Sweet potatoes (Ipomoea batatas L.), 'Brazlândia Roxa', 'Brazlândia Branca' and 'Princesa' were harvested at optimum maturity to evaluate respiratory activity and browning susceptibility of minimally processed roots. After harvest, non-blemished roots were graded for size (18±2cm) and diameter (5±1cm), and minimally processed inside a cold room. Processed roots were placed in sealed glass jars and stored at 3±0.5°C to evaluate respiratory activity during a 4-hour period or were packed in plastic films with partial vacuum to evaluate development of browning. Packages were stored under refrigerated conditions (3±0.5°C) for 5 days. Daily, minimally processed roots were evaluated for browning according to a scale ranging from 0 (extremely browned) to 5 (no browning) and using an objective assay (absorbance at 340 nm). Minimally processed roots showed a pronounced increase in carbon dioxide evolution immediately after processing. 'Princesa' had the highest respiratory activity among the evaluated cultivars, being 40% higher two hours after processing than the other cultivars. 'Brazlândia Roxa' and 'Brazlândia Branca' were significantly less susceptible to browning compared to 'Princesa', which was rated as unacceptable for commercial use at the end of the storage period. 'Brazlândia Roxa' and 'Brazlândia Branca' were still marketable at the end of the storage period.

Figure 5. Total carotenoids (mg.kg -1 fresh weight) of tomato fruits treated with 1-MCP, stored for 2 days at ambient conditions (23±1°C; RH 80-85%), with subsequent storage for 15 days at 20±1°C and 85-95% RH. Vertical bars indicate ± SD.

A lthough commercialized at higher prices when compared to fresh products, fresh-cut fruits and vegetables have the advantage of being perceived by customers to be fresher than other products, such as frozen or canned food. Since 1994, "fresh" has remained the most desirable food label claim for 79% of american customers, followed by low fat (62%), and natural MORETTI, C.L.; ARAÚJO, A.L.; MATTOS, L.M. Evaluation of different oxygen, carbon dioxide and nitrogen combinations employed to extend the shelf life of fresh-cut collard greens. Horticultura Brasileira, Brasília, v. 21, Embrapa Hortaliças, C. Postal 218, 70359-970 Brasília-DF; 2. Universidade Federal de Lavras, 37200-000 Lavras-MG; E-mail: celso@cnph.embrapa.br (41%). Besides that, freshness is a serious issue for shoppers and retailers, being the third reason for selecting a primary supermarket, just behind high quality and a "clean and neat store" (Sloan, 2000). In Brazil, the fresh-cut industry started at the beginning of the 1980's and is increasing considerably every year. This increase is partly due to the enormous growth of the foodservice segment (150% during the last 7 years) (Moretti & Sargent, 2002).Fresh-cut products represent around 10% of the American fresh fruit and vegetable market, resulting in a volume of 8 to 10 billion dollars per year (Cantwell, 2000). The consumption of fresh-cut products is increasing year after year, showing many advantages when compared to fresh products. ABSTRACTCollard greens (Brassica oleracea var. acephala) "Manteiga" were harvested in commercial fields in Brasilia, Brazil, aiming to evaluate different oxygen, carbon dioxide and nitrogen combinations to extend the shelf life of the fresh-cut product. After harvest, leaves were taken to the postharvest laboratory, selected for external blemishes and minimally processed (3 mm thick) inside a cold room (13±2°C). After processing, fresh-cut collard greens were stored under two controlled atmosphere (CA) conditions (3% O 2 , 4% CO 2 ; 5% O 2 , 5% CO 2 /balance N 2 ), and normal air (control), at 5°C (95±2% RH), for six days. Daily, minimally processed collard greens were evaluated for total vitamin C, total chlorophyll, total soluble solids content, and titratable acidity. Total vitamin C content decreased for all treatments during the storage period. Storage under CA conditions delayed total vitamin C degradation for both atmospheres studied. At the end of the storage period, fresh-cut collard greens stored under 3% O 2 , 4% CO 2 showed around 25% and 56% more vitamin C than the material stored under 5% O 2 , 5% CO 2 and control, respectively. Total chlorophyll content decreased during the storage period. At the end of the experiment, fresh-cut collard greens stored under 3% O 2 , 4% CO 2 showed 24% and 45% more total chlorophyll than the product stored under 5% O 2 , 5% CO 2 and control, respectively. CA storage delayed organic acid degradation. On the sixth day, freshcut collard greens stored under 3% O 2 , 4% CO 2 presented around 44% more organic acids than co...