Browsing by Author "Hussein, Zaharan"

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    Bruise damage susceptibility of pomegranates and impacts on fruit quality
    (Stellenbosch : Stellenbosch University, 2019-03) Hussein, Zaharan; Opara, Umezuruike Linus; Fawole, Olaniyi Amos; Sigge, G. O.; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: The consumption of pomegranate (Punica granatum, L) fruit is attributed to its health and nutritional benefits, which are linked with reported high antioxidant capacity, antimutagenic, anti-inflammatory, anti-atherosclerotic and anti-hypertension activities. Postharvest handling of pomegranate fruit takes a couple of weeks (5 – 8) and includes a series of operations from harvest to export (i.e. harvesting, sorting, packing/repacking and transportation). In the course of these operations, there are various situations where pomegranate fruit are subjected to multiple modest drop impacts that predispose the fruit to varying levels of excessive external forces resulting in bruise damage. Impacts may occur as the result of sudden fall of fruit onto other fruit, parts of the tree, harvesting bucket and bin, or any other uncushioned surfaces in the course of loading and offloading. The presence of a bruise on pomegranate fruit causes produce quality deterioration that contributes to downgrading, rejection of produce and ultimately, to postharvest losses. It is therefore important to understand the mechanism of bruising and how to minimise it. The overall aim of this research was to investigate the bruise damage susceptibility of selected pomegranate fruit cultivars, to ascertain the effects of bruising and storage duration on fruit quality attributes and finally, to explore the feasibility of non-destructive measurements to detect and characterise bruise damage. The studies reported in Chapter 4 investigated the susceptibility of three pomegranate fruit cultivars (‘Acco’, ‘Herskawitz’ and ‘Wonderful’) to impact bruising. The impact threshold required to bruise pomegranate fruit was investigated for each cultivar with a view to identify the cultivar that is most susceptible to bruising. The probability of bruise occurrence (PBO) was determined from the population of selected fruit impacted at minimal drop heights (0.10, 0.15, 0.20 m). At the drop impact of 0.10 m, results showed that ‘Wonderful’ had the lowest impact threshold, with a PBO value of 0.44 and an impact energy of 371.87 mJ, whereas neither ‘Acco’ nor ‘Herskawitz’ showed any signs of bruising. At the drop impact height of 0.15 m the highest bruise occurrence was seen in ‘Wonderful’ (PBO = 1; 692.98 mJ), followed by ‘Acco’ (PBO = 0.75; 406.26 mJ) and ‘Herskawitz’ (PBO = 0.5; 511.57 mJ). These results showed that ‘Wonderful’ fruit had a higher susceptibility to bruising compared to the other investigated cultivars, and therefore needs to be handled with extra care during harvest and postharvest handling. Furthermore, the study investigated the effect of cold (5 ºC) and ambient (20 ºC) storage temperatures on bruise damage susceptibility. Fruit were dropped at higher drop impact levels (0.2, 0.4 and 0.6 m), stored for a period of 10 d at either 5 ºC or 20 ºC, during which the physiological responses including weight loss and respiration rate were evaluated. Bruise size were determined in terms of bruise volume (BV) and bruise area (BA), while bruise susceptibility was calculated as the BV per unit of impact energy. The results revealed that bruise size and bruise susceptibility at higher drop heights (0.2, 0.4 and 0.6 m) were cultivar dependent and in the order of ‘Wonderful’ > ‘Herskawitz’ > ‘Acco’. The bruise size of cold (5 ºC) conditioned pomegranate fruit was significantly higher than that of fruit conditioned at an ambient (20 ºC) temperature. Further results showed that drop impact bruising had a larger effect on the fruit physiological response (respiration rate and weight loss) for bruised fruit in comparison to non-bruised fruit. Fruit impacted at higher drop impact levels (0.4 or 0.6 m) exhibited two to three-fold higher respiration rate than fruit bruised at a lower impact level (0.2 m) or nonbruised fruit. Respiration rate and weight loss increased with prolonged storage duration and at an ambient temperature, both in bruised and non-bruised fruit. Further study to evaluate the feasibility of X-ray micro-computed tomography (X-ray µCT) in detection and characterization of bruise damage on pomegranate fruit is reported in Chapter 5. Pomegranate fruit bruised by dropping at 0.6 m was scanned with X-ray µCT. The results showed that two-dimensional CT images of fruit scanned at 0 h (immediately after drop impact), 48 h, 3 d and 5 d after impact bruising showed no evidence of bruise damage. Changes in bruise-damaged tissue as characterised by a darker appearance were observed in pomegranate fruit scanned after 7 d of impact bruising. Furthermore, visual assessment of two-dimensional X-ray µCT images were buttressed by the results of quantitative µCT data analysis. The latter demonstrated that bruised pomegranate fruit can be visualised and differentiated from 7 d after impact bruising with lower grey values (18000 - 30000) compared with non-bruised fruit (26000 - 34000). The image analysis and quantitative µCT data obtained in this study confirmed that X-ray µCT is not a suitable non-destructive method to detect and characterise fresh bruises (immediately bruised) on pomegranate fruit. Studies to explore alternative non-invasive techniques, such as a hyperspectral imaging system for early detection of fresh bruises on pomegranate fruit, are warranted. Chapter 6 focused on evaluating the physical, biochemical and microstructural changes of impact-bruise damaged pomegranate fruit. The results showed that there were significant changes in colour (browning), peel electrolyte leakage (PEL), polyphenol oxidase (PPO) enzyme activity and accumulation of reaction oxygen species (ROS) measured in pomegranate fruit peel with increasing drop impact bruising. The combination of time and temperature (in which fruit was incubated) significantly (p < 0.05) contributed to changes in PEL, PPO enzyme activity and fruit browning. Cellular microstructural differences between control and bruised fruit tissues were visible in scanning electron microscope images after 4 and 48 h of drop impact. These findings provided evidence that the loss of membrane integrity of pomegranate fruit skin cells are caused by impact bruising. Chapter 7 covered the study on bruise damage of pomegranate during long-term cold storage, focusing on susceptibility to bruising and changes in textural properties of fruit. Fruit from cold (5 ºC) storage were impact bruised from different drop heights (0.2, 0.4 and 0.6 m). The bruise volume and bruise area of pomegranate fruit increased with increasing drop impact heights and storage duration for the first two months of storage, and then decreased in the last month of storage. Similarly, the results of textural properties showed that increase both in puncture resistance, cutting and compression strength were dependent on impact bruising and storage duration. These results have demonstrated that bruise damage would result in significant changes in fruit textural attributes with concomitant low consumer appeal. Studies in Chapter 8 investigated the effects of bruising and long-term cold (5 ºC) storage on the physiological response, physico-chemical quality attributes, textural properties and antioxidant content of pomegranate fruit. Respiration rate and weight loss of whole fruit were both influenced by increasing drop impact bruising and storage duration. Furthermore, there were increases in chemical quality attributes (total soluble solids, titratable acidity, Brix-to-acid ratio and BrimA), and antioxidant content of bruised pomegranate fruit during long-term storage. This was partly attributed to the concentration effect due to an increased moisture loss from bruise damaged fruit. Results on changes in aril colour and texture were dependent on both bruising and storage duration (p < 0.05). Overall, this research represents a pilot study aimed at providing scientific insights to broaden the understanding of pomegranate fruit susceptibility to bruising during postharvest handling and its impacts on fruit quality. The findings in this dissertation have established that bruise susceptibility of pomegranate fruit is dependent on the level of drop impact, cultivar, storage temperature and duration. Furthermore, this study showed that bruising, storage conditions and duration play a crucial role on physiological responses (i.e. respiration rate and weight loss), textural properties and chemical quality attributes of the fruit. From a practical point of view, the study has revealed that, bruise damage affects the sensory appeal of pomegranate fruit during storage, which could result in downgrading of fruit market value or complete fruit loss.
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    Harvest and postharvest factors affecting bruise damage of fresh fruits
    (KeAi Communications Co., Ltd., 2019) Hussein, Zaharan; Fawole, Olaniyi A.; Opara, Umezuruike Linus
    Fresh fruits are susceptible to bruising, a common type of mechanical damage during harvest and at all stages of postharvest handling. In quest of developing and adoption of strategies to reduce bruise damage, it is of utmost importance to understand major factors influencing bruise susceptibility of fresh produce at these stages. This review presents a critical discussion of factors affecting bruising during harvest and postharvest handling of fresh fruits. Excessive compression forces during harvesting by handpicking or machines, and a series of impacts during harvesting, transport and packhouse operations can cause severe bruise damage. The review has further revealed that bruising is dependent on a number of other factors such as produce maturity, ripening, harvest time (during the day or season) and time lapse after harvest. The susceptibility to bruising is partly dependent on how these factors alter the produce physiological and biochemical properties, and the environmental conditions such as temperature, humidity and several other postharvest treatments. Hence, the successful applications of harvesting techniques by use of trained personnel and proper harvesting equipment are essential to reduce both the incidence and severity of bruising. Furthermore, the careful selection of postharvest handling temperature and other treatments can increase resistance of fresh produce to bruise damage.
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    Perforation-mediated modified atmosphere packaging (PM-MAP) and shelf-life of pomegranate fruit arils (cv. ACCO)
    (Stellenbosch : Stellenbosch University, 2014-12) Hussein, Zaharan; Opara, Umezuruike Linus; Marena, Manley; Caleb, Oluwafemi James; Stellenbosch University. Faculty of AgriSciences. Dept. of Food Science.
    ENGLISH ABSTRACT: Perforation-mediated modified atmosphere packaging (PM-MAP) offers the possibility of optimising polymeric films in order to compensate for barrier limitations of conventional modified atmosphere packaging (MAP). The aim of this study was to investigate the effects of PM-MAP and storage duration on the physico-chemical quality attributes, microbial quality, phytochemicals (anthocyanins, phenolics and ascorbic acid) and antioxidant activities of arils from fresh minimally processed pomegranate (cv. Acco). The effects of number of perforations (0, 3, 6 and 9; Ø = 0.8 mm) and storage temperature (5, 10 and 15 ºC) on water vapour transmission rate (WVTR, g/m2.day) of synthetic ‘Polylid’ and biodegradable (Nature flexTM) polymeric films were investigated. The results showed that non-perforated biodegradable film had higher WVTR at all storage temperatures, and irrespective of film type, increasing the number of perforations (from P-3 to P-9) had higher impact on WVTR than increasing storage temperature (from 5 to 15 ºC). Furthermore, this study investigated the effects of PM-MAP on the physico-chemical properties, phytochemicals components and antioxidant activities of fresh minimally processed arils. Arils (100 g) were packaged in polypropylene trays (10.6 x 15.1 cm2) and heat-sealed with a polymeric film POLYLID®. Perforations (0, 3, 6 and 9; Ø = 0.8 mm) were made on the top of the film and all samples were stored at 5 ± 1 ºC and 95 ± 2% relative humidity for 14 days. Samples were analysed at intervals of 3, 6, 9, 12 and 15 days. Microbial analysis included tests for Escherichia coli, aerobic mesophilic bacteria, yeast and moulds at days 0, 6, 10 and 14. The results showed that headspace gas composition was significantly influenced by the number of perforations, which helped balance the decrease in O2 with corresponding increase in CO2 levels, thus preventing anoxic conditions. Total soluble solids, titratable acidity and firmness of arils were slightly reduced by PM-MAP compared to clamshell trays. Colour attributes was generally maintained across all treatments and throughout the storage duration. The highest counts of aerobic mesophilic bacteria (5.5 log CFU/g), yeast and moulds (5.3 log CFU/g) were observed in P-0 and P-9 packages, respectively. Overall, P-3 and P-6 better maintained the physico-chemical properties and microbial quality of arils. Total phenolics and anthocyanin contents were higher in arils packaged in PM-MAP while ascorbic acid was slightly reduced. Antioxidant activities tested against FRAP and DPPH radical-scavenging activity increased across all types of MAP over storage duration. However, antioxidant activities were significantly higher in pomegranate arils packaged in PM-MAP due to O2-promoted biosynthesis of phenolics and anthocyanins which constitute the antioxidant properties. Overall, the results reported in this study showed that the use of PM-MAP in cold chain could be suitable for the preservation of physico-chemical quality, phytochemical contents and antioxidant properties of arils packaged in passive PM-MAP compared to clamshell and non-perforated packages during postharvest handling and storage. Perforating MAP films showed potential in preventing the incidence of in-package moisture condensation which is a common problem during postharvest handling and storage of fresh produce packaged inside non-perforated MAP. The results also showed the importance of keeping PM-MAP packs in closed refrigerated shelves to avoid cross contamination or ingress of foodborne pathogens.