Influence of a combined hot air and UV‐C treatment on quality parameters of fresh‐cut broccoli florets at 0 °C

Broccoli is a horticultural product with a high nutritional value that can be consumed fresh but also minimally processed. However, broccoli is highly perishable since it develops a senescence quickly that deteriorates commercial and nutritional quality of the product. In this work we analysed the effect of a combination of UV‐C and heat treatment on quality and senescence of fresh‐cut broccoli florets stored at 0 °C. Combined treatment delayed yellowing as evidenced by higher Hue values and lower chlorophyll degradation. The treatment diminished respiratory activity indicating higher tissue integrity. Treated samples showed higher phenolic content and antioxidant capacity. On day 21 of storage, treated samples had higher levels of total sugars, and total proteins. The results suggest that a combined treatment with heat and UV‐C may reduce senescence, tissue damage and helps to maintain a better quality of the product during storage at 0 °C.     

Effect of hot air treatments on senescence and quality parameters of harvested broccoli (Brassica oleracea L var Italica) heads

Treatments with hot air were applied to broccoli (Brassica oleracea L) florets to investigate the effect on several quality and senescence parameters. To select the optimum treatment, florets were treated with different combinations of time/temperature ranging from 1 to 3 h and 37 to 50 °C and then placed in darkness at 20 °C. Most treatments delayed yellowing and loss of chlorophylls, except those performed at 37 °C, which accelerated senescence. Treatment at 48 °C for 3 h caused the highest delay in chlorophyll loss and was chosen to analyse its effect on quality and senescence. Non‐treated florets showed yellowing and reduced their chlorophyll content during storage. Heat treatment delayed the onset of chlorophyll catabolism by 1 day and slowed down the rate of degradation. Treated florets also showed lower losses of total sugars and proteins and an inhibition of protein solubilisation. Control heads showed an increment in CO₂ production, which was not detected in heat‐treated florets. Total antioxidants decreased and thiobarbituric acid‐reactive substances (TBARS) increased during storage. The treatment delayed the decrease in antioxidant content and inhibited the increment in TBARS. In conclusion, treatment at 48 °C for 3 h delayed broccoli senescence at 20 °C and contributed to maintaining an overall better quality of the product. Copyright © 2005 Society of Chemical Industry     

Hot air treatment decreases chlorophyll catabolism during postharvest senescence of broccoli (Brassica oleracea L. var. italica) heads

A hot air treatment was applied to broccoli (Brassica oleracea L. var. italica) florets and its effect on chlorophyll catabolism during postharvest senescence was analyzed. Florets were treated at 48 °C for 3 h and then placed in darkness at 20 °C. During storage, the yellowing of florets occurred simultaneously with a decrease in chlorophylls and an increase in pheophytins. Heat treatment delayed the appearance of yellowing by 2–3 days and a similar extension of shelf‐life could be inferred. Also, the treatment delayed the onset of chlorophyll catabolism and slowed both the rate of chlorophyll a degradation and pheophytin accumulation. No effect on chlorophyll b degradation was found. Chlorophyllase and Mg‐dechelatase activities increased from the first day of storage in untreated florets, whereas peroxidase‐linked chlorophyll bleaching activity increased from day 3. In heat‐treated florets, chlorophyllase activity did not increase until day 2 and then increased at lower rate than in controls. Mg‐dechelatase and peroxidase‐linked chlorophyll bleaching activities were similar in treated and control florets during the first 2 days of storage, but thereafter the activity of both enzymes was lower in heat‐treated samples. In conclusion, a treatment at 48 °C for 3 h delayed chlorophyll a catabolism in broccoli during postharvest senescence and decreased the activities of chlorophyllase, Mg‐dechelatase and peroxidase, three of the enzymes probably involved in chlorophyll degradation in plants. Copyright © 2006 Society of Chemical Industry     

Effect of visible light treatments on postharvest senescence of broccoli (Brassica oleracea L.)

BACKGROUND: Broccoli (Brassica oleracea L.) is a rapidly perishable vegetable crop. Several postharvest treatments have been applied in order to delay de‐greening. Since light has been shown to have an effect on pigment accumulation during development and darkness is known to induce senescence, the effect of continuous and periodic exposure to low‐intensity white light at 22 °C on postharvest senescence of broccoli heads was assayed. RESULTS: Exposure to a constant dose of 12 µmol m^?2 s^?1 was selected as the most suitable treatment and was employed for subsequent experiments. During the course of the treatments, hue and L* values as well as chlorophyll content and visual observation of florets indicated an evident delay in yellowing in treated samples compared with controls. No statistically significant differences in total protein content were found, but soluble protein content was higher in treated samples. Total and reducing sugar as well as starch levels decreased during postharvest senescence, with lower values in control samples. CONCLUSION: The results of this study indicate that storage under continuous low‐intensity light is an efficient and low‐cost treatment that delays postharvest senescence while maintaining the quality of harvested broccoli florets. Copyright © 2010 Society of Chemical Industry     

Maintaining quality and bioactive compounds of broccoli by combined treatment with 1‐methylcyclopropene and 6‐benzylaminopurine

BACKGOUND: Broccoli deteriorates very quickly after harvest at ambient temperature due to the loss of green colour and the consequent yellowing of florets. To search for an effective method to control quality deterioration, the effect of 1‐methylcyclopropene (1‐MCP) combined with 6‐benzylaminopurine (6‐BA) treatment on visual quality, antioxidant enzymes and bioactive compounds in broccoli florets were investigated. RESULTS: A combined treatment of 2.5 µL L^?1 1‐MCP and 200 mg L^?1 6‐BA significantly reduced the increase of lightness (L*) value, and retained a high level for the hue value (H) and chlorophyll content. Superoxide dismutase, ascobate peroxidase and catalase activities increased while the activity of peroxidase decreased during storage in treated samples in comparison with the controls. The combined treatment enhanced the biosynthesis of glucosinolate and the formation of the anticarcinogen sulforaphane, which improved the health benefit of broccoli. CONCLUSION: These results indicate that a combined treatment of 1‐MCP and 6‐BA could be a good candidate for maintaining the visual quality and enhancing the nutritional value in broccoli during storage at 15 °C. © 2012 Society of Chemical Industry     

Effect of UV‐C radiation on quality of minimally processed spinach leaves

BACKGROUND: The fresh‐cut vegetable industry commonly uses sodium hypochlorite (NaOCl) for disinfection. However, certain problems with NaOCl usage have led to the investigation of alternative sanitisation treatments. In this respect, UV‐C radiation could be of interest. RESULTS: The effect of four pre‐packaging UV‐C radiation doses (0, 4.54, 7.94 and 11.35 kJ m^?2) and two storage temperatures (5 and 8 °C) on the quality of minimally processed spinach (Spinacia oleracea L.) leaves was studied over a period of 13 days. UV‐C radiation decreased mesophilic and psychrophilic counts just after its application compared with conventional sanitisation washing (150 mg L^?1 NaOCl). However, UV‐C had no residual effect on microbial growth from 6 to 13 days at 5 and 8 °C. During shelf‐life a slight loss of lightness was found, probably related to superficial tissue damage induced particularly in higher‐UV‐C treated leaves. Total antioxidant activity and polyphenol content decreased gradually throughout storage, being more evident in higher‐UV‐C treated leaves stored at 8 °C. The general trend was to maintain the initial chlorophyll content during shelf‐life. CONCLUSION: Low to moderate UV‐C radiation can be an effective alternative to chlorine for sanitising minimally processed spinach leaves and preserving their quality. Copyright © 2008 Society of Chemical Industry     

Soluble protein content in minimally processed vegetables during storage

Soluble protein content (SPC) and electrophoretic protein profile in minimally processed broccoli, Dutch carrot and Cos lettuce were determined after 0, 3, 5, 7, 10 and 12 days of storage at 12 °C and 95±2% relative humidity. An increase in SPC in broccoli tissues (florets, stems and whole) was observed on day 3, followed by a slight fluctuation thereafter. Similar observations were recorded in shredded carrot, which showed a significant (P<0.05) increase in SPC after 3 days at 12 °C. However, changes in SPC in Cos lettuce were different from broccoli and carrot, and showed a significant (P<0.05) decrease after 3 days. The SDS-PAGE profile revealed a continuous decrease in the band intensity of soluble proteins from broccoli, Dutch carrot and Cos lettuce throughout the storage period. Complete disappearance of some bands was observed in Cos lettuce leaves and shredded carrot after 12 days of storage at 12 °C.     

Improving the quality of fresh‐cut melon through inactivation of degradative oxidase and pectinase enzymatic activities by UV‐C treatment

This work investigated the effect of exposure of fresh‐cut melon (Cucumis melo L. var. reticulatus) to ultraviolet‐C (UV‐C, 254 nm, 0.04 kJ s^?1 m^?2) radiation for different times (30, 60, 120 s) on main degradative enzymatic activities (polyphenol oxidase, peroxidase, pectin methylesterase and polygalacturonase) and quality parameters (firmness, colour) during storage at 5 °C. Enzymatic activities in samples washed with water and treated with UV‐C radiation were similar to samples washed with 100 mg L^?1 NaOCl and significantly lower than untreated samples, especially after 7 days of storage at 5 °C. Tissue softening was noticed in all samples although those treated with UV‐C light resulted 7–12% firmer than untreated ones. The lowest perceptible colour variation, expressed as ΔE*, was in samples exposed to 120 s radiation (ΔE = 8.58), while the highest value was noticed in untreated sample (ΔE = 11.06). Postcut UV‐C fruit treatment was effective in extending the shelf life of minimally processed ‘Galia’ melon.     

Alleviation of chilling injury in postharvest tomato fruit by preconditioning with ultraviolet irradiation

BACKGROUND: Tomato fruit is usually stored at low temperatures for delayed ripening and extended shelf life. However, tomato fruit is susceptible to chilling injury when exposed to low temperatures. In this study, the potential effects of preconditioning with UV‐C or UV‐B irradiation on chilling injury of postharvest tomato fruit were investigated. RESULTS: Mature–green tomato fruit were exposed to 4 kJ m^?2 UV‐C or 20 kJ m^?2 UV‐B irradiation and stored for 20 days at 2 °C and subsequently 10 days at 20 °C. UV irradiation was effective in reducing chilling injury index and delaying ethylene peak. Furthermore, UV irradiation preserved storage quality as manifested by reduced weight loss, better retention of firmness, and higher contents of total soluble solids, soluble protein and soluble sugar during subsequent storage at 20 °C. UV‐C irradiation significantly delayed the development of the red colour after 10 days of storage at 20 °C. On the other hand, UV irradiation decreased total phenolics content and antioxidant capacity, suggesting possibly reduced stress response to low temperature resulted from enhanced physiological adaptation by UV preconditioning. CONCLUSION: Our results suggest that preconditioning with UV‐C or UV‐B irradiation in appropriate doses had a positive effect on alleviating chilling injury in postharvest tomato fruit. Copyright © 2012 Society of Chemical Industry     

Hot air treatment delays senescence and maintains quality of fresh-cut broccoli florets during refrigerated storage

A postharvest treatment with hot air (48 °C during 3 h) was applied to fresh-cut broccoli to investigate its effect on quality and senescence during storage at 0 °C. The treatment delayed yellowing as evidenced by lower decrease of Hue values during storage. After 21 days of storage, treated broccoli had chlorophyll content approximately 40% higher than controls. The treatment did not affect either weight loss or respiratory activity but induced lower electrolyte leakage, indicating that treated samples conserved higher tissue integrity. Heating reduced phenolic content and antioxidant capacity during the first two weeks, but the samples recovered after 3 weeks reaching values similar to controls. Finally, after 3 weeks of storage, treated samples had higher levels of total sugars, and total and soluble proteins. The results suggest that a short postharvest heat treatment may reduce senescence, tissue damage and contribute to maintain a better quality of the product during storage at 0 °C.     

Effects of N6-Benzyladenine and Storage Temperature on Shelf-Life and Quality of Raw and Cooked Broccoli (Brassica oleracea L. var. italica)

Fresh broccoli heads were dipped in solutions containing 20 ppm N⁶-benzyladenine (BA) with 0.1% Tween-20 or water with 0.1% Tween-20 for 30 sec then stored for 5 wk at 2° and 5°C. Broccoli heads receiving BA treatments maintained higher subjective quality ratings for color, turgidity, aroma, flavor, and texture throughout the 5-wk period. Gardner color measurements and total chlorophyll were significantly higher for samples treated with BA and stored at 2°C than for controls. Samples stored at 2°C had lower shear resistance than those kept at 5°C. The content of hot water insoluble materials (fiber) was much less in broccoli heads treated with BA than in untreated heads. Maintenance of good quality by BA treatment and 2°C storage was reflected in all parameters of sensory evaluations for cooked broccoli. Loss of color and reduction of quality were observed in raw and cooked broccoli during 4 wk of storage. Evaluations of quality parameters and color measurements were greatly influenced by the turgidity factor.     

ASCORBIC ACID RETENTION OF BROCCOLI HELD ON A REFRIGERATED SALAD BAR

Reduced ascorbic acid (RAA) was analyzed in raw broccoli florets held at two different locations from the cooling source of a commercial salad bar unit. The temperatures of the broccoli were 13±2°C and 22±2°C respectively. To simulate the salad bar environment, broccoli samples were placed on the salad bar unit for 8 h, refrigerated (4°C) for 16 h and returned to the unit for 2 h. RAA was analyzed at 0, 2, 4, 8, 24 and 26 h. The value for percent RAA retention calculated on a dry weight basis was significantly decreased (p≤0.05) in the 22°C treatment at 8 h storage on the salad bar. The 8 h RAA retention values were 94.8±3.2% at 13°C and 88.9±7.1% at 22°C. There were no significant treatment differences observed at other time periods. There were no significant treatment differences in moisture content or RAA content.     

THE EFFECT OF ULTRAVIOLET IRRADIATION ON SHELF-LIFE AND RIPENING OF PEACHES AND APPLES

“Loring” and “Elberta” peaches and “Golden Delicious” apples were irradiated with UV (254nm) to doses of 0.84 × 10⁴ to 40 × 10⁴ erg/mm² then stored. “Loring” were stored 10 days and “Elberta” 20 days at 12°C. “Golden Delicious” were stored 30 days at 20–25°C in a dark room. Fruit were examined and differences in percentage rot and in physical-chemical properties determined. Percentage rot decreased with increasing UV dose. Fruit were firmer, pH and soluble solids lower and acidity higher for UV-treated than for nontreated peaches; pH was lower and acidity and ascorbic acid higher in UV treated than in nontreated apples. Percentage weight loss was less for UV-treated apples. The results indicated that UV treatment not only reduced storage rots but also delayed ripening of peaches and apples.     

UV‐C irradiation reduces breakdown and chilling injury of peaches during cold storage

Pre‐storage exposure of peaches (Prunus persica cv Jefferson) with UV‐C irradiation for 3, 5 or 10 min significantly reduced chilling injury after 14 and 21 days of storage at 5 °C plus 7 days of shelf‐life at 20 °C. Similar reduction in fungal decay was also found by these treatments. Skin browning and UV damage were found to be moderate to severe in peaches after the 15 or 20 min of UV‐C treatments. The 20 min of exposure accelerated deterioration. Fruit treated with UV‐C for 3, 5 or 10 min remained firmer and softened more slowly than the control and those treated with longer durations of exposure. No differences were found in weight loss or respiration rates among the treatments. However, ethylene production was stimulated by all of the UV‐C treatments compared with the control. Putrescine levels increased initially after 3 or 5 min of exposure to UV‐C. A tendency toward higher accumulation of spermidine and spermine was found in peaches after UV exposure. These higher levels of polyamines apparently are a response to the UV‐C irradiation and might be beneficial in increasing the resistance of fruit tissue to deterioration and chilling injury. Copyright © 2004 Society of Chemical Industry     

1‐Methylcyclopropene affects the antioxidant system of apricots (Prunus armeniaca L. cv. Búlida) during storage at low temperature

BACKGROUND: Apricots (Prunus armeniaca cv. Búlida) were treated with 1 mL L^?1 1‐methylcyclopropene (1‐MCP) immediately after harvest and stored in air at 2 °C for 21 days. Antioxidant levels (ascorbic acid and carotenoids), enzymatic antioxidant activities (superoxide dismutase (SOD) and unspecific peroxidase (POX)) and total antioxidant capacity (trolox equivalent antioxidant capacity (TEAC)) were determined. The level of oxidative stress was also established by measuring ion leakage during storage. The changes in the antioxidant potential of apricots were related to the capacity of 1‐MCP to increase their commercial life. RESULTS: 1‐MCP‐treated fruits exhibited higher SOD activity, whereas POX activity was significantly higher only after 21 days at 2 °C. Treated fruits also exhibited better retention of ascorbate and carotenoids and higher TEAC during storage. In accordance with these observations, lower ion leakage values were detected in 1‐MCP‐treated apricots. CONCLUSION: Taken together, these results suggest that 1‐MCP conferred a greater resistance to oxidative stress. This, along with the reduction in ethylene production, could contribute to the increase in commercial life and nutritional value observed in 1‐MCP‐treated apricots. Copyright © 2010 Society of Chemical Industry     

Physiology and Quality Responses of Fresh-cut Broccoli Florets Pretreated with Ethanol Vapor

ABSTRACT:  The exposure of intact broccoli to 6 mL/kg ethanol for 5 h was effective in inhibiting the senescence of fresh-cut broccoli florets. During the 8 d of storage at 10 °C, the weight loss, protein, and chlorophyll degradation of the treated broccoli florets were significantly retarded. The ethanol content of the ethanol-treated broccoli rose sharply and then descended rapidly to a level close to that of the control broccoli stored at 10 °C after 8 d. The acetaldehyde level of the treated broccoli was higher than that of the control broccoli over the whole storage period. The alcohol dehydrogenase activity of the treated broccoli was significantly higher than that of the control after 6 d. There had been higher activities of peroxidase, superoxide dismutase, and catalase in ethanol-treated broccoli. Our study showed that the fresh-cut broccoli treated with ethanol maintained better quality during the storage. Ethanol vapor would be commercially a good candidate for extending the shelf-life of fresh-cut broccoli florets and reducing the loss in postharvest.     

Optimal Controlled Atmosphere Conditions for Storage of Broccoli Florets

Minimally processing broccoli heads into florets increased the rate of respiration throughout storage at 4°C in air, in response to wounding stress. Ethylene production was also stimulated after 10 days. At-mospheres for optimal preservation of the florets were evaluated using continuous streams of the following defined atmospheres (%CO₂/%O₂): O/20 (air control), 6/1, 6/2, 6/3, and 3/2, 6/2, 9/2. The atmosphere consisting of 6% CO₂+ 2% O₂ resulted in extended storage of broc-coli florets from 5 wk in air to 7 wk. This was demonstrated by delayed yellowing, prolonged chlorophyll retention, reduced development of mold and offensive odors (by sensory observation), and better water retention. These beneficial effects were especially noticeable when the florets were returned from CA at 4°C to air at 20°C.     

Retention of Phytochemicals in Fresh and Processed Broccoli

Our objective was to determine whether steam blanching, storage and preparation affected concentrations of sulforaphane (SF), sulforaphane nitrile (SFN), cyanohydroxybutene (CHB), iberin (I) or iberin nitrile (IN) in fresh and frozen broccoli. Broccoli (var. “Arcadia”) was grown in St. Charles, IL over three seasons. Samples were steam blanched (2 min at 93 ± 5°C) within 24h of harvest, frozen and stored at ?20°C up to 90 days, and fresh broccoli was stored at 4°C up to 21 days. Samples were analyzed uncooked or microwave cooked. SF, SFN, I, IN and CHB were determined by GC in dichloromethane extracts from lyophilized samples. Rates of loss for CHB and SF were similar during storage of fresh broccoli. Blanching, storage, and microwave cooking decreased (p < 0.01) concentrations of each compound in fresh and frozen broccoli.     

Influence of combined hot air and UV-C treatment on the antioxidant system of minimally processed broccoli (Brassica oleracea L. var. Italica)

Broccoli develops a fast senescence that deteriorates the nutritional quality of the product. In this work, a combined treatment with hot air and UV-C were applied to minimally processed broccoli florets to investigate their effects on the antioxidant system during storage at 20 °C. Application of UV-C and heat enhanced by approximately 13% the levels of total antioxidants immediately after treatment. These levels were lower than initials in both control and treated samples. Nevertheless, higher values (ranged from 12 to 50%) were also detected in treated samples during storage. In general, higher values of antioxidants were correlated with elevated levels of phenols (from 10 to 17%) and ascorbic acid (from 11 to 17%) in treated florets. The increment in the content of phenolics in treated broccolis was correlated to an increased phenylalanine ammonia lyase (PAL) activity. The combined treatment also affects the activity of enzymes involved in removal of reactive oxygen species. An increase of about 50% in superoxide dismutase activity was detected after treatment. During the first days of storage this higher activity was about 40%. Enzymes that remove H₂O₂ like catalase and ascorbate peroxidase showed an enhanced activity toward the end of storage. The combined treatment diminished the peroxidase (POX) activity approximately 60% after the treatment and near 50% after two days of storage, suggesting a minor role of this enzyme in detoxification of H₂O₂. In conclusion, combined treatment may contribute to enhance the protection against oxidative molecules not only by increasing levels of phenolics and ascorbic acid but also by enhancing the activity of enzymes involved in removing reactive oxygen species.     

THE INFLUENCE OF POSTHARVEST STORAGE, TEMPERATURE AND DURATION ON QUALITY OF COOKED BROCCOLI FLORETS

Fresh broccoli heads (Brassica oleracea L. var, italica) were stored at 1C, 5C or 10C from 0 to 14 days. After this postharvest treatment, heads were cut into florets, which were given a short heat treatment and afterwards stored in plastic bags for a period of 8 days. Storage time and storage temperature before processing affected the texture and color, chlorophyll, vitamin C and β-carotene of cooked florets. The texture of cooked florets was highly correlated with water loss of the raw heads. Significant correlations were found between yellowness, instrumental color measurements and chlorophyll for cooked broccoli. Vitamin C content was affected significantly by subsequent chill temperature storage of cooked florets, which previously were stored at 5C for a period from 0 to 14 days. After 3 or 8 days of subsequent chill temperature storage of cooked broccoli florets, the vitamin C content seemed to reach almost the same level irrespective of the duration of storage of the raw heads, β-carotene content of cooked broccoli florets was stable when raw broccoli heads were stored at 1C and 5C, whereas it decreased towards the end of the storage period when the heads were stored at 10C. After cooking, β-carotene content remained stable during subsequent chill temperature storage.