Unraveling the role of probiotics in affecting the structure of monoglyceride gelled emulsions: A low-field 1H NMR study.

The capacity of monoglyceride (MG) gelled emulsions (MEs) in protecting probiotic cells of Lacticaseibacillus rhamnosus against stresses suffered during food processing, storage, and human digestion has been recently demonstrated. These findings open new perspectives on the possible participation of probiotics in the stabilization of emulsion structure. To unravel this aspect, rheological analysis and Low-Field 1H NMR investigations were performed on MEs having different aqueous phases (water or skimmed milk) and stored for increasing time (1 and 14 days) at 4 °C. Loaded and unloaded samples were considered. Results highlighted that probiotics initially hindered the ability of MG to self-assemble in the multiphase environment, interacting in some way with MG crystalline lamellar structure, as confirmed by rheological and 1H NMR analysis. During storage, an increase of proton compartmentation was observed in loaded MEs indicating the role of probiotics in stabilizing MG structure at a molecular level. Such a result was more evident when the system was composed of milk, suggesting that the presence of milk-native components (i.e., lactose, proteins, and minerals) favored the cell-structure interactions. Such preliminary results could open new perspectives in considering probiotic cells as having an active role in the stabilization of food structure.

Effect of moderate hydrostatic pressure on crystallization of palm kernel stearin-sunflower oil model systems.

Lipid crystallization under moderate hydrostatic pressure treatments (200 MPa, 20 °C, 1-24 h) was studied in palm kernel stearin (PS 100%) and its blends with sunflower oil (PS 80, 90 % w/w). Hyperbarically-crystallized samples exhibited significantly higher firmness, elastic modulus and critical stress values as compared to those of the samples crystallized at atmospheric pressure. These data indicate that moderate hydrostatic pressure favored the formation of a higher amount of small palm kernel stearin crystals as compared to those formed at atmospheric pressure. Pressurization did not affect fat polymorphism, but was able to enhance nucleation instead of crystal growth. This work clearly demonstrated the efficacy of moderate hydrostatic pressure in steering lipid crystallization, opening interesting possible applications of high-pressure processing technology in the fat manufacturing sector.

Upcycling soy processing waste (okara) into structured emulsions for fat replacement in sweet bread.

BACKGROUND: Okara is the main waste of soy processing and represents a large economic and environmental burden. Nevertheless, the fibre and protein content of okara supports the upcycling of this critical waste. This study aimed at assessing the potentialities of okara as an innovative oil-structuring ingredient. RESULTS: Structured emulsions containing up to 520 g oil kg-1 and having oil holding capacity higher than 75% were prepared by high-shear mixing of okara with liquid oil. Microstructural analysis showed that the oil phase was evenly distributed in the okara matrix, probably due to the emulsification ability of the okara fibre-protein network. The performance of okara structured emulsions as palm margarine replacer were tested in the preparation of sweet bread. Okara emulsions (500 g oil kg-1 ) resulted not only in a significant reduction of saturated fatty acids (>50%), but also in an increased protein and fibre content. Compared to the use of liquid oil solely, okara emulsions allowed reducing the oil released from bread loaf. Bread containing okara emulsion also presented physical and sensory properties similar to those of palm margarine bread, the only exception being a more perceivable oiliness and rancid defect, which are, however, easily preventable by applying appropriate formulation strategies. CONCLUSION: The use of okara as innovative ingredient for oil structuring would answer the current demand for sustainable heathy diets, based on clean-label foods with low-saturated fat content, and increased protein and fibre supply. This approach would also allow the complete upcycling of this critical waste. © 2022 Society of Chemical Industry.

Raw milk preservation by hyperbaric storage: Effect on microbial counts, protein structure and technological functionality.

The possibility to apply hyperbaric storage (HS) at room temperature (20 °C) as a sustainable approach for preservation of raw skim milk was studied. Samples were stored at 200 and 150 MPa for up to 6 days. Optimal pressure for milk HS was found to be 150 MPa, since no clotting was detected for up to 6 days. 150 MPa-HS caused the irreversible inactivation of inoculated Escherichia coli (5.13 ± 0.33 logCFU mL-1) and Staphylococcus aureus (5.66 ± 0.93 logCFU mL-1) within 2 and 6 days, respectively. Inactivation of total and faecal coliforms (3.0 log reductions) below the detection limit was achieved after just 2 days, whereas lactic acid bacteria and coagulase-positive Staphylococci were inactivated after 6 days. Pressurized storage also caused an increase in proteose peptones and the release of submicelles from casein micelles. Micelles progressively aggregated with pressure-unfolded ß-Lactoglobulin. These phenomena led to milk presenting up to 4-fold better foaming capacity, probably due to ß-Lactoglobulin unfolding or higher proteose peptones content. This work demonstrated the capability of HS to guarantee milk preservation during storage, and brought attention on the opportunity to consider the technology for milk pasteurization and functionality improvement.

Correction: Effect of the formulation and structure of monoglyceride-based gels on the viability of probiotic Lactobacillus rhamnosus upon in vitro digestion.

Correction for 'Effect of the formulation and structure of monoglyceride-based gels on the viability of probiotic Lactobacillus rhamnosus upon in vitro digestion' by Sofia Melchior et al., Food Funct., 2021, DOI: 10.1039/D0FO01788D.

Effect of the formulation and structure of monoglyceride-based gels on the viability of probiotic Lactobacillus rhamnosus upon in vitro digestion.

This research was conducted to evaluate the potential use of saturated monoglyceride (MG)-based gels in the protection of probiotics upon in vitro digestion. For this purpose, a Lactobacillus rhamnosus strain was inoculated into binary and ternary systems, containing MGs, a water phase composed of an aqueous solution at controlled pH or UHT skimmed milk, and in ternary gels, sunflower oil. Gel structure characterization was initially performed just after preparation and after 14 days of storage at 4 °C by rheological, mechanical, thermal, and microscopy analyses. Afterwards, probiotic viability upon in vitro digestion was evaluated. The results highlighted that all freshly prepared samples showed good capability to protect L. rhamnosus with the exception of the binary system containing milk. However, the digestion of samples after 14 days of storage showed that the ternary system containing skimmed milk exhibited the best protection performance ensuring a L. rhamnosus viability of almost 106 CFU g-1 at the end of the gastrointestinal passage. Confocal microscopy results demonstrated that bacterial cells were located prevalently within the aqueous domain near the monoglycerides and protein aggregates. Under these conditions, they can simultaneously achieve physical protection and find nutrients to survive environmental stresses. These findings suggest that MG-based gels can be proposed as efficient carriers of probiotic bacteria not only during food processing and storage but also upon digestion.

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 °C. 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.

Effect of different biopolymer-based structured systems on the survival of probiotic strains during storage and in vitro digestion.

BACKGROUND: This study aimed to evaluate the protective effect of different biopolymer systems on the viability of two probiotics (Lactobacillus rhamnosus and Streptococcus thermophilus) during storage and in vitro digestion. Methylcellulose (MC), sodium alginate (SA), and whey protein (WP)-based structures were designed and characterized in terms of pH, rheological properties, and visual appearance. RESULTS: The results highlighted that the WP-system ensured probiotic protection during both storage and in vitro digestion. This result was attributed to a combined effect of the physical barrier offered by the protein gel network and whey proteins as a nutrient for microbes. On the other hand, surprisingly, the viscous methylcellulose-based system was able to guarantee good microbial viability during storage. However, this was not confirmed during in vitro digestion. The opposite results were obtained for sodium alginate beads. CONCLUSION: The results suggest that the capacity of a polymeric structure to protect probiotic bacteria is a combination of structural organization and system formulation. © 2020 Society of Chemical Industry.

Temperature Dependence of Oxidation Kinetics of Extra Virgin Olive Oil (EVOO) and Shelf-Life Prediction.

Producers have to guarantee the extra virgin olive oil (EVOO) quality characteristics reported in the Regulation (CEE) 2568/91 throughout the product shelf-life (SL). Unfortunately, due to the development of oxidative reactions, some quality indices change during storage leading to a progressive deterioration of EVOO quality. To avoid the risk of product downgrading in the virgin oil category, the development of effective shelf-life prediction models is extremely important for the olive oil industry. In this research, the accelerated shelf-life testing (ASLT) protocol was applied to evaluate the temperature dependence of selected oxidation indexes as well as to develop a shelf-life predictive model. The evolution of conventional (peroxide value, K232, K270, polyphenols, tocopherols and hexanal) and unconventional parameters (conjugated trienes and pyropheophytin a) was monitored in bottled EVOO stored in the dark at increasing temperature (25, 40, 50 and 60 °C). Accordingly, for well-packed products with reduced oxygen in headspace, the best shelf-life index allowing the ability to predict EVOO SL turned out to be K270. In addition, pyropheophytin a (%) has been shown to be more sensitive to temperature changes than the secondary oxidation indices, thus suggesting its use as a freshness indicator for storage temperatures higher than 25 °C.

Microemulsions as delivery systems of lemon oil and ß-carotene into beverages: stability test under different light conditions.

BACKGROUND: Microemulsions have been proposed as delivery systems for different lipophilic substances in transparent water-based systems. The chemical stability of the delivered compounds is a key factor to broaden the application of microemulsions in the food sector. The stability of a model beverage containing a microemulsion delivering ß-carotene and lemon oil was tested under increasing light intensity up to 6000 lx at 20 °C. RESULTS: The transparent microemulsion resulted physically stable during storage indicating that no coalescence phenomenon occurred. On the contrary, both colour and flavour of the microemulsion degraded as a consequence of limonene and ß-carotene oxidation. Kinetic data obtained at increasing light intensity were used to estimate the light dependence of beverage spoilage and the mathematical relationship obtained was used to predict spoilage rate under different light conditions. Finally, a shelf life predictive model was proposed. CONCLUSIONS: Transparent microemulsions can be successfully used to deliver flavoured oil and colourants into beverages. However, the photostability of the delivered compounds should be carefully studied to estimate product shelf life. To this aim, the availability of models predicting shelf life as a function of enlightening conditions could largely contribute to speed up the process. © 2019 Society of Chemical Industry.

ß-Carotene degradation kinetics as affected by fat crystal network and solid/liquid ratio.

The aim of this research was to study ß-carotene degradation kinetics into lipid systems containing different fat crystal networks in the presence of increasing liquid oil amounts. To this purpose, fat blends containing liquid saturated medium chain triacylglycerols (MCT) with increasing content of saturated monoglycerides (MG), tripalmitin (PPP) and tristearin (SSS) were added with 0.6mg/g ß-carotene. The fat crystal networks formed in the fat blends were characterized by using polarized light microscopy and synchrotron X-ray diffraction (XRD). In addition, ß-carotene degradation was monitored during storage in the dark at 20°C. Results highlighted that fat crystallization could differently affect ß-carotene stability. In bulk SSS and PPP, ß-carotene degradation proceeded at comparable rate, whereas when the saturated liquid oil MCT is included in the fat network, the rate of oxidation slightly decreased. Interestingly, the oxidation rate was not significantly affected by the solid/liquid ratio of the systems. A completely different behavior was observed in MG containing systems: the rate of ß-carotene oxidation was in every case significantly lower than that observed in SSS and PPP containing samples. Also in this case, the MG protective effect was independent on its content in the fat mixtures.

Effect of pulsed light on structure and immunoreactivity of gluten.

The effect of pulsed light (from 1.75 to 26.25Jcm(-2)) on selected properties of wheat gluten powder and aqueous suspension (absorbance, particle size and microstructure, free sulfhydryl content, protein fractions, protein electrophoretic mobility and immunoreactivity) was investigated. Gluten photoreactivity was strongly affected by hydration. While minor photo-induced structure modifications were observed in gluten powder, pulsed light induced the development of browning and promoted partial depolymerisation of hydrated gluten proteins by disulphide exchange. These changes were associated with a significant decrease in immunoreactivity, suggesting that pulsed light could be exploited to efficiently modify structure and thus functionality of gluten.

Shelf-life Assessment of Food Undergoing Oxidation-A Review.

Oxidation is the most common event leading to the end of shelf life of microbiologically stable foods. Thus, a reliable shelf-life assessment is crucial to verify how long the product will last before it becomes oxidized to an unacceptable level to the consumers. Shelf-life assessment strategies of foods and beverages suffering oxidation are critically discussed focusing on definition of the acceptability limit, as well as the choice of the proper oxidative indicators, and methodologies for shelf-life testing. Testing methodologies for shelf-life determination under actual and accelerated storage conditions are considered, highlighting possible uncertainties, pitfalls, and future research needs.

Structural and viscoelastic characterization of ternary mixtures of sunflower oil, saturated monoglycerides and aqueous phases containing different bases.

The structure at different length scales and the viscoelastic properties of ternary mixtures composed of saturated monoglycerides, sunflower oil and aqueous solutions of weak bases (KHCO3, NaHCO3, and NH4HCO3) or strong bases (NaOH and KOH) were investigated. The characteristics of ternary mixtures were studied systematically by using polarized light microscopy, differential scanning calorimetry (DSC), synchrotron X-ray diffraction (XRD) and rheological analysis. Results showed that the base type and concentration greatly affected the structure of the mixtures. The use of strong bases allowed gelled systems to be obtained only at low concentrations (<10mM). On the contrary, the presence of weak bases induced gelling at all concentrations considered (from 1 to 1000mM). The increase of base concentration led to a reduction of the mean droplet diameter and melting temperature. At the same time, the viscoelastic characteristics as a function of base concentration followed a more complex behavior: G' and G″ progressively decreased as the salt concentration increased in a concentration range from 1 to 100mM, while the rheological parameters increased when salt concentration increased from 100 to 1000mM. The structural and viscoelastic behavior of systems prepared with different salts were commonly independent of the cation present in the medium. Results highlight that it is possible to tailor the structure of these gels by using specific bases.

Surface processing: existing and potential applications of ultraviolet light.

Solid foods represent optimal matrices for ultraviolet processing with effects well beyond nonthermal surface disinfection. UV radiation favors hormetic response in plant tissues and degradation of toxic compound on the product surface. Photoinduced reactions can also provide unexplored possibilities to steer structure and functionality of food biopolymers. The possibility to extensively exploit this technology will depend on availability of robust information about efficacious processing conditions and adequate strategies to completely and homogeneously process food surface.

Nanoemulsion-based delivery systems for polyunsaturated (ω-3) oils: formation using a spontaneous emulsification method.

Nanoemulsion-based delivery systems are finding increasing utilization to encapsulate lipophilic bioactive components in food, personal care, cosmetic, and pharmaceutical applications. In this study, a spontaneous emulsification method was used to fabricate nanoemulsions from polyunsaturated (ω-3) oils, that is, fish oil. This low-energy method relies on formation of fine oil droplets when an oil/surfactant mixture is added to an aqueous solution. The influence of surfactant-to-oil ratio (SOR), oil composition (lemon oil and MCT), and cosolvent composition (glycerol, ethanol, propylene glycol, and water) on the formation and stability of the systems was determined. Optically transparent nanoemulsions could be formed by controlling SOR, oil composition, and aqueous phase composition. The spontaneous emulsification method therefore has considerable potential for fabricating nanoemulsion-based delivery systems for incorporating polyunsatured oils into clear food, personal care, and pharmaceutical products.

Effect of vacuum roasting on acrylamide formation and reduction in coffee beans.

Coffea arabica beans were roasted in an oven at 200 °C for increasing lengths of time under vacuum (i.e. 0.15 kPa). The samples were then analysed for colour, weight loss, acrylamide concentration and sensory properties. Data were compared with those obtained from coffee roasted at atmospheric pressure (i.e. conventional roasting), as well as at atmospheric pressure for 10 min followed by vacuum treatment (0.15 kPa; i.e. conventional-vacuum roasting). To compare the different treatments, weight loss, colour and acrylamide changes were expressed as a function of the thermal effect received by the coffee beans during the different roasting processes. Vacuum-processed coffee with medium roast degree had approximately 50% less acrylamide than its conventionally roasted counterpart. It was inferred that the low pressure generated inside the oven during the vacuum process exerted a stripping effect preventing acrylamide from being accumulated. Vacuum-processed coffee showed similar colour and sensory properties to conventionally roasted coffee.

Microstructure and bioaccessibility of different carotenoid species as affected by high pressure homogenisation: a case study on differently coloured tomatoes.

The effect of high pressure homogenisation (HPH) on structure (Bostwick consistency, particle size distribution and microstructure) and carotenoid in vitro bioaccessibility of different tomato pulps was investigated. HPH decreased tomato particle size due to matrix disruption and increased product consistency, probably due to the formation of a fibre network. Homogenisation also resulted in a decrease of in vitro bioaccessibility of lycopene, ζ-carotene, and lutein. Such decrease was attributed to the structuring effect of HPH. An inverse relation between tomato consistency and carotenoid in vitro bioaccessibility was found. This dependency was affected by carotenoid species and its localisation within the matrix. It could be observed that one matrix (e.g. (homogenised) red tomato pulp) can contain carotenoids with a very low bioaccessibility (lycopene) as well as carotenoids with a very high bioaccessibility (lutein), indicating that carotenoid bioaccessibility is not solely dependent on the matrix.

Inactivation of polyphenoloxidase by pulsed light.

The effect of pulsed light on the inactivation of polyphenoloxidase (PPO) in model solutions was investigated focusing on the effect of enzyme concentration and total energy dose of the treatment. PPO inactivation increased with the dose of the treatment. Complete enzyme inactivation was achieved by pulsed light doses higher than 8.75 J cm(-2) . At low PPO concentrations (4 to 10 U), the enzyme resulted highly inactivated by pulsed light treatment. Further increase in enzyme units determined a progressive decrease in PPO inactivation. The latter was attributed to protein structural modifications including cleavage and unfolding/aggregation phenomena. PPO amounts higher than 10 U probably favoured enzyme conformations that were less prone to intermolecular rearrangements leading to inactivation.

Monitoring dry-curing of S. Daniele ham by magnetic resonance imaging.

S. Daniele hams were collected at different stages during dry-curing and submitted to magnetic resonance imaging (MRI) according to the acquisition Spin-Echo sequences T1 and T2. The intensity of the MR signals in the images of the Semimembranosus, Semitendinosus, Rectus femoris and Biceps femoris muscles of the hams was computed and expressed in grey levels. Muscles were also submitted to traditional analyses, including aw, soluble solids, sodium chloride, total and water soluble nitrogen. T1 and T2 MR signals well described the evolution of the phenomena occurring in the different muscles during dry-curing. MR signal acquired in T2 mode well correlated with traditional indicators in Semitendinosus, Rectus femoris and Biceps femoris muscles. Predictive models estimating the value of aw, moisture, salt content and proteolysis extent on the basis of the MR signal intensity were proposed.