Abstract
This research explored the potential of the zero-waste concept in relation to the storability of fresh food products. In particular, the prickly pear (Opuntia ficus-indica) peel (usually perceived as a by-product) and the pulp were dehydrated, reduced in powder, and used as food additives to slow down the growth of the main spoilage microorganisms of fresh cod fish burgers. The proportion between peel and pulp powder was such as to respect the zero-waste concept. The antibacterial activity of the peel and pulp in proper proportion was first assessed by means of an in vitro test against target microorganisms. Then, the active powder was added at three concentrations (i.e., 2.5 g, 7.5 g, and 12.5 g) to cod fish burgers to assess its effectiveness in slowing down the microbial and sensory quality decay of burgers stored at 4 °C. The results from the in vitro test showed that both the peel and pulp were effective in delaying microbial growth. The subsequent storability test substantially confirmed the in vitro test results. In fact, a significant reduction in growth rate of the main fish spoilage microorganisms (i.e., Pseudomonas spp., psychrotrophic bacteria, and psychrotolerant and heat-labile aerobic bacteria) was observed during 16 days of refrigerated storage. As expected, the antimicrobial effectiveness of powder increased as its concentration increased. Surprisingly, its addition did not affect the sensory quality of fish. Moreover, it was proven that this active powder can improve the fish sensory quality during the storage period.
Highlights
Over the past few years, the amount of food waste produced and lost through the supply chain has become a severe problem for the world, causing nutrient loss, climate changes due to the production of greenhouse gas, and losses of resources like water and cultivated land [1].One of the approaches suggested to reduce this global concern is the concept of zero-waste, a philosophy that prompts to find a way for all products to be recycled, so that no kind of waste will be sent to landfills or incinerators [2]
A preliminary in vitro test was performed on target bacteria (Pseudomonas spp.), before testing the active powder on fish burgers
From the above mentioned data, it can be inferred that the Ctrl had a steady growth during all 72 h of the test, whereas for the active samples a reduction of the Pseudomonas spp. viable cell concentration was observed
Summary
Over the past few years, the amount of food waste produced and lost through the supply chain has become a severe problem for the world, causing nutrient loss, climate changes due to the production of greenhouse gas, and losses of resources like water and cultivated land [1]. The peel, that represents the major waste in prickly pear, is considered an agricultural by-product, even though it is a source of dietary fibers, proteins and antioxidant compounds [7]. Both the fruit and the peel are rich in polyphenolic compounds that show biological and antimicrobial activity against different microorganisms [9,11,12,13]. In the perspective of a more sustainable food production, the current study, for the first time explored the possibility to adopt all parts of prickly pear fruit for preserving fish burger quality during storage. The study demonstrated that the newly developed fish burgers, enriched with bioactive compounds from prickly pears, exerted good antimicrobial activity against the traditional fish spoilage, but they were more appreciated than the control sample in terms of sensory quality, demonstrating the feasibility of the sustainable approach
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