Effect of modified atmosphere packaging and storage temperature on volatile composition and postharvest life of minimally-processed pomegranate arils (cvs. ‘Acco’ and ‘Herskawitz’)

This study investigated the effects of passive modified atmosphere packaging (MAP), storage temperature (5, 10 and 15 °C) and duration of 14 days on the postharvest quality attributes, compositional change in flavour attributes and microbiological quality of minimally processed pomegranate arils (Punica granatum L.), cvs ‘Acco’ and ‘Herskawitz’. Volatile compounds were extracted via headspace solid phase micro-extraction (HS-SPME) and analyzed by gas chromatography–mass spectrometry (GC–MS). A total of 17 and 18 volatiles were detected and identified in the headspace of pomegranate juices of ‘Acco’ and ‘Herskawitz’, respectively. Based on the physicochemical attributes and microbial evaluation, the postharvest life of MA-packaged ‘Acco’ and ‘Herskawitz’ was limited to 10 days due to fungal growth ≥2 log CFU g⁻¹ at 5 °C. However, the concentration (%) and compositional changes in volatile compounds indicated that the flavour/aroma life (7 days) was shorter than the postharvest shelf-life based on appearance and other physicochemical (10 days) for both cultivars.     

Effects of base removal and heat treatment on visual and nutritional quality of minimally processed leeks

Freshly harvested leeks (Allium ampeloprasum L. var. porrum) were trimmed (leaf tips, roots), had the decayed leaves removed, washed with tap water, cut at 50 cm length and subjected to heat treatment at 55 °C for 0 and 17.5 min. They were then trimmed at the root base and leaves to produce stalks 22 cm in length with or without removal of a 2 cm portion of the base. Minimally processed leeks were tray-packaged, wrapped with 16 μm stretch film and stored at 10 °C for 7 days to determine the effects of base removal and heat treatment on visual (leaf growth, fresh weight loss and discoloration) and nutritional quality after storage. CO₂ and ethylene concentrations of packages containing minimally processed leeks showed a wound-induced pattern typical of other fresh cut vegetable tissues. Base removal did not significantly affect respiration but increased ethylene production, while heat treatment increased respiration rate and suppressed ethylene production. Storage of minimally processed leeks at 10 °C for 7 days resulted in a slight decrease of chroma and hue angle of base cross section as well as a decrease of chroma of the upper cross section. Heat treatment prevented the decrease of chroma of the base and upper cross section. Base removal reduced, but did not totally control leaf growth of stored minimally processed leeks. Moreover, it resulted in a decrease of dry matter, soluble solids, total soluble phenols, antioxidant capacity and total thiosulfinates at the end of the storage. A combination of base removal and heat treatment efficiently controlled leaf growth, but these treatments resulted in increased fresh weight and total thiosulfinate loss.     

Combined effect of ultrasound,mild heat shock and citric acid to retain greenness,nutritional and microbiological quality of minimally processed broccoli (Brassica oleracea L.): An optimization study

Response surface methodology (RSM) and Box–Behnken design were used to study the combined hurdle effect of mild heat time (1–5 min) at 50 °C, ultrasonic processing time (0–10 min) and citric acid concentration (0–2%) on the quality of refrigerated broccoli after 10 d of storage at 5 °C. Treatment effects were evaluated on weight loss, superficial colour (hue angle (H°) and total colour difference (ΔE)), headspace gas composition (O₂ and CO₂), overall browning potential, chlorophyll content, ascorbic acid content, mesophilic counts and overall visual quality (OVQ) and optimize the process by means of the desirability function. Predicted models were found to be significant with high regression coefficients (91–97%). High regression coefficients indicated that second-order polynomial models could be used to predict and optimize the quality retention in minimally processed broccoli during storage. The mesophilic counts, ascorbic acid content and the overall visual quality were significantly influenced by the three independent variables either independently or interactively. Both thermal and ultrasonic treatments were found to be critical factors influencing changes in chlorophyll content, O₂ concentration inside the package, hue angle and ΔE. On the other hand, thermal treatment and citric acid concentration were found to be significant on overall browning potential. By using the desirability function approach and considering superficial colour parameters, O₂ concentration, mesophilic counts, browning potential, ascorbic acid and chlorophyll content, the optimum processing conditions were 7.5 min of ultrasonic treatment, 3 min of a heat shock treatment and a citric acid concentration of 1.5%. These results were in good agreement with the maximum found from the canonical analysis performed from the response surface when only considering sensorial analysis. Under these optimal processing conditions it is possible to employ citric acid treatment in combination with ultrasonic and thermal treatments as hurdles for retention of green colour, nutritional quality, microbial control and for extending shelf life of refrigerated minimally processed broccoli.     

High oxygen combined with high carbon dioxide improvesmicrobial and sensory quality of fresh-cut peppers

The effects of high O₂ and high CO₂ throughout storage on the microbial and sensory quality of fresh-cut bell peppers from two commercial ‘California’ cultivars grown under different climatic conditions were studied. The ‘Meteor’ cultivar was minimally processed in Leuven (Belgium) and the ‘Requena’ cultivar in Cartagena (Murcia, Spain). The storage conditions were (kPa O₂/kPa CO₂/kPa N₂) 100/0/0, 80/15/5, 60/0/40, 50/15/35, 20/15/65 and 21/0.03/≅79 as control. Bell peppers freshly-cut in cubes were stored at 5 °C up to 9–10 days. Changes in total counts of mesophilic, psychrotrophic, yeasts and mould as well as Enterobacteriaceae were monitored. Individual and total sugars and organic acids contents, visual appearance, color, shriveling, off-aroma, crunchiness, flavor and overall quality were also evaluated. The results in both experiments showed that 80 or 50 kPa O₂ combined with 15 kPa CO₂ maintained the main sensory quality attributes and inhibited growth of the spoilage microorganisms and Enterobacteriaceae in minimally processed bell peppers.     

Impact of edible coatings and mild heat shocks on quality of minimally processed broccoli (Brassica oleracea L.) during refrigerated storage

The effects of edible coatings and mild heat shocks on quality aspects of refrigerated broccoli were studied. Minimally processed broccoli was coated with either chitosan or carboxymethyl-cellulose with or without a previous application of a mild heat shock of 1.5 min at 50 °C. Product was packaged in multilayered polyolefin bags and stored at 5 °C for 18 d. Quality parameters such as weight loss, texture, colour, ascorbic acid content, total chlorophyll content, oxygen concentration inside the bags, browning potential, mesophilic aerobic counts, and sensory quality, were evaluated during storage. Edible coatings exhibited a beneficial impact on broccoli quality. The weight loss in uncoated broccoli was found to be between 2 and 5 times higher compared to coated samples. During storage, coated florets from both thermally and non-thermally treated samples, presented higher retention of the (?a*/b*) ratio indicating better green colour retention and a reduced rate of floret yellowing. Chitosan coating always presented the lower ascorbic acid degradation rates (twofold lower compared with control samples). Broccoli texture for uncoated samples increased significantly during storage. However, for carboxymethyl-cellulose coated broccoli a slight increase in texture was observed while for chitosan coated broccoli no significant changes in texture were observed throughout the storage period. After the edible coating application the microbial broccoli load dropped by around 1.5 and 0.9 logarithmic units in chitosan and carboxymethyl-cellulose films, respectively. During storage, the application of chitosan coating significantly reduced total microbial counts in the thermally and non-thermally treated uncoated samples. Among the assayed edible coatings, chitosan effectively maintained quality attributes and extended shelf life of minimally processed broccoli. The single application of a mild heat shock had a measurable influence in reducing weight loss, enzymatic browning in broccoli stems, and in delaying yellowing of broccoli florets. Moreover, chitosan coating combined with a mild heat shock showed the best performance for long-term refrigerated storage of minimally processed broccoli.     

Storage temperature and type of cut affect the biochemical and physiological characteristics of fresh-cut purple onions

Minimal processing of onion (Allium cepa L.) results in convenience and freshness in a single product. However, inappropriate storage of fresh-cut onion results in losses of nutritional and sensory characteristics. To further understand this phenomenon, we evaluated the effect of the storage temperature and type of cut on the quality of fresh-cut purple onions. Purple onions (cv. Crioula Roxa) were minimally processed using two types of cut (10 mm cubes and 3–5 mm thick slices) and stored at different temperatures (0, 5, 10 and 15 °C) with 85–90% relative humidity (RH) for 15 days. The following analyses were performed to evaluate the shelf life of the purple onion: pungency, total phenolic content, anthocyanin content, quercetin content, respiratory rate, color, soluble solids content, titratable acidity, pH, dryness and deterioration index (DDI), and decay index (DI). Fresh-cut onions stored at 0 °C showed less pungency, lower respiratory rate levels and less variation of total phenolic, anthocyanin and quercetin contents. In addition, the physicochemical aspects and appearance changed less with fresh-cut onions stored at 0 °C. Moreover, slicing enabled a higher stability of the physicochemical and biochemical aspects in comparison to dicing. Storage of slices at 0 °C allowed preservation for up to 15 days.     

NIR spectroscopy for the optimization of postharvest apple management

Apples can be stored for long time under controlled temperature and atmosphere conditions, and therefore, non-destructive and rapid tools are required to assess fruit quality and to monitor changes during the postharvest period. The aim of this study was to evaluate the feasibility of NIR spectroscopy to optimize postharvest apple management and to follow changes in fruit quality during storage. An FT-NIR system operating in diffuse reflectance in the range 12,500–3600 cm⁻¹ was used to evaluate the physico-chemical (dry matter, soluble solids, colour and firmness) and some nutraceutical characteristics (total phenolics, total flavonoids and antioxidant activity) of ‘Golden Delicious’ apples, which were stored for about six months at 1 °C in controlled atmosphere, over two subsequent years. Spectral data were elaborated by PLS regression and LDA classification techniques. Good correlation models between spectral data and chemical and physical parameters were obtained for soluble solids, a* colour coordinate and firmness (0.81 < R² < 0.90 in calibration and 0.79 < R² < 0.89 in cross validation). Even higher correlation values (0.89 < R² < 0.95 in calibration and 0.86 < R² < 0.92 in cross validation) were obtained for indexes correlated to the antioxidant capacity of apples. The classification technique Linear Discriminant Analysis was applied to spectral data, in order to discriminate apples on the basis of storage time. Average correct classification was higher than 93% in validation and close to 100% in calibration, indicating high potential of NIR spectroscopy for the estimation of storage time of apple lots.     

Effect of UV-C treatments on phenolic compounds and antioxidant capacity of minimally processed Satsuma mandarin during refrigerated storage

The effect of UV-C treatments (0.75, 1.5 and 3.0 kJ/m²) on fruit quality, phenolic compounds and antioxidant capacity of minimally processed Satsuma mandarin during 12 days of storage at 4 °C was studied. The results showed that UV-C treatments had no adverse effects on quality attributes, ascorbic acid, phenolic acids and antioxidant capacity of mandarin segments. Significant increases of flavonoids (22.20% and 21.34% for narirutin, 11.75% and 33.25% for hesperidin) and total phenolics (5.73% and 8.13%) were found in 1.5 and 3.0 kJ/m² UV-C treated fruit at 3 days of storage. Further study confirmed that the increase of flavonoids occurred during the first 3 days and diminished after 4 days of storage. UV-C dose at 3.0 kJ/m² did not further improve the increase of flavonoids, and 0.75 kJ/m² had no significant effects on phenolics. Proper application of UV-C treatment could be a new way to enhance the functional quality of minimally processed citrus fruit.     

Impact of a decontamination step with peroxyacetic acid on the shelf-life,sensory quality and nutrient content of grated carrots packed under equilibrium modified atmosphere and stored at 7 °C

Peroxyacetic acid (PAA) is a strong oxidizer and exerts antimicrobial properties. The effect of a decontamination step with 80 and 250 mg L⁻¹ PAA on shelf-life of grated carrots stored under equilibrium modified atmospheric packaging at 7 °C was determined and compared with the shelf-life of unwashed and water-washed carrots. Microbial parameters, including total aerobic plate count, numbers of lactic acid bacteria, Lactobacillae and yeasts, and sensory quality were evaluated. Next to these parameters, atmospheric gas composition, pH and nutrient content were also monitored. The suggested packaging configuration prevented CO₂ accumulation, but at the end of the study anoxic conditions were reached for unwashed carrots and carrots washed with 80 mg L⁻¹ PAA. The microbial shelf-life of water-washed carrots was 4 d based on the yeast count, whereas the flavour was not acceptable after 5 d. The total aerobic plate count and the yeast count determined the shelf-life of carrots treated with 80 mg L⁻¹ PAA on 5 d, whereas the flavour was unacceptable after 7 d. None of the microbial parameters determined the shelf-life of carrots washed with 250 mg L⁻¹ PAA. However, this treatment had already a pronounced adverse effect on the initial sensory quality. Water washing already decreased the content of all individually studied nutrients (−16 to −28%), except for lutein content and the antioxidant capacity. Additional losses after adding PAA on day 0 were found for α-tocopherol and phenols. Regardless of the applied treatment, α- and β-carotene remained stable during storage, whereas ζ-carotene, lutein and α-tocopherol were unstable. The phenol content and the antioxidant capacity of unwashed, water-washed and 80 mg L⁻¹ PAA-treated carrots increased significantly at the end of the storage period, whereas no changes were found in carrots treated with 250 mg L⁻¹ PAA.On the condition that carrots were packed under an adequate EMA, the 80 mg L⁻¹ PAA treatment showed possibilities for extending shelf-life without pronounced effects on nutrient content.     

Conventional and emergent sanitizers decreased Ectomyelois ceratoniae infestation and maintained quality of date palm after shelf-life

Several methods have been used to prevent pest diseases and microbial contamination of dates, although their use is being restricted due to harmful effects on humans and/or to the environment. Sustainable sanitation techniques for keeping overall quality and safety of harvested dates should be developed and implemented. The current work studied the effect of NaClO, UV-C, ozonated water and alkaline and neutral electrolyzed water (NEW) on natural infestation by Ectomyelois ceratoniae or moth of pyrale, and on overall quality of ‘Deglet Nour’ dates stored for 30 days at the commercially used temperature of 20 °C. As controls, untreated samples were used. The skin color, firmness, pH, titratable acidity, total soluble solids content, sugar content, total polyphenols, antioxidant activity, microbial counts, sensory quality and moth infestations were monitored. Phenolics content increased after shelf-life. As expected, all sanitizers lowered microbial counts and moth infestation. A dose of 6 kJ UV-C m⁻² was the most efficient treatment against yeast and molds (without differences with NaClO and O₃), and coliforms, maintaining overall quality of dates after shelf-life. UV-C and NEW (pH 7.2, ORP 814 mV, and 300 mg L⁻¹ of free chlorine) were the most effective against moth proliferation, and could be considered as promising useful tools for commercial disinfection of fresh dates and extending shelf-life. As far as we know, no other comparative studies on these postharvest sanitizers on dates have been reported.     

Effect of high hydrostatic pressure (HHP) treatment on texture changes of water bamboo shoots cultivated in China

It is well known that high hydrostatic pressure (HHP) treatment will increase the shelf life of different fruit. However, texture changes associated with these responses are not well understood in vegetables. The objective of this work was to study the effects of HHP treatment on quality and lignification of minimally processed water bamboo shoots cultivated in China. Water bamboo shoots were exposed to HHP treatment for 10 min at room temperature (25 °C) and then stored for 7 days at 4 °C. Firmness, lignin and cellulose contents, and enzyme activities of phenylalanine ammonia lyase (PAL) and peroxidase (POD), were investigated during storage. An increase in firmness of water bamboo shoots was observed, and this increase after harvest was positively correlated with higher lignin and cellulose contents, r = 0.96, P < 0.05; r = 0.98, P < 0.01 respectively. Accumulation of lignin in flesh tissue was also positively correlated with activities of PAL and POD, r = 0.97, P < 0.01; r = 0.90, P < 0.05 respectively. PAL and POD activities showed a persistent rise over the whole 7 days. HHP treatment resulted in lower firmness, delayed activities of PAL and POD, and retardation of lignin and cellulose accumulation. These studies showed that HHP might be an efficient nonthermal alternative for extended shelf life of water bamboo shoots.     

Effect of temperature on shelf life and microbial population of lightly processed cactus pear fruit

The possibility of using cactus pear fruit (Opuntia ficus indica Mill, cv. Gialla) to produce ready-to-eat fruit was investigated. Changes in sensory quality and proliferation of spoilage microorganisms on lightly processed and packaged fruit as a function of storage temperature and modified atmosphere packaging were measured. The shelf life of the samples was kinetically modelled in order to check the effects of storage temperature and to assess the most relevant microbial indices for the product quality. Minimally processed cactus pear fruit had longer shelf life at 4 °C than at temperatures recommended for whole fruit when these were greater than 4 °C. The packaging of processed cactus pear fruit in modified atmospheres during storage resulted in a homogeneous bacterial population compared to that isolated from fruit stored in air, and favored the growth of Leuconostoc mesenteroides. Our results suggest that mathematical modelling might allow the industry to use more objective measurements to determine the shelf life of their products.     

Effect of hot water treatment on leaf extension growth,fresh weight loss and color of stored minimally processed leeks

Freshly harvested leeks (Allium porrum L.) were heated by immersion in water at 50, 52.5, 55 or 57.5 °C for 0–60, 0–35, 0–20 and 0–15 min, respectively. After hot water treatment, leeks were cooled in water at ambient temperature for 10 min and then cut at 22 cm from the compressed stem of the root base, weighed, had color measured and stored at 4 °C for 9 days. Untreated stalks (without immersion in a hot water bath) were used as controls. Hot water treatments at 50 °C for 40–60 min, 52.5 °C for 25–35 min, 55 °C for 17.5–20 min and 57.5 °C for 10–15 min efficiently controlled postharvest leaf extension growth in stalks stored for 9 days. However, treatments that controlled leaf extension growth showed fresh weight loss significantly higher than the control. There was only a slight effect of heat treatment on color attributes of stored minimally processed leek.     

Hot water and ethanol treatments can effectively inhibit the discoloration of fresh-cut sunchoke (Helianthus tuberosus L.) tubers

The main problem affecting the quality of fresh-cut sunchoke tubers is cut surface discoloration. Pre- and post-cutting hot water and ethanol treatments were evaluated for their potential to inhibit discoloration, color changes, and associated phenolic metabolism in tuber slices stored in air at 5 °C. Some of the treatments tested inhibited discoloration and changes in a* and hue color values. Slices that were post-cut treated with hot water at 50 °C for 6–8 min or 55 °C for 3–4 min and pre-cut treated with water at 50 °C for 20–25 min maintained good color for 8–12 days at 5 °C. Post-cut ethanol fumigation (150–750 μL/L for 5 h at 5 °C) can prevent discoloration for 30 d at 5 °C. Post-cut dips with ethanol solutions (3, 5, 8 or 10% for 5 min) increased shelf-life twofold or longer compared to untreated slices. Ethanol fumigation retarded the onset of wound-induced respiration rates as well as reducing maximum rates. A post-cut 10% ethanol dip also reduced respiration rates and reduced PAL activity and total phenolics. Ethanol dips had no effect and hot water treatments had no persistent effect on microbial loads over 12 d.     

Gamma irradiation increases storability and shelf life of minimally processed ready-to-cook (RTC) ash gourd (Benincasa hispida) cubes

Radiation treatment in a dose range of 0.5–2.5 kGy in combination with low temperature storage (4–15 °C) was attempted for improvement in shelf life of ready-to-cook (RTC) ash gourd (Benincasa hispida). Parameters such as microbial load, color, firmness and sensory attributes were monitored during storage. Optimum processing conditions (2 kGy; 10 °C) resulted in improved shelf life of seven days compared to the non-irradiated controls. Total bacterial count of 1.57 × 10³ CFU/g was recorded at the end of storage period (12 d). Higher total phenolic content and total antioxidant activity was observed in irradiated samples as compared to control. Irradiated samples had total phenolic content of 103.3 ± 5.2 mg kg⁻¹ and total antioxidant activity of 384.2 ± 9.7 mg kg⁻¹ while corresponding values for control samples were 67.8 ± 5.4 and 115.5 ± 7.0 mg kg⁻¹ at the end of storage period. Irradiated samples (2 kGy) showed excellent sensory and visual qualities during entire storage period.     

Cold quarantine responses of ‘Tarocco’ oranges to short hot water and thiabendazole postharvest dip treatments

This study investigated the effects of brief hot water and thiabendazole (TBZ) postharvest dip treatments on ultrastructural changes of fruit epicuticular wax (ECW), TBZ residues, decay development and quality traits of ‘Tarocco’ oranges [Citrus sinensis (L.) Osbek] subjected to cold quarantine, subsequent simulated transport and shelf-life. Commercially mature fruit were submerged in water at 20 °C (control fruit) or TBZ at 1000 mg/L and 20 °C for 60 s, or in hot water without or with TBZ at 300 mg/L and 53, 56, or 59 °C for 60, 30, and 15 s respectively. Following treatments, fruit were stored for 3 weeks at 1 °C (simulated quarantine conditions for fruit disinfestations against Mediterranean fruit fly, Medfly), followed by 4 days at 3 °C (simulated long distance transport), and finally kept at 20 °C for 3 days (shelf-life, SL). Scanning electron microscopy (SEM) analysis of ‘Tarocco’ orange surface showed that the typical wax platelets, lifting around edges of wax plates and areas free of epicuticular wax (ECW), that disappeared after hot water dips at 53–59 °C for 60–15 s, become visible again after storage for 21 days at 1 °C (quarantine conditions), and changes involving the appearance of rough ultrastructure, presence large curled plates, fissured wax crusts, and areas with ECW deficiencies, became much more pronounced after shelf-life. These occurrences were related to the transient effect of hot water treatment in decay control. Conversely, treatments with 300 mg/L TBZ 53 °C for 60 s or 56 °C for 30 s effectively reduced decay after quarantine. These treatments were as effective as standard treatment with 1000 mg/L TBZ at 20 °C and produced similar TBZ residue levels in fruit, without impairing fruit quality traits such as visual appearance, weight loss, compression test, sensory attributes, juice color parameters (a*, b*, h, L*, and Chroma), and juice chemical characteristics (soluble solids content, titratable acidity, ascorbic acid, glucose, sucrose, citric acid, total phenols, total anthocyanins, and total antioxidant activity).     

Quantitative assessment of intact green asparagus quality by near infrared spectroscopy

NIR spectroscopy was used to assess textural parameters (maximum shear force and cutting energy) in intact green asparagus. At the same time, two commercially available spectrophotometers, which differ primarily in terms of measurement principles, were evaluated: a scanning monochromator (SM) of 400–2500 nm and a combination of diode array and scanning monochromator (DASM) of 350–2500 nm. A total of 468 green asparagus spears cv. ‘UC-157’ were used to obtain calibration models based on reference data and NIR spectral data. Both instruments provided good precision for maximum shear force, with r² values between 0.55 and 0.67 and standard error of cross-validation (SECV) ranging from 7.81 to 8.43 N, and also for cutting energy (r² = 0.60–0.74; SECV = 0.06–0.07 J). The results obtained suggest that NIR spectroscopy is a promising technology for predicting intact green asparagus quality in terms of texture. They also show that the two spectrophotometers tested provided a similar degree of accuracy for texture measurements in intact green asparagus.     

Physiology of fresh-cut ‘Galia’ (Cucumis melo var. reticulatus) from ripe fruit treated with 1-methylcyclopropene

‘Galia’ (Cucumis melo var. reticulatus L. Naud. cv. Galia) fruit were harvested at the three-quarter slip stage and treated with 1 μL L⁻¹ 1-methylcyclopropene (1-MCP) at 20 °C for 24 h. The fruit were processed and stored as fresh-cut cubes and intact fruit for 10 d at 5 °C. Ethylene production of fresh-cut cubes was approximately 4–5-fold higher than intact fruit at day 1. Afterward, the ethylene production of fresh-cut cubes declined significantly whereas that of intact fruit remained relatively constant at about 0.69–1.04 ng kg⁻¹ s⁻¹. 1-MCP delayed mesocarp softening in both fresh-cut and intact fruit and the symptoms of watersoaking in fresh-cut fruit. Continuously stored fresh-cut cubes and cubes derived from intact fruit not treated with the ethylene antagonist softened 27% and 25.6%, respectively, during 10 d storage at 5 °C while cubes derived from 1-MCP-treated fruit softened 9% and 17%, respectively. Fresh-cut tissue from 1-MCP-treated fruit exhibited slightly reduced populations of both total aerobic organisms and Enterobacterium, although the differences did not appear to be sufficient to explain the differences in keeping quality between 1-MCP-treated and control fruit. Based primarily on firmness retention and reduced watersoaking, 1-MCP treatment deferred loss of physical deterioration of fresh-cut ‘Galia’ cubes at 5 °C by 2–3 d compared with controls.     

Application of citric acid and mild heat shock to minimally processed sliced radish: Color evaluation

The aim of this research was to study the effects of two hurdle technologies, citric acid application (CA) at 0.3%, 0.6% and 0.9% and thermal treatments (IT) for 1, 2 and 3 min at 50 °C, on the color of radish slices over 10 d of refrigerated storage. Contribution of the hurdles and their interactions were evaluated by examining the treatment effects on the following parameters: chromatic coordinates (L*, a* and b*) and the indices: chroma (ΔC*), total color difference (ΔE) and Color Index (CI*).The chromatic parameters for fresh radish (control samples) were L₀ = 69.43 ± 0.62, a₀ = −0.46 ± 0.05 and b₀ = 5.37 ± 0.37, while the calculated color indices were chroma = 5.39 ± 0.36, ΔE = 0 and CI* = −1.19 ± 0.17. Regarding control samples, the b* values showed an increasing trend during storage, which was associated with browning of the slices. Both ΔE and ΔC* values presented similar trends as reported for b*. Based on statistical analysis of the parameters and indices tested, the single hurdle application of low citric acid concentration (0.3%) or intermediate immersion time (2 min) at 50 °C minimized the radish slices color changes during storage. However, better results were obtained when two hurdles in series were applied. According to analysis, the treatment T7 (1 min IT, 0.3% CA) was selected as the best treatment to improve the retention of typical natural color of the minimally processed sliced radishes.     

Effect of treatment with dimethyl dicarbonate on microorganisms and quality of Chinese cabbage

The effects of dimethyl dicarbonate (DMDC) (200 mg L⁻¹) treatment on microorganisms and quality of Chinese cabbage were investigated. The results indicated that in the different tissues treated by DMDC, a significant reduction (P < 0.05) of total aerobic plate count (TAPC) of the leaf (ca. 4.49 log cfu g⁻¹) and stalk (ca. 4.45 log cfu g⁻¹), as well as the count of total yeasts and molds of the leaf (ca. 3.02 log cfu g⁻¹) and stalk (ca. 3.62 log cfu g⁻¹), was obtained in comparison with the control (sterile water dip). However, in the flower bud and/or flower treated by DMDC, the reduction of TAPC (ca. 2.74 log cfu g⁻¹) and counts of total yeasts and molds (ca. 2.26 log cfu g⁻¹) were much lower. DMDC treatment affected appearance and texture early in storage, but an impact on the nutritional composition of Chinese cabbage during storage was not found. Additionally, DMDC treatment significantly (P < 0.05) inhibited the activity of polyphenol oxidase (PPO) and peroxidase (POD) late during storage. Therefore, DMDC is a new and effective alternative for sanitation of Chinese cabbage where a protective measure of appearance quality needs to be adopted.