Browsing by Author "Arendse, Ebrahiema"
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- ItemDetermining optimum storage conditions for pomegranate fruit (cv. Wonderful)(Stellenbosch : Stellenbosch University, 2014-04) Arendse, Ebrahiema; Opara, U. L.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.ENGLISH ABSTRACT: The development of science-based management tools and appropriate postharvest handling protocols are required for the determination of optimal storage performance of pomegranate fruit. The South African pomegranate industry experiences considerable fruit quality losses due to the lack of knowledge on optimal storage and handling practices. The cultivar ‘Wonderful’ is the widely grown in South Africa; however, to date there is currently limited scientific knowledge on the storage requirements. To develop quality standards for the export market, knowledge of optimum storage conditions are required to provide an understanding of postharvest quality attributes and consumer organoleptic perceptions. The overall aim of this research was to provide science-based management tools for the storage performance of pomegranate fruit (cv. Wonderful). The research reported in Chapter 3 focused on the physiological responses of pomegranate fruit at different storage temperatures. Commercially harvested fruit were stored at 5±0.7°C, 7.5±0.3°C and 10±0.5°C with 92±2% RH and at room temperature (21±3°C, 65±6% RH) for 5 months. Fruit respiration and physiological disorders during long term storage were investigated. During storage, low temperatures evidently resulted in lower respiration rates; however, respiration rate increased gradually after 2 months resulting in higher respiration rates at 5°C than 7.5°C after 3 month storage period. Overall, fruit became more susceptible to internal and external disorders as storage period progressed. Storage of fruit longer than 2 months at 5°C resulted in chilling injury and this was observed over the 5 month storage period. Fruit stored at 21°C and 10°C were discarded after 1 and 4 months, respectively, due to complete fruit loss to decay and peel shrinkage. Furthermore, the severity of browning increased with storage temperatures, although this became more severe at 5°C after 3 months. Therefore, to maintain a relatively low respiration rate and minimize physiological disorders, the cv. Wonderful should be stored at 5°C and >92% RH for storage period up to 3 months. In Chapter 4, the effects of temperature and storage duration on pomegranate fruit quality and mechanical properties were conducted. This study revealed that weight loss increased with rise in temperature and storage duration with the primary source of moisture loss being the fruit skin (peel), which resulted in significant reduction in peel thickness with prolonged storage period. The CIE (L*, a*, b* and C*) colour parameters of fruit and arils decreased during storage. However, the hue (hº) for whole fruit increased as a result of browning incidence, and decreased in arils suggesting an increase in redness. Significant increases in total soluble solids (TSS), pH, TSS:TA and BrimA were observed with significant decreases in titratable acidity (TA) occurring throughout the storage period. Storage temperature and duration significantly affected majority of the investigated mechanical properties. Puncture resistance, fruit and aril compression strength decreased with storage temperature and duration. These findings showed that fruit may be stored between 2 to 3 months at 5°C to ensure the best internal and external quality attributes. The studies in Chapter 5 investigated the effects of storage temperature and duration on phytochemical and antioxidant properties. Fresh pomegranate juice was assessed for concentrations of total phenolic compounds, total anthocyanin and ascorbic acid. The antioxidant property of the fruit juice was tested against 2, 2-diphenyl–1–picryl hydrazyl (DPPH). The results showed that total phenolic and total anthocyanin concentration increased up to 3 months of storage at 5°C, 7.5°C, 10°C and 21°C and decreased gradually over time. For antioxidant activity, storage of fruit at 5°C, 7.5°C and 10°C significantly (p< 0.05) reduced the radical scavenging activity of juice by more than 56% when stored beyond 2 months. Furthermore, ascorbic acid concentration gradually declined with increasing storage duration, resulting in reduced juice antioxidant capacity. These findings are beneficial to pomegranate export industries, especially where fruit are stored for long for use in health-promoting purposes. The research conducted in Chapter 6 focused on determining suitable storage conditions based on the combination of instrumental measurements and sensory attributes. During storage, individual fruit were evaluated by trained sensory panel based on the overall appearance, taste and aril texture. Discriminant analysis at different storage temperatures was used to distinguish fruit from each other at 2 months of storage with sensory attributes such as overall pomegranate flavour (R2 = 0.56), total anthocyanin (R2 = 0.46) and Chroma (C*) colour index (R2 = 0.37). Discriminant analysis further showed that storage time rather than storage temperature led to the reduction in overall quality when storing fruit beyond 2 months. Based on sensory attributes, suitable storage temperature and duration were found to be 5°C and 2 months when overall flavor were highly rated; thereafter, significant reductions in overall appearance, aril and kernel texture were observed. Furthermore, the proposed storage conditions were supported with instrumental measurements, which revealed a decline in important fruit attributes such as total phenolics, total anthocyanin, aril colour and aril texture after 2 months of storage. Overall, this study provides science-based tools required for developing cold chain handling protocols needed to manage the long supply chain of ‘Wonderful’ pomegranate fruit grown in South Africa.
- ItemEffect of different extraction methods on the quality and biochemical attributes of pomegranate juice and the application of Fourier transformed infrared spectroscopy in discriminating between different extraction methods(Frontiers Media, 2021-08-23) Arendse, Ebrahiema; Nieuwoudt, Helene; Fawole, Olaniyi Amos; Linus Opara, UmezuruikeThis study investigated the effects of extraction methods on the physicochemical, phytochemical, and antioxidant properties of pomegranate juice (cv. Wonderful). In addition, the application of attenuated total reflectance Fourier transformed mid-infrared (ATR-FT-MIR) spectroscopy and chemometrics were explored in order to discriminate between different extraction methods. Juice variants evaluated included juice extracted without crushing the seeds (arils only) using a juice extractor (JE), juice extracted by crushing the seeds using a blender (arils plus seed) (JB), and juice extracted from half fruit using a commercial hand press juicer (CH). Juice extracted from CH had higher total soluble solid (TSS) content (18.20%), TSS/TA ratio (15.83), and color properties (a* = 32.67, b* = 11.80, C* = 34.77) compared with extraction methods JE and JB. The juice extracted from JB showed the highest titratable acidity (2.17%), cloudiness (0.43), and lowest pH value (2.69). The total phenolics and anthocyanin content in the investigated juice ranged from 1.87 to 3.04 g gallic acid equivalent (GAE)/L and 37.74–43.67 mg cyanidin 3-glucoside equivalent/L of crude juice, respectively. Juice extracted from JB and CH was significantly higher in phenolic and anthocyanin compared with JE. Orthogonal partial least squares discriminant analysis (OPLS-DA) and principal component analysis (PCA) were used for classification. Classification accuracy of 100% was achieved between the three methods. The S-line plot revealed that the corresponding wavelength bands within the following regions 1,090, 1,250, 1,750, and 3,200 cm−1 were responsible for discrimination between the different extraction methods. Our results suggest that the main contributor to the discrimination between extraction methods were TSS, TSS/TA, color attributes, and anthocyanin content. Overall, this study has demonstrated that ATR-FT-MIR spectroscopy provides a powerful way to discriminate between juice extraction methods.
- ItemNon-destructive measurement of pomegranate fruit quality(Stellenbosch : Stellenbosch University, 2017-12) Arendse, Ebrahiema; Opara, Umezuruike Linus; Fawole, Olaniyi Amos; Magwaza, Lembe Samukelo; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.ENGLISH ABSTRACT: Pomegranate (Punica granatum L.) is an emerging fruit within the South African horticultural industry, which has experienced dramatic growth in annual production from 350 tonnes in the 2009 season to over 8000 tonnes in 2017. Literature shows that the fruit consists of considerable amount of sugars, organic acids, vitamins, mineral elements and possess potent pharmacological activities due to an array of phytochemical compounds found in the fruit. However, the fruit is highly susceptible to pest and disease infestation, including the development of physiological rind disorders during storage and shipping. The increased growth of the pomegranate industry has coincided with consumer demand for consistent supply of safe, nutritious and traceable fruit and processed products. Hence, non-destructive assessment of fruit quality and its processed products can contribute to the implementation of suitable management strategies to predict and control desired quality attributes. This will ensure delivery of high quality fruit and its derived products without the presence of defects in international and local markets. Therefore, the overall aim of this study was to develop non-destructive methods to predict external and internal quality attributes of pomegranate fruit. Section I of the thesis focuses on a critical review of non-destructive techniques for assessing the external and internal quality of fruit with thick rind. Thick rind fruits, such as pomegranate, have been reported to interfere with accurate measurement of internal quality using near-infrared spectroscopy. Hence, this review provides an overview of the issues related to quality measurement using non-destructive methods, including a concise summary of the current research and potential commercial applications. In section II (chapter 3), the feasibility of X-ray micro-computed tomography (μCT) as a non-destructive technique to characterise and quantify the internal structure of pomegranate fruit was investigated. μCT in combination with image analysis successfully characterised and quantified the volumes of the internal fruit components (arils, peel, kernel, juice content, air space). The calculated volume for total arils, peel, and air space were 162.45 ±16.21, 163.87 ±21.42 and 10.89 ±2.57 mL, respectively, which accounted for 48.04, 48.46 and 3.22% of the total fruit volume (338.19 ±22.4 mL). The calculated volume of juice content and kernels were 146.07 ±16.28 and 16.38 ±1.81 mL per fruit which were equivalent to an average of 89.92 and 10.08% of the total aril volume. Destructive validation results showed no significant difference with those obtained from the μCT-based non-invasive method. This study has demonstrated the potential use of μCT and associated image analysis as a promising tool for non-destructive characterization of the internal and external structure of pomegranate fruit. In chapter 4, the prospects of Fourier-transform near-infrared (FT-NIR) spectroscopy (FT-NIRS) and associated chemometric analysis were evaluated for the prediction of external and internal quality parameters of intact pomegranate fruit. Two diffuse reflectance spectral acquisition modes were assessed, namely, direct contact between the sample with an integrating sphere (IS) using the Multi-Purpose Analyser (MPA) and a contact-less measurement (distance 17 cm) using an optic fibre coupled emission head (EH) of the MATRIXTM-F analyser. Partial least squares (PLS) regression was used to construct calibration models over a spectral region of 800-2500 nm, and the results showed that optimal model performance was obtained using first derivative and second derivative spectral pre-processing methods. It was found that models obtained from the EH spectral data predicted fruit firmness, colour components (a* and C*), total soluble solids, titratable acidity, BrimA, total phenolics and vitamin C with high accuracy (RPD values ranging from 2.06 to 3.34), while the IS showed good prediction ability for h° colour component (RPD = 2.50), TSS:TA (RPD = 2.72) and total anthocyanin (RPD = 1.64). The results suggest that the contactless option of the MATRIX-F could be used to evaluate quality attributes of intact pomegranate fruit. In chapter 5, the development of calibration models by FT-NIRS for the evaluation of pomegranate aril quality was investigated using two different FT-NIR acquisition methods (IS and EH) over 800-2500 nm spectral region. Model development was based on pre-processing methods that yielded higher values of coefficient of determination (R2) and residual predictive deviation (RPD), lower root mean square error estimation (RMSEE) and root mean square error of prediction (RMSEP). The results showed that models based on the EH provided good prediction of TSS, pH, TA, BrimA, aril hue, total phenolic, total anthocyanin and vitamin C concentration, while those based on IS provided the best results for TSS:TA, firmness, arils redness (a*) and colour intensity (chroma). Furthermore, a follow-up study was conducted to compare near and mid infrared (MIR) spectrometers for predicting organoleptic and phytochemical quality attributes of pomegranate juice (chapter 6 (section II)). Three Fourier transform infrared (FT-IR) spectrometers (representing three different spectral acquisition modes) were assessed; namely, MPA FT-NIR spectrometer, Alpha-P FT-MIR spectrometer and WineScan FT-NIR/MIR spectrometer. Results obtained showed that spectral acquisition mode affected model ability to accurately predict various pomegranate quality attributes, with the WineScan in the NIR/MIR region outperforming the Alpha-P and MPA instruments. However, statistical comparison using Bland and Altman and Passing-Bablok analytical algorithms showed no statistical differences among the three spectrometers for the prediction of selected aril quality parameters. Section III of the thesis investigated the prospects for non-destructive detection and classification of pomegranate fruit affected by internal defects and postharvest rind scald. In chapter 7, the feasibility of μCT with a calibration function to differentiate between fruit fractions (albedo and arils) and detect the presence of false codling moth and blackheart disease in pomegranate fruit was assessed. A calibration function was implemented using different homogenous polymeric materials with a density ranging from 910 to 2150 kg m−3. The estimation of fruit density was successfully accomplished within the calibration range. The density of whole fruit (1070 ±20 kg m−3), arils (1120 ±40 kg m−3) and albedo 1040 ±30 kg m−3) were significantly higher compared to the larva of codling moth (940 ±40 kg m−3) inside the fruit. Furthermore, healthy fruit had significantly higher density (1070 ±20 kg m−3) compared to those with blackheart (870–1000 ±50 kg m−3). An increase in the severity of blackheart infestation was characterised by a decrease in density of affected fruit. The results of this study suggested that the use of X-ray μCT, in combination with a calibration function of polymers and image analysis, could be applied to non-destructively identify and differentiate between fruit fractions, and detect the presence of larva of false codling moth and blackheart in pomegranate fruit. The research reported in chapter 8 (section III) evaluated several biochemical markers associated with the development of husk scald (peel browning) and based on these markers, assess the feasibility of non-destructive discrimination of healthy and scalded affected fruit using Fourier transform near-infrared (FT-NIR) spectroscopy. The results suggest that enzymatic browning was the main cause of husk scald, phenolic compounds such as tannins acting as substrates for polyphenol oxidase and peroxidase activity. The severity of browning index increased with storage temperature and duration. FT-NIR reflectance spectroscopy spectral data and reference data were subjected to orthogonal partial least squares discriminant analysis (OPLS-DA) to discriminate between healthy and scalded fruit. Resulting in high classification accuracy (100%, 93% and 92.6% for healthy, severe and moderately scalded fruit, respectively). Therefore, this study has successfully demonstrated that biochemical markers associated with the development of husk scald could potentially be used to non-destructively discriminate between healthy and scalded fruit.
- ItemPostharvest physiological responses of pomegranate fruit (cv. Wonderful) to exogenous putrescine treatment and effects on physico-chemical and phytochemical properties(Elsevier, 2020-02-28) Fawole, Olaniyi Amos; Atukuri, Julian; Arendse, Ebrahiema; Opara, Umezuruike ObiaPomegranate fruit (cv. Wonderful) were treated with putrescine (1, 2 and 3 mmol/L) before storage for 4 months at 5 °C and 95 % RH and the effects on postharvest life and quality attributes were studied. Results showed that incidence of physiological disorders such as external decay, husk scald, chilling injury and aril browning increased with progressive storage but treating pomegranate fruit with putrescine reduced incidence of most disorders. Control fruit had higher levels of external decay (1.72 %–33.26 %), chilling injury (10.53 %–38.77 %) and scalding (15.04 %–100 %) with less attractive color during 4 month storage. Variations were observed on other fruit quality parameters although treatment with putrescine at 2 and 3 mmol/L concentration reduced changes in color, total soluble solid, Titratable acidity and ascorbic acid. Sensory parameters were best preserved in fruit treated with 2 mmol/L concentration of putrescine with respect to juiciness and crispness. Treatment of pomegranate fruit with putrescine resulted in improved storability and fruit quality during storage. Therefore, for short term storage, 2 mmol/L concentration of putrescine could be recommended for maintaining fruit quality especially in the first two months of storage. However, for longer storage period, a higher concentration is recommended, as 3 mmol/L concentration was the most effective in alleviating disorders and maintaining physico-chemical parameters and sensory attributes during storage in this study.