Non-destructive evaluation of maturity and quality parameters of pomegranate fruit by visible/near infrared spectroscopy

In this study, the potential of visible and near infrared spectroscopy was investigated to classify the maturity stage and to predict the quality attributes of pomegranate variety “Ashraf” such as total soluble solids content, pH, and titratable acidity during four distinct maturity stages between 88 and 143 days after full bloom. Principal component analysis was used to distinguish among different maturities. The prediction models of internal quality attributes of the pomegranate were developed by partial least squares regression. The transmission spectra of pomegranate were obtained in the wavelength range from 400 to 1100 nm. In this research several preprocessing methods were utilized including centering, smoothing (Savitzky–Golay algorithm, median filter), normalization (multiplicative scatter correction and standard normal variate) and differentiation (first derivative and second derivative). It concluded that different preprocessing techniques had effects on the classification performance of the model using the principal component analysis method. In general, standard normal variate and multiplicative scatter correction gave better results than the other pretreatments. The correlation coefficients (r), root mean square error of calibration and ratio performance deviation for the calibration models were calculated: r = 0.93, root mean square error of calibration = 0.22 °Brix and ratio performance deviation = 6.4 °Brix for total soluble solids; r = 0.84, root mean square error of calibration = 0.064 and ratio performance deviation = 4.95 for pH; r = 0.94, root mean square error of calibration = 0.25 and ratio performance deviation = 5.35 for titratable acidity.     

Rapid and non-destructive analysis of apricot fruit quality using FT-near-infrared spectroscopy

A non-destructive optical method based on near-infrared spectroscopy has been used for the evaluation of apricot fruit quality. Diffuse reflectance measurements (800–2500 nm), physical, physiological and biochemical measurements were performed individually on 877 apricot fruits from eight contrasted cultivars harvested at different ripening stages. Relationships between spectral wavelengths and quality attributes were evaluated by application of chemometric techniques based on partial least squares (PLS) on fruit set divided randomly into two groups: 598 fruits for calibration and 279 for validation. Good prediction performance was obtained for soluble solids and titratable acidity with correlation coefficients of 0.92 and 0.89 respectively and root mean square errors of prediction of 0.98% Brix and 3.62 meq 100 g⁻¹ FW respectively. For the other quality traits such as firmness, ethylene, individual sugars and organic acids, the prediction models were not satisfactorily accurate due to the high error of calibration and prediction.     

Data Mining-Based Wavelength Selection for Monitoring Quality of Tomato Fruit by Backscattering and Multispectral Imaging

The aim of this research was to predict quality factors of tomato fruit during storage using backscattering and multispectral imaging techniques. To gather the required information for developing prediction models, batches of 200 tomatoes (cv. Pannovy) harvested at two maturity stages, were stored at standard condition up to four weeks. During storage, the modulus of elasticity, moisture content, soluble solid content, titratable acidity, hyperspectral data, and backscattering images were acquired on 40 tomatoes at regular intervals of one week. After extracting the spectral data from 40 points on each sample, they were subjected to preprocessing operations. Several feature selection techniques, including filter (Relief F, Fisher-Score, and t-Score) and wrapper (genetic algorithm) methods were used to find the sensitive wavelengths for each fruit quality parameter. With the novel strategy used, the wavelengths found by the fusion of genetic algorithm and t-Score techniques showed good prediction performance for all considered qualitative parameters. In order to verify the usefulness of selected wavelengths, backscattering and multispectral imaging techniques were applied. The artificial neural network produced the calibration models which gave a reasonably good correlation for estimating the modulus of elasticity, soluble solid content, and titratable acidity at 660 nm and moisture content at 830 nm of tomato from backscattering images. The correlation coefficient between the multispectral and backscattering imaging prediction results and reference measurement results were 0.952 and 0.891 for modulus of elasticity, 0.727 and 0.539 for moisture content, 0.736 and 0.561 for soluble solid content, and 0.811 and 0.706 for titratable acidity, respectively.     

Characterisation of Pomegranate Juices from Ten Cultivars Grown in Turkey

Pomegranate juices obtained from ten pomegranate cultivars of Turkey were analysed for their sugars, organic acids and the other quality parameters including pH, total soluble solids, and titratable acidity. Statistically significant differences were determined among the cultivars for parameters analysed. Citric acid was the predominant acid of all the cultivars studied. Cultivar “Zivzik,” one of the most popular cultivar in Turkey, showed best scores for total soluble solids (16.9 ± 0.06 °Brix), glucose (84.18 ± 0.42 g/l) and fructose (83.34 ± 0.81 g/l). Pomegranate juices were classified into three groups according to principal component analysis and cluster analysis.     

Maturity criteria for litchis (lychees)

Five varieties of litchi (lychee) were harvested from five different locations over a period of two years. The fruit varied from immature to almost fully mature. It was subjected to taste testing and analysed for total soluble solids (TSS) and titratable acidity (A). TSS (°Brix) was not suitable as a maturity indicator whereas titratable acidity and the TSS/A ratio were both good predictors of taste. A titratable acidity of 4.4 cmol H⁺ kg⁻¹ juice or a TSS/A ratio of 4.3 Brix.kg juice cmol⁻¹ H⁺ would be suitable maturity indexes.     

石榴贮藏期间间歇升温处理对果实品质的影响

以陕西临潼净皮甜石榴为试材,研究了间歇升温处理对石榴果实贮藏期间品质变化的影响。结果表明:石榴在(5.0±0.5)℃条件下贮藏,每隔6 d在(15±0.5)℃下间歇升温处理24 h,能有效保持果粒可溶性固形物含量、总糖含量和可滴定酸含量,减缓果皮褐变指数升高速率,降低果实腐烂率,贮藏120 d果实外观色泽鲜艳.籽粒感官品质良好,保鲜效果理想。     

不同pH值CMC涂膜对石榴果实采后生理指标及贮藏品质的影响

以陕西临潼净皮甜石榴为试材,研究了不同pH值CMC涂膜对石榴果实采后生理指标及贮藏品质的影响。结果表明:石榴在(4.0±0.5)℃条件下贮藏,采用pH值5.0、0.5%CMC溶液涂膜,能有效保持石榴籽粒可溶性固形物含量、总糖含量和可滴定酸含量,减缓果皮相对电导率和褐变指数升高速率,降低果实呼吸速率和腐烂率,抑制果皮抗坏血酸氧化酶(AAO)和多酚氧化酶(PPO)活性,保持果皮过氧化物酶(POD)活性相对较高水平。贮藏120d果实外观色泽鲜艳,籽粒感官品质良好,保鲜效果理想。     

柑橘浮皮果与可溶性固形物光谱同时在线检测

柑橘浮皮果和可溶性固形物是评价柑橘品质的重要指标,在运动速度5个/s、积分时间100ms条件下,采集350~1 150nm范围内的柑橘光谱,探讨在同一条生产线上同时在线检测浮皮果与可溶性固形物的可行性,同时探索柑橘正常果,轻度、重度浮皮果的光谱响应特征,建立柑橘浮皮果与正常果的定性判别模型,并对比分析两种判别模型,同时还建立柑橘可溶性固形物的定量检测模型,最终实现了柑橘浮皮果与可溶性固形物同时在线检测。采用未参与建模的35个样品对模型在线分选的准确性进行评价,其中柑橘浮皮果都被正确的推入预设的浮皮果出口,正确判别率为100%,而可溶性固形物正确分级率为97%。研究可为柑橘在线分选提供分选策略与理论依据。     

Non-destructive evaluation of the internal fruit quality of black mulberry (Morus nigra L.) using visible-infrared spectroscopy and genetic algorithm

The present study aims at assessing a non-destructive optical method for determining the internal quality of mulberry juice. First, UV-IR spectra (300–1100 nm) were acquired for each sample with a spectral resolution of 2 nm. Then the calibration set, composed of 70 and 38 samples, was used as the validation set. Next, two types of pre-processing multiplicative scatter correction)MSC(and standard normal variate)SNV(were used before analysing the data with multivariate calibration methods of PLS and GA-PLS. The following results were obtained including the correlation coefficient (r) of 0.94, 0.89, 0.98, and 0.95 and root mean square error of validation (RMSEV) 1.31°Brix, 0.52, 0.014, and 0.014 for total soluble solid (TSS), titratable acidity (TA), ascorbic acid (AA), and total anthocyanin content (AC) of mulberry juice, respectively. After that, GA-PLS was applied to select the efficient spectral regions. Model using 31 variables and 15 factors presented and yielded the best prediction results. The best combinations of 21 spectral intervals among 40 intervals selected by GA-PLS also yielded good results with RMSEV = 0.03096, r = 0.96; RMSEV = 0.062, r = 0.98, RMSEV = 0.041, r = 0.98; RMSEV = 0.0006, r = 0.96 for TSS, AA, TA, and AC of mulberry juice, respectively. Finally, it was concluded that using the UV-IR measurement technique, spectral range (300–1100 nm), it was possible to assess the quality characteristics of mulberry juice.     

Characterization of New Tart Cherry (Prunus cerasus L.): Selections Based on Fruit Quality,Total Anthocyanins,and Antioxidant Capacity

Tart cherries (Prunus cerasus L.) are rich in anthocyanins and possess high antioxidant activity. The objective of this study was to evaluate six Michigan tart cherry selections for different quality attributes; fruit weight, firmness, total soluble solids (TSS), titratable acidity, instrumental color parameters, total anthocyanins, and antioxidant capacity, determined as Oxygen Radical Absorbance Capacity (ORAC). Generally, significant (p < 0.01) differences were observed across tart cherry selections for fruit weight, firmness, total soluble solids, titratable acidity, and color values. As compared to 13.7°B for Montmorency (control), the TSS contents of all the tart cherry selections were significantly higher; ranging from 15.8 °B in selection 27–10(50) to 20.2°B in Erdi Jubileum. Fruit weight also showed significant differences, which were in the range of 3.95–8.17 g/fruit. In comparison to Montmorency, other tart cherry selections showed significantly higher titratable acidity (1.20–1.41% vs. 1.132%); higher anthocyanins (78.9–391.4 μg/g vs. 33.1 μg/g, as gallic acid equivalent); and higher ORAC values (up to 145.4% more). With respect to cost and better marketability, the results of this study could be useful for the cherry juice/concentrate industry.     

Variable selection for partial least squares analysis of soluble solids content in watermelon using near-infrared diffuse transmission technique

This work is focused on the variable selection in building the partial least squares (PLS) regression model of soluble solids content (SSC) that is used to evaluate quality grading of watermelon. The spectra were obtained by the near infrared (NIR) spectrometer with the device designed for on-line quality grading of watermelon and the spectra of 680–950 nm were adopted to analysis. The variable selection was based on Monte-Carlo uninformative variable elimination (MC-UVE) and genetic algorithm (GA). In comparison of the performances of the full-spectra (680–950 nm) PLS regression model and the feature wavelengths PLS regression model showed that the MC-UVE–GA–PLS model with baseline offset correction combined multiplicative scatter correction (MSC) pretreatment was much better and 14 variables in total were selected. The correlation coefficients between the predicted and actual SSC were 0.885 and 0.845, the root mean square errors were 0.562 °Brix and 0.574 °Brix for calibration and prediction set, respectively. This work can make a great contribution to the research of on-line quality grading for watermelon nondestructively.     

SHELF-LIFE OF FRESH-LIKE READY-TO-USE DICED SQUASH

The shelf-life of fresh-like ready-to-use diced squash during storage for 16 days at 10–12C and 95% of relative humidity was investigated. The ascorbic acid (AA) content, moisture, soluble solid content, titratable acidity, pH, weight loss and microbiological counts were determined. At the end of storage, a 1.5% weight loss was observed. Water content did not show significant changes during storage. The soluble solids content and the Brix/titratable acidity ratios increased during storage, following a linear correlation. The evolution of AA content followed a 2° polynomial correlation, with a maximum between 7–9 days of storage and a final value of 17 mg AA/100 g of fresh weight. The total microbial count increased continuously throughout storage but showed an acceptable level until day 10.     

Effects of ethephon, methanol, ethanol and girdling treatments on berry maturity and colour development in Cardinal table grapes

To hasten berry maturity and improve skin colour, the early-season table grape variety Cardinal was treated (post veraison) with a bunch + foliar spray using either 240 or 480 mg/L ethephon, as well as with 30% methanol, 30% ethanol (v/v); or by girdling. Treatment effects were evaluated in a randomised experimental design, with 10 replications of one plant per plot, down a single row. Ethephon at 480 mg/L applied twice, on July 2 when 5% of the berries showed colouring and on July 9 when 20% of the berries developed partial colour, increased total soluble solids, °Brix/titratable acidity and skin colour. Girdling, methanol and ethanol also increased total soluble solids and berry colouration and caused faster ripening. Ethephon at 480 mg/L was generally the most effective means of hastening ripening and improving colour.     

Nondestructive Determination of Soluble Solids in Tomatoes using Near Infrared Spectroscopy

A nondestructive optical method for determining the soluble solids content of fresh whole tomatoes was investigated. The method, based upon near infrared spectrophotometric techniques, could predict the soluble solids content of tomatoes (r = 0.92, SEC = 0.27°Brix). Tomatoes from more than 30 popular fresh market cultivars at stages of maturity from mature green to ripe red fruit were studied.     

Effects of sucrose polyester coating on fruit quality of apricots (Prunus armenaica (L))

Mature apricots were coated with different concentrations of a mixture containing sucrose polyesters (Semperfresh(tm) fruit coating) to determine the effect of that coating on shelf-life, post-storage life and quality of apricots. Respiration rates, weight loss, colour change, variations in soluble solids, ascorbic acid content, titratable acidity and pH of apricots were effectively reduced by both the 10 g litre^?1 and 15 g litre^?1 concentrations during ambient storage. After 10 days of cold storage both concentrations caused firmer fruit, higher pH, titratable acidity, soluble solids and ascorbic acid.     

Compositional variations and sensory acceptability of apple juice drink

Apple juice drinks containing 60% of Granny Smith or Jonathan juice, 8–14% soluble solids and Brix: acids ratios of 15:1 to 30:1 were assessed by a panel of twenty-five tasters. Sweetness and sourness increased with increasing levels of soluble solids and acidity respectively. Sourness showed little change with soluble solids at constant Brix: acid ratio but sweetness changed significantly. Intensity of flavour increased with soluble solids but the changes differed in the two types of drinks. Drinks having different soluble solids or Brix:acid ratios sometimes had similar flavour acceptabilities. Sweetness or lack of sourness, and intensity of flavour appeared to account for much of the flavour acceptability of the drinks. Equations for predicting flavour acceptance, based on Brix and Brix:acid ratios, were also developed.     

基于近红外高光谱成像技术的涩柿SSC含量无损检测

对150个涩柿采集900~1 700nm波段的近红外高光谱图像信息,利用蒙特卡罗—无信息变量消除(MC-UVE)和连续投影算法(SPA)对感兴趣区域光谱进行波长优选。通过MC-UVE-SPA优选出924.69,928.05,1 112.72,1 270.91,1 365.3,1 402.42,1 453.06,1 547.69nm 8个特征波长,对应的光谱反射率作为柿子可溶性固性物含量(SSC)检测的偏最小二乘回归(PLSR)检测模型输入,其预测集相关系数rpre=0.942,预测集均方根误差RMSEP=1.009°Brix。结果表明,MC-UVE-SPA可以有效提取与柿子SSC含量相关的特征信息,从而保留较少的波长建立较好的预测模型。     

EFFECT OF SOLUBLE SOLIDS AND TEMPERATURE ON ASCORBIC ACID DEGRADATION IN LEMON JUICE STORED IN GLASS BOTTLES

Lemon juice at concentrations of 9°, 20°, 30°, 40° and 50°Brix was stored at 10°, 20° and 36°C for 16 weeks and sampled regularly for total soluble solids (TSS), pH, titratable acidity and ascorbic acid. No significant differences were found in the first two of these factors as a function of storage time. There was a small but significant decrease in citric acid concentration over 16 weeks. Ascorbic acid loss was greater at higher temperatures; at a constant temperature, the loss was smaller as TSS increased. Ascorbic acid degradation data fitted zero-, first- and second-order models equally well at all five TSS. Rate constants in 9°Brix juice were significantly higher than those for the other four concentrations at all three temperatures. E_a values of 47.8 and 24.1 kJ mol^?1 were calculated for ascorbic acid degradation in 9° and 20°Brix juices. The effect of temperature far outweighed the effect of TSS on ascorbic acid degradation. Over the 16-week storage period, maximum retention of ascorbic acid (95.7%) was obtained in the 50°Brix lemon juice concentrate stored at 10°C.     

哈姆林甜橙果实内在品质的可见-近红外光谱无损检测法

采用可见- 近红外漫反射光谱技术,结合偏最小二乘法,以不同时间采摘的哈姆林甜橙果实为样品建立其可溶性固形物、含酸量和VC 的无损检测数学模型,同时对不同光谱预处理方法和不同建模波段范围对模型的预测性能进行对比分析。结果表明：原始光谱在400～1000nm 波段的模型预测精度较高。经多元散射校正和5 点移动平均平滑预处理后,果实可溶性固形物含量的PLS 模型最好,校正集样品的相关系数为0.995RMSEC和RMSEP分别为0.026%、0.028%;预测集样品的相关系数为0.992。经多元散射校正和9 点移动平均平滑预处理后,果实含酸量的PLS 模型最好,校正集样品的相关系数为0.997,RMSEC 和RMSEP 分别为0.012%、0.013%;预测集样品的相关系数为0.997。经多元散射校正和9 点移动平均平滑预处理后,果实VC 含量的PLS 模型最好,校正集样品的相关系数为0.998,RMSEC 和RMSEP 分别为0.009%、0.009%;预测集样品的相关系数为0.999。可见由不同时间采摘的果实组成的样品集所建立的数学模型可以提高模型的预测精度,从而提高模型的适用范围。应用可见-近红外漫反射光谱检测哈姆林甜橙果实的内在品质可行。     

Changes in chemical composition during storage of peaches (Prunus persica)

 Effects of storage time have been studied through 21 physical and chemical parameters in different batches of peaches stored at a controlled temperature (10–12  °C). The parameters were analyzed in order to assess possible differences between nutritional composition and consumer acceptability. The parameters studied were: weight, pH, titratable acidity, soluble solids (°Brix), moisture, vitamin C, soluble sugars, protein, dietary fiber (NDF, ADF, pectic substances), ashes, and mineral content (macroelements: Na, K, Ca, Mg, and P; microelements: Fe, Cu, Mg, and Zn). Analysis of variance revealed significant differences based on storage time and batch. Received: 22 June 1998 / Revised version: 25 September 1998