Application of modified-atmosphere storage (MA) (high carbon dioxide and/or low oxygen) extends the shelf life of several fruits. This study was done to determine the effects of MA on quality and flavor of blackberries. `Navaho' and `Arapaho' blackberries were harvested in 1998 and 1999, precooled overnight at 2 °C, and placed in 0.5-L treatment jars. Treatments of 15% CO2/10% O2 or of air (0.03% CO2/21% O2) were applied at 2 °C for 3, 7, or 14 days. After treatment application, jars were held at 2 °C for an additional 11, 7, or 0 days, respectively. Seven and 14 days of application of CO2 reduced the incidence of decayed and leaky berries by 10% to 20% for both `Arapaho' and `Navaho', but firm berries decreased 10% after 14 days of treatment. Titratable acidity was slightly lower, and pH higher, in control fruit but soluble solids content was not affected by treatment. Anthocyanin content was not affected by treatment in `Arapaho' berries but was lower in `Navaho' berries after 7 and 14 days of treatment. Samples taken for taste tests after 3 and 7 days of treatment had no off-odors or off-flavors. `Arapaho' and `Navaho' blackberries benefitted from high CO2 storage, with a minimum of 7 days of treatment application needed to increase marketable berries by 10%.
P. Perkins-Veazie and J.K. Collins
Nazir A. Mir, Najma Khan, and Randolf M. Beaudry
The effects of 1-MCP on ripening and shelf life in fruit of five classes of maturity (1, mature green; 2, turning; 3, half-ripe; 4, ripe; and 5, over-ripe) of `Plum' tomato (Lycopersicon × esculentum, Mill) at 22 °C were evaluated. 1-Methylcylopropene (1-MCP) reduced the rate of red color development in fruit of all maturity classes. However, the effect was more discernable in fruit with higher hue angle value. Single application of 1-MCP delayed the color development by 10 days. While a second application of 1-MCP at day 10 delayed color development by another 10 days for mature green tomatoes, it did not influence the color change in all other classes of maturity. The effects of 1-MCP on firmness loss were similar to color development. Compared to the control, 1-MCP reduced the ripening-related rate of respiration by approximately 40%. Contrary to this, ethylene production was not affected by 1-MCP application. Potential exists to use 1-MCP in tomato to reduce ethylene-associated changes in texture and color.
Teresa L. Walker, Justin R. Morris, Renee T. Threlfall, Gary L. Main, Olusola Lamikanra, and Stephen Leong
Muscadine grapes (Vitis rotundifolia Michx.), native to the southeastern United States, have a distinct flavor, and grocers are interested in marketing them as table grapes. Two studies using 'Fry' muscadines were conducted to assist the muscadine industry in providing quality table grapes. Study 1 (1998 and 1999) evaluated density sorting and relationships between maturity, color, soluble solids, firmness, shelf life, and sensory evaluation of grapes. Study 2 (1998) determined the effect of storage on quality attributes of different maturities of grapes and evaluated use of polyethylene bags to extend their storage. Density separation successfully sorted grapes by maturity. Muscadine berry color may allow for visual or electronic sorting to eliminate immature fruit. Sensory panelists could distinguish differences in maturities for all sensory attributes. In 1999 maturities 3 and 4 (≈24-33 soluble solids: acid ratio) were preferred overall by panelists. As maturity increased, soluble solids and pH increased, and acidity decreased. Firmness decreased as maturity and storage at 2 °C increased. Percent decay increased with maturity and storage time. Grapes stored in polyethylene bags had reduced decay. A chart developed from the 1999 data related berry color to soluble solids: acid ratio, soluble solids, tartaric acid, and pH. Data from these studies can be used by industry to establish harvest parameters and enhance marketability of 'Fry' muscadine grapes.
I.G. Rubeiz, M.M. Freiwat, and A.M. Chehab
Floating rowcover (R), Dupont's “Lawn and Garden Blanket”, with 75% to 80% light transmittance, was applied on black plastic mulch (M) and over transplanted seedlings of tomato (Lycopersicon esculentum). Peto Seed's fresh market (F) `Al Wadi' and long shelf-life (L) `PSX 19392' were transplanted on 11 Apr. 1995 to drip-irrigated beds that were covered with M or not covered (C). The R was removed 4 (R1) or 5 (R2) weeks after its application. The climate is temperate with ≈200 days frost-free and 400 mm rainfall. Each cultivar was grown in a field with the treatments randomized in a complete block with four replications. Fruit harvest was done weekly for 6 weeks. Yield of the first 2 weeks was considered indicative of earliness. Yield earliness was enhanced by the shorter period treatment (R1) with the L cultivar showing more response to R1 (P < 0.05) than the F cultivar. Early average fruit weight was comparable among all treatments (P > 0.05) in both cultivars, but total average fruit weight was increased by R1 in L cultivar. (P<0.05). Total yield was comparable among the treatments in F cultivar (P > 0.05) and was lowest under M treatment in the L cultivar (P < 0.05). We recommend using R for shorter periods on tomato grown in a dry temperate climate, where clear skies can cause excess heat build up under rowcovers during day time.
Ji Heun Hong and Ken Gross
Fresh-cut produce continues to be a rapidly growing industry. However, there is little information available on storage conditions for many commodities, particularly for fresh-cut tomato slices. A major problem with fresh-cut tomato slices is their short shelf-life. The best method to extend shelf-life is refrigerated storage, preferably around 4 to 5 °C. Unfortunately, tomato tissue is susceptible to chilling injury at such temperatures. Experiments were conducted to compare changes in quality of slices from red tomato (Lycopersicon esculentum Mill.) fruit during storage at 5 or 10 °C under various modified-atmosphere conditions. In this study, we used the fourth uniform slice from the stem end and analyzed for various quality attributes during the storage period. At both 5 and 10 °C storage temperatures, ethylene concentration in containers sealed with Film A (oxygen transmission rate of 60.3 or 77.9 ml per hour per m2 at 1 atm and 99% relative humidity at 5 or 10 °C, respectively) was higher than that sealed with Film B (oxygen transmission rate of 87.4 or 119.4 ml per hour per m2 at 1 atm and 99% relative humidity at 5 or 10 °C, respectively), during storage. In addition, chilling injury, as measured by percent of slices showing some water soaked-areas, in containers sealed with Film B was higher than that of slices in containers sealed with Film A. The percent of visible fungal growth of slices was roughly correlated with the degree of chilling injury, as measured by the percent of slices showing some water soaked-areas. After 13 days of storage at 5 °C, slices stored in containers with a beginning atmospheric composition of 12% CO2 /1% O2 were firmer, compared to slices given the other treatments. After 9 days of storage at 10 °C, no visible fungal growth was observed on slices in containers with a beginning atmospheric composition of 12% CO2/1% O2 or 12% CO2/20% O2. However, slices in containers with a beginning atmospheric composition of air, or 4% CO2/1 or 20% O2 and 8% CO2/1 or 20% O2 did show visible signs of fungal growth at 25%, 33%, 46%, 29%, and 100% of infected slices, respectively. Slices in containers given all treatments, with the exception of 12% CO2/1% O2, had visible fungal growth after 15 days of storage at 5 °C. Slices in containers containing eight slices had less chilling injury and visible fungal growth than those containing four slices. Chilling injury of slices stored in completely enclosed plastic containers, similar to those commonly observed in grocery food stores, was over 7-fold higher than chilling injury observed in slices containers covered with Film A after 12 days of storage at 5 °C. However, there were no significant differences in the amounts of the volatiles we measured, i.e., ethanol, ethyl acetate, hexanol and hexanal, between the two container types. These results suggested that modified-atmosphere packaging storage can extend shelflife, as well as inhibit chilling injury in fresh-cut tomato slices.
Sarah Stephenson, Jennifer DeEll, Dennis Murr, and Rickey Yada
The objectives of this research were to determine if 1-methylcyclopropene (1-MCP) improves fruit quality and extends shelf life of Ontario greenhouse tomatoes. `Beefsteak' tomatoes between breaker and turning maturity stages were harvested from commercial growers in Leamington, Ontario, and randomly sorted into uniform lots for 1-MCP treatment. Application of 1-MCP concentrations from 0 to 1200 nL/L was done at 22 °C for 12 hours in sealed bags. After treatment, fruit were held at 22 °C. Color change, fruit firmness, and production rates of CO2 and ethylene were followed for a period of 2 weeks. Significant differences (P ≤ 0.05) were found in color, ethylene, and CO2 production rates between treatments. However, there were few significant differences among cultivars and growers. This suggests that different tomato cultivars respond similarly to 1-MCP, and that commercial growing conditions and practices may not affect its efficacy. Over the 2-week ripening period, fruit from treatments of less than 300 nL/L 1-MCP exhibited similar color changes while treatments of more than 600 nL/L resulted in blotchy ripening, causing fruit to be unmarketable. 1-MCP treatment led to an increase in the rates of ethylene and CO2 production, two processes correlated with the onset of fruit ripening. This increase was unexpected and other studies showed that 1-MCP delayed the onset of these processes in tomatoes, and inhibited them in other fruits. Tomatoes treated at a maturity between breaker and turning did not respond well to 1-MCP, perhaps due to the ripening process having already begun. This implies that maturity stages earlier than breaker to turning may respond better to 1-MCP, and it may be more beneficial to target greenhouse tomatoes at an earlier maturity.
Justin Butcher, Teddy Morelock, and Danielle Williams
Postharvest storage of southernpeas, Vigna unguiculata (L.) Walp., is a crucial point of the production process. Governed by consumer demands, farmers strive for a product that is high in quality and freshness, and has an appropriate texture and appealing color. Improper storage of southernpeas will result in their eventual deterioration, unacceptance, and possible loss of profit. Because of this, an appropriate storage facility and temperature should be devised that will benefit both farmer and consumer. In an effort to prevent potential losses of southernpeas, a study was conducted to determine the best environmental condition at which to store them to potentially extend their shelf-life. In 2004, five southernpea varieties—`Early Acre,' `Early Scarlet,' `Excel Select,' `Coronet,' and `Arkansas Blackeye #1'—were planted in a randomized block design on the University of Arkansas horticulture farm. Upon maturity, 12 green pods of each variety were subjected to a sweated and unsweated treatment and then shelled. After shelling, the seeds were subjected to four different environmental conditions evaluating each on the basis of changes in physical appearance. Further objectives of the study were to determine the best variety, environmental condition, and treatment to maintain product quality in a manner that would relate to growers on a commercial basis. Results showed that a refrigerated environment at or near 3 to 5 °C is a good environment to store this particular crop for nearly 2 weeks. It also appeared that the sweated treatment assisted with the shelling process and maintained the appearance of each variety longer. From the results, temperature and percent relative humidity are arguably two important components of postharvest storage that have the potential of negatively affecting the crop.
Jonathan M. Frantz*, Dharmalingam S. Pitchay, and James C. Locke
There are several commercial materials available that have remarkable hydrating properties and many claim them to be ideal for use in horticulture and deliver water to the roots better than other soilless media. These are often referred to as “hydrogels.” There is general agreement in the literature that the physical characteristics of hydrogels are altered in the presence of divalent cations such as Ca and Mg. Tap water can reduce the water holding capacity by 70% or more. Unfortunately, the literature agrees on little else in terms of the performance of hydrogels. Some of the confusion is caused in part by comparing one type of hydrogel to another but treating all as equal. There has been no mathematical performance evaluation of hydrogel and what affect the environment may play in that performance to predict potential irrigation savings or shelf life extension. In a series of greenhouse and laboratory studies, we have evaluated the physical characteristics of several types of hydrogels and characterized bedding plant performance throughout a typical growth cycle. We measured leaf expansion, water content of the media, root growth, flowering, and fresh and dry masses. We have found little to no differences in the rate of leaf expansion when using hydrogels, but enhanced root growth early in production with the hydrogels. Our results indicated that plant growth was enhanced early in production, but any advantage they may have was lost by the end of production. Plants grown in hydrogels needed irrigation less frequently than those without hydrogel, but the effect was diminished over time. Since the use of the material can add about 15% to the cost of potting media, this data is designed to assist growers in hydrogel use and to determine any benefits of the added costs.
Hui-juan Zhou, Xia-nan Zhang, Ming-shen Su, Ji-hong Du, Xiong-wei Li, and Zheng-wen Ye
effect of UVC pretreatment on sugar metabolism at substrate, enzyme, and regulation levels, together with associated gene expression levels, are available for peaches and their shelf life. In this study, the concentrations of soluble sugars and related
Quirien. E.A. van Oirschot, Debbie Rees, and Julia Aked
Sweet potato is an important staple food crop in East Africa, but under local marketing conditions it has a shelf life of generally no longer than 2 weeks. As a result, the potential for marketing over longer distances is limited. The role of changes in sensory properties and weight loss as limiting factors for shelf-life were investigated. The important sensory attributes of five sweet potato cultivars were determined in discussion sessions with four taste panels and were: floury, sweet, chestnutty, grainy, smooth, soft, fibrous, discoloration, and moist. The sensory profiles of the five cultivars (KSP20, Kemb10, Yanshu 1, Pumpkin, and SPK004) differed significantly (P < 0.001). However, after 4 and 8 weeks under simulated tropical storage conditions (26 °C, 80% to 90% RH) no significant changes in the attributes were detected in most cases (P > 0.05). Changes in sensory properties were therefore not considered to limit shelf life. Shelf life experiments in Tanzania under simulated marketing conditions (26 + 5 °C, 50% to 60% RH) with 29 local cultivars revealed that roots with high rates of weight loss also rot rapidly. It was found that weight losses (primarily due to water loss) were high and varied significantly among cultivars (12% to 45% loss in 21 days). Further studies will investigate the structure and strength of the periderm as the main barrier to water loss to facilitate future cultivar selection.