Development and optimization of antifungal packaging for sliced pan loaf based on garlic as active agent and bread aroma as aroma corrector

Abstract

13The aim of the present work was the development of antimicrobial films containing garlic 14 extract to be applied as active packaging for preservative-free sliced pan loaf, with the goal of 15 extending its shelf-life. First, the antimicrobial capacity of garlic extract, a compound used as 16 active agent, was tested against Penicillium expansum by the disc diffusion method. The 17 extract showed high antimicrobial activity, 0.1 µL per Petri dish being the minimum inhibitory 18 amount, and 0.25 µL the minimum fungicidal amount. Bread aroma was also used to mask the 19 pungent odour of garlic and it was confirmed to have no antimicrobial activity. Subsequently, 20 polyethylene (PE) aqueous emulsion and ethylene-vinyl alcohol copolymer (EVOH) and zein 21 hydroalcoholic solutions containing 0.25 and 0.5% (w/w per dry polymer) of garlic extract and 22 34 INTRODUCTION 35Bread is an essential food product in the traditional diet in Europe, the Middle East, India, 36America and Oceania. According to the Codex Alimentarius, bread is the product resulting from 37 baking dough obtained by mixing flour and water, with or without addition of edible salt, 38 fermented by baker's yeast, Saccharomyces cerevisiae. Bread slowly deteriorates after baking, 39owing to a combination of chemical and physical processes called staling and owing to 40 microbiological spoilage. 41Pan loaf is a type of bread baked in a pan, with a soft texture and high water activity 42 (0.94<aw<0.97) (Legan, 1993), and commonly sold sliced. To delay staling and dehydration, the 43 sliced bread is packaged in bags, keeping a humid headspace and, consequently, great 44 conditions for fungal spoilage. 45Fungal spores are very resistant to thermal treatments employed by the food industry, including 46 baking, which explains their prevalence in a wide range of products. Under favourable 47

Active EVOH/PE bag for sliced pan loaf based on garlic as antifungal agent and bread aroma as aroma corrector

“…As described above, this work focuses on the development of an active bag for sliced wheat pan loaf, based on an LDPE film coated with EVOH incorporating garlic extract as antifungal agent and bread aroma to reduce any potential sensory effect on the bread. In a previous work (Heras-Mozos, et al, 2018), a PE bag with an 8 µm EVOH coating incorporating 0.5% of GE and 0.5% of BA was able to inhibit P. expansum growth on a single bread slice. In the present work, the development of an active packaging that could be manufactured industrially and be valid for active packaging of a whole sliced pan loaf was attempted.…”

“…In the present work, the development of an active packaging that could be manufactured industrially and be valid for active packaging of a whole sliced pan loaf was attempted. The presence of several sulfur compounds in the garlic extract was considered responsible for the antifungal activity of the extract (Casella, Leonardi, Melai, Fratini, & Pistelli, 2013;Heras-Mozos, et al, 2018). Bread aroma containing several compounds responsible for the baked aroma was used to mask the garlic flavour (Cho & Peterson, 2010).…”

“…LDPE with an µm EVOH coating containing 0.5% of GE and 0.5% of BA was reported to present a considerable antifungal activity in laboratory tests with a package containing a single bread slice (Heras-Mozos, et al, 2018). Since (as already explained above) industrial flexographic coatings are ca.…”

“…In a previous work (Heras-Mozos, Muriel-Galet, López-Carballo, Hernández-Muñoz, & Gavara, 2018), garlic extract was reported to be an excellent inhibitory agent against Penicillium expansum in pan loaf. In that paper, LDPE film was coated with zein, EVOH and PE and used to package bread slices.…”

“…However, industrial production of that particular coating was unfeasible because the final coating was very thick and rigid, modifying the mechanical properties unacceptably, the film solution was too viscous to be applicable in an industrial printing or coating technology and the odourless, colourless zein used is an expensive material for packaging purposes. Considering that polyethylene film coated with EVOH incorporating garlic extract also provided a considerable improvement of bread stability (Heras-Mozos, et al, 2018), EVOH was used in the present work to produce active packaging for sliced pan loaf. The known effect of the sensory impact caused by the addition of plant essential oils to products (garlic extract has a characteristic pungent aroma) was counteracted by bread crust aroma, used as an aroma-masking product.…”