Research Articles (Horticulture)

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Advances in design and performance evaluation of fresh fruit ventilated distribution packaging : a review
(Publishers version, 2020-02-17) Mukama, Matia; Ambaw, Alemayehu; Opara, Umezuruike Linus
This review was initiated to realise the state-of-the art in optimising the ventilation and structural requirements of corrugated packaging carton design. Researchers have been using computational methods: computational fluid dynamics, particularly, the finite volume method, to analyse the airflow and heat transfer performances, and computational structural dynamics, particularly, the finite element method, to analyse the loss of compression strength due to vent-holes. Models are validated using actual testing: wind tunnel based forced air cooling system to study the produce cooling kinetics and box compression test machine for the package industry to study the structural dynamics. Studies on the rate and uniformity of produce cooling and the loss of structural strength in corrugated cartons as a function of size, shape, and location of vent-holes are reviewed. Based on experimental data, results show that the loss in strength can range between 10–40 % on addition of vent and hand holes on cartons, and reasonable increase in cooling rates is only achieved with increase in carton face ventilation area only up to 7–8 %. With regards to internal packaging components, increasing awareness of consumers to the environmental degradation of especially disposable plastic packaging means packers and suppliers must devise means to cut back and eventually eliminate plastic packaging from fruit and vegetables.
Application of dynamic controlled atmosphere technologies to reduce incidence of physiological disorders and maintain quality of 'Granny Smith' apples
(MDPI, 2021-05-26) Kawhena, Tatenda Gift; Fawole, Olaniyi Amos; Opara, Umezuruike Linus
The efficacy of dynamic controlled atmosphere technologies; repeated low oxygen stress (RLOS) and dynamic controlled atmosphere-chlorophyll fluorescence (DCA-CF) to control superficial scald development on ‘Granny Smith’ apples during long-term storage was studied. Fruit were stored for 2, 4, 6, 8, and 10 months at 0 °C in DCA-CF (0.6% O2 and 0.8% CO2), regular atmosphere (RA)(≈21% O2 and 90–95% RH), and RLOS treatments: (1) 0.5% O2 for 10 d followed by ultra-low oxygen (ULO) (0.9% O2 and 0.8% CO2) for 21 d and 0.5% O2 for 7 d or (2) 0.5% O2 for 10 d followed by controlled atmosphere (CA) (1.5% O2 and 1% CO2) for 21 d and 0.5% O2 for 7 d. Development of superficial scald was inhibited for up to 10 months and 7 d shelf life (20 °C) under RLOS + ULO and DCA-CF treatments. Apples stored in RLOS + ULO, RLOS + CA, and DCA-CF had significantly (p < 0.05) higher flesh firmness and total soluble solids. The RLOS phases applied with CA or ULO and DCA-CF storage reduced the development of superficial scald by possibly suppressing the oxidation of volatiles implicated in superficial scald development.
Application of gum arabic and methyl cellulose coatings enriched with thyme oil to maintain quality and extend shelf life of “Acco” pomegranate arils
(MDPI, 2020-12-01) Kawhena, Tatenda Gift; Tsige, Alemayehu Ambaw; Opara, Umezuruike Linus; Fawole, Olaniyi Amos
The effects of gum arabic (GA; 1.5% w/v) and methyl cellulose (MC; 1% w/v) enriched with thyme oil (TO; 0.25 and 0.5% v/v) on the quality of “Acco” pomegranate arils were studied. Coating treatments, namely, MC, MC + TO0.5%, MC + TO0.25%, GA, GA + TO0.5% and GA + TO0.25% were applied on arils by dipping, and evaluations were made on physicochemical and microbiological quality, phytochemicals and antioxidant capacity of arils stored (5 ± 1 ◦C, 95 ± 2% RH) for 16 days. Dipping arils in GA or MC, both containing TO (0.5% v/v) significantly (p < 0.0001) reduced weight loss and enhanced antioxidant activity (FRAP) (p = 0.0014). However, dipping arils in GA combined with TO (0.25% v/v) had the highest influence on reducing aril respiration rate compared with other treatments. Overall, results showed that application of coatings (GA + TO0.5% and GA + TO0.25%) reduced total yeast and mould and total plate counts and maintained quality up to 8 days of storage. These findings suggest that either GA + TO0.5% or GA + TO0.25% coatings have the capability to extend storage life of “Acco” pomegranate arils.
An architectural analysis of pear cultivars grown under South African conditions and the relevance to local maintenance pruning strategies.
(International Society for Horticultural Science -- ISHS, 2005) Cook, Nigel C.; Du Plooy, Pierre
To quantify the growth habit of locally important pear varieties, initially, 2- year-old pear branches were classified into groups based on the length and position of lateral shoots. Four groups were formed that ranged from cultivars with a spurred growth habit and strong apical control, to cultivars with a spreading growth habit and weak apical control. Secondly, the development of fruiting branches was observed for up to five years by observing the five developmental alternatives of the terminal buds of laterals, i.e., dormant, vegetative, reproductive without fruit, reproductive with fruit, and abortion. Under local conditions two general problems were observed. A large proportion of buds remain vegetative giving rise to poor flowering, and many buds remain dormant, probably due to the use of vigorous rootstocks and inadequate winter chilling. Local training systems address these shortcomings through the use of rest-breaking agents, girdling, and winter pruning techniques. Winter pruning strategies for locally important cultivars can be split into two broad approaches. In one approach spurs are renewed within spur systems primarily via bourse shoots. In the other approach spurs are renewed via year-old shoots. The motivation for the use of these systems is discussed in light of the above architectural findings.
Berry abscission in vitis vinifera L. cv. Waltham Cross : changes in abscission-related factors during berry development
(South African Society for Enology and Viticulture, 2005) Burger, D. A.; Jacobs, G.; Huysamer, M.; Taylor, M. A.
During the 1999 season, changes in total soluble solids (TSS), titratable acids (TA), pedicel diameter, berry diameter, berry mass and fruit removal force (FRF) were determined at biweekly intervals from 27 until 111 days after full bloom (DAFB) for Waltham Cross table grapes. In addition, at each assessment stage, grape bunches were detached and held in the dark at about 25°C for 80 h. Thereafter, moisture loss, FRF, berry abscission potential as well as percentage berry abscission were determined. During stages I and II of fruit growth (27 to 54 DAFB), TSS did not change significantly, while TA increased. FRF increased significantly during this early stage of berry development, indicating a strengthening of the abscission zone tissue. During stage III (after 54 DAFB), a decline in FRF occurred, which coincided with a perceptible increase in TSS and a decrease in TA. Berry mass increased significantly from 27 to 111 DAFB. Pedicel diameter only increased significantly for the period 27 to 41 DAFB, while berry diameter increased significantly for the period 27 to 97 DAFB. Grapes sampled at 27 DAFB had a significantly lower FRF and significantly higher levels of berry abscission and moisture loss after the 80-hour period in the dark, compared with grapes sampled at a later stage. At 27 DAFB, the abscission zone developed between the pedicel and the rachis, thereafter it developed between the pedicel and the berry. Although FRF did not change significantly as berries ripened (from 83 to 111 DAFB), abscission potential and percentage berry abscission were significantly higher for grapes harvested at 83 DAFB at a TSS of 12.3°Brix than for grapes harvested more mature, at a higher TSS. Moisture loss correlated significantly (P<0.0001) with berry abscission, with a correlation coefficient of 0.84. Berry abscission also correlated significantly (P<0.0001) with abscission potential, pedicel and berry diameter, FRF (at sampling), FRF (after 80 h) and berry mass, but not with TSS or TA.
CFD model development and validation of a thermonebulisation fungicide fogging system for postharvest storage of fruit
(Elsevier, 2012-01) Delele, M. A.; Vorstermans, B.; Creemers, P.; Tsige, A. A.; Tijskens, E.; Schenk, A.; Opara, Umezuruike Linus; Nicolai, B. M.; Verboven, P.
Postharvest treatments of fruits in storage rooms using a fogging system is a recent development that offer a promising means to reduce the use of fungicides in the orchards, where ecological and environmental risks are higher than in the closed environment of the storage room. To investigate the effectiveness of postharvest storage fungicide fogging systems, a computational fluid dynamics (CFD) model was developed and validated. A discrete element (DE) method was applied to generate a random stacking of spherical fruits in a typical bin. The CFD model was then employed to study explicitly the air and fungicide particle flow through the bin vent holes and through the voids of the stack, and to predict the deposition behaviour of the fungicide particle on the products. For model validation purposes, a standardized set-up was used with a single fruit bin positioned in a cold store that was operated at different air flow rates. Good agreement was found between measured and predicted results of deposition profiles of fungicide particles. The deposition on the top layer of the fruit stack was higher than the bottom one, and higher deposition was observed on the top sides than on the bottom sides of the fruit. The effect of air flow rates and different bin handling parameters on fungicide particles flow and deposition were investigated. Air circulation rates of 0 m3 h 1 (no air circulation), 4080 m3 h 1 and 6800 m3 h 1 and 9520 m3 h 1 were used. The highest fungicide deposition on the fruit was observed during fogging without air circulation while the lowest deposition corresponded to fogging with the highest air circulation rate. Covering the top of the bin with foil and removing the bottom plastic foam that is usually placed on the bottom floor of the bin improves the uniformity of fungicide deposition throughout the bin. Removing the bottom plastic liner increased the average deposition of the fungicide particles, while covering the top of the bin decreased the average deposition
Chemical and phytochemical properties and antioxidant activities of three pomegranate cultivars grown in South Africa
(Springer Verlag, 2011-02) Fawole, Olaniyi A.; Opara, Umezuruike Linus; Theron, K. I.
A comparative study of chemical contents and antioxidant activities of three pomegranate cultivars (‘Arakta’, ‘Bhagwa’ and ‘Ruby’) grown in South Africa was conducted. Fresh pomegranate juice (PJ) of each cultivar were assessed for soluble solid contents (SSCs), pH and titratable acidity (TA), while extracted juice samples were evaluated for total phenolic (TP), including total tannins (TT), proanthocyanidins (Pcy), total flavonoids, anthocyanins and gallic acids (GA) using spectrophotometric methods. The antioxidant properties of the juice samples were evaluated against stable 2, 2– diphenyl–1–picryl hydrazyl, as well as in ferric reducing ability of plasma (FRAP) and QuantiChrom™ (TAC) antioxidant assays. There were significant differences in the chemical properties of the cultivars. SSC, TA and pH varied between the range of 14.07–15.10 °Brix, 0.22– 0.28 g/100 ml and 3.32–3.64, respectively. ‘Bhagwa’ had the highest TP (449.9 mg/100 ml), 1.3-fold and 1.6-fold higher than ‘Arakta’ and ‘Ruby’, respectively. The strongest total antioxidant activity was exhibited by ‘Bhagwa’ with an antioxidant index of 95.7%, followed by ‘Arakta’ (93.2%) and ‘Ruby’ (79.9%). PJ phytochemical properties (TP, TT, Pcy, GA) and antioxidant activity (FRAP and TAC) were significantly correlated (r2= 0.509–0.885) with each other.
Classification learning of latent bruise damage to apples using shortwave infrared hyperspectral imaging
(MDPI, 2021-07-22) Nturambirwe, Jean Frederic Isingizwe; Perold, Willem Jacobus; Opara, Umezuruike Linus
Bruise damage is a very commonly occurring defect in apple fruit which facilitates disease occurrence and spread, leads to fruit deterioration and can greatly contribute to postharvest loss. The detection of bruises at their earliest stage of development can be advantageous for screening purposes. An experiment to induce soft bruises in Golden Delicious apples was conducted by applying impact energy at different levels, which allowed to investigate the detectability of bruises at their latent stage. The existence of bruises that were rather invisible to the naked eye and to a digital camera was proven by reconstruction of hyperspectral images of bruised apples, based on effective wavelengths and data dimensionality reduced hyperspectrograms. Machine learning classifiers, namely ensemble subspace discriminant (ESD), k-nearest neighbors (KNN), support vector machine (SVM) and linear discriminant analysis (LDA) were used to build models for detecting bruises at their latent stage, to study the influence of time after bruise occurrence on detection performance and to model quantitative aspects of bruises (severity), spanning from latent to visible bruises. Over all classifiers, detection models had a higher performance than quantitative ones. Given its highest speed in prediction and high classification performance, SVM was rated most recommendable for detection tasks. However, ESD models had the highest classification accuracy in quantitative (>85%) models and were found to be relatively better suited for such a multiple category classification problem than the rest.
Classification of 'Granny Smith' apples with different levels of superficial scald severity based on targeted metabolites and discriminant analysis
(German Botanical Society, 2016) Mditshwa, Asanda; Fawole, Olaniyi A.; Vries, Filicity; Van der Merwe, Kobus; Crouch, Elke; Opara, Umezuruike Linus
To study the metabolic changes in ‘Granny Smith’ apples with different severities of superficial scald, fruit were stored in normal refrigerated air (0°C, 95% RH) for 12 weeks followed by 7 d shelf-life under room conditions (20°C, 65% RH). Fruit were graded to five groups based on scald severity and analysed for ethylene, α-farnesene and 6-methyl-5-hepten-2-one (MHO) levels. Reactive oxygen species (ROS) were measured by confocal laser-scanning microscopy on apple peel treated with fluorescent probe 2’,7’-dichlorodihydrofluorescein diacetate. Ethylene production rate, α-farnesene and MHO contents and ROS intensity increased with increasing scald severity but declined in severely scalded fruit. Malondialdehyde (MDA) concentration in fruit peel, a measure of membrane damage, increased linearly (R=0.891) with increase in scald severity. Discriminant analysis was used to classify fruit by scald severity on the basis of metabolites accumulated. The stepwise model indicated that three attributes (ROS, ethylene production and MDA) contributed significantly (R2≥0.5) to the separation of the five scald severity indexes, with ROS having the highest contribution (partial R² =0.961; p<0.0001), followed by ethylene (R2=0.718; p<0.0001) and MDA (R2=0.578; p<0.0001).
Drying kinetics of pomegranate fruit peel (cv. Wonderful)
(Elsevier, 2019) Mphahlele, Rebogile R.; Pathare, Pankaj B.; Opara, Umezuruike Linus
Pomegranate juice processing produces large amount of peel as by-product or waste which is a potential source of raw material for food and other bioprocessing industries. Drying the peel offers opportunities for value addition into novel products, thus reducing waste from the fruit processing operations. This study presents the mathematical models of thin layer drying behaviour of pomegranate peels (initial thickness 5.00 ± 0.05 mm and moisture content 70.30% wet basis) using three air temperatures (40 °C, 50 °C and 60 °C) at a constant air velocity of 1.0 m/s. The results obtained showed that drying time decreased as the oven drying temperature increased. The drying process took place mainly in the falling rate period. Ten thin layer drying models were evaluated based on coefficient of determination (r2) and standard error (es). Among the tested drying models, Midilli et al. mathematical model was found to be the best fit for establishing the drying kinetics of pomegranate peel. Furthermore, the effective moisture diffusivity of pomegranate peel ranged from 4.05 × 10−10 to 8.10 × 10−10 m2/s over the temperature range investigated, with mean activation energy (Ea) of 22.25 kJ/mol.
Early prediction of ripening and storage quality of pear fruit in South Africa
(International Society for Horticultural Science -- ISHS, 2005-04) Lotze, E.; Bergh, O.
Maturity index records for the principal pear cultivars in the two most important pear producing areas in South Africa were compiled to study the fluctuation in total soluble solids (TSS), fruit firmness and starch breakdown during consecutive seasons. Temperatures (heat units, hu), sunlight hours (ssh), fruit size (diameter), days after bloom (dafb) and soil type were used to calculate the rate of change in TSS levels, firmness and starch breakdown during the last five to six weeks before the picking date. These variables were shown to have an effect on the internal fruit quality. High temperatures were found to result in a faster drop in firmness levels and increased sunlight hours improved the TSS levels. Orchards on sandy soils showed consistently lower TSS levels and firmness when different orchards were compared during consecutive seasons. Equations were fitted to the data for each cultivar and area to develop models for the prediction of the different indices. The predicted rates of change of the different indices were compared with the actual values to test the accuracy and proved to explain more than 80% of the variation during consecutive seasons. The results also showed that the rate of change for these indices could be estimated as early as the middle of December. These models are considered important tools to assist growers, pack houses and marketers in identifying seasons when fruit will have a short shelf life. Picking dates, cold storage and marketing can be adapted to ensure the best possible fruit quality.
Effect of blanching pomegranate seeds on physicochemical attributes, bioactive compounds and antioxidant activity of extracted oil
(MDPI, 2020-05-31) Kaseke, Tafadzwa; Opara, Umezuruike Linus; Fawole, Olaniyi Amos
This study investigated the effect of blanching pomegranate seeds (PS) on oil yield, refractive index (RI), yellowness index (YI), conjugated dienes (K232), conjugated trienes (K270), total carotenoid content (TCC), total phenolic compounds (TPC) and DPPH radical scavenging of the extracted oil. Furthermore, phytosterol and fatty acid compositions of the oil extracted under optimum blanching conditions were compared with those from the oil extracted from unblanched PS. Three different blanching temperature levels (80, 90, and 100 °C) were studied at a constant blanching time of 3 min. The blanching time was then increased to 5 min at the established optimum blanching temperature (90 °C). Blanching PS increased oil yield, K232, K270, stigmasterol, punicic acid, TPC and DPPH radical scavenging, whereas YI, β-sitosterol, palmitic acid and linoleic acid were decreased. The RI, TCC, brassicasterol, stearic acid, oleic acid and arachidic acid of the extracted oil were not significantly (p > 0.05) affected by blanching. Blanching PS at 90 °C for 3 to 5 min was associated with oil yield, TPC and DPPH. Blanching PS at 90 °C for 3 to 5 min will not only increase oil yield but could also improve functional properties such as antioxidant activity, which are desirable in the cosmetic, pharmaceutical, nutraceutical and food industries.
The effect of different rates of prohexadione-calcium and girdling on shoot growth and fruit quality when applied to different pear cultivars
(International Society for Horticultural Science -- ISHS, 2005-04) Meintjes, J. J.; Stassen, P. J. C.; Theron, K. I.
Prohexadione-Calcium (P-Ca) is a promising new shoot growth retardant that is already registered on apples in North America (Apogee®) and in Europe (Regalis®). This gibberellin biosynthesis inhibitor with limited persistence and low toxicity was tested on five Pyrus communis cultivars: ‘Rosemarie’, ‘Flamingo’, ‘Early Bon Chretien’, ‘Packham’s Triumph’ and ‘Forelle’. P-Ca was able to reduce shoot growth in all of the cultivars, but there was a marked difference in sensitivity towards different rates of P-Ca between the different cultivars. Fruit set was improved in ‘Rosemarie’, ‘Forelle’ and ‘Early Bon Chretien’, which led to a decrease in final fruit size of ‘Rosemarie’. P-Ca caused a decrease in return bloom in ‘Packham’s Triumph’ and ‘Forelle’. Girdling only reduced shoot growth in ‘Forelle’ but did not improve fruit set in any of the cultivars. Girdling improved final fruit weight of ‘Flamingo’, increased fruit length in ‘Early Bon Chretien’ and increased return bloom in all of the cultivars except ‘Packham’s Triumph’. The five cultivars are categorised according to their sensitivity towards P-Ca: ‘Rosemarie’ > ‘Flamingo’ = ‘Early Bon Chretien’ = ‘Packham’s Triumph’ > ‘Forelle’.
The effect of fruit maturity and storage duration on friction discolouration of Packham's Triumph and Doyenne du Comice pears
(International Society for Horticultural Science -- ISHS, 2005-04) Burger, G. E.; Griessel, H. M.; Huysamer, M.
Friction discolouration (FD) is causing the South African pear industry multi-million rand losses due to blemished fruit being rejected for the export market and being sold locally. The occurrence of FD was studied over two seasons using ‘Packham’s Triumph’ and ‘Doyenne du Comice’ (Pyrus communis) fruit. The influence of fruit maturity and storage duration were investigated by harvesting over three maturities and storing fruit for up to three months. FD was induced using a modified laboratory shaker that was shown to closely mimic pack line damage. Polyphenol oxidase (PPO) activity and total phenolics (TP) content were also evaluated. ‘Doyenne du Comice’ was more prone to FD than ‘Packham’s Triumph’. Harvest maturity significantly influenced FD susceptibility, with the middle picking maturity generally giving higher FD ratings. Increasing storage duration generally increased FD ratings, although not consistently. PPO activity was not influenced by harvest maturity, but was influenced by storage duration. In ‘Packham’s Triumph’, the TP content was not affected by harvest maturity or storage duration, whereas both these factors significantly influenced TP content in ‘Doyenne du Comice’. Susceptibility to development of FD symptoms is not easily linked to either PPO activity or TP content, and seasonal differences in susceptibility make prediction of possible levels of FD very difficult.
Effect of hot-air and freeze-drying on the quality attributes of dried pomegranate (Punica granatum L.) arils during long-term cold storage of whole fruit
(MDPI, 2020-10-22) Adetoro, Adegoke Olusesan; Opara, Umezuruike Linus; Fawole, Olaniyi Amos
: This study investigated the effect of hot-air and freeze-drying on the physicochemical, phytochemical and antioxidant capacity of dried pomegranate arils during long-term cold storage (7 ± 0.3 ◦C, with 92 ± 3% relative humidity) of whole fruit over a single experiment. Extracted arils were processed at monthly intervals during 12 weeks of cold storage of whole fruit. After the 12-week storage period, hot-air and freeze-dried arils showed the least (3.02) and highest (23.6) total colour difference (TCD), respectively. Hot-air dried arils also contained 46% more total soluble solids (TSS) than freeze-dried arils. During the storage of pomegranate fruit, total phenolic content (TPC) steadily increased from 20.9 to 23.9 mg GAE/100 mL and total anthocyanin content (TAC) increased from 6.91 to 8.77 mg C3gE /100 mL. Similarly, an increase in TPC and TAC were observed for hot-air (9.3%; 13%) and freeze-dried arils (5%; 5%), respectively. However, the radical scavenging activity (RSA) reduced by 8.5 and 17.4% for hot-air and freeze-dried arils, respectively, after 12 weeks of cold storage. Overall, the parameters such as colour, TPC and TAC as well as the lower degradation in RSA stability during storage showed distinct differences in quality when using the freeze-drying method, which is, therefore, recommended.
Effect of pruning severity and branch quality on fruit set and fruit dry weight of Packham's Triumph pears (Pyrus communis L)
(International Society for Horticultural Science -- ISHS, 2005-04) Reynolds, L. P.; Jacobs, G.; Theron, K. I.
The effect of dormant pruning and the quality of 2-year-old bearing units(BU) on fruit set and mean fruit dry weight of ‘Packham’s Triumph’ pears wasdetermined during the 2002/03 season. Fruit set on short BU (28 cm long) was 20percent higher and mean fruit dry weight were 20 percent more than for long BUs(56 cm). On thick BU (14 mm basal diameter) 70 percent more fruit set than on thinBU (8 mm) and mean fruit dry weight was 20 percent more than on thick BU.
The effect of scoring during flower induction or the initiation phase on return bloom in Pyrus communis L
(International Society for Horticultural Science -- ISHS, 2005-04) Reynolds, L. P.; Jacobs, G.; Theron, K. I.
The influence of scoring during the flower induction phase was investigated. Pear trees, Pyrus communis L. cv. Doyenne du Comice, Forelle and Rosemarie were used in the study, conducted in the Western Cape, South Africa. The yield of ‘Doyenne du Comice’ increased by 38% in scored trees compared to the control. The increase in yield was due to 50% more fruits on the scored trees than on the control trees. The increase in fruit number per tree was due to a higher percentage of reproductive buds per tree and the improved quality of these buds. Scoring of ‘Rosemarie’ at the correct time resulted in a 40% increase in reproductive buds. Scoring disrupts basipetal transport in the phloem, which results in the removal of apical dominance and an increase in root-derived cytokinins. More meristems can respond to inductive conditions and the higher concentration of cytokinins during inductive conditions leads to improved flower quality.
Effect of the rate and duration of forced air cooling on the quality of Imperial apricots and Pioneer and Songold plums
(Acta Horticulturae, 2005-06) Jooste, M. M.; Khumalo, P.
Gel breakdown (GB) and overripeness (OR) remain the biggest internal Problems with Prunus armeniaca L. ‘Imperial’, which makes the biggest contribution to the total volume of apricots exported from South Africa per annum. Prunus salicina L. ‘Pioneer’, an early season South African plum cultivar, ripens quickly on and off the tree which results in rejections for soft fruit at packing and on arrival overseas. ‘Songold’, a yellow, midseason plum cultivar tends to develop GB and OR during cold-storage in some seasons, which renders the fruit inedible and results in high rejection rates. Prompt cooling and good temperature management are essential to lower the rate of physiological deterioration of stone fruit. In some commercial depots in South Africa, forced air cooling (FAC) of stone fruit can take as long as 48 to 72 h, depending on the type of packaging. Consequently, the objective of this study was to determine the effect of the rate and duration of FAC on the fruit quality of different stone fruit cultivars. Fruit was subjected to the following FAC rates at a delivery air temperature of -1.0°C to a pulp temperature of 0°C for 6 h, 12 h, 24 h stepwise cooling and 48 h stepwise cooling for the apricot, and 12 h, 24 h, 48 h stepwise cooling, and 72 h stepwise cooling for the two plum cultivars. The fruit was evaluated after cold-storage and a simulated shelf-life period. The trial was conducted in two consecutive seasons. ‘Imperial’ apricots had the best internal quality after 6 h of FAC, ‘Pioneer’ plums were not affected by FAC rate or duration, and ‘Songold’ plums had the best internal quality when FAC was applied for 12 h and longer. These results on plums demonstrate that cultivar differences must be considered when drawing up handling protocols for stone fruit, as a blanket recommendation may lead to the induction of quality defects.
Effects of packaging liners on cooling rate and quality attributes of table grape (cv. Regal Seedless)
(Wiley Blackwell, 2011-07) Ngcobo, Mduduzi E. K.; Opara, Umezuruike Linus; Thiart, G. D.
Table grapes are commonly packed in multi‐layered packages consisting of cardboard carton, plastic liners and carry bag/pouch to maintain product quality along the cold chain. Each liner is characterized by the number and the size of perforations, which influence the environmental conditions around the produce inside the package. This study investigated the effects of different carton liners on the cooling rate and quality attributes of ‘Regal Seedless’ table grapes. Fruit quality attributes measured include weight loss, stem dehydration and browning, SO2 injury, decay, berry firmness and colour. Non‐perforated liners maintained relative humidity (RH) close to 100% during cold storage and during a 7 day shelf life period, which resulted in delaying the loss of stem quality but significantly (p≤0.05) increasing the incidence of SO2 injury and berry drop during storage, as compared with perforated liners. Perforated liners improved fruit cooling rates but significantly (p≤0.05) reduced RH. Low RH in perforated liners resulted in significant (p≤0.05) increase in stem dehydration and browning as compared with non‐perforated liners. Berry firmness decreased by 78% after 42 days of storage at −0.5°C. Significant (p≤0.05) differences in berry firmness between the different packages were observed only during the first 7 days of storage. Berry colour changed from greenish‐yellow to yellowish‐green in all types of plastic liner during the storage period. Fruit decay occurred in all packages after a 7 day shelf life, with the highest incidence of decay occurring in liners with less perforation
The effects of postharvest treatments and sunlight exposure on the reproductive capability and viability of Phyllosticta citricarpa in citrus black spot fruit lesions
(MDPI, 2020-12-21) Moyo, Providence; Fourie, Paul H.; Masikane, Siyethemba L.; Fialho, Regis de Oliveira; Mamba, Lindokuhle C.; Du Plooy, Wilma; Hattingh, Vaughan
Citrus black spot (CBS) is caused by Phyllosticta citricarpa, which is classified as a quarantine organism in certain countries whose concerns are that CBS-infected fruit may be a pathway for introduction of the pathogen. This study evaluated the reproductive capability and viability of P. citricarpa under simulated conditions in which the whole fruit, peel segments, or citrus pulp with CBS lesions were discarded. Naturally infected ‘Midknight’ Valencia orange and ‘Eureka’ lemon fruit, either treated using standard postharvest sanitation, fungicide, and wax coating treatments or untreated, were placed into cold storage for 5 weeks (oranges at 4 ◦C and lemons at 7 ◦C). Thereafter, treated and untreated fruit were incubated for a further 2 weeks at conditions conducive for CBS symptom expression and formation of pycnidia. The ability of pycnidia to secrete viable pycnidiospores after whole fruit and peel segments or peel pieces from citrus pulp were exposed to sunlight at warm temperatures (±28 ◦C) and ±75% relative humidity levels was then investigated. The combination of postharvest treatments and cold storage effectively controlled CBS latent infections (>83.6% control) and pycnidium formation (<1.4% of lesions formed pycnidia), and the wax coating completely inhibited pycnidiospore release in fruit and peel segments. Pycnidiospores were secreted only from lesions on untreated fruit and peel segments and at low levels (4.3–8.6%) from peel pieces from pulped treated fruit. However, spore release rapidly declined when exposed to sunlight conditions (1.4% and 0% after 2 and 3 days, respectively). The generally poor reproductive ability and viability of CBS fruit lesions on harvested fruit, particularly when exposed to sunlight conditions, supports the conclusion that citrus fruit without leaves is not an epidemiologically significant pathway for the entry, establishment, and spread of P. citricarpa.

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