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Sweet corn is classified among highly perishable horticultural commodities. Thus, it can be deteriorated rapidly after harvest resulting in high loss and poorer produce quality. Sweet corn's sugar loss is about four times higher at 10°C compared to 0°C. Precooling, immediately after harvest, has shown to be an effective method to maintain the quali...
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... An assessment of precooling technologies for sweet corn by using forced-air, water and vacuum cooling has been carried out by Cortbaoui (2005) in Canada. It was found out that water-immersed treatment resulted in better maintenance of general quality index and of higher soluble solids concentration and moisture content for Canadian grown sweet corn among the three precooling technologies used. ...
... In a similar work, sweet corn ears with initial temperature of 17 °C needed 2 and 5 h to achieve 5.5 and 4.5 °C of core temperature, respectively (Maurer et al. 1969). This indicated that hydro-cooling is a time-consuming process though it yields better quality sweet corn ears than other precooling methods (Cortbaoui 2005). Practically, it may not be feasible for grower and/or handlers to hydrocool sweet corn ears for 6 h to achieve 7/8 CT with initial core temperature of 30 °C after considering ears volume, capacity of hydro-coolers and energy consumption to obtain 4 °C of chill water. ...
Sweet corn ear is a highly perishable produce with short postharvest life due to its high respiration rate which depletes sugar concentration in kernel. As a result, ear loses its sweetness and quality within 1 to 2 days under room temperature. Hydro-cooling after harvest is a good practice as it can reduce the metabolism and respiration rate of the produce. Thus, the objective of this study was to determine the effectiveness of hydro-cooling in retaining quality of sweet corn ears. Freshly harvested sweet corn ears were immersed in hydro-cooler to achieve its half and seven-eighth cooling time. Pre-cooled and non-pre-cooled ears were then stored at 12±2 and 25±2 °C for 8 days and quality index, weight loss, pH, soluble solids concentration, titratable acidity and ascorbic acid of ears were evaluated at 2 days interval. The experiment was arranged in randomized complete block design with factorial arrangement (three cooling times × two storage temperatures × five storage days) and then repeated thrice. Differences between cooling time × storage temperature, cooling time × storage day, storage temperature × storage day and cooling time × storage temperature × storage day were significant on quality index of ears. Storage temperature × storage day was also significant on ears weight loss, soluble solids concentration and pH. Seven-eight cooling time and storage at 12±2 °C provide the best quality index of ears; retain higher soluble solids concentration and pH with significantly lower weight loss compared to other cooling time treatment and 25±2 °C storage temperature. In short, temperature management is crucial in manipulating sweet corn ears quality.
... For best flavor, tenderness and shelf life, sweetcorn is harvested when the kernels are physiologically immature. One consequence of harvesting at this stage is the sweetcorn is very perishable and susceptible to rapid losses in quality during handling and shipping (Cortbaoui, 2005). Sweetcorn can be stored at 0ºC, but still has a storage life of only about 2 weeks with satisfactory quality as long as also maintained at 90-98% RH (Brecht, 2016). ...
Growers hydrocool corn with chilled water to reduce the field heat and maintain its freshness. Efficacy of hydrocooling without (HW) or with free Cl (FC), using sodium hypochlorite as sanitizer to reduce microbial load from whole corn was tested in a mobile hydrocooler.
Evaluate the efficacy of hydrocooling with FC to reduce microbial load from whole corn. Corn was field-packed into wooden crates on pallets and hydrocooled for ~60 min with plain water (HW) and with 75 or 150 ppm FC (n=3). Water samples were collected from the front, middle, and back of the cooling tank at the start and end of each run. Water samples were analyzed for FC, pH, total dissolved solids (TDS), turbidity, temperature, and chemical oxygen demand (COD). Corn samples from top, middle, and bottom layers of the pallet were collected before and after each run. All corn and water samples were analyzed for aerobic plate count (APC) and yeast and mold (Y&M) counts.
The COD in water increased from 53 ppm to 135 ppm when hydrocooled with 75 ppm FC and had a final TDS of >1700 ppm and ORP of >890. With 150 ppm FC, the water had an initial COD of >270 ppm, TDS of >3000 ppm and ORP of >830. Unwashed corn had APC and Y&M counts (log CFU/corn) of 9.75±0.29 and 8.40±0.14, respectively. APC and Y&M counts remained unaffected by HW but were reduced to 7.06±0.36 and 6.53±0.29, respectively by hydrocooling with 75 ppm FC. Reduction of microbes from corn was less by hydrocooling with 150 ppm than with 75 ppm FC. HW showed no effect on APC and Y&M counts, while FC reduced microbial load from corn. The lower reduction seen in higher FC could be due to excessive COD and TDS in the water.
... For best flavor, tenderness and shelf life, sweetcorn is harvested when the kernels are at a physiologically immature stage. One consequence of this practice is the sweetcorn is highly perishable and susceptible to a rapid loss in quality during handling and shipping (Cortbaoui, 2005). Sweetcorn can be stored at 0ºC, but still has a limited storage life of 2 weeks while maintaining satisfactory quality (Brecht, 2016). ...
Growers typically pack corn in to crate and hydrocool quickly with chilled water to remove field heat. Efficacy of hydrocooling with 150 ppm free Cl (FC) or 80 ppm peroxyacetic acid (PAA) as sanitizer, and without sanitizer was tested in reducing microbial load from whole corn. Compare the efficacies of hydrocooling with FC (HC) and PAA (HP) in reducing microbial load from whole corn and effect these treatments have on their shelf life. Corn was hydrocooled for ~60 min with plain water (wet control; WC), whereas unwashed corn was used as a dry control (DC). Water was amended with 150 ppm FC (HC) or 80 ppm PAA (HP), respectively. Three trials (n=3) were run for each hydrocooling experiment. Water was analyzed for sanitizer concentration, pH, total dissolved solids (TDS), turbidity, temperature, and chemical oxygen demand (COD). Corn and water were analyzed for aerobic plate count (APC) and yeast and mold (Y&M). Dry control and hydrocooled whole corn were incubated at 5°C for 21 days. Representative samples were taken on days 3, 7, 14, and 21 for microbiological analysis.
APC (log CFU/corn) were 9.58±0.18, 9.40±0.21, 8.64±0.15, and 8.72±0.29 on DC, WC, HC, and HP per ear of corn, respectively. Y&M counts (log CFU/corn) on DC, WC, HC, and HP corn were 8.22±0.20, 8.12±0.26, 7.03±0.10, and 7.54±0.07, respectively. Water in HC trails had no detectable microbes during the first two trials. Water in HP trials had >3 log CFU/corn of microbes in all trials. At day 21, APC and Y&M were the lowest on HC corn. Both HC and HP reduced initial microbial load from whole corn. HC would be beneficial in preventing cross contamination as no microbes survived in the water. HC, compared to HP, resulted in better microbiological quality of whole corn during storage.
... Horticultural crops are classified based on their respiration rates (Kader, 2002) ranging between very low (<5 mg CO 2 ·kg -1 ·hr -1 ) such as dates, dried fruits and vegetables; and extremely high (>60 mg CO 2 ·kg -1 ·hr -1 ) including asparagus and mushrooms. Several factors influence the produce respiration rate such as temperature, commodity and genotype, maturity, climacteric behaviour, and chemical composition of the atmosphere (Cortbaoui, 2005). During respiration, the commodity accelerates the use of its internal energy and water reserves causing losses in nutritive values and general appearance . ...
... Transpiration is a process by which fresh crops lose their water by evaporation (Becker et al., 1996). Moisture inside the produce is moved through the outer skin, and then evaporated resulting in a cooling of the commodity (Cortbaoui, 2005). Kader (2002) showed that direct losses in mass and appearance occur during transpiration that cause wilting and death of the produce in addition to firmness and nutritional losses. ...
... Storage at low humidity facilitates the transmission of water vapour from the commodity surface into the surrounding air. The transpiration rate is also dependent on internal factors such as the morphology and the anatomy of the horticultural commodity, surface-to-volume ratio and maturity stage (Cortbaoui, 2005). ...
One-third of global food produced for human consumption, which amounts to about 1.3 billion tons is lost or wasted annually. Measuring postharvest losses is an essential operational strategy to enhance postharvest management and to curtail quality loss of fresh horticultural commodity. The goal of this study was to develop and test different methods that characterize and quantify postharvest losses of cucumber and eggplant in St. Kitts-Nevis and Guyana. The study also allowed investigating the influence of temperature and light on quality changes during handling practices of freshly harvested crops.
Three approaches were deployed in the study. The first approach consisted of field-based activities in St. Kitts-Nevis and Guyana using producer household surveys (PHS) and modified count and weight (MCW) method. Results from PHS baseline surveys revealed that farmers sell most of their harvested crops to local markets, keeping the remaining crops for household consumption. In Guyana, the majority of farmers (97%) reported selling their crops at harvest, while in St. Kitts-Nevis, 61% of farmers stored them before selling. While farmers in St. Kitts-Nevis reported 30% postharvest losses of crops due to spoilage, those in Guyana reported considerably less. Results from modified count and weight method revealed that small producers experienced greater postharvest loss compared to large ones due to spoilage and lack of market access. As the produce travelled throughout the supply chain, it started to lose significantly (P < 0.05) its freshness and its marketable value as well. This loss was due to inappropriate handling and exposure to undesirable environmental conditions.
The second approach entailed laboratory-based work to simulate the environmental conditions during postharvest handling process in the studied countries. This approach was associated with activities investigating the effect of constant and fluctuating environmental factors including temperature and light on quality changes of eggplant and cucumber such as color, texture, weight loss, quality index and phytochemical content. Under isothermal conditions, four storage combinations of temperatures and light were studied for 10 day-period as follows: SC1=10oC/with light, SC2=30oC/with light, SC3=10oC/without light, and SC4=30oC/without light. Under non-isothermal conditions, another four combinations of temperatures and light were conducted (S1=25°C/2 hours without light, S2=25°C/3 hours with light, S3=30°C/12 hours with light and 20°C/12 hours without light for a total of 72 hours, and S4=10°C/144 hours without light). This scenario represented all steps of the supply chain of fresh produce starting at the producer level, followed by the distributor, the retailer and end up at the consumer level. Major postharvest losses occurred after 10 days of storage at 30oC in the presence of light. Under these conditions, the firmness of eggplant samples decreased from 5.31 N to 0.77 N (85.5% loss), the weight loss increased up to 21%, significant (P < 0.05) color difference was observed, and the crops became unmarketable after 8 days of storage. However, when the crops were wrapped using food grade polyethylene film, quality losses were reduced significantly (P < 0.05) with the exception of color attribute. Under non-isothermal conditions, the majority of losses happened after 77-hour period of storage (S3) due to the effect of fluctuating temperature and light every 12-hour period. Crude extracts of freeze-dried produce were used to determine the total phenolic contents (TPC) using the Folin-Ciocalteu method. Exposing vegetables to high temperature (30oC) and direct light was found to significantly degrade their phenolic content. However, a rise in TPC was observed (P < 0.05) when the crops were maintained at 10oC in complete darkness. In addition, storage at fluctuating environmental conditions was found to be the main driver to worsen the phenolic degradation in fresh eggplant (49.7% loss) and cucumber (83.8% loss). Kinetic models were used to provide a structural framework for quantitatively describing and predicting those losses.
In the third approach, the Taguchi method was used to quantify postharvest quality loss of both cucumber and eggplant and to optimize environmental conditions during the handling process. The Taguchi method has been widely and successfully used in various subject areas, but no application of this method to postharvest quality management has been reported until the present time. The experimental design included the 4 three-level factors and an L-9 orthogonal array. Traditionally, the Taguchi approach was used to express loss in monetary terms. For the purpose of the study, the word “loss” means the loss of quality and is expressed in unit scale. The results revealed that fresh cucumber lost some of its quality attributes immediately after harvest. At firmness of 15.68 N, the loss was equivalent to 13.68 units. However, at 7.68 N firmness, the loss value was increased by almost 4 times (56.98 units). In terms of quality index (QI), it was noticed that even when the score was high (QI = 9 points), the produce had lost 8.74 units of its quality. In theory, the only time when the loss is equal to zero is when the cucumber fruit is still attached to its mother plant. When the quality index dropped to 1.67 points, the loss was increased by almost 30 times more (loss = 254.91 units). The results showed how large the extent of loss could be when fresh cucumber is stored under undesirable conditions. The Taguchi approach was successfully used to quantify and to predict postharvest quality losses in response to different combinations of environmental factors and their levels. In addition, this approach enabled the identification of optimum conditions of temperature, light and relative humidity, for the storage of fresh produce.
