High-pressure homogenisation combined with blanching to turn lettuce waste into a physically stable juice

Lettuce waste was blanched, ground, pre-homogenised at 40\u202fMPa and subjected to high pressure homogenisation (HPH) at 80 (1 pass) and 150\u202fMPa (1, 10 passes) to obtain an ingredient intended for blended juice formulation. When lettuce was subjected to HPH without previous blanching, physically unstable juices were obtained. By contrast, the combination of HPH with a blanching pre-treatment allowed obtaining juices showing no physical separation and characterised by a bright green colour. This high stability was attributed to the modification of lettuce fibrous structure and to a 90% and 60% inactivation of polyphenoloxidase and pectin methylesterase, respectively. Juices presented a phenolic content of 3.5\u202f\ub1\u202f1.3\u202fmg GAE/100\u202fg and a microbial count at least 1 Log lower than that of corresponding not-blanched samples and below limits usually indicated for juice quality (4.7 Log CFU/g). During storage (4\u202f\ub0C), no phase separation was observed but microbial counts rapidly increased, suggesting the need for a further stabilization step. Industrial application Solid waste generated by fresh-cut processing of lettuce could be valorised by the application of blanching and HPH, leading to an innovative ingredient potentially exploitable in the formulation of healthy blended juices, smoothies and comminuted food. This effort is worth making considering that HPH is being increasingly introduced as processing operation in various industrial contexts, showing good feasibility and cost effectiveness, and could allow valorisation of different leaf discards

Exploring the potentialities of photoinduced glycation to steer protein functionalities: The study case of freeze-dried egg white proteins/carbohydrates mixtures

The capacity of UV-C light to induce glycation and modify functional properties of systems containing freeze-dried egg white proteins and carbohydrates with increasing molecular weight (i.e., glucose, maltose, trehalose and maltodextrin) was studied. Color changes induced by light exposure were taken as typical indicators of glycation. Samples were then analyzed for selected physical (critical concentration, particle size and viscosity), chemical (ovalbumin content) and technofunctional properties (gelling temperature and foaming capacity). The presence of sugars during exposure to UV-C light promoted intense browning and decreased ovalbumin content by circa 30%. Concomitantly, up to a 3-fold increase in critical concentration of the aqueous suspensions of the irradiated protein-carbohydrate powders and changes in particle size were detected. These modifications were consistent with the development of non-enzymatic browning reactions upon UV-C light irradiation. Photoinduced glycation was associated to a decrease in viscosity, a tendency to form gel at temperature lower by up to 8\u25e6C and a better capacity of foam stabilization. The intensity of these changes seems to be affected by the nature of the carbohydrates reacting with proteins, with longer carbohydrates able to produce systems with higher foam stability capacity

Application of different drying techniques to fresh-cut salad waste to obtain food ingredients rich in antioxidants and with high solvent loading capacity

Wastes from iceberg salad fresh-cut processing were submitted to air-drying, freeze-drying, and supercritical-CO2-drying with or without ethanol as co-solvent. Drying was combined with grinding to obtain flours. Samples were analysed for macro- and micro-appearance, particle size, dietary fibre, polyphenol content, antioxidant activity, water vapour sorption, water and oil holding capacity. Air-drying produced a collapsed brown material allowing a flour rich in fibre (>260 g/kg) and polyphenols (3.05 mg GAE/gdw) with antioxidant activity (6.04 OD 123/min/gdw) to be obtained. Freeze-drying maintained vegetable structure and colour while partly retaining polyphenols (1.23 mg GAE/gdw). Supercritical-CO2-drying with ethanol as co-solvent, produced an expanded material able to entrap huge amounts of water and oil (43.2 and 35.2 g of water and oil for g of dry sample). Air-dried salad waste derivatives could be used as functional food ingredients, while supercritical-CO2-dried ones can be exploited as bulking agents and absorbers of oil spills or edible oils. \ua9 2017 Elsevier Lt

Effect of Hyperbaric Storage at Room Temperature on the Activity of Polyphenoloxidase in Model Systems and Fresh Apple Juice

The effect of hyperbaric storage (HS) on polyphenoloxidase activity (PPO) was studied in model solutions and apple juice. Model solutions containing increasing amounts of mushroom (Agaricus bisporus) PPO (up to 26 U) were stored at room temperature at pressure up to 200 MPa. During HS, samples were assessed for residual PPO activity. The enzyme was completely inactivated according to a first-order kinetic model that was used to calculate PPO decimal reduction time (Dp) and pressure sensitivity (zp = 140.8 MPa) in diluted model solutions (2 U PPO). The increase in enzyme concentration (6–26 U) nullified the effect of HS, probably due to protein structure stabilization by self-crowding. The application of HS at 100 and 200 MPa to apple juice promoted a decrease in total bacteria, lactic acid bacteria, yeasts, and molds. These changes occurred in concomitance with the inactivation of PPO (zp = 227.3 MPa). At 200 MPa, PPO inactivation followed a biphasic first-order kinetic, suggesting the presence of PPO isozymes with different pressure sensitivity. The inactivation of PPO was observed to occur more rapidly with increasing storage pressure and led to the maintenance of the original bright juice color. This study proves the capability of HS to control enzyme-related quality decay in fruit juices and, potentially, in many other food matrices suffering enzymatic alteration

Evaluating the environmental and economic impact of fruit and vegetable waste valorisation: The lettuce waste study-case

The fruit and vegetable sector generates large amounts of waste, which poses both environmental and economic issues. Different strategies can be applied to valorise fruit and vegetable waste (FVW) by turning it into value-added products. However, the economic and environmental impact of such strategies is largely unknown. In this paper, the environmental and economic impact of FVW valorisation on an industrial scale was evaluated by developing a Decision Support System (DSS). To this aim, the lettuce waste study-case was considered, since different innovative laboratory-scale strategies have been recently proposed for its valorisation. Investment and running costs, energetic demand and yields of lettuce waste valorisation processes were collected based on laboratory tests and industrial surveys. The application of the DSS estimated that if 30% of lettuce waste annually produced by a large company was valorised by using a system configuration that involves not only anaerobic digestion and composting, but also high pressure homogenisation to produce fresh juices, and ultrasound-assisted extraction to produce antioxidant extracts, this configuration would lead to an investment lower than 10 million \u20ac, a 1 year-pay-back time and a 72 tons-reduction of carbon dioxide emissions, thus representing a rational compromise between economic returns and environmental advantage. The developed multi-objective DSS is a valuable tool to identify the most sustainable and investment-worthy processes for the valorisation of FVW

Understanding the impact of moderate-intensity pulsed electric fields (MIPEF) on structural and functional characteristics of pea, rice and gluten concentrates

Aim: The effect of moderate-intensity pulsed electric fields (MIPEF) was evaluated on vegetable protein concentrates from pea, rice, and gluten. Methods: Five percent (w/w) suspensions of protein concentrates (pH 5 and 6) were exposed to up to 60,000 MIPEF pulses at 1.65\ua0kV/cm. Both structural modifications (absorbance at 280\ua0nm, free sulfhydryl groups, FT-IR-spectra) and functional properties (solubility, water and oil holding capacity, foamability) were analyzed. Results: MIPEF was able to modify protein structure by inducing unfolding, intramolecular rearrangement, and formation of aggregates. However, these effects were strongly dependent on protein nature and pH. In the case of rice and pea samples, structural changes were associated with negligible modifications in functional properties. By contrast, noticeable changes in these properties were observed for gluten samples, especially after exposure to 20,000 pulses. In particular, at pH 6, an increase in water and oil holding capacity of gluten was detected, while at pH 5, its solubility almost doubled. Conclusion: These results suggest the potential of MIPEF to steer structure of proteins and enhance their technological functionality

Modeling the effect of the oxidation status of the ingredient oil on stability and shelf life of low-moisture bakery products: The case study of crackers

In packed low-moisture foods such as crackers, oxidation is generally the main cause of quality depletion during storage. It is commonly believed, but scarcely investigated, that product shelf life depends on the oxidative status of the lipid ingredients. In this study, the influence of oxidation degree of the ingredient sunflower oil on cracker oxidative stability and hence shelf life was investigated. To this aim, oil with increasing peroxide values (PVs) (5, 11, and 25 mEqO2/kgoil) was used to prepare crackers. Just after production, crackers presented similar peroxide and rancid odor intensity, probably due to the interactive pathways of oxidative and Maillard reactions. Crackers were packed and analyzed for PV and rancid odor during storage at 20, 40, and 60 \u25e6C. Rancid odor well discriminated cracker oxidative status. Relevant oxidation rates were used to develop a shelf life predictive model based on the peroxide value of the ingredient oil. It was estimated that an oil PV from 5 to 15 mEqO2/kgoil shortens cracker Shelf Life (SL) by 50%, independently of storage temperature. These results demonstrate the critical impact of ingredient quality on product performance on the market

Impact of high-pressure carbon dioxide on polyphenoloxidase activity and stability of fresh apple juice

Freshly-extracted apple juice was exposed to high pressure carbon dioxide (HP-CO2) treatment at 20, 35 and 45 °C at different pressure conditions (6.0, 12.0 and 18.0 MPa) for up to 30 min. Samples were analysed for residual enzymatic activity. The time needed for 90% enzyme inactivation (Dp) decreased when CO2 pressure increased, while the CO2 pressure sensitivity of the enzyme (zp) showed no variation with temperature. The HP-CO2 treatment at 12 MPa and 35 °C allowed the minimum residual enzyme activity (20%) to be reached in 10 min. Samples treated under these conditions showed lower polyphenoloxidase activity and higher microbial stability than untreated apple juice while presenting a sensory fresh-likelihood higher than thermally pasteurized apple juice. © 2016 Elsevier Lt

Modelling the recovery of biocompounds from peach waste assisted by pulsed electric fields or thermal treatment

The recovery of non-purified bioactive extracts (70% ethanol) from peach pomace (PP) was assisted by conventional thermal treatment (CTT, 50 \ub0C up to 90 min) or pulsed electric fields (PEF, specific energy input, EV, of 0.0014\u20132.88 kJ/kg). The maximum concentration of biocompounds and antioxidant activity, assessed with spectrophotometric and HPLC methods, was obtained upon 40 min by CTT and 0.0014 kJ/kg by PEF, which took 16 \u3bcs. A two-step mechanism was proposed when CTT was applied, considering a first step (zero-order kinetic) in which the PP biocompounds were released into the extraction media and a second degradation stage (first-order). A significant relationship was found between EV and PP biocompound degradation during PEF extraction, and a two-term degradation model was proposed to explain obtained data. The CTT or PEF-assisted recovery of biocompounds from PP was adequately explained by the proposed mechanistic and empirical kinetic models, which are feasible tools to understand the involved phenomena in the extraction procedures

Modelling the recovery of biocompounds from peach waste assisted by pulsed electric fields or thermal treatment

The recovery of non-purified bioactive extracts (70% ethanol) from peach pomace (PP) was assisted by conventional thermal treatment (CTT, 50 \ub0C up to 90 min) or pulsed electric fields (PEF, specific energy input, EV, of 0.0014\u20132.88 kJ/kg). The maximum concentration of biocompounds and antioxidant activity, assessed with spectrophotometric and HPLC methods, was obtained upon 40 min by CTT and 0.0014 kJ/kg by PEF, which took 16 \u3bcs. A two-step mechanism was proposed when CTT was applied, considering a first step (zero-order kinetic) in which the PP biocompounds were released into the extraction media and a second degradation stage (first-order). A significant relationship was found between EV and PP biocompound degradation during PEF extraction, and a two-term degradation model was proposed to explain obtained data. The CTT or PEF-assisted recovery of biocompounds from PP was adequately explained by the proposed mechanistic and empirical kinetic models, which are feasible tools to understand the involved phenomena in the extraction procedures