Commercial Bio-Packaging to Preserve the Quality and Extend the Shelf-Life of Vegetables: The Case-Study of Pumpkin Samples Studied by a Multimethodological Approach

Abstract

A multidisciplinary protocol is proposed to monitor the preservation of fresh pumpkin samples (FP) using three commercial polymeric films: A made of biodegradable cellophane from regenerated cellulose pulp; B from corn starch, cassava and eucalyptus, C made of polylactic acid from corn starch, and a polyethylene film used as reference (REF). Chemical, mechanical and microbiological analyses were applied on packaging and fresh and packaged samples at different times. After an 11-day period, NMR spectroscopy results showed a sucrose increase and a malic acid decrease in all the biofilms with respect to FP; fructose, glucose, galactose levels remained quite constant in biofilms B and C; the most abundant amino acids remained quite constant in biofilm A and decreased significantly in biofilm B. From microbiological analyses total microbial count was below the threshold value up to 7 days for samples in all the films, and 11 days for biofilm C. The lactic acid bacteria, and yeasts and molds counts were below the acceptability limit during the 11 days for all packages. In the case of biofilm C, the most promising packaging for microbiological point of view, aroma analysis was also carried out. In this paper, you can find all the analysis performed and all the values found.

Keywords: NMR relaxometry; NMR spectroscopy; SPME-GC-MS analysis; biofilm; biogenic amines; mechanical characterization; metabolomics; microbiological analysis; pumpkin; shelf life.

Figure 1

Pumpkin cubes packaged in the commercial biofilms (A, B, C) and polyethylene film (REF).

Figure 2

Set-up for gas permeability testing (a) and experimental “permeated gas volume-time” curve extrapolated from oxygen permeability test (b).

Figure 3

Tensile test results: tensile strength (a), elastic modulus (b), and elongation-at-break (c).

Figure 4

Cutting on B (Corn starch, cassava, and eucalyptus) biopolymer film to evaluate the mechanical properties with respect to the lamination direction.

Figure 5

Histograms of total phenolic content (A) expressed in mg GAE/kg ± SD; total carotenoid content (B) expressed in mg BCE/kg± SD; chlorophyll a (C) and chlorophylls b (D) content expressed in mg/g± SD; ABTS (E) and DPPH (F) assays expressed as Inhibition %± SD, evaluated in fresh and packaged pumpkin samples, during shelf-life. FP: Fresh pumpkin (light blue trace); REF: polyethylene (yellow trace); A: biodegradable cellophane from regenerated cellulose (orange trace); B: biofilm obtained from maize starch, cassava, eucalyptus (grey trace); C: poly-lactate obtained from maize starch (green trace).

Figure 6

Biogenic amines content in fresh (t₀) and packaged pumpkin samples (t₁₁). FP: Fresh pumpkin (light blue trace); REF: polyethylene (yellow trace); A: biodegradable cellophane from regenerated cellulose (orange trace); B: biofilm obtained from maize starch, cassava, eucalyptus (grey trace); C: poly-lactate obtained from maize starch (green trace). β-PEA: β-phenylethylamine; PUT: putrescine; CAD: cadaverine; HIS: histamine; SER: serotonin; TYR: tyramine; SPD: spermidine; SPM: spermine.

Figure 7

(a) Mass loss percentage, (b) water activity (a_w), (c) total microbial count, (d) lactic acid bacteria load, (e) yeasts and molds count, and (f) pH evaluated in fresh and packaged pumpkin samples, during shelf-life; (g) carbon dioxide concentration in headspace of pumpkin package in different films. REF: Polyethylene film; commercial biofilms: A, B and C.

Figure 8

Pictures of pumpkins stored in biofilm C and in REF packaging at time 0 and after 11 days. (a) C at 0 days; (b) REF at 0 days; (c) C at 11 days; (d) REF at 11 days.

Figure 9

(a) Longitudinal relaxation times of packaged pumpkin; (b) mean transverse relaxation times and (c) proton density of packaged pumpkin in biofilm B and biofilm C as function of storage time.