Influence of pre-cutting operations on quality of fresh-cut artichokes (Cynara scolymus L.): Effect of harvest dates

The effect of harvest date on post-cutting quality of two cultivars (‘Violetto foggiano’, and ‘Catanese’) of artichokes (Cynara cardunculus L. subsp. scolymus (L.) Hayek) was studied. Artichoke heads were harvested from December 2009 to May 2010 for ‘Violetto foggiano’ (7 harvest dates), and from January to April 2010, for‘Catanese’ (4 harvest dates) from a commercial orchard in the Apulia Region, always from the same 20 randomly-chosen and labeled plants (for each cultivar). Freshly harvested artichoke heads were trimmed, cut into quarters, then stored in a humidified air flow at 5 °C. Initially, and after 2, 5 and 7 days of storage, quality parameters were analyzed, including total phenol content, antioxidant activity, color attributes (outer bract surface, cut-bract surface, and cut receptacle) and visual appearance. Global color variations (ΔE*), for receptacle, cut surfaces and outer bracts, were calculated, in order to compare samples of different initial color and to evaluate variation in terms of browning. Artichokes ‘Catanese’ harvested in February showed the lowest ΔE* on cut surfaces after 7 days of storage which then increased with the proceeding of the season. Also for ‘Violetto foggiano’ after 7 days of storage, samples harvested in February showed lowest values of ΔE* on cut surfaces (bracts and receptacle), if compared to other harvesting dates. Visual quality of fresh-cut quarters decreased with the progress of the season, and for ‘Violetto foggiano’, with the decrease of the antioxidant activity. Total phenolic content and antioxidant activity were different among harvest dates for both cultivars studied, and for ‘Violetto foggiano’ showed a significant polynomial trend, denoting 2 phases of antioxidant accumulation from December to February and then from middle of March to May. The natural decline of plants at the end of production may be the reason of the poor quality of cut-artichokes in the last sampling date, and in general, considering the average temperatures at harvest, quality of fresh-cut artichokes could be positively affected by the lowest temperatures occurring in February.     

A multispectral vision system to evaluate enzymatic browning in fresh-cut apple slices

Increased regulation of chemical fumigants has forced the almond industry to seek alternatives for postharvest control of insect pests in raw almonds. This paper reports developments of non-chemical treatment for postharvest disinfestation of almonds using radio frequency (RF) energy. A pilot-scale 27 MHz RF unit was used to evaluate effects of a RF treatment protocol on quality attributes in treated in-shell and shelled almond samples. The RF treatment protocol used 0.75 kW RF power, a forced hot air at 63 °C, back and forth movements on the conveyor at 0.56 m/min, and single mixing, which all improved the final heating uniformity. RF treatments sharply reduced the heating time from 86 and 137 min for hot air heating to only 6.4 and 8.8 min for the center of 1.5 kg in-shell and 2.4 kg shelled almond samples to reach 63 °C, respectively. Almond quality was not affected by the RF treatments because peroxide values, fatty acid and kernel color of treated almonds were better than or similar to untreated controls after 20 d at 35 °C, simulating 2 years of storage at 4 °C. RF treatments did not significantly affect the kernel moisture content of both types of almonds but reduced the moisture content in the shell. RF treatments may hold great potential to replace chemical fumigation for disinfesting almonds.     

Post-cutting quality changes of fresh-cut artichokes treated with different anti-browning agents as evaluated by image analysis

Fresh-cut processing can add convenience to artichoke consumption, although post-cutting browning is still a major problem. Different compounds (ascorbic acid, citric acid, cysteine, and their combination, ethanol, sodium chloride, 4-hexylresorcinol) were tested at different concentrations in two experiments. An algorithm for rapid colour measurements by means of image analysis was implemented, and allowed measurement of L*, a*, and b* values from the whole quarter surface and from the browned areas, while the external appearance of artichoke quarters was evaluated using an anchored subjective scale. Cysteine (0.5%) was the most effective treatment to prevent browning as evaluated by colour attributes and appearance score. Its effectiveness was improved by increasing the pH of the solution from the natural pH (2.1) to pH 3, resulting in L* values of browned areas about 30% higher than controls (27.4 and 21.5 respectively). The mean values of appearance scores for cysteine treated samples were all above the limit of marketability (score 3), significantly higher than in control samples which had mean values below this limit. All colour parameters were significantly correlated with appearance scores, and L* of the whole quarter surface had the highest correlation. The results represent a step forward in research on anti-browning treatments for fresh-cut artichokes, also providing an objective tool for colour evaluation.     

Influence of pre-cutting operations on quality of fresh-cut artichokes (Cynara scolymus L.): Effect of storage time and temperature before cutting

The effect of pre-processing storage time and temperature on post-cutting quality of two artichoke cultivars (‘Catanese’ and ‘Violetto Foggiano’) was studied. Artichoke heads were harvested in January 2010 for ‘Catanese’ and in March 2011 for ‘Violetto Foggiano’ from commercial plantations. Freshly harvested artichoke heads were stored at 0, 5, and 12 °C in a humidified flow of air. Initially, and after 3 and 7 days of storage, respiration rate, weight loss, and electrolytic leakage were monitored. Moreover, at each sampling, artichokes were cut in quarters and stored for additional 3 days at 5 °C. On cut artichokes, soon after cutting and after post-cutting storage, visual appearance, color attributes (on outer bract surface, on cut bracts, and on cut receptacle surface) and phenol content were determined. Time and temperature of storage influenced quality attributes of cut artichokes, but to a different extent depending on the cultivar, whereas temperature did not affect the phenol content. ‘Violetto Foggiano’ artichokes benefited from pre-cutting low storage temperature (0 °C), whereas ‘Catanese’ showed physiological injuries on outer bract surfaces, where brown spots occurred. In both cases low temperatures during pre-cutting storage (5 and 0 °C) reduced the browning rate of the cut surface which maintained a higher L* value, compared to artichokes stored at 12 °C. Moreover, pre-cutting storage at 12 °C resulted in a reduction of quality of artichokes due to growth of floral primordia in the form of reddish tissues at the base of the receptacle for both cultivars. Management of storage conditions before cutting is therefore critical in fresh-cut processing operations of artichokes.     

Effect of nitric oxide (NO) and associated control treatments on the metabolism of fresh-cut apple slices in relation to development of surface browning

Surface browning is an important cause of deterioration of fresh-cut apples during postharvest handling. ‘Granny Smith’ apple slices treated with NO gas (10 μL/L) and the NO donor compound 2,2′-(hydroxynitrosohydrazino)-bisethanamine (diethylenetriamine nitric oxide (DETANO) (10 mg/L) dissolved in phosphate buffer (pH 6.5) showed delayed development of surface browning during storage at 5 °C and also resulted in a lower level of total phenols, inhibition of PPO activity, reduced ion leakage and reduced rate of respiration but had no significant effect on ethylene production or lipid peroxide level as measured by malondialdehyde (MDA) and hydrogen peroxide levels. The two control treatments of phosphate buffer (pH 6.5) and water dips also had significant effects compared to untreated slices. The relative effectiveness of treatments in extending postharvest life and reducing total phenols, PPO activity, ion leakage and respiration was DETANO > NO gas > phosphate buffer > water > untreated. Apple slices dipped in chlorogenic acid dissolved in water showed surface browning soon after application but dipping in DETANO solution negated the effect of chlorogenic acid whether applied before or after dipping in chlorogenic acid solution while the buffer and NO gas were also effective. It is suggested that an increase in phenols occurs on the apple surface soon after cutting, possibly as a defensive mechanism of the apple to limit damage to surface cells. The effectiveness of the applied treatments to inhibit development of surface browning may relate to their ability to minimize the level of phenols active on the cut surface possibly in conjunction with a reduced PPO activity.     

Effect of oxalic acid on quality attributes of artichokes stored at ambient temperature

The effect of oxalic acid (OA) on the overall quality of artichokes (Cynara cardunculus L. subsp. scolymus (L.) Hayek, formerly Cynara scolymus L. cv. Blanca de Tudela) was investigated for the first time in this vegetable. Artichokes were dipped in OA solution at 1 mM for 10 min and then stored at 20 °C. OA application delayed the deterioration process in artichokes during storage by retarding weight loss, softening, colour changes and chlorophyll degradation. In addition OA significantly reduced mesophilic aerobics and yeast and moulds counts with respect to controls. Finally, the content of total phenolics and antioxidant activity were not affected negatively by OA treatment. Thus, OA treatment might be a promising method for delaying postharvest deterioration and maintaining the overall quality of artichokes.     

Salinity of nutrient solution influences the shelf-life of fresh-cut lettuce grown in floating system

Quality, microbiological and enzymatic characteristics of fresh-cut lettuce (Lactuca sativa var. longifolia, ‘Duende’), grown in floating system with three electrical conductivities of nutrient solutions (2.8, 3.8 and 4.8 mS cm^?1), were investigated in order to evaluate the effect of salinity on product shelf-life during cold storage (9 d at 4 °C). Pre-harvest salinity of 3.8 and 4.8 mS cm^?1 improved the properties of fresh-cut lettuce, since CO₂ production was reduced with a subsequent control of the decay process. Fresh-cut processing caused an activation of polyphenol oxidase and peroxidase; in all cases the product obtained by salinity treatments was less subject to oxidase activity and browning phenomena during storage. Increased salinity reduced the number of mesophilic bacteria and of moulds and yeasts, assessed by plate counts on different culture media; in contrast, Enterobacteriaceae levels were unaffected by pre-harvest treatments. The research demonstrated that an increase in nutrient solution electrical conductivity, through the use of floating system, affects fresh-cut lettuce characteristics, improving shelf-life of the product.     

Effect of harvest maturity on quality of fresh-cut pear salad

Texture of an unripe pear is firm and crisp, similar to an apple. However, at the crisp stage, the flavor of pears is flat. This study evaluated the effect of harvest maturity on the quality of fresh-cut pear salad. Fruit were harvested at commercial maturity and 1-month delayed. After 2 and 5 months (1 and 4 months for delayed-harvest fruit) storage at ?1 °C, fruit were sliced into 8–12 wedges per fruit, dipped in an antibrowning solution, packaged in Ziploc bags and stored at 1 °C for up to 21 d. Delayed-harvest fruit were larger in size (≈20% increase in weight), had lower flesh firmness (≈17% decrease), lower titratable acidity content (≈20% decrease), and lower phenolic content (≈45% and 13% decreases in pulp and peel, respectively). There was no significant difference in soluble solids content. After 2 months storage, ethylene production and respiration rate were initially lower in the slices from delayed-harvest fruit, but tended to become similar after 7 d in storage at 1 °C. Delayed-harvest fruit had lower hydroxycinnamic acids and flavanols, and higher ester, alcohol, and aldehyde volatile compounds after 2–5 months storage. The results indicated that fruit salad produced with delayed-harvest pears had less browning potential and better flavor. Sensory evaluation results showed that about 80% of the panel liked slices from delayed-harvest fruit over commercial harvested, especially in terms of visual quality (65–85%), sweetness (75–95%), taste (70–80%), and overall quality (75–80%) during 21 d storage at 1 °C. The cut surface of slices appeared dry in delayed-harvest fruit when processed after 5 months in storage. However, sensory evaluation showed that panels still preferred the delayed-harvest fruit.     

Effect of new sanitizing formulations on quality of fresh-cut iceberg lettuce

In the present study, three recently patented decontamination agents: peroxyacetic acid combined with lactic acid, and two different combinations of hydrogen peroxide with citric acid (with and without propylene glycol), were compared with sodium hypochlorite and tap water washing regarding their effect on equilibrium modified atmosphere packaged (EMAP) fresh-cut iceberg lettuce. Effects of these sanitizers on respiration rate, electrolyte leakage, microbial levels, and sensory quality of the product after decontamination and during storage (3 d at 4 °C followed by 4 d at 7 °C) were elucidated. Hydrogen peroxide based sanitizers provoked a significant increase in the respiration rate and the electrolyte leakage of fresh-cut iceberg lettuce compared with tap water washing. Peroxyacetic acid combined with lactic acid resulted in similar results to those of tap water washing for all the parameters analyzed. However, other aspects of the combination of peroxyacetic and lactic acids (e.g. efficacy for cross-contamination avoidance) should be assessed in the future in order to determine its suitability for fresh-cut iceberg lettuce processing.     

Effect of ultraviolet-C light on quality and microbial population of fresh-cut watermelon

The influence of ultraviolet (UV-C) light (1.4–13.7 kJ m⁻² at 254 nm) on the quality and microbial populations of fresh-cut watermelon [Citrulus lanatus (Thunb.) Matsum. and Nakai] was investigated and compared to that of common sanitizing solutions used for fresh-cut produce. Dipping cubes in chlorine (40 μL L⁻¹) and ozone (0.4 μL L⁻¹) was not effective in reducing microbial populations and quality was lower in cubes receiving these aqueous treatments compared to UV-irradiated cubes or control. In commercial trials, exposing packaged watermelons cubes to UV-C light at 4.1 kJ m⁻² produced >1 log reduction in microbial populations by the end of the product's shelf life without affecting juice leakage, color and, overall visual quality. In further experimentation, lower UV-C dose (1.4 kJ m⁻²) reduced microbial populations to a lower degree and only when complete surface exposure was ensured. Higher UV-C doses did not show any difference in microbial populations (6.3 kJ m⁻²) or result in quality deterioration (13.7 kJ m⁻²). Spray applications of hydrogen peroxide (2%) and chlorine (40 μL L⁻¹), without subsequent removal of excess water, failed to further decrease microbial load of cubes exposed to UV-C light at 4.1 kJ m⁻². When properly utilized, UV-C light is the only method tested in this study that could potentially be used for sanitizing fresh-cut watermelon.     

Preharvest and postharvest factors related to off-odours of fresh-cut iceberg lettuce

The influence of different preharvest and postharvest factors affecting off-odour development of fresh-cut iceberg lettuce in low-O₂ modified atmospheres (MA) was investigated. Fresh-cut iceberg lettuce developed undesirable off-odours under low O₂ and elevated CO₂ atmospheres. A strong relationship between CO₂ concentration and off-odour development was observed. Significant differences in off-odour development existed among different cultivars in two harvests in consecutive years. The influence of maturity stage was evaluated, comparing fresh-cut product from immature and over-mature heads with commercial ones. Higher CO₂ concentrations and higher accumulation of ethanol and acetaldehyde were detected in the headspace of MA-packed lettuce from immature heads. Differences in respiration rate of the fresh-cut product from heads cultivated during the winter–spring seasons were around 30%. Respiration rate of fresh-cut iceberg lettuce increased when medium temperature during cultivation increased. Changes in the product weight generated different CO₂ levels which correlated with the production of ethanol and acetaldehyde and other off-odour metabolites related with the lipoxygenase (LOX) pathway such as hexanal, 1-hexanol, and cis-3-hexen-1-ol. Volatile compounds such as cis-3-hexen-1-ol, β-elemene, ethyl acetate and dimethyl sulphide increased their content more than 10 times compared with other volatiles. Moreover, differences in the initial flushed gas-mixture with or without CO₂ showed higher CO₂ concentrations and the development of stronger off-odours when samples were flushed with an enriched CO₂ gas-mixture. In summary, visual quality of fresh-cut iceberg lettuce is important but so are odour and flavour. MAP currently used for fresh-cut lettuce may need some modification to inhibit off-odours and achieve better aroma and flavour qualities for preserving “freshness” of the cut product. Screening for cultivars with low browning potential and fermentation, harvested at optimum maturity stage and with an adequate package design are recommended.     

Effect of atmospheric modification, 1-MCP and chemicals on quality of fresh-cut banana

Fresh-cut banana slices have a short shelf-life due to fast browning and softening after processing. The effects of atmospheric modification, exposure to 1-MCP, and chemical dips on the quality of fresh-cut bananas were determined. Low levels of O₂ (2 and 4 kPa) and high levels of CO₂ (5 and 10 kPa), alone or in combination, did not prevent browning and softening of fresh-cut banana slices. Softening and respiration rates were decreased in response to 1-MCP treatment (1 μL L⁻¹ for 6 h at 14 °C) of fresh-cut banana slices (after processing), but their ethylene production and browning rates were not influenced. A 2-min dip in a mixture of 1% (w/v) CaCl₂ + 1% (w/v) ascorbic acid + 0.5% (w/v) cysteine effectively prevented browning and softening of the slices for 6 days at 5 °C. Dips in less than 0.5% cysteine promoted pinking of fresh-cut banana slices, while concentrations between 0.5 and 1.0% cysteine delayed browning and softening and extended the post-cutting life to 7 days at 5 °C.     

Evaluation of the cold chain of fresh-cut endive from farmer to plate

In this study, the cold chain and its impact on food stuff microbiology was evaluated for fresh-cut endive. A survey was carried out to analyze endive temperature throughout the supply chain from producer, via processor and distributor to the restaurant. Data loggers accompanying the endive on its route provided a temperature profile of the endive. The effect of the outdoor temperature on initial cooling was evaluated and critical points regarding cold chain management in the supply chain were identified. Our experiments indicate that the cold chain is generally properly maintained. In parallel with temperature monitoring, indicator microorganisms were assessed at different points in the supply chain to examine the effects of endive temperature, temperature fluctuations, and the outdoor temperature on microbial food safety. Small temperature fluctuations in the supply chain had a small effect on the total level of aerobic mesophilic bacteria. However, at the best before-date, total coliforms and Enterobacteriaceae levels were significantly higher in endive samples subject to temperature fluctuations in the supply chain, compared to endive stored in optimal conditions. To our knowledge, this is the first study that combines microbiological analysis with the temperature profile of fresh-cut produce in a realistic food supply chain.     

Effect of chitosan-based edible coatings applied by vacuum impregnation on quality preservation of fresh-cut carrot

Edible coatings based on high molecular weight chitosan, pure or combined with methylcellulose or oleic acid, were applied to fresh-cut carrots cv. Nantesa by simple immersion and by applying a vacuum pulse (5 kPa for 4 min). Water vapour resistance, colour, mechanical properties and respiration rates of non-coated and coated samples were determined. Coatings improved sample appearance, since they diminished the occurrence of the white blush during storage. When applied by simple immersion, they neither conferred significant barrier properties nor the preservation of the mechanical properties of fresh-cut carrot samples. In contrast, coating application with a vacuum pulse enhanced all the positive effects, since the resistance of water vapour transmission of the samples was significantly improved, and better preservation of the sample colour and mechanical response during cold storage was obtained. Differences in film composition did not significantly affect the coating behaviour, probably due to the variability induced by different factors when coatings were applied to the carrot surface.     

Effect of packaging conditions on quality and shelf-life of fresh-cut pineapple (Ananas comosus)

Influence of packaging conditions on fresh-cut ‘Gold’ pineapple shelf-life were studied during 20 d of storage at 5 °C. Fresh-cut fruit pieces were packed in polypropylene trays (PP) and wrapped with 64 μm polypropylene film under active (high 40% or low oxygen, 11.4%) or passive modified atmospheres (air or cut fruit coated with 1%, w/v alginate). Changes in headspace composition, titratable acidity, pH, soluble solids content, juice leakage, color, texture, and microbial growth were evaluated over time. For all packaging conditions, oxygen concentration continuously decreased below its initial concentration over 20 d storage, but never reached levels below 2% O₂. Meanwhile, CO₂ concentration inside all packages continuously increased over time up to 10.6–11.7% from the initial conditions. Ethylene concentrations were always less than 0.4 μl L⁻¹ while ethanol was detected only after 13 d of storage. Color parameters L^* and b^* significantly decreased over time in all packaging conditions and were directly attributed to the translucency phenomenon in the fruit flesh. When alginate coating was used, juice leakage was significantly reduced in contrast with the substantial juice accumulation observed in the rest of the packaging conditions. Texture profile analysis (TPA) parameters, did not significantly change over time, suggesting that structural characteristics of fresh-cut pineapple pieces were preserved throughout storage. From the microbial point of view, the shelf-life of ‘Gold’ fresh-cut pineapple was limited to 14 d by mesophilic bacterial growth. Further studies are needed to evaluate the sensory aspects, as well as to characterize the flesh translucency phenomenon and reduce juice leakage of fresh-cut pineapple.     

High-throughput NMR based metabolic profiling of Braeburn apple in relation to internal browning

NMR is a valuable tool for metabolomics due to its short analysis time and reproducibility. However, this technique remains little used due to its high cost. Recently, cheaper NMR machines for high-throughput screening have been developed. In this study, NMR was used to study the effect of several pre- and postharvest factors on apple metabolite levels during air and controlled atmosphere storage, including metabolic changes related to the incidence of internal browning. The results show that the selected fertilizer treatments and fruit side (green versus red side) did not affect the metabolite levels. However, the different postharvest storage conditions (optimal CA and brown inducing CA) did result in significant changes in metabolite levels. In addition, differences (e.g., pyruvate, citrate, fumarate, alanine, chlorogenate, methanol, ethanol, acetaldehyde and acetoine) between brown and unaffected apples stored under the applied CA conditions could be demonstrated.     

Recent approaches using chemical treatments to preserve quality of fresh-cut fruit: A review

This review covers some recent advances for the maintenance of fresh-cut fruit quality with respect to the use of chemical compounds, including plant natural antimicrobials and antioxidants, as well as calcium salts for maintaining texture. It focuses especially on the use of natural preservatives, which are of increasing interest because of toxicity and/or allergenicity of some traditional food preservatives. The difficulties in the application of these substances on fresh-cut fruit without adversely affecting sensory characteristics of the product are reviewed. Edible coatings are presented as an excellent way to carry additives since they are shown to maintain high concentrations of preservatives on the food surfaces, reducing the impact of such chemicals on overall consumer acceptability of fresh-cut fruit.     

Evaluation of alternative sanitizers to chlorine disinfection for reducing foodborne pathogens in fresh-cut apple

The risk of undesirable by-products from chlorine disinfection in fresh-cut industries, together with its limited efficacy, has led to a search for alternative agents. The aim of this study was to test several alternative putative antimicrobial substances to reduce Escherichia coli O157:H7, Salmonella spp. and Listeria spp. populations on fresh-cut apple. Carvacrol, vanillin, peroxyacetic acid, hydrogen peroxide, N-acetyl-l-cysteine and Citrox were selected for their results in in vitro assays against E. coli O157:H7 and Listeria spp., to be tested on fresh-cut apple plugs. Apple flesh was inoculated by dipping in a suspension of a mix of the studied pathogens at 10⁶ cfu mL^?1, and then treated with the antimicrobial substances. All treatments were compared to deionized water and a standard sodium hypochlorite treatment (SH, 100 mg L^?1, pH 6.5). Pathogen population on apple plugs was monitored for up to 6 days at 10 °C. Bacterial reductions obtained by peroxyacetic acid (80 and 120 mg L^?1), vanillin (12 g L^?1), hydrogen peroxide (5, 10, 20 mL L^?1) and N-acetyl-l-cysteine (5 and 10 g L^?1) were similar or higher than reduction obtained by SH. In addition, bacterial populations were maintained at low levels throughout storage. No cells of any of the pathogens were detected in the peroxyacetic acid, hydrogen peroxide, Citrox and SH washing solutions after apple treatment. Peroxyacetic acid, hydrogen peroxide and N-acetyl-l-cysteine could be potential disinfectants for the fresh-cut industry as an alternative to chlorine disinfection. However, their effect on sensory quality and effectiveness under commercial processing conditions should be evaluated.     

样品处理方法对肉的pH值测定结果影响

为了准确检测肉的pH值和正确判断肉的品质,以兔肉和羊肉为原料,分析了样品处理方法对其pH值测定结果的影响。通过比较绞碎和不绞碎兔肉和羊肉的pH值,发现绞碎兔肉和羊肉的pH值均显著(p<0.05)低于未绞碎兔肉和羊肉。绞碎羊肉的pH值显著(p<0.05)低于绞碎兔肉,但未绞碎羊肉的pH值显著(p<0.05)高于未绞碎兔肉。为了使肉的pH值更准确,应明确样品的处理方法。