chlorophyll measurement tool, the delta absorbance (DA) meter, was used to develop an optimal harvest maturity model for ‘Ambrosia’ apple (Malus × domestica Borkh.) fruit. Fruit from four commercial orchards in the Annapolis Valley, Nova Scotia, Canada, were sampled (25 fruit from three or four trees per location) over nine consecutive weekly harvests during the 2011 and 2012 growing seasons, and 8 weeks in the 2013 season. At each harvest, five fruit from each orchard site had their index of absorbance difference (IAD) values, firmness, mass, titratable acidity (TA), soluble solids content (SSC), red skin colouration and internal core ethylene concentrations measured. Following approx. 3 months of storage at 3.5°C, 20 fruit from each site were removed and assessed for the incidence of disorders such as senescent breakdown, cortical browning and coreflush. Chlorophyll concentrations in the epidermis were strongly and positively related to IAD values in the same tissue (P ≤ 0.001), confirming the assumption that chlorophyll was the basis for the DA meter IAD signal. In addition, IAD values declined significantly during fruit maturity and were negatively related to harvest week (P ≤ 0.001). The optimum harvest period was identified by aligning all ‘at harvest’ IAD values, fruit quality measurements, and ‘post-storage’ disorder data with the corresponding harvest week. IAD values associated with harvests having the highest commercial fruit quality then delineated the optimal harvest boundaries. The upper boundary IAD value of 0.47 was defined as ‘when to begin harvest’, while the lower boundary IAD value of 0.28 was considered to be ‘when to end harvest’ for long-term storage. The use of a DA meter and its IAD value to define the optimal harvest boundaries may be applicable to all commercial apple cultivars, but should be developed for each cultivar and growing region.

COLORED LIGHT-TO-VOLTAGE CONVERTERS BASED ABSORBANCE METER

A low-cost absorbance meter for dissolved compounds identification and concentration evaluation is proposed. The main elements of the system are a white light source and a set of three colored light-to-voltage converters. The system includes auto-calibration capabilities and compensates spectral sensitivity variation of the optical source and detectors. A neural network-processing scheme is used to identify dissolved compounds and evaluate the correspondent concentrations.

Determination of optimal harvest boundaries for Honeycrisp™ fruit using a new chlorophyll meter

DeLong, J., Prange, R., Harrison, P., Nichols, D. and Wright, H. 2014. Determination of optimal harvest boundaries for Honeycrisp™ fruit using a new chlorophyll meter. Can. J. Plant Sci. 94: 361–369. In this study, a new chlorophyll measurement tool [the delta absorbance (DA) meter] was used to develop an optimal harvest maturity model for Honeycrisp™ fruit. Apples from nine commercial orchards in the Annapolis Valley, Nova Scotia, Canada, were sampled over 11 consecutive weekly harvests during the 2010, 2011 and 2012 growing seasons. At each harvest, a sample of fruit was measured for its DA (IAD) values, firmness, titratable acidity (TA),% soluble solids content (SSC), red skin coloration and internal core ethylene. Following approximately 3 mo of storage at 3.5°C, samples were removed and assessed for disorder incidence. The optimal harvest period was identified by aligning all “at harvest” IAD values, fruit quality measurements and “post-storage” disorder data with the corresponding harvest week. Then, the IAD values associated with the harvests having high commercial fruit quality and the least collective expression of disorders, delineated the optimal harvest boundaries. As IAD units declined during fruit maturity, the upper boundary value of 0.59 was deemed “when to begin” harvest, while the lower boundary value of 0.36 was deemed “when to end” harvest for long-term storage. The use of the DA model approach for optimal harvest delineation is potentially applicable to all commercial apple cultivars, but should be developed for each within a distinct growing region.

Effect of microbubbled water on the removal of a biofilm attached to orthodontic appliances — An in vitro study —

Orthodontic appliances often cause oral diseases such as dental caries and gingivitis due to the attachment of an oral biofilm. However, there are few reliable methods to remove the biofilm from the orthodontic appliances. The aim of this study was to investigate the effects of microbubbled water on the removal of biofilms made with Streptococcus mutans or Candida albicans on orthodontic appliances. The orthodontic appliances with biofilm were immersed with microbubbled water and the remaining biofilm on the appliances was detected and measured using a micro-plate reader and an absorbance meter. The microbubbled water had a sufficient effect on the removal of biofilm from orthodontic appliances. The effects of microbubbled water were significantly higher than those of tap water (S. mutans: p<0.05, C. albicans: p<0.01). The results of this study suggest that microbubbled water is effective in the removal of biofilm from the mouth of orthodontic patients.

The Essential Role of p53 in Hyperpigmentation of the Skin via Regulation of Paracrine Melanogenic Cytokine Receptor Signaling

Hyperpigmentation of the skin is characterized by increases in melanin synthesis and deposition. Although considered a significant psychosocial distress, little is known about the detailed mechanisms of hyperpigmentation. Recently, the tumor suppressor protein p53 has been demonstrated to promote ultraviolet B-induced skin pigmentation by stimulating the transcription of a melanogenic cytokine, POMC (pro-opiomelanocortin), in keratinocytes. Given that p53 can be activated by various kinds of diverse stresses, including sun exposure, inflammation, and aging, this finding led us to examine the involvement of p53 in cytokine receptor signaling, which might result in skin hyperpigmentation. Immunohistochemical and reverse transcription-PCR analyses revealed the increased expression and phosphorylation of p53 in the epidermis of hyperpigmented spots, accompanied by the higher expression of melanogenic cytokines, including stem cell factor, endothelin-1, and POMC. The involvement of p53 in hyperpigmentation was also indicated by the significantly higher expression of p53 transcriptional targets in the epidermis of hyperpigmented spots. Treatment of human keratinocytes and melanocytes with known p53 activators or inhibitors, including pifithrin-alpha (PFT), demonstrated significant increases or decreases, respectively, in the expression of melanogenic factors, including cytokines and their receptors. Additionally, PFT administration abolished stem cell factor-induced phosphorylation of mitogen-activated protein kinase in human melanocytes. Furthermore, when organ-cultured hyperpigmented spots, in vitro human skin substitutes, and mouse skin were treated with PFT or p53 small interfering RNA, the expression of melanogenic cytokines and their receptors was significantly decreased, as were levels of tyrosinase and melanogenesis. Taken together, these data reveal the essential role of p53 in hyperpigmentation of the skin via the regulation of paracrine-cytokine signaling, both in keratinocytes and in melanocytes.

System for detecting environmental ppb-level nitrogen dioxide I

Coloration reactions have been found between nitrogen dioxide (NO 2) and organic compounds, such as aromatic amine derivatives, impregnated in porous glass. A single absorption peak in the visible region was detected after the reactions for all compounds. Linear relationships were obtained between environmental NO 2 concentrations and absorbance changes at peak wavelength for some compounds. A system is proposed for detecting low-levels of NO 2 using these coloration reaction in porous glass. Our designed system is composed of an organically-impregnated porous glass sensor and a simple absorbance meter having a single-wavelength light source. It was clarified that environmental ppb-levels of NO 2 could be detected using our system and that values for hourly average concentrations of NO 2 obtained by our system agreed well with those obtained using commercial analytical instruments. A coloration reaction mechanisms are also proposed based on the experimental results obtained.

Nitrogen Requirements of Drip-irrigated Peppers

The response of bell pepper (Capsicum annuum L.) to five rates of N fertigation between 0 and 336 kg N/ha was studied at two drip-irrigated sites [Univ. of California, Davis (UCD) and West Side Field Station, Five Points (WSFS)] in California in 1992. Nitrogen application, in the form of a urea: ammonium nitrate mixture (UN-32), was applied in eight (WSFS) or 10 (UCD) equal weekly increments, beginning after transplant establishment. At both sites, fruit yield and mean fruit size peaked at 252 kg N/ha, with additional N retarding crop productivity. Maximum fruit yield was obtained by fertility treatments that maintained petiole NO3-N concentration &gt;5000 μg·g-1 through the early fruit bulking period. Two techniques for monitoring crop N status, designed for field use, were evaluated. There was a close relationship between the NO3-N concentration of fresh petiole extracts, as measured by a portable, battery-operated nitrate selective electrode, and dry tissue analyzed by conventional laboratory technique (r2 = 0.89). Relative chlorophyll concentration, measured nondestructively by a dual-wavelength leaf absorbance meter, was poorly correlated with whole-leaf N concentration (r2 = 0.55). However, the ratio of such chlorophyll readings for a treatment compared to an in-field reference of known N sufficiency (252 kg·ha-1 treatment) showed promise as a technique for identifying N deficiency.