Traditional engineering instruction is deductive, beginning with theories and progressing to the applications of those theories Alternative teaching approaches are more inductive Topics are introduced by presenting specific observations, case studies or problems, and theories are taught or the students are helped to discover them only after the need to know them has been established This study reviews several of the most commonly used inductive teaching methods, including inquiry learning, problem-based learning, project-based learning, case-based teaching, discovery learning, and just-in-time teaching The paper defines each method, highlights commonalities and specific differences, and reviews research on the effectiveness of the methods While the strength of the evidence varies from one method to another, inductive methods are consistently found to be at least equal to, and in general more effective than, traditional deductive methods for achieving a broad range of learning outcomes

Inductive Teaching and Learning Methods: Definitions, Comparisons, and Research Bases

Recent advances in transition metal catalyzed oxidation of organic substrates with molecular oxygen.

Essential oils are aromatic and volatile liquids extracted from plants. The chemicals in essential oils are secondary metabolites, which play an important role in plant defense as they often possess antimicrobial properties. The interest in essential oils and their application in food preservation has been amplified in recent years by an increasingly negative consumer perception of synthetic preservatives. Furthermore, food-borne diseases are a growing public health problem worldwide, calling for more effective preservation strategies. The antibacterial properties of essential oils and their constituents have been documented extensively. Pioneering work has also elucidated the mode of action of a few essential oil constituents, but detailed knowledge about most of the compounds’ mode of action is still lacking. This knowledge is particularly important to predict their effect on different microorganisms, how they interact with food matrix components, and how they work in combination with other antimicrobial compounds. The main obstacle for using essential oil constituents as food preservatives is that they are most often not potent enough as single components, and they cause negative organoleptic effects when added in sufficient amounts to provide an antimicrobial effect. Exploiting synergies between several compounds has been suggested as a solution to this problem. However, little is known about which interactions lead to synergistic, additive, or antagonistic effects. Such knowledge could contribute to design of new and more potent antimicrobial blends, and to understand the interplay between the constituents of crude essential oils. The purpose of this review is to provide an overview of current knowledge about the antibacterial properties and antibacterial mode of action of essential oils and their constituents, and to identify research avenues that can facilitate implementation of essential oils as natural preservatives in foods.

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Essential oils in food preservation: mode of action, synergies, and interactions with food matrix components.

Food wastes are today considered as a cheap source of valuable components since the existent technologies allow the recovery of target compounds and their recycling inside food chain as functional additives in different products. The goal of the current article is to classify food waste sources and high-added value ingredients prior to exploring the recovery stages, conventional and emerging technologies applied from the raw material to the final or encapsulated product. Safety and cost aspects were discussed, too, while a survey of patented methodologies leading to real products was listed, with a final purpose of discussing the prevalent problems that restrict the commercialization of similar procedures.

Recovery of high added-value components from food wastes: Conventional, emerging technologies and commercialized applications

In May 2019, the International Scientific Association for Probiotics and Prebiotics (ISAPP) convened a panel of nutritionists, physiologists and microbiologists to review the definition and scope of synbiotics. The panel updated the definition of a synbiotic to “a mixture comprising live microorganisms and substrate(s) selectively utilized by host microorganisms that confers a health benefit on the host”. The panel concluded that defining synbiotics as simply a mixture of probiotics and prebiotics could suppress the innovation of synbiotics that are designed to function cooperatively. Requiring that each component must meet the evidence and dose requirements for probiotics and prebiotics individually could also present an obstacle. Rather, the panel clarified that a complementary synbiotic, which has not been designed so that its component parts function cooperatively, must be composed of a probiotic plus a prebiotic, whereas a synergistic synbiotic does not need to be so. A synergistic synbiotic is a synbiotic for which the substrate is designed to be selectively utilized by the co-administered microorganisms. This Consensus Statement further explores the levels of evidence (existing and required), safety, effects upon targets and implications for stakeholders of the synbiotic concept. Gut microbiota can be manipulated to benefit host health, including the use of probiotics, prebiotics and synbiotics. This Consensus Statement outlines the definition and scope of the term ‘synbiotics’ as determined by an expert panel convened by the International Scientific Association for Probiotics and Prebiotics in May 2019.

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The International Scientific Association for Probiotics and Prebiotics (ISAPP) consensus statement on the definition and scope of synbiotics

Edible coatings are considered an environmentally friendly technology, able to extend the shelf-life of fruit and vegetables. In the present work, a novel approach to the preservation of vegetable products is proposed, through the development of edible coatings, containing nanoemulsified natural antimicrobial compounds.Modified chitosan was initially selected as film-forming biopolymer, owing to its inherent antimicrobial activity. Different essential oil nanoemulsions, with variable composition, mean droplet size and surface charge, containing lemon, mandarin, oregano or clove essential oils, were developed to maximize in vitro the interaction with the modified chitosan coating and promote the resulting antimicrobial activity.The combined use of nanoemulsified lemon essential oil with modified chitosan resulted in the remarkable increase in antimicrobial activity, with respect to other essential oils. Therefore, this formulation, comprising 0.05%wt modified chitosan and 0.1%wt nanoemulsified lemon essential oil, was further tested in product for the stabilization of a leaf vegetable, such as rucola, during a shelf-life, consisting of storage at 4°C for 3 d and then at 8°C for a total of 21 d. Microbial viability as well as colour and texture changes were monitored during the shelf-life.The obtained results showed that the incorporation of nanoencapsulated lemon essential oil into the modified chitosan coating prolonged the shelf life of rucola leaves from 3 to 7 d, in comparison to the untreated sample. Moreover, the modified chitosan containing the nanoemulsified antimicrobial caused a significantly longer shelf-life also in comparison to a coating made of modified chitosan or essential oil alone.In conclusion, thanks to this novel treatment it is possible to prolong the shelf life of delicate leaf vegetables to about 10 - 14 d, without causing any significant alteration of the organoleptic properties of the product, preventing the loss of firmness and colour changes and preserving palatability during storage.

Novel Edible Coating Containing Essential Oil Nanoemulsions to Prolong the Shelf Life of Vegetable Products

Influence of emulsifier type on the antifungal activity of cinnamon leaf, lemon and bergamot oil nanoemulsions against Aspergillus niger

Annurca apple juice was processed by high pressure homogenization (HPH) to inactivate the endogenous microbial flora, with the aim of maintaining the organoleptic properties and the polyphenolic content of the fresh juice. In particular, it was shown that the shelf life of clear juice can be prolonged for many weeks of storage both at 4°C and 37°C upon HPH treatment at 250 MPa. Instead, the juice with pulp required higher pressure levels (300 MPa) for microbial stabilization both at 4°C and 37°C. The sample stored at 37°C exhibited a physical instability, with deviation in color and pH, which reduced the shelf life, but the samples stored at 4°C exhibited an excellent microbial stability and no observable variation of pH and color, suggesting that HPH can represent a good option for non thermal pasteurization of Annurca apple juice.Interestingly, the HPH treatment delivered also significant changes to the distribution of suspended particles, whose comminution had a measurable effect on viscosity.

Francesco Donsì

Papers

Novel Edible Coating Containing Essential Oil Nanoemulsions to Prolong the Shelf Life of Vegetable Products

Influence of emulsifier type on the antifungal activity of cinnamon leaf, lemon and bergamot oil nanoemulsions against Aspergillus niger

Production of shelf-stable Annurca apple juice with pulp by high pressure homogenization.

Freeze–thaw stability of lecithin and modified starch-based nanoemulsions

Decontamination of fresh-cut cucumber slices by a combination of a modified chitosan coating containing carvacrol nanoemulsions and pulsed light