Viability of Lactobacillus plantarum on Fresh-Cut Chitosan and Alginate-Coated Apple and Melon Pieces

Abstract

There is an increasing trend toward foods with probiotics; the awareness of healthy diet and wellbeing is the leading cause of this increase. As a result, food producers and stakeholders require new probiotic products. The increased incidence of lactose intolerance and the new lifestyles (vegan and vegetarian styles) have led to a renewed interest in non-dairy probiotic carriers. The use of biopolymeric matrices to develop active food packaging carrying probiotics has been studied and proposed as an alternative method to design new solutions. The main topic of this paper was the design of fresh-cut fruits (apples and melons) as carriers for a promising Lactobacillus plantarum; fruit pieces were coated with either alginate or chitosan. Apple (Granny Smith) and melon pieces (Cucumis melo, var. Cantalupensis) were preliminary treated with an anti-browning solution (citric and ascorbic acids). Then, fruit pieces were dipped in a solution containing L. plantarum c19 (9 log cfu/ml) and coated with alginate or chitosan. Samples without probiotic and/or coatings were used as controls. All samples were stored at 4°C for 14 days under air or modified atmosphere (65% N₂, 30% CO₂, and 5% O₂); the following analyses were done: pH, color, O_2, and CO₂ in the head space, microbiology (mesophilic bacteria, lactic acid bacteria, yeasts, and molds). The most important results can be summarized as follows: (a) Alginate coating showed better performances than chitosan-coating, as it did not affect the viability of L. plantarum. (b) The inoculation of probiotics in the controls negatively affected the color, but the coating was able to counteract this effect. This paper supports the combination of edible coatings and probiotic as a promising way to design new fruit-based functional foods; further investigations are required to study the effect of this combination on the sensory scores.

Keywords: edible coating; fresh-cut; fruit pieces; probiotic; shelf life.

FIGURE 1

Decomposition of the statistical hypothesis for the effect of the kind of treatment and the storage time on the viability of Lactobacillus plantarum c19 on apple pieces. Vertical bars denote 95% confidence intervals. (A) effect of the storage time; (B) effect of the treatment; (C) interaction time/treatment. For the acronyms of samples see Materials and Methods.

FIGURE 2

Evolution of oxygen (v/v) in the head space of the samples of apple pieces packed in the modified atmosphere. The points represent the mean of two replicates. The lines represent the best fit through a negative Gompertz equation. For the acronyms of samples see Materials and Methods. (A) Apple pieces; (B) Apple pieces with alginate; (C) Apple pieces with chitosan.

FIGURE 3

Decomposition of the statistical hypothesis for the effect of the kind of treatment and the storage time on the instrumental color. Vertical bars denote 95% confidence intervals. For the acronyms of samples see Materials and Methods. (A) effect of the treatment on L; (B) effect of the storage time on L; (C) effect of the treatment on b; (D) effect of the storage time on b.

FIGURE 4

Decomposition of the statistical hypothesis for the effect of the kind of treatment and the storage time on the viability of L. plantarum c19 on melon pieces. Vertical bars denote 95% confidence intervals. For the acronyms of samples see Materials and Methods. (A) effect of the treatment; (B) effect of the storage time.

FIGURE 5

Evolution of O₂ (A) and CO₂ (B) in the head-space of melon pieces inoculated with L. plantarum c19 and packed in modified atmosphere. Mean ± standard deviation. For the acronyms of samples see Materials and Methods.