Application of an Eco-Friendly Antifungal Active Package to Extend the Shelf Life of Fresh Red Raspberry (Rubus idaeus L. cv. 'Kweli')

Abstract

The main objective of this study was to extend the shelf life of fresh red raspberry (Rubus idaeus. L. cv. 'Kweli') by using active film-pads inside commercial compostable packages. The pads were produced with chitosan (Ch) with the incorporation of green tea (GTE) and rosemary (RSME) ethanolic extracts as natural antifungal agents. Pads were placed on the bottom of commercial fruit trays underneath the fruits, and the trays were heat-sealed with a polyacid lactic (PLA) film. Preservation studies were carried out over 14 days of storage at refrigeration temperature (4 °C). Raspberry samples were periodically analyzed throughout storage, in terms of quality attributes (fungal decay, weight loss, firmness, surface color, pH, total soluble solids), total phenolic content and antioxidant activity. Gas composition inside the packages was also analyzed over time. From the packaging systems tested, the ones with active film-pads Ch + GTE and Ch + RSME were highly effective in reducing fungal growth and decay of raspberry during storage, showing only around 13% and 5% of spoiled fruits after 14 days, respectively, in contrast with the packages without pads (around 80% of spoiled fruits detected). In addition, fruits preserved using packages with Ch + RSME active film-pads showed lower mass loss (5.6%), decreased firmness (3.7%) and reduced antioxidant activity (around 9% and 15% for DPPH and FRAP methods, respectively). This sustainable packaging presents a potential strategy for the preservation of raspberries and other highly perishable small fruits.

Keywords: antifungal active packaging; chitosan; green tea extract; raspberry; rosemary extract.

Figure 1

Changes in headspace gas composition: (a) O₂ and (b) CO₂ concentrations (%), of raspberry (Rubus idaeus L. cv. ‘Kweli’) fruit packages (no film-pad_Ctr, ○; with film-pad containing green tea extract_Ch + GTE, ◆, rosemary extract_Ch + RSME ▲, only chitosan ■), stored for 14 days at 4 °C under passive MAP conditions. Vertical bars indicate standard deviation of five replicates. Means with equal letters are not statistically different by Tukey’s test with 5% significance level.

Figure 2

Evolution of fungal decay (a) and appearance at 14 days of storage (b) of packaged raspberry (Rubus idaeus L. cv. ‘Kweli’) fruits (no film-pad _Ctr; with film-pad containing green tea extract_Ch + GTE, rosemary extract_Ch + RSME and only chitosan_Ch) stored for 14 days at 4 °C under passive MAP conditions. Means with equal letters are not statistically different by Tukey’s test with 5% significance level.

Figure 3

Changes in weight loss (a) and firmness (b) of packaged raspberry (Rubus idaeus L. cv. ‘Kweli’) fruits (no film-pad _Ctr, ○; with film-pad containing green tea extract_Ch + GTE, ◆, rosemary extract_Ch + RSME ▲, only chitosan ■), stored for 14 days at 4 °C under passive MAP conditions. Vertical bars indicate standard deviation of five replicates. Means with equal letters are not statistically different by Tukey’s test with 5% significance level.

Figure 4

Total phenolic content (a) and antioxidant activity (AOA) [by DPPH (b) and FRAP (c) methods] of packaged raspberry (Rubus idaeus L. cv. ‘Kweli’) fruits (no film-pad_Ctr ○; with film-pad containing green tea extract_Ch + GTE ◆, rosemary extract_Ch + RSME ▲, only chitosan ■), stored for 14 days at 4 °C under passive MAP conditions. Vertical bars indicate standard deviation of three replicates. TEAC: Trolox equivalent antioxidant capacity; GAE: gallic acid equivalents. Means with equal letters are not statistically different by Tukey’s test with 5% significance level.

Figure 5

Correlations between AOA measured by DPPH and FRAP methods (TEAC mmol Trolox 100 g⁻¹) with TPC (mg GAE 100 g⁻¹). For both correlations, all data of the study (all sample types and all days of storage) were used.