Shelf-Life and Quality Changes in Summer Storage Onions (Allium cepa)

Jumbo and medium sized summer onions (Allium cepa) of three cultivars were stored at 1, 4, 21°C for 6 months. Medium yellow onions held best at 1°C; jumbo sizes showed lowest losses at 4 and 21°C. Highest losses occurred in white onions. Major losses were due to decay. Sprouting occurred after 3 months at 4°C; none was observed at 1°C. Pungency increased and sugar decreased at 4 and 21°C; onions remained dormant at 1°C. Changes in quality parameters were factors of size and cultivar and may influence sprouting and decay over storage. Weight loss was an index to onion size change. Sprouting increased on reconditioning onions. Medium yellow Grano onions stored best on transfer to higher temperatures.     

Use of Ionizing Radiation to Improve Sensory and Microbial Quality of Fresh-cut Green Onion Leaves

: Fresh‐cut green onion leaves that received γ radiation doses of 0,1,2, and 3 kGy were stored at 3 °C for up to 14 d. Although 2 and 3 kGy of radiation completely eliminated microflora, the treatments frequently resulted in increased loss of aroma and deterioration of visual quality. In addition, radiation caused cellular membrane damage. Samples treated with 1 kGy of radiation had similar or better sensorial quality and a reduced microbial population than the controls throughout the 14 d of storage. Our results suggest that irradiation at a dose of 1 kGy can be used to enhance microbial safety of fresh‐cut green onions without loss in quality attributes.     

Effect of Hot Water Treatments on Quality of Highbush Blueberries

ABSTRACT:  Highbush blueberries, cv 'Burlington', were treated with 22, 45, 50, or 60 °C water for 15 or 30 s along with an untreated control. Fruit were then stored for 0, 1, 2, or 4 wk at 0 °C and 2 or 9 d at 20 °C prior to evaluation of microbial population and fruit quality. After 4 wk of storage, the hot water treatment at 60 °C resulted in 92% marketable berries, followed by 90% at 50 °C, 88% at 45 °C, and 83% at 22 °C compared with 76% in untreated controls. Decay incidence was reduced to 0.6%, 1.2%, 1.4%, or 2.8% with 60, 50, 45, or 22 °C water treatments, respectively, compared with 5.1% in controls following 4 wk at 0 °C and 2 d at 20 °C. After an additional 7 d at 20 °C, decay in fruit treated at 60 °C for 15 or 30 s remained at 1.8% and 0.4%, respectively, compared to 37.4% in controls. Weight loss of berries treated with hot water was 0.4% against 3.8% in controls, and shriveled and split berries were also reduced compared to controls ( P < 0.001). Aerobic plate count and yeast and mold count were reduced by 0.45 to 0.7 log at 60 °C for 30 s. Botrytis cinerea and Colletotrichum sp. were the dominant fungal pathogens causing decay of Burlington blueberries during storage. Hot water treatments also immediately induced an increase in ethanol and reduced fruit titratable acidity and soluble solids content, but had no significant effect on fruit firmness, pH, or most flavor volatile concentrations.     

GAMMA IRRADIATION, HOT WATER AND IMAZALIL TREATMENTS ON DECAY ORGANISMS AND PHYSICAL QUALITY OF STORED NETTED MUSKMELON FRUIT

Nonchemical treatments of gamma irradiation (2 Kilograys) and hot water (57°C) and the fungicide imazalil (1000 ppm) were compared with and without shrink-film wrap for effects on decay and physical quality of netted muskmelon fruit stored at 4°C for 0 through 60 days. Gamma irradiation was ineffective in controlling decay and surface molds, and injurious to physical quality by decreasing firmness, increasing fresh weight loss, membrane leakage and vein track browning. Hot water treatment coupled with shrink-film wrap was effective in controlling decay activity and maintaining physical quality up to 20 days storage. Imazalil coupled with shrink-film wrap controlled the incidence and severity of decay and maintained fruit firmness, moisture loss, membrane permeability and vein track browning for almost 60 days storage.     

Use of UV-C irradiation to prevent decay and maintain postharvest quality of ripe 'Tommy Atkins' mangoes

Ripe mangoes 'Tommy Atkins' were exposed to UV-C irradiation for 10 and 20 min, prior to storage for 14 days at 5 or 20 °C and a shelf-life period of 7 days at 20 °C. UV-C-treated fruit maintained better visual appearance than unirradiated controls. UV-C irradiation for 10 min was the most effective regime in suppressing decay symptoms and maintaining firmness during storage at 5 or 20 °C. Such fruit (treated with UV-C for 10 min) showed greater levels of putrescine and spermidine after cold storage than controls and those treated with UV-C for 20 min. Higher levels of sugars and lower levels of organic acids were observed in mangoes treated with UV-C for 20 min. However, the most effective UV-C treatment (10 min) for reducing decay maintained sugar and organic acid levels similar to the controls. No UV-damage was observed on treated fruits after storage. These results indicate that UV-C irradiation could be used as an effective and rapid method to preserve the postharvest life of ripe mangoes without adversely affecting certain quality attributes.     

Ripening Associated Phytochemical Changes in Mangos (Mangifera indica) Following Thermal Quarantine and Low-Temperature Storage

ABSTRACT: Fresh mangos entering the United States must be subjected to a thermal quarantine treatment to eliminate invasive pests, commonly followed by cold storage to extend shelf-life. Changes in phytochemicals and their resultant antioxidant capacity after such treatments are unknown. These studies evaluated mature, green mangos subjected to a simulated quarantine treatment using hot water immersion at 50°C for 60 min and subsequent storage at 5°C and 20°C against their respective controls. Fruit held at 5°C were transferred to 20°C after 8 d of storage to complete ripening, whereby symptoms of chill injury were observed. Phytochemical, antioxidant capacity, and quality parameters were then assessed every 4 d as the fruit ripened over the next 20 d. Storage temperature during ripening and not the hot water treatment was the major factor contributing to changes in polyphenolic content, with antioxidant capacity unaffected by either postharvest treatments or ripening. Major polyphenolics identified were free gallic acid and 4 gallotannins that collectively increased in concentration by 34% as the fruit ripened, also independent of postharvest and storage treatments. Carotenoid concentrations were highest in hot water-treated fruit stored at 20°C, whereas storage at 5°C initially delayed ripening. Despite appreciable differences in fruit quality during quarantine treatment or low temperature storage, only minor differences in antioxidant phytochemicals were observed.     

Effect of irradiation on Salmonella survival and quality of 2 varieties of whole green onions

Abstract: Two varieties of green onions, Banner and Baja Verde, were inoculated with a cocktail of 3 Salmonella strains using dip and spot inoculation and irradiated at 0, 0.3, 0.6, 0.9, and 1.2 kGy using electron beam. Salmonella survivors were enumerated using a XLD underlay/TSAYE overlay plating method. The D values were in the range of 0.26 to 0.32 kGy depending on variety but not on the method of inoculation. This indicated that a 5‐log reduction of Salmonella can be achieved at a dose of 1.6 kGy. For the quality study, both varieties of green onions were irradiated at 0, 1.5, 2.0, and 2.5 kGy and evaluated for changes in microbial counts, color, texture, and visual quality during storage at 4 °C. Irradiation reduced total plate counts and psychrotrophs by 3 logs. Although the counts increased during storage, they did not exceed the initial counts of control. No significant difference was observed in color and texture between irradiated samples and control. The control maintained good visual quality for about 13 d as compared to 15 d for 1.5 and 2.5 kGy samples. The 2.0 kGy samples maintained good visual quality for 17 d suggesting that irradiation can increase shelf life by reducing spoilage microorganisms but higher doses can be detrimental to quality. At the dose levels required to achieve a 5‐log reduction in Salmonella, the shelf life of whole green onion can be extended. This study shows that irradiation can be used to enhance safety without adverse effects on quality.     

The effect of packaging treatment on the storage quality of minimally processed bunched onions

Storage quality of minimally processed (MP) bunched onions, as affected by plastic film packaging, was investigated to determine the optimum packing method for this vegetable product. Five different packaging treatments, including two passive modified atmosphere packaging (MAP), two active MAP and a moderate vacuum packaging (MVP), were used for MP bunched onions. Quality attributes of the samples were evaluated periodically in terms of weight loss, colour, decay ratio, microbial counts and sensory properties during storage at 10 °C for 28 days. Various sealed‐packaging treatments did not significantly influence changes in colour of white stem and green leaf tissues, flesh weight loss and microbiological populations including mesophiles, psychrotrophs and lactic acid bacteria. However, sensory attributes and disease incidence were affected by packaging type. MVP with a gas‐permeable plastic film retained better quality bunched onions, with reduced microbial decay and visual sensory aspects, as compared with the other packages.     

Modified Atmosphere Packaging of Pomegranate

ABSTRACT: Spanish 'Mollar de Elche' sweet pomegranates (Punica granatum L.) were stored at 2 or 5 °C for 12 wk in unperforated polypropylene (UPP) film of 25 μm thickness in modified atmosphere packaging (MAP). Perforated polypropylene (PPP) film of 20 μm thickness and conventional cold storage were applied as control treatments. Quality was evaluated after storage and after shelf life of 6 d at 15 °C and 75% RH. PPP at 5 °C was the best treatment for maintaining red skin-color of the arils at the end of storage. All treatments suffered a decrease in total anthocyanins content at the end of shelf life. After shelf life, UPP fruits had higher values of absorbance at 510 and 446 nm. MAP strongly reduced water loss and chilling injuries without incidence of decay.     

EFFECT OF RELATIVE HUMIDITY, TEMPERATURE AND LENGTH OF STORAGE ON DECAY AND QUALITY OF POTATOES AND ONIONS

Long term storage tests at 0–10°C indicated that for potatoes the optimum relative humidity was 98–100%, whereas for onions a lower humidity was required. For potatoes, the high relative humidity minimized moisture loss, generally reduced decay and maintained firmness and a thin skin. While onions stored at 98–100% RH were firmer and juicier than those held at 75–95% RH, decay was generally greater and the surface layers were not as light and crisp. Sample size (from 1 bu to 11/2 tons) did not affect results. With the larger samples, a study of temperature, relative humidity and air movement in the stored produce was also made.