A study on quality loss of minimally processed grapes as affected by film packaging

Postharvest Biology and Technology 51 (2009) 21–26

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A study on quality loss of minimally processed grapes as affected by film packaging M.A. Del Nobile a,b,∗ , A. Conte b , C. Scrocco b , I. Brescia b , B. Speranza b , M. Sinigaglia a,b , R. Perniola c , D. Antonacci c a b c

Istituto per la Ricerca e le Applicazioni Biotecnologiche per la Sicurezza e la Valorizzazione dei Prodotti Tipici e di Qualità, BIOAGROMED - Via Napoli, 52 - 71100 Foggia, Italy Department of Food Science, University of Foggia, Via Napoli, 25 - 71100 Foggia, Italy CRA-UTV Unità di Ricerca per l’uva da tavola e la vitivinicoltura in ambiente mediterraneo, Via Casamassima, 148 - 70010 Turi, Italy

a r t i c l e

i n f o

Article history: Received 4 February 2008 Accepted 8 June 2008 Keywords: Biodegradable material Grape Packaging Shelf life

a b s t r a c t The influence of film barrier properties on the quality loss of minimally processed grapes stored at 5 ◦ C was addressed. Table grapes (Vitis vinifera cv. Italia) differing in quantity and frequency of irrigation, were tested with five different packaging films. Two commercially available films were used: a multilayer film obtained by laminating nylon and a polyolefin layer (NP), an oriented polypropylene film (OPP), along with three biodegradable polyester-based films (NVT-100, NVT-50 and NVT-35). The packed grape quality during storage was determined by monitoring the headspace oxygen and carbon dioxide concentration, the grape sensory qualities, and the viable cell concentration of the following spoilage microorganisms: total viable bacterial count, lactic acid bacteria, yeasts and molds. All the investigated films successfully preserved the quality of packed produce for the entire observation period (35 d). However, the best results were obtained using high barrier films such as NP and NVT-100. Slight differences were recorded between the two sets of table grapes in terms of respiratory activity and sensory quality. © 2008 Elsevier B.V. All rights reserved.

1. Introduction Minimally processed fruit and vegetables include fresh, washed and chopped produce packaged in sealed polymeric films or trays. The market for fresh-cut products is increasing due to premium product quality, convenience and freshness (Vasconcellos, 2000; Rico et al., 2007). The table grape is a non-climacteric fruit with problems during postharvest handling, storage and marketing. Grey mold, caused by Botrytis cinerea, is the principal cause of postharvest decay of table grapes both in the field and after harvest (Cappellini et al., 1986). Weight loss, colour changes and accelerated softening can also be an issue (Valero et al., 2006). Recently, many studies dealing with table grape preservation techniques have found that the use of ethanol, as a common food additive with antimicrobial activity, suppressed microbial growth and prevented berry decay (Lichter et al., 2002, 2003; Karabulut et al., 2004; Mlikota-Gabler et al., 2005; Lichter et al., 2005; Del Nobile et al., 2008).

∗ Corresponding author at: Department of Food Science, University of Foggia, Via Napoli, 25 - 71100 Foggia, Italy. Tel.: +39 0 881 589 242; fax: +39 0 881 589 242. E-mail address: [email protected] (M.A. Del Nobile). 0925-5214/$ – see front matter © 2008 Elsevier B.V. All rights reserved. doi:10.1016/j.postharvbio.2008.06.004

There is growing pressure in the food-packaging field to replace petrochemical-based packaging material with environmentally friendly films (Tharanathan, 2003). Among the commercially available biodegradable packaging materials, films based on polysaccharides, in particular starch, currently have the most potential (Davis and Song, 2006). Bio-packaging still represents a niche market because of the cost of biodegradable films compared to traditional plastic materials. However, the polymeric matrices able to biodegrade into CO2 , water and biomass, or methane and biomass (Avella et al., 2005), could present a real contribution towards the reduction of environmental pollution. Sustained multidisciplinary research efforts are needed for a successful implementation and commercialization of eco-friendly packaging materials. In earlier work, Del Nobile et al. (2008) investigated the influence of postharvest treatments (ethanol, chlorinated water and hot water) on the quality loss kinetics of freshly processed grapes packaged in biodegradable films. Results suggested that ethanol was the best solution to preserve the microbial stability of the fresh produce without affecting its respiration rate to any great extent. Based on these results, the influence of film permeability on the quality loss of grapes has been addressed in this work. In particular, clusters of table grapes (Vitis vinifera cv. Italia) grown under two irrigation water volumes, were treated in ethanol solution prior to packaging

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in different bags made of two types of commercially available films and in three biodegradable polyester-based films. This was done in order to determine the role of the barrier properties of the selected packaging materials in influencing the loss of grape quality during storage.

Rønnedevej 18, DK-4100 Ringsted, Denmark). The volume taken from the package headspace for gas analysis was about 10 cm3 . To avoid modifications in the headspace gas composition, due to gas sampling, each package was used only for a single determination of the headspace gas composition.

2. Materials and methods

2.4. Microbiological analyses

2.1. Raw materials

Microbiological analyses were performed during storage. For each sample, 25 g of grapes (five berries) were detached from different clusters, immersed in 225 mL of sterile distilled water and shaken for 30 min at 200 rpm on a rotary shaker. The wash was serially diluted and two aliquots of each dilution were spread over appropriate media in Petri dishes. The media, all from Oxoid (Milan, Italy), and conditions were as follows: Plate Count Agar (PCA), modified by adding 0.17 g L−1 of cycloheximide (Sigma–Aldrich, Milan, Italy) after autoclaving, incubated at 32 ◦ C for 48 h, for total bacterial count; Sabouraud dextrose agar, supplemented with chloramphenicol (0.1 g L−1 ) (C. Erba, Milan, Italy), incubated at 25 ◦ C for 48 h, for yeasts; deMan Rogosa Sharpe agar (MRS), modified by adding 0.17 g L−1 of cycloheximide after autoclaving, incubated at 30 ◦ C for 4 d under anaerobiosis, for lactic acid bacteria; Potato Dextrose Agar (PDA), supplemented with chloramphenicol (0.1 g L−1 ), incubated at 20 ◦ C for 7–10 d, for moulds.

Grapes were harvested on a farm located in a wine-growing area southeast of Bari (Casamassima) from a vineyard installed in 2002 with “140 Ru” (Vitis berlandieri x Vitis rupestris du Lot) rootstock, which was grafted with V. vinifera L. cv. Italia b. in 2003. The vineyard has a row spacing of 2.5 m × 2.5 m (with 1600 plants/ha) with the “Apulia tendone” training system and is covered with net to protect against hail. It is managed according to the typical cultivation technique of the zone. The vineyard is irrigated with local water, supplied by pipes (two per plant). In order to appraise the effects induced by the various irrigation volumes, two different treatments were studied. Each treatment was realized by delimiting 95 vines (5 rows per 19 vines). For each treatment, 45 plot replications (3 rows per 15 vines) placed along three central rows were designed. The supply of the two different irrigation volumes, considered constant for the duration of the interventions (24 h) and the turns (9 d), was obtained using pipes with different hourly outputs. For this, pipes able to supply an hourly output equal to 8 or 16 L/vine were used. As a consequence, the seasonal irrigation volumes obtained were 2500 and 5000 m3 ha−1 , respectively. Grapes obtained from the two different irrigation volumes will be referred to as A and B, respectively. 2.2. Sample preparation After harvest, the grapes were transported to the laboratory and selected to obtain homogeneous batches based on colour, size, lack of damage, health and greenish rachises. After selection, the samples were washed with tap water to remove residues and dipped in a solution of ethanol (50%) for 5 min to control microbial spoilage. After dipping, 100 g of each grape sample were packed using different packaging materials: two biodegradable monolayer films (NVT-100, thickness 100 ␮m, NVT-50, thickness 50 ␮m) and one multilayer polyester-based co-extruded film (NVT-35 thickness 35 ␮m), kindly provided by Novamont (Novara, Italy); an Oriented Polypropylene film (OPP, thickness 20 ␮m), kindly provided by Metalvuoto (Milano, Italy); a multilayer film obtained by laminating a nylon layer with a polyolefin-based film (NP, thickness 95 ␮m) (Cianfano, Italy); and a multilayer material obtained by an aluminium-based layer co-laminated with a polyethylene film (AllPE, thickness 133 ␮m), kindly provided by Goglio (Daverio, Varese, Italy). The filled bags, having a surface area of about 500 cm2 , were hermetically sealed and stored at 5 ◦ C for more than 1 month. The package headspace volume was determined by the difference between the total volume of the packages and the volume of the sample. The total volume was measured by dipping the packages containing the fruit into a graduated water container and by observing the increase in the water level. Similarly, the volume of the samples was calculated by immersion of the clusters in a graduated cylinder with water, and by measuring the increase in water level. 2.3. Headspace gas composition O2 and CO2 contents of the packaged grapes were measured using an O2 and CO2 meter (PBI Dansensor, Checkmate 9900,

2.5. Product appearance A panel of seven judges carried out the sensory analysis of the table grape samples to discriminate the sensory characteristics (odour, colour, firmness and general visual quality). Freshly cut products from the batch were used as controls. The intensity of the attributes evaluated was quantified on a scale from 1 to 5, where 1–2 = very poor, 3–4 = fair, and 5 = excellent, according to the procedure reported by Giménez et al. (2003). Scores below 3 for any of the attributes assessed were considered as an indicator of the end of the acceptable visual quality. 2.6. Statistical analysis To determine whether significant differences (p < 0.05) existed among the values of the fitting parameters, the one-way analysis of variance (ANOVA) and Duncan’s multiple range test, with the option of homogeneous groups, were used by means of STATISTICA 7.1 for Windows (StatSoft, Inc, Tulsa, OK, USA). 3. Modelling In previous papers, Del Nobile et al. (2006, 2007, 2008) presented a mathematical model that predicts the respiration rate of minimally processed produce. The above-mentioned model is based on a simplified version of the Michaelis–Menten equation: rO2 = A1 · exp{−A2 · [CO2 ]} · [O2 ]

(1)

where: rO2 is oxygen consumption rate expressed as [mL/kg h], [O2 ] is the percentage oxygen concentration, [CO2 ] is the percentage carbon dioxide concentration, A1 is the pre-exponential term expressed as [mL/kg h], and is the maximum oxygen consumption rate, A2 is the exponential factor and accounts for the carbon dioxide induced respiration inhibition, which is dimensionless. Del Nobile et al. (2006, 2007, 2008) also assumed that the ratio between carbon dioxide produced and oxygen consumed (respiratory quotient, RQ) is constant, but not necessarily equal to one: rCO2 = K1 · {A1 · exp{−A2 · [CO2 ]} · [O2 ]}

(2)

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where: rCO2 is carbon dioxide production rate expressed as [mL/kg h], K1 is the ratio between the moles of carbon dioxide produced and the moles of oxygen consumed, which is dimensionless.To describe the time course during storage of oxygen and carbon dioxide concentration inside the package, the mass balance of these two substances in the package headspace is written as: d(nO2 (t)) dt

= S · PO2 ·

− nO2 (t) · R · T/Vst ] [pest O 2



+ −mp · 4.615 · 10−6

· {A1 · [O2 ] · exp{−A2 · [CO2 ]}}

d(nCO2 (t)) dt

= S · PO2 ·

(3)

− nCO2 (t) · R · T/Vst ] [pest CO 2



+mp · 4.615 · 10−6 · {K1 · {A1 · [O2 ] · exp{−A2 · [CO2 ]}}} (4) where: nO2 (t) is the mole of oxygen in the package head space at time t, S is the area of the package surface, PO2 is the package oxygen permeability, pest is the external oxygen partial pressure, mp O2 is the mass of the packed product, Vst is the volume of the package headspace, T is the temperature expressed in K, R is the universal gas constant,  is the film thickness, nCO2 (t) is the moles of carbon dioxide in the package head space at time t, PCO2 is the package carbon dioxide permeability, pest is the external carbon dioxide CO2 partial pressure. Eqs. (3) and (4) are a set of two ordinary differential equations, which were integrated numerically using the fourth-order Runge–Kutta formula (Press et al., 1989). The goodness of fit was evaluated by means of the Root Mean Square Error (RMSE), which is defined as:

  nobs  1  p 2 RMSE =  (yi − yi ) nobs

i=1 p

where nobs is the number of observations and yi and yi , i = l, . . ., are experimental and the predicted values, respectively. The lower the value of RMSE the better the ability of the model to fit the experimental data. 4. Results and discussion The quality loss of the fresh processed grapes during refrigerated storage was determined by monitoring the following quality properties: grape respiratory activity, microbiological stability and product sensory quality. In particular, the influence of packaging film permeability on the changes in the above properties during refrigerated storage was determined. The results obtained are presented separately.

Fig. 1. Time course during storage of headspace gas composition for grapes packed in aluminum bags. The curves are the best fit of Eqs. (3) and (4) to oxygen and carbon dioxide data.

be considered impermeable to low molecular weight compounds. This film was used with the sole aim of evaluating the respiratory activity of the grapes with greater accuracy. As shown in Fig. 1, the above model satisfactorily describes the experimental data. Results from fitting are listed in Table 1, along with the calculated RMSE values, that denote a satisfactory prediction. As shown in the table, the values of A1 (the maximum respiration rate), as well as that of K1 (i.e., the ratio between moles of carbon dioxide produced and moles of oxygen consumed), do not show any significant statistical difference, whereas, the values of A2 of the two grapes are statistically different. By comparing the calculated parameter values one by one, it seems that raw material slightly influences the respiration activity of the table grapes. However, further work should be done to confirm that the recorded differences can be ascribed to the different irrigation regimes used. Eqs. (3) and (4) were also fitted to the respiratory data obtained for the grapes packaged with the following films: NVT-100, NVT-50, NVT-35, OPP, and NP. According to a previous paper (Del Nobile et al., 2008), fitting was run as follows: the values of K1 , A1 and A2 were set equal to those previously evaluated (see Table 1), whereas the oxygen and carbon dioxide permeability coefficients were used as fitting parameters. This procedure gives a double advantage: a separate evaluation of the respiration activity of the packed produce and the gas barrier properties of the packaging film; the determination of the oxygen and carbon dioxide permeability coefficients of the investigated films in real working conditions. As also reported in the literature, the determination of the actual mass transport properties of the packaging film is not a simple task to accomplish (Del Nobile et al., 2002, 2003a,b, 2004). As an example, Fig. 2

4.1. Respiratory activity Fig. 1 shows the oxygen and carbon dioxide concentrations in the package headspace plotted as a function of storage time for samples packed with All-PE film. As expected, a decrease in the headspace oxygen concentration, as well as an increase in the headspace carbon dioxide concentration was observed. To quantitatively determine the respiratory activity of the grapes, Eqs. (3) and (4) were simultaneously fitted to the experimental data. It is worth noting that the oxygen and carbon dioxide permeability coefficients of All-PE film were set equal to zero. As also reported in a previous paper (Del Nobile et al., 2008), it can be assumed that for the period of investigation, the All-PE film used in this study can

Fig. 2. Time course during storage of headspace gas composition for grape set B packed in NVT-35 bags. The curves are the best fit of Eqs. (3) and (4) to oxygen and carbon dioxide data.

0.65 1.37 0.71 0.64 0.56 0.76 5.67E−07 9.30E−06 1.70E−05 3.60E−05 3.94E−05 1.57E−23 0.00 1.28E−06 4.37E−06 2.65E−05 5.60E−9a 5.59E−9de 3.10E−9cd 4.20E−9g 4.20E−9bc ± ± ± ± ± 5.95E−9 9.30E−8 8.50E−8 1.26E−7 7.89E−8

1.00E−9 1.14E−7 9.72E−8 1.36E−7 7.59E−8

1.05E−25a 0.00a 9.60E−10a 9.13E−10b 1.46E−8d

1.00E−11a 5.25E−27a 1.00E−9ab 6.87E−10b 4.68E−9c

± ± ± ± ±

± ± ± ± ±

1.65E−25 0.00 6.40E−9 1.53E−8 5.30E−8

9.90E−11 4.15E−26 8.90E−9 1.58E−8 3.19E−8

2.2 0.3 2.9 0.1 0.5

2.2 0.3 2.9 0.1 0.5

Data in a column with different letters are significantly different (p < 0.05). a Oxygen Transmission Rate. b RMSE: Root Mean Square Error.

47.2 252 673 1159 1738 7.21 ± 0.79a

0.12 ± 0.03b

0.63 ± 0.04a Grape B All NP NVT-100 NVT-50 NVT-35 OPP

± ± ± ± ±

± ± ± ± ± 47.2 252 673 1159 1738 0.65 ± 0.04a 0.03 ± 0.02a 5.81 ± 0.80a

shows the oxygen and carbon dioxide concentrations in the package headspace plotted as a function of storage time for the B set of grapes packed using NVT-35 film. The curves shown in the same figure were obtained according to the procedure reported above. As can seen in Fig. 2, the model used to describe the respiratory activity of the two sets of grapes satisfactorily describes the data. Similar results were obtained for the other samples. Results from fitting are also listed in Table 1, along with the relative RMSE values. In the same table the ratio between the permeability coefficient and the film thickness (permeance) is also reported. As expected, there are only minor differences between the permeability coefficients of the same film calculated for the A and B sets of grapes, and in most cases the differences are not statistically significant, probably due to the wide range of gas permeance of the investigated films. In fact, NP film had a very low oxygen and carbon dioxide permeance, whereas OPP had the lowest gas barrier properties among the investigated films. It is worth noting that the differences in the gas permeance values of the two films can be as high as four orders of magnitude. With regard to the gas permeance of the biodegradable films, NVT-100 had gas barrier properties similar to those of NP film, whereas NVT-35 was similar to OPP. NVT-50 possessed gas barrier properties between NVT-100 and NVT-35 films. It is worth noting that the gas barrier performances of the investigated biodegradable films in real working conditions covered a range of values similar to those of commercially available films such as NP and OPP. Fig. 3 shows the time course during storage of the ratio between the amount of oxygen consumed by the packaged grape and the initial amount of oxygen in the package headspace as predicted by means of equation (1) using the data listed in Table 1. It is worth noting that the total amount of oxygen consumed by the packed produce is directly related to the extent of metabolic activities (senescence level) associated with its respiration (Böttcher et al., 2003). As shown in Fig. 3, higher senescence levels are strictly

0.0105 0.0100 0.0050 0.0035 0.0020

0.0105 0.0100 0.0050 0.0035 0.0020 1.00E−10a 9.3E−9f 3.30E−9e 3.50E−9h 2.69E−9b ± ± ± ± ±

CO2 permeability O2 Permeability OTRa [mL/m2 d] K A2 A1 [mL/kg h]

Grape A All NP NVT-100 NVT-50 NVT-35 OPP

Sample

Table 1 Mean values of model’s parameters obtained by fitting Eqs. (3) and (4) to the experimental data, along with their standard deviation.

Thickness [cm]

9.43E−09 4.15E−24 1.78E−06 4.51E−06 1.59E−05

O2 permeance

9.52E−08 1.14E−05 1.94E−05 3.90E−05 3.79E−05

CO2 permeance

0.89 1.27 0.93 0.66 0.75 1.11

M.A. Del Nobile et al. / Postharvest Biology and Technology 51 (2009) 21–26 RMSEb

24

Fig. 3. Variation during storage of the ratio between the moles of oxygen consumed and the moles of oxygen initially present in the aluminum package headspace, as predicted by means of Eq. (1) using the data listed in Table 1 for grape set A (a) and for grape set B (b).

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Table 2 Mean values of model’s parameters obtained by fitting Eqs. (5) to the experimental data, along with their standard deviation Sample Grape A OPP NP NVT-100 NVT-50 NVT-35 Grape B OPP NP NVT-100 NVT-50 NVT-35

K

Qin 0.06a 0.90d 0.24abc 0.08a 0.07a

4.84 4.99 4.95 4.8 4.87

± ± ± ± ±

0.24a 0.35a 0.22a 0.24a 0.18a

2.96 3.3 3.12 2.88 2.9

± ± ± ± ±

0.20abc 0.12acd 0.08ac 0.16ab 0.11ab

0.25 0.29 0.18 0.24 0.17

0.03 ± 0.04a 0.46 ± 0.27ab 0.99 ± 0.48bcd 0.03 ± 0.05a 0.02 ± 0.04a

4.62 4.87 4.95 4.57 4.61

± ± ± ± ±

0.21a 0.27a 0.26a 0.24a 0.21a

2.85 3.60 3.62 2.86 2.59

± ± ± ± ±

0.38ab 0.11d 0.10d 0.43ab 0.39b

0.27 0.23 0.21 0.30 0.27

0.153 1.41 0.62 0.21 0.24

± ± ± ± ±

RMSEa

Qend

Data in a column with different letters are significantly different (p < 0.05). a RMSE: Root Mean Square Error.

Fig. 4. General visual quality plotted as a function of storage time for grape set A (a) and set B (b) packed with OPP, NVT-100, and NVT-35.

related to higher gas permeance. In fact, films with higher gas permeance bring about both a lower headspace oxygen concentration and a higher headspace carbon dioxide concentration, which in turn reduce the respiratory activity (see Eq. (1)), and consequently the senescence level. 4.2. Sensory evaluation A panel test was used to determine the sensory loss kinetics of packed grapes during refrigerated storage. In particular, several sensory attributes were monitored: odor, colour, texture and general visual quality. As an example, Fig. 4 shows the general visual quality plotted as a function of storage time for grapes packed with OPP, NVT-100, and NVT-35. Similar results were obtained for grapes packed with the other films tested in this work. To quantitatively determine the influence of film permeability on the grape sensory quality loss, a first order type equation was fitted to the above data: Q (t) =

Qend − Qin · exp(−k · tend ) 1 − exp(−k · tend )



+ Qin −



Qend − Qin · exp(−k · tend ) · exp(−k · t) 1 − exp(−k · tend )

(5)

where: Q(t) is the grape general visual quality at time t, Qend is the packed grape general visual quality at the end of the observation period, Qin is the initial value of the packed grape general visual quality, k is the kinetic constant, tend is the time at the end of the experimental observation (35 d), and t is the storage time. As can be seen in Fig. 4, Eq. (5) successfully described the rate of overall quality loss for the investigated grapes. Results from fitting are listed in Table 2, along with the RMSE values that show a satisfactory prediction of the sensorial trend. The Qend values listed in the above table are all close to 3 (the acceptability limit). In fact, even when Qend was lower than the acceptability limit, the difference was not statistically significant, suggesting that all the tested films successfully preserve the sensory quality of packed grapes for at

least 35 d. No undesirable after-taste developed within the fruit, even when the grapes were packaged in the thicker film (NP and NVT-100). Instead, a slightly higher score was observed for NVT-100 and NP, probably due to the combined effect of ethanol postharvest treatment and high gas barrier properties of the packaging system. Between the two sets of grapes, B (i.e., the grapes with a lower respiratory activity) obtained a slightly higher score than A. Results suggest that respiratory activity plays a major role in determining the sensory quality loss of the packed grape. In fact, the higher Qend was obtained for the films with the highest gas barrier properties and for the grapes with the lowest respiratory activity, probably due to the benefits of carbon dioxide-enriched headspace atmosphere in the packages (Crisosto et al., 2002; Retamales et al., 2003). 4.3. Microbiological stability In previous work, the efficiency of several grape pre-treatments in reducing the quality loss of minimally processed grapes was tested (Del Nobile et al., 2008). Ethanol pre-treatment was the most effective as it successfully reduced the cell load of the main spoilage microorganisms, without affecting the respiratory activity of the minimally packed produce nor its appearance. Literature data confirm that ethanol has a very pronounced effect on prevention of decay, whether it is applied during a dipping treatment or with a pad-generating vapour (Lichter et al., 2002, 2005; Chervin et al., 2005). Therefore, in this work all samples were pre-treated with ethanol according to the procedure reported in Section 2. The packed grape microbial stability was determined by monitoring the cell loads of four different spoilage microbial groups: total bacterial count, lactic acid bacteria, yeasts and moulds. As expected, the viable cell load of the above spoilage microorganisms was below the detection limit (102 cfu/g) for the entire period of observation, suggesting that the above pre-treatment guarantees the microbial stability of packed grapes for at least 35 d. 5. Conclusions The rate of quality loss of minimally processed grapes stored at 5 ◦ C was determined and its relationship to packaging film barrier properties discussed in this study. Two different sets of table grapes were tested along with five different packaging films. Two commercially available films, as well as three biodegradable materials were used in this study. The headspace oxygen and carbon dioxide concentration, the grape sensory quality, and the viable cell concentration of the main spoilage microorganisms were monitored for about 35 d. Results suggest that the respiratory activity of packed

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fresh processed produce is the main reason for its quality loss during storage. In fact, the best results in terms of grape quality were obtained using the grapes with lower respiratory activity and high barrier films, such as NP and NVT-100. However, it must be highlighted that all the investigated films can successfully preserve the quality of packed produce for the entire observation period. Acknowledgements The research has been co-funded by University of Foggia, Agricultural Faculty, Department of Food Science (DISA) and MiPAAF-CIPE through Project Vitivin-Valut, “Progetto per il miglioramento qualitativo delle produzioni vitivinicole e dell’uva da tavola nel Mezzogiorno d’Italia”. References Avella, M., De Vlieger, J.J., Errico, M.E., Fischer, S., Vacca, P., Volpe, M.G., 2005. Biodegradabile starch/clay nanocomposite films for food packaging applications. Food Chem. 93, 467–474. Böttcher, H., Gunther, I., Kabelitz, L., 2003. Physiological postharvest responses of Common Saint-John’s worth herbs (Hypericum perforatum). Postharvest Biol. Technol. 29, 342–350. Cappellini, R.A., Ceponis, M.J., Lightner, G.W., 1986. Disorders in table grape shipments to the New York market 1972–1984. Plant Dis. 70, 1075–1079. Chervin, C., Westercamp, P., Monteils, G., 2005. Ethanol vapours limit Botrytis development over the postharvest life of table grapes. Postharvest Biol. Technol. 36, 319–322. Crisosto, C.H., Garner, D., Crisosto, G., 2002. Carbon dioxide-enriched atmosphere during cold storage limit losses from Botrytis but accelerate rachis browning of “Red globe” table grape. Postharvest Biol. Technol. 26, 181–189. Davis, G., Song, J.H., 2006. Biodegradable packaging based on raw materials from crops and their impact on waste management. Industr. Crops Prod. 23, 147–161. Del Nobile, M.A., Fava, P., Piergiovanni, L., 2002. Water transport properties of cellophane flexible films intended for food packaging applications. J. Food Eng. 53, 295–300. Del Nobile, M.A., Buonocore, G.G., Altieri, C., Battaglia, G., Nicolais, L., 2003a. Modeling the water barrier properties of nylon film intended for food packaging applications. J. Food Sci. 64, 1334–1340. Del Nobile, M.A., Buonocore, G.G., La Notte, E., Nicolais, L., 2003b. Modeling the oxygen barrier properties of nylon film intended for food packaging applications. J. Food Sci. 68, 2017–2021.

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