Inhibition of browning on the surface of apple slices by short term exposure to nitric oxide (NO) gas

Freshly cut slices of apple (Malus x domestica Borkh cv. Granny Smith) were fumigated with nitric oxide (NO) gas at concentrations between 1 and 500 μl l⁻¹ in air at 20 °C for up to 6 h followed by storage at 0, 5, 10 and 20 °C in air. Exposure to nitric oxide delayed the onset of browning on the apple surface with the most effective treatment being fumigation with 10 μl l⁻¹ NO for 1 h. While nitric oxide inhibited browning in slices held at all temperatures, it was relatively more effective as the storage temperature was reduced with the extension in postharvest life over the respective untreated slices increasing from about 40% at 20 °C to about 70% at 0 °C. In a smaller study on ‘Royal Gala’, ‘Golden Delicious’, ‘Sundowner’, ‘Fuji’ and ‘Red Delicious’ slices stored at 10 °C, 10 μl l⁻¹ NO for 1 h was found to be effective in inhibiting surface browning in all cultivars.     

Polyphenoloxidase activity and browning in fresh-cut ‘Rocha’ pear as affected by pH,phenolic substrates,and antibrowning additives

The effect of pH, phenolic substrates, and food additives on polyphenoloxidase (PPO) activity and on tissue browning was studied in fresh-cut ‘Rocha’ pear. Substrates 4-methylcatechol, caffeic acid, (+)-catechin hydrate, catechol, chlorogenic acid, dopamine hydrochloride, and pyrogallol, were prepared in citric acid-phosphate buffer at pHs ranging from 3.0 to 8.0. pH optima for PPO activity depended on the phenolic substrate. Activity was optimal at pH 5.0 for catechol and 4-methylcatechol; pH 6.0 for chlorogenic acid; pH 7.0 for dopamine, caffeic acid, and catechin; and pH 8.0 for pyrogallol. Discrepancies were observed between the pH dependency of PPO activity and browning, as assessed by objective color measurement. Significant correlations were obtained between enzyme activity and metric-hue difference (ΔH*) over the pH range 3.0–8.0 for four of the eight phenolics. Chlorogenic acid, the main PPO substrate in ‘Rocha’ pear, induced high tissue browning but very low PPO activity at pH 3.0–4.0. Chemical inhibition of PPO was tested using catechol as substrate, and buffer solutions containing 250 mM Ca²⁺ in four salts (ascorbate, chloride, lactate and propionate), 57 mM ascorbic acid, 61 mM N-acetyl-l-cysteine and 3 mM 4-hexylresorcinol. PPO inhibition by additives was affected by the pH of the buffer, and was more effective with ascorbic acid, N-acetyl-l-cysteine and calcium ascorbate. It was concluded that inferences on tissue browning based on PPO activity can be misleading. Measurement of tissue color is proposed as a reliable means to assess the antibrowning effectiveness of additives and the pH of additives for cut pear should be corrected to reduce the browning potential.     

Surface decontamination of fresh-cut apple by pulsed light: Effects on structure,colour and sensory properties

The effect of pulsed light at increasing fluence (17.5, 52.5, 105.0 and 157.5 kJ/m²) was studied with reference to germicidal efficiency and changes in fresh-like appearance of sliced apple. Independent of fluence, viable counts and inoculated bacteria were reduced by 1 and 3 logs respectively. Fluence significantly affected weight loss, colour and sensory attributes of apple slices during storage at 6 °C. Pulsed light at 17.5 kJ/m² resulted in apple slices comparable to the untreated samples, with limited quality changes. By contrast, at higher fluence, apple slices underwent dehydration and browning due to loss of cell integrity. Exposure to high fluence treatments was also associated with negative changes in the flavour profile of sliced apple during storage.     

Hydrogen ion concentration affects quality retention and modifies the effect of calcium additives on fresh-cut ‘Rocha’ pear

‘Rocha’ pear (Pyrus communis L.) was used as a model system to assess the effect of pH of dipping solutions on quality retention of fresh-cut fruit and its interaction with calcium additives. Pear slices were dipped for 60 s in a buffer solution at pH 3.0, 5.0 or 7.0 and stored at 4.5 °C for 13 days. In other experiments, pear slices were dipped for 60 s in buffer solutions containing 250 mM of calcium ascorbate, lactate, chloride, and propionate, at pH 3.0 or 7.0, and stored at 4.5 °C for 6 days. Browning and softening were more intense in slices dipped in a solution at pH 3.0 than at pH 5.0 or 7.0, but microbial growth was lower in slices treated at pH 3.0. The effect of calcium additives depended on the anion and significant interactions between the effects of calcium salt and pH were observed. Calcium ascorbate was very effective in preserving color and reducing microbial growth irrespective of pH, but enhanced pectin solubilization and tissue softening at pH 3.0. Slices treated with 250 mM calcium propionate or calcium lactate were softer and had higher electrolyte efflux when treated at pH 3.0 than at pH 7.0. Calcium lactate enhanced browning and reduced microbial growth at pH 3.0 but did not affect color or microbial counts at pH 7.0. All calcium treatments enhanced electrolyte leakage. pH of the dipping solution can affect, per se, the quality of fresh-cut fruit. The choice of calcium additives to prevent undesirable changes on visual and sensory quality of cut produce should involve pH ranges that provide the expected benefits.     

1-Methylcyclopropene (1-MCP) delays senescence,maintains quality and reduces browning of non-climacteric eggplant (Solanum melongena L.) fruit

Ethylene action can be counteracted by 1-methylcyclopropene (1-MCP), which has been used during postharvest storage to maintain quality. In this work, we evaluated the effect of 1-MCP treatments on eggplant quality and phenolic metabolism during refrigerated storage. Eggplants (cv. Lucía) were harvested at commercial maturity, treated with 1-MCP (1 μL/L, 12 h at 20 °C), stored at 10 °C for 21 d and subsequently held at 20 °C for 2 d. Corresponding controls were stored at 10 °C and then transferred to 20 °C for 2 d. During storage calyx color, damage and chlorophyll content, fruit weight loss and firmness, pulp sugar content, acidity, browning and total phenolics were measured. In addition, polyphenol oxidase (PPO), pyrogallol peroxidase (POD), and phenylalanine ammonia-lyase (PAL) activities were evaluated. Fruit calyxes showed reduced damage and remained greener in 1-MCP treated than in control fruit. 1-MCP treated eggplants showed lower weight loss. Pulp browning was clearly prevented as a consequence of 1-MCP exposure, and this was associated with delayed senescence, lower accumulation of total phenolics and reduced activity of PAL. The activity of the enzymes PPO and POD involved in the oxidation of phenolics compounds was also decreased in 1-MCP treated fruit. Results suggest that 1-MCP treatments delay senescence, prevent browning and are beneficial to complement low temperature storage and maintain quality of non-climacteric eggplant fruit.     

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.     

Effect of alginate coating on physicochemical and sensory qualities of button mushrooms (Agaricus bisporus) under a high oxygen modified atmosphere

Button mushrooms (Agaricus bisporus) were dipped for 2 min in different concentrations (1%, 2% and 3%) of alginate, then placed in jars and ventilated continuously with 100% O₂ for up to 16 d at 4 °C. Mushroom respiration rate, weight loss, texture, color, percent open caps, chemical properties and activities of polyphenol oxidase (PPO), and peroxidase (POD) were measured. The results indicate that treatment with alginate coating (2%) + 100% O₂ maintained a high level of firmness, and delayed browning and cap opening. In addition, alginate coating (2%) + 100% O₂ also delayed changes in the soluble solids concentration, total sugars and ascorbic acid, and inhibited the activity of PPO and POD throughout storage. Our study suggests that the use of alginate coating under a high oxygen modified atmosphere has the potential to maintain button mushroom quality and extend its postharvest life to 16 d.     

Surface decontamination of fresh-cut apple by UV-C light exposure: Effects on structure,colour and sensory properties

The effect of UV-C light treatments at 1.2, 6.0, 12.0 and 24.0 kJ/m² was studied with reference to germicidal efficiency and changes in fresh-like appearance of fresh-cut apple. Independently of UV-C light fluence, all treatments imparted the same germicidal effect with 1–2 log reduction in total viable counts. Treatments at a fluence exceeding 1.2 kJ/m² caused the loss of compartmentalisation of surface apple cells, activating dehydration and oxidative phenomena. By contrast, mild treatments resulted in apple slices much more stable than the untreated control in terms of microbial growth and development of browning and off-flavours. These effects were attributed not only to the direct inactivation of spoilage microrganisms and enzymes by UV-C light, but also to the formation of a thin, dried film on the surface of the product. This edible protective film inhibited microbial growth and hindered dehydration during storage but was too thin to be perceived by consumers. UV-C light exposure was demonstrated to be an effective non-visible technology for food surface decontamination, but only if applied at mild intensity.     

Effects of hot water treatment on the storage stability of satsuma mandarin as a postharvest decay control

Satsuma mandarins (Citrus unshiu Marc., cv. Gungchun) of an early harvesting cultivar were treated by hot water dipping at 52 °C for 2 min, 55 °C for 1 min, and 60 °C for 20 s, and then stored at 5 °C for 3 weeks and subsequently at 18 °C for 1 week (simulated shelf-life) to examine the possible use of hot water treatment (HWT) as an environmentally benign method to maintain mandarin quality characteristics during postharvest storage and sale. The initial respiration rate, just after heat treatment, was significantly higher in the treated fruit than in the untreated controls. During storage, however, the respiration rate was at a similar level in all treatments. HWT also had no adverse effects on quality attributes, including pH, titratable acidity, soluble solids contents, weight loss, firmness and peel color. The development of stem-end rots, mold decay, and black rots was manifestly lower in heat-treated fruit than in untreated controls. Sensory evaluation showed that HWT at 60 °C for 20 s markedly improved fruit appearance, making them cleaner and glossier. The results confirmed that hot water dipping could be applied to satsuma mandarin as an effective pretreatment to maintain postharvest quality during storage and marketing.     

Preharvest application of methyl jasmonate (MeJA) in two plum cultivars. 2. Improvement of fruit quality and antioxidant systems during postharvest storage

‘Black Splendor’ (BS) and ‘Royal Rosa’ (RR) plums were treated preharvest with methyl jasmonate (MeJA) at three concentrations (0.5, 1.0 and 2.0 mM) along the on-tree fruit development: 63, 77 and 98 days after full blossom (DAFB). Both control and treated fruit were harvested at the commercial ripening stage and stored in two temperature conditions: 9 days at 20 °C or at 2 °C + 1 day at 20 °C for 50 days. Preharvest MeJA at 2.0 mM significantly accelerated whereas 0.5 mM delayed the postharvest ripening process for both cultivars, since ethylene production, respiration rate and softening were reduced significantly at the two storage conditions for 0.5 mM. In these fruit, total phenolics, total antioxidant activity (hydrophilic fraction, HTAA) and the antioxidant enzymes peroxidase (POD), catalase (CAT) and ascorbate peroxidase (APX) were found at higher levels in treated than control plums during postharvest storage, which could account for the delay of the postharvest ripening process and the extension of shelf-life.     

Chitosan applications pre- or postharvest prolong raspberry shelf-life quality

Raspberries are fruit with high metabolism that makes them very perishable, impairing their storage and shelf-life. Chitosan coatings have the potential to improve their postharvest life by reducing water loss, respiration rate and decay incidence. The purpose of this work was to study the effect of different concentrations of chitosan, applied pre- or postharvest, on the retention of quality attributes of fresh raspberries. The chitosan concentrations tested were 0 (control), 0.5, 1.0 or 2.0%. The postharvest treatment was applied immediately after harvest, dipping the fruit in the solutions for 5 min. The pre-harvest treatment was done with one hand-spray application per week for three weeks, starting when the fruit were just turning pink. In both experiments the fruit were stored at 0 °C and 90% RH. Pre- or postharvest use of chitosan at 1 or 2% was effective in maintaining titratable acidity and retarding respiration and ethylene production, weight loss and decay incidence. Application by both means resulted in the highest chitosan concentrations accelerating a reduction of ascorbic acid contents. Firmness was maintained only when the fruit were treated pre-harvest at 2%. Thus, application of chitosan at 1 or 2% postharvest and 2% pre-harvest was able to retain key raspberry quality attributes for 15 and 12 days, respectively.     

Postharvest physiology and volatile production by flowers of Ptilotus nobilis

Ptilotus nobilis (Lindl.) F. Muell. has potential in the floriculture industries as a cut flower crop. Ethylene production and respiration rates, fresh weight changes and volatile scent production from cut inflorescences of P. nobilis cultivars Passion (dark pink flowers) and Purity (white-green flowers) were measured during vase life. Inflorescence weight loss was significant (P < 0.001) during vase life with wilting and colour loss being the primary reasons for loss of vase life. Inflorescences ready for the cut market stored and at 22 °C had vase lives of >12 d. Ethylene production by inflorescences was low to negligible. Treatment with silverthiosulphate (STS) and ethylene had no effects on vase life. Evidently, ethylene did not play a role in determining the postharvest longevity of cut P. nobilis flowers. Respiration rates of inflorescences were high at harvest (>700 mg CO₂ kg⁻¹ FW h⁻¹) and declined gradually thereafter during vase life. Total volatile emissions followed a similar pattern. For Passion, respiration rates of immature florets were significantly greater (P = 0.02) than florets from other developmental stages while the calyx produced the most CO₂. For Purity, respiration rates of florets of different maturities did not differ and the reproductive tissue produced the most CO₂. Only fully opened mature florets with their stigma and anthers revealed, emitted significant quantities of volatiles (P < 0.001) and primarily from the calyx tissue for both cultivars. The individual volatiles differed somewhat for the two cultivars. However, both produced significant quantities of benzaldehyde, 3,5-dimethoxytoluene and benzyl alcohol. These compounds have previously been associated with desirable floral scent.     

Use of chlorine dioxide fumigation to alleviate enzymatic browning of harvested ‘Daw’ longan pericarp during storage under ambient conditions

Pericarp browning reduces both the shelf-life and market value of harvested longan fruit stored at room temperature. Our study investigated the efficiency of chlorine dioxide (ClO₂) fumigation at reducing pericarp browning of longan (Dimocarpus longan Lour.) cv. Daw. Fresh longan fruit were fumigated with 0 (control), 2.5, 5, 10 and 25 mg/L ClO₂ for 10 min, before being packed in cardboard boxes, and stored at 25 ± 1 °C, RH 82 ± 5% for 7 days. Fruit treated with ClO₂ had a lower browning index, but higher hue angle (true color), L* (lightness) and b* (yellowness) values than non-treated fruit. The 10 and 25 mg/L ClO₂ treatments were the most effective at extending shelf-life from 1 to 5 days, compared with the control, by reducing pericarp browning, the activities of polyphenol oxidase (PPO) and peroxidase (POD), disease development and by maintaining the highest total phenolic content. However, quality acceptance of fruit treated with 10 mg/L ClO₂ was higher than fruits treated with 25 mg/L, as determined by odor and flavor. Consequently, ClO₂ fumigation at a concentration of 10 mg/L was considered to be the most effective treatment to reduce pericarp browning of longan, whilst maintaining fruit quality.     

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.     

High oxygen levels promote peel spotting in banana fruit

We studied the effect of high oxygen on early peel spotting in ‘Sucrier’ bananas held at 25 °C and 90% RH. Fruit first ripened to colour index 3–4 (about as yellow as green) and were then held in containers with a continuous gas flow of 18 ± 2 kPa (control) or 90 ± 2 kPa oxygen. High oxygen promoted peel spotting. The in vitro activities of phenylalanine ammonia lyase (PAL) and polyphenol oxidase (PPO), measured both in the whole peel and in peel spots, were lower in high oxygen than in the controls. The level of total free phenolics, both in the whole peel and in peel spots, was lower in the high oxygen treatment. Dopamine content in the peel spots decreased rapidly, earlier in the high oxygen treatments than in controls. It is concluded that peel spotting was not correlated with in vitro PAL and PPO activities. Decrease in dopamine levels correlated with peel spotting, indicating that it might be used as a substrate for the browning reaction.     

Improved quality retention of packaged ‘Anjou’ pear slices using a 1-methylcyclopropene (1-MCP) co-release technology

After three months storage at 0.5 °C one quarter of a lot of ‘Anjou’ pears (Pyrus communis L.) were treated with 1 μL L^?1 of 1-methylcyclopropane (1-MCP) for 8 h at 20 °C and three quarters of the fruit were left untreated at 20 °C for the same time. Treated and untreated pears were then sliced, dipped in a commercial anti-browning solution and packaged in modified atmospheric bags. Packages, containing slices from 1-MCP treated fruit, were labelled as MCP1. Slices from two thirds of the untreated fruit had one of two secondary treatments applied: (1) multi-functional co-release sachets added to the package at the time of sealing (NT), or (2) an injection of 1-MCP to sealed packages to achieve a final concentration of 1 μL L^?1 (MCP2). The last third of the slices from the untreated lot of pears were sealed into packages with no further treatment (CK). The packages were kept at 5 °C. In-package ethylene concentrations were significantly lower for the NT treated slices. NT also significantly delayed and reduced net oxygen consumption in the package headspace compared with other treatments. The NT treatment also reduced incidence of browning induced by enzymes of microbial origin, termed secondary browning (SB), and better maintained the measured juiciness of slices. In contrast, the CK, MCP1 and MCP2 treatments showed a more rapid appearance and severity of SB. Slices in packages treated with NT retained higher tissue levels of butyl, hexyl and pentyl acetate, 6-methyl-5-hepten-2-one, butanol and hexanol during storage than any of the other three treatments.     

Effects of preharvest nitric oxide treatment on ethylene biosynthesis and soluble sugars metabolism in ‘Golden Delicious’ apples

In order to examine the influence of preharvest nitric oxide (NO) treatment on ethylene biosynthesis and soluble sugar metabolism in ‘Golden Delicious’ apples, apple trees were sprayed with 50 μM sodium nitroprusside (SNP) (a donor of NO) 14 days before harvest. The results indicated that preharvest SNP treatment can increase the NO content and the NOS activity in apple fruit, therefore, delay the accumulation of ethylene due to its inhibition on the activities of 1-aminocyclopropane-1-carboxylate synthase (ACS) and 1-aminocyclopropane-1-carboxylate oxydase (ACO). Fructose is the main sugar in ‘Golden Delicious’ apple. The synthesis of sucrose was stimulated and the decomposition of sucrose was inhibited by this treatment, thus causing the accumulation of sucrose. We can draw a conclusion that pre-harvest SNP (50 μM) treatment can increase the NO content of fruit during storage, while higher NO content can further regulate fruit ripening through its effect on ethylene and sugar metabolism in ‘Golden Delicious’ apple fruit during storage at 18 °C.     

Involvement of ethylene in browning development of controlled atmosphere-stored ‘Empire’ apple fruit

‘Empire’ apples [Malus sylvestris (L.) Mill var. domestica (Borkh.) Mansf.] are susceptible to development of chilling injury, expressed as firm flesh browning, during controlled atmosphere (CA) storage. Because of this susceptibility, fruit are typically stored at 2–4 °C, but the incidence of flesh browning can be increased by 1-methylcyclopropene (1-MCP) treatment at these temperatures. In this study, flesh browning development has been investigated in relationship to ethylene production, internal ethylene concentration (IEC), flesh firmness, total phenolic concentrations, and the activities of polyphenol oxidase (PPO) and peroxidase (POX) in the flesh tissues. Fruit were harvested from two orchards, either untreated or 1-MCP treated, and then stored under CA conditions at either 0.5 or 4 °C. Fruit were removed from storage at 1.5-month intervals for 10.5 months. 1-MCP treated apples were firmer than those of untreated apples, and had lower IECs, at all removals. Flesh browning incidence and severity developed earlier in 1-MCP-treated apples than untreated apples stored at either temperature. Total phenolic concentrations differed by orchard, but no major differences in concentrations were detected between untreated and 1-MCP treated apples. However, PPO activities were higher in the flesh of 1-MCP treated apples than untreated apples from both orchards and at both storage temperatures. POX activity was not consistently affected by 1-MCP treatment or storage temperature. Overall, our results suggest that inhibited ethylene production, either as a result of storage at 0.5 °C, or by treatment with 1-MCP at either temperature, may cause stress and damage to cells and result in higher PPO activity that leads to progressive flesh browning development during CA storage.     

Control of postharvest diseases of fruit with an invert emulsion formulation of Trichoderma harzianum Rifai

Control of primary postharvest diseases caused by Rhizopus stolonifer, Botrytis cinerea, and Penicillium expansum on a variety of fresh fruit was evaluated with an invert emulsion formulation of Trichoderma harzianum. Diseases evaluated were quantified by the period of protection conferred by the antagonist and the diameter of decay lesions. Treatment of the various fruit species with formulated T. harzianum conidia in an invert emulsion significantly (P ≤ 0.05) reduced the mean lesion diameters of R. stolonifer on apple, pear, peach and strawberry, B. cinerea on grape, pear, strawberry, and kiwifruit, and P. expansum on grape, pear, and kiwifruit in comparison with the control treatment. Significant differences (P ≤ 0.05) were obtained in the mean percent reduction in lesion diameter caused by the same postharvest pathogens on the same fruit species due to the treatment with the formulated T. harzianum conidia relative to control treatment. The greatest mean percent reduction (86.7%) was obtained on apple fruit for the infection with R. stolonifer. Significant differences (P ≤ 0.05) were also obtained in the mean durations of the minimum protection period due to treatment with the formulated T. harzianum against the infection with the same postharvest pathogens on the same fruit species. The longest mean duration of the minimum protection period (up to 59 days) was obtained for unwounded apple fruit against the infection with R. stolonifer. Overall, the results indicate that the treatment with the invert emulsion formulation of T. harzianum protected fruit from infection by the primary postharvest pathogens of the fruit tested for up to 2 months and reduced the diameters of decay lesion up to 86% and is a promising treatment to prolong the postharvest shelf-life of fresh fruit.     

Physical and visual properties of grape rachis as affected by water vapor pressure deficit

Rachis browning of table grapes after harvest is a significant problem, and water loss is considered the primary factor in browning. The major rachis desiccation and browning occurs during marketing at ambient temperatures and relative humidity (RH) which create high water vapor pressure deficits (WVPD). In this study the effect of WVPD and its components on rachis browning were examined on the two white seedless cultivars ‘Superior’ and ‘Thompson’. The grape clusters were stored at 20 °C or at 10 °C with low (70%) or high (>95%) RH, thus creating 4 WVPD levels. At each WVPD the clusters were held in open punnets, punnets sealed with low density polyethylene film or microperforated polyethylene, and examed every 2 or 3 d for weight loss, berry firmness, rachis dry weight and subjective rachis index. In addition, the rachis were photographed and image analysis employed to identify the level of browning. The results show that image analysis gave very similar patterns to subjective evaluation of rachis browning with correlation coefficients up to 0.90. However, image analysis detected an increase in browning before subjective evaluation. There was poor overall correlation between cluster weight loss and rachis dry weight to browning for ‘Superior’ grapes but a good correlation for ‘Thompson’. Rachis of ‘Superior’ suffered extensive browning at 20 °C even at high RH while rachis of ‘Thompson’ remained relatively green under similar conditions. ‘Thompson’ grape rachis remained green during the entire examination period (11 d) when held at high RH in either 10 °C or 20 °C. At high WVPD, microperforated packaging offered better control of browning in ‘Superior’ grapes than closed packaging, while clusters of ‘Thompson’ retained green rachis after 4 d in open punnets, and after 7 d in covered punnets. In summary, detailed analysis of rachis browning shows that water loss is an important but not the only factor in browning. Quantitative and objective measurement of rachis browning is likely to facilitate better communication of experimental data and higher resolution of processes which lead to browning.