Effects of ultrafiltration combined with high-pressure processing,ultrasound and heat treatments on the quality of a blueberry–grape–pineapple–cantaloupe juice blend

This study investigated the effect of ultrafiltration (UF) combined with high-pressure processing (HPP) at 550 MPa, 25 °C for 5 min, ultrasound (US) at 520 W, 40 °C for 10 min and heat treatment (HT) at 90 °C for 3 min on the microbial, physicochemical and sensory properties of a blueberry–grape–pineapple–cantaloupe juice blend during 104 days of storage at 4 °C. After UF, the shelf life of the HPP- and US-treated clear juice blends were 104 and 72 days during the storage at 4 °C respectively. HPP, US and HT treatment minimally affected the anthocyanin and total phenol contents, while HPP better maintained the ascorbic acid levels and sensory properties in the clear juice blend during the storage. Therefore, HPP combined with UF was identified as a prospective processing technique in the fruit juice industry.     

Anthocyanins,non-anthocyanin phenolics,tocopherols and antioxidant capacity of açaí juice (Euterpe oleracea) as affected by high pressure processing and thermal pasteurization

We studied the effect of high pressure processing (HPP) (400, 450, 500, and 600 MPa/5 min/20 °C) and thermal pasteurization (85 °C/1 min) on anthocyanins, non-anthocyanin phenolic compounds, tocopherols and antioxidant capacity toward oxygen and nitrogen reactive species of açaí juice. HPP was more effective for the preservation of anthocyanins than thermal pasteurization (up to 40%), probably due to its thermal-sensitivity. A significant increase was observed for the non-anthocyanin compounds' content at 500 MPa, possibly related to cell wall rupture due to the applied pressure. As a result, this sample showed greater antioxidant capacity (ORAC and total phenolic compounds). On the other hand, H₂O₂ scavenging capacity_, tocopherols and vitamin E activity were not affected, whereas scavenging capacity against HOCl and NOC formation was not well correlated with bioactive compounds concentration. Nevertheless, these properties were effectively preserved in HPP treatments. These results indicate that HPP may provide açaí juice with high functional quality.Industrial relevanceAçaí juice (AJ) has been increasingly valued worldwide due to its bioactive compounds and health-promoting effects, however, thermal pasteurization (TP), usually applied to AJ preservation, may cause degradation of these compounds and damage AJ bioactivities. Our results contribute to understanding how the main bioactive compounds and functional properties of AJ are affected by high pressure processing (HPP) and TP. In addition, they represent an important advance in the field of emerging preservation technologies as it indicates optimal high pressure conditions for AJ processing. Ultimately, given that HPP adds values to food products, our results may be used by the food industry to produce new açaí-based formulations with high market value.     

Characteristics of a calcium–milk coagulum

The texture, microstructure and composition of a milk coagulum obtained by coagulating milk with calcium chloride and heat were evaluated. A direct relationship was established between the microstructure and texture of the calcium–milk coagulum. The microstructure was comprised of casein micelles that were interlinked by appendages or fused with each other depending on the nature of the pre-heat treatment employed. The casein micellar network also entrapped fat globules. The pre-heat treatment of milk and the pH of milk during coagulation affected the hardness, adhesiveness, protein content and microstructure of the calcium–milk coagulum significantly. This study characterises a calcium–milk coagulum as a novel dairy product which differs from an acid coagulum in texture, microstructure and composition.     

Heating of milk powders at low water activity to 95°C for 15 minutes using hot air-assisted radio frequency processing achieved pasteurization

Salmonella persistence in milk powders has caused several multistate foodborne disease outbreaks. Therefore, ways to deliver effective thermal treatment need to be identified and validated to ensure the microbial safety of milk powders. In this study, a process of hot air-assisted radio frequency (HARF) followed by holding at high temperatures in a convective oven was developed for pasteurization of milk powders. Heating times were compared between HARF and a convection oven for heating milk powders to a pasteurization temperature, and HARF has been shown to considerably reduce the come-up time. Whole milk powder (WMP) and nonfat dry milk (NFDM) were inoculated with a 5-serotype Salmonella cocktail and equilibrated to a water activity of 0.10 to simulate the worst case for the microbial challenge study. After heating the sample to 95°C using HARF, followed by 10 and 15 min of holding in the oven, more than 5 log reduction of Salmonella was achieved in WMP and NFDM. This study validated a HARF-assisted thermal process for pasteurization of milk powder based on previously collected microbial inactivation kinetics data and provides valuable insights to process developers to ensure microbial safety of milk powder. This HARF process may be implemented in the dairy industry to enhance the microbial safety of milk powders.     

Principles and recent applications of novel non-thermal processing technologies for the fish industry—a review

Thermal treatment is a traditional method for food processing, which can kill microorganisms but also lead to physicochemical and sensory quality damage, especially to temperature-sensitive foods. Nowadays consumers’ increasing interest in microbial safety products with premium appearance, flavor, great nutritional value and extended shelf-life has promoted the development of emerging non-thermal food processing technologies as alternative or substitution to traditional thermal methods. Fish is an important and world-favored food but has a short shelf-life due to its extremely perishable characteristic, and the microbial spoilage and oxidative process happen rapidly just from the moment of capture, making it dependent heavily on post-harvest preservation. The applications of novel non-thermal food processing technologies, including high pressure processing (HPP), ultrasound (US), pulsed electric fields (PEF), pulsed light (PL), cold plasma (CP) and ozone can extend the shelf-life by microbial inactivation and also keep good sensory quality attributes of fish, which is of high interest for the fish industry. This review presents the principles, developments of emerging non-thermal food processing technologies, and also their applications in fish industry, with the main focus on microbial inactivation and sensory quality. The promising results showed great potential to keep microbial safety while maintaining organoleptic attributes of fish products. What’s more, the strengths and weaknesses of these technologies are also discussed. The combination of different food processing technologies or with advanced packaging methods can improve antimicrobial efficacy while not significantly affect other quality properties under optimized treatment.     

Short communication: Evaluation of a sol-gel–based stainless steel surface modification to reduce fouling and biofilm formation during pasteurization of milk

Milk fouling and biofilms are common problems in the dairy industry across many types of processing equipment. One way to reduce milk fouling and biofilms is to modify the characteristics of milk contact surfaces. This study examines the viability of using Thermolon (Porcelain Industries Inc., Dickson, TN), a sol-gel-based surface modification of stainless steel, during thermal processing of milk. We used stainless steel 316L (control) and sol-gel-modified coupons in this study to evaluate fouling behavior and bacterial adhesion. The surface roughness as measured by an optical profiler indicated that the control coupons had a slightly smoother finish. Contact angle measurements showed that the modified surface led to a higher water contact angle, suggesting a more hydrophobic surface. The modified surface also had a lower surface energy (32.4 ± 1.4 mN/m) than the control surface (41.36 ± 2.7 mN/m). We evaluated the susceptibility of control and modified stainless steel coupons to fouling in a benchtop plate heat exchanger. We observed a significant reduction in the amount of fouled layer on modified surfaces. We found an average fouling weight of 19.21 mg/cm² and 0.37 mg/cm² on the control and modified stainless steel coupons, respectively. We also examined the adhesion of Bacillus and biofilm formation, and observed that the modified stainless steel surface offered greater resistance to biofilm formation. Overall, the Thermolon-modified surface showed potential in the thermal processing of milk, offering significantly lower fouling and bacterial attachment than the control surface.     

Formation of the aroma of a raw goat milk cheese during maturation analysed by SPME–GC–MS

The volatile profile of the Spanish goat raw milk cheese of the protected designation of origin (PDO) “Queso Ibores” was studied at four stages of maturation (day 1, 30, 60, and 90) by the method of solid-phase micro-extraction–gas chromatography–mass spectrometry (SPME–GC–MS) to determinate the characteristic volatile compounds of this cheese and to know the changes in the volatile profile of this cheese during maturation. According to the PDO, Ibores cheese aroma varies between sweet and mild and it has a strong taste, slightly tart. A total of 64 compounds were detected: 14 acids, 18 alcohols, 13 esters, 6 ketones and 13 compounds which could not be classified in these groups. Carboxylic acids were the most abundant volatile compounds in the headspace of Ibores cheese. Content of volatile compounds was significantly modified (P < 0.05) during ripening. The relative total amounts of acids, esters and ketones increased during the first 60 days of maturation. The most characteristic compounds of Ibores cheese aroma were butanoic, hexanoic and octanoic acids, some alcohols (2-butanol and 2-heptanol), ethyl esters of hexanoic and butanoic acids, some methyl ketones (2-butanone, 2-pentanone and 2-heptanone) and δ-decalactone.     

Effect of high pressure processing on rheological and structural properties of milk–gelatin mixtures

There is an increasing demand to tailor the functional properties of mixed biopolymer systems that find application in dairy food products. The effect of static high pressure processing (HPP), up to 600 MPa for 15 min at room temperature, on milk–gelatin mixtures with different solid concentrations (5%, 10%, 15% and 20% w/w milk solid and 0.6% w/w gelatin) was investigated. The viscosity remarkably increased in mixtures prepared with high milk solid concentration (15% and 20% w/w) following HPP at 300 MPa, whereas HPP at 600 MPa caused a decline in viscosity. This was due to ruptured aggregates and phase separation as confirmed by confocal laser scanning microscopy. Molecular bonding of the milk–gelatin mixtures due to HPP was shown by Fourier-transform infrared spectra, particularly within the regions of 1610–1690 and 1480–1575 cm⁻¹, which reflect the vibrational bands of amide I and amide II, respectively.     

Effect of temperature and substrate on Pef inactivation of Lactobacillus plantarum in an orange juice–milk beverage

The inactivation kinetics of Lactobacillus plantarum in an orange juice–milk beverage treated by Pulsed Electric Fields (PEF) were studied. Experimental data were fitted to Bigelow and Hülsheger kinetic models and Weibull frequency distribution function. Results indicate that both Hülsheger model and Weibull function fit well the experimental data being Accuracy factor values (Af) closer to 1 and Mean Square Error (MSE) closer to 0. The parameter of the Weibull model can be considered as a kinetic indicator as it expresses the microorganism's resistance to treatment by electric pulses. An increase in temperature favoured the inactivation of L. plantarum by PEF as reflected by a decreased in value. Under the same conditions to those studied by other authors we reached less inactivation of L. plantarum in the beverage used in this study than in substrates with a simpler composition.     

Development and characterization of dehydrated peanut–cowpea milk powder for use as a dairy milk substitute in chocolate manufacture

This study explored the feasibility of producing peanut–cowpea milk for use in vegetable milk chocolates. Development of the vegetable milk followed a 3 × 2 factorial design, with peanut–cowpea ratio (1:1, 1:2 and 1:3), and treatment with enzyme (i.e. enzyme hydrolyzed and non-hydrolyzed milk) as the factors. The milk was dehydrated and then milled using a hammer mill (mesh size 40). It was then used in recipes to produce chocolates and evaluated sensorially based on ranking for preference. Skimmed milk powder was used to produce the control chocolate. The ratio of cowpea to peanut affected the chemical and functional characteristics of the vegetable milk. Vegetable milk made from 1:2 ratios of peanuts:cowpea produced the most preferred chocolates. The successful application of this by industry will improve the utilization of the legume crops and enhance their market value.     

Fermentation parameters,antioxidant capacities,and volatile flavor compounds of tomato juice–skim milk mixtures fermented by Lactobacillus plantarum ST-III

Food Science and Biotechnology - This study evaluated the influence of tomato juice enriched with the probiotic strain Lactobacillus plantarum ST-III on the flavor and health-promoting effects of...     

Effects on the carotenoid pattern and vitamin A of a pulsed electric field-treated orange juice–milk beverage and behavior during storage

The effect of pulsed electric fields (PEF; electric field intensities 15, 25, 35, and 40 kV/cm, and treatments times from 40 to 700 μs) on the carotenoid and vitamin A profile of an orange juice–milk beverage was evaluated and compared with a pasteurization treatment (90 °C, 20 s). Subsequently, the evolution of these parameters during storage of the beverage at 4 and 10 °C was studied. The results obtained indicate that the application of the electric field influenced the concentration of the extracted carotenoids producing a slight increase at 15 kV/cm and a slight decrease at 40 kV/cm. On the other hand, when pasteurization was applied, it was found a reduction in total carotenoid concentration. The reductions in carotenoids with provitamin A activity were very small after pasteurization, the decreases in lutein and zeaxanthin must be taken into account. The degradation kinetics of the carotenoids during storage were similar for the pasteurized and PEF-treated beverages. However, they were less affected initially in the beverages treated by the new technology and were therefore maintained in greater quantities throughout the storage period.     

Application of dispersive liquid–liquid microextraction for the determination of selected organochlorine pesticides in honey by gas chromatography–mass spectrometry

Dispersive liquid–liquid microextraction (DLLME) is a rapid and easy technique that consumes minute amounts of organic solvents. In this work, we present chemometric study on optimization of DLLME parameters for the extraction of aldrin, endrin, lindane, α-endosulfan, 4,4′-DDT and its metabolites from honey matrix. Method quantification limits (MQLs) vary between 0.3 ng/g for 2,4′-DDE and 4,4′-DDE to 13.2 ng/g for α-endosulfan and enable determination at levels below EU-established Maximum Residue Limits. The developed method is linear (R ² > 0.994) in the investigated range (MQL—100 ng/g), with preconcentration factors of 13.2–30.5 and good repeatability (CV ≤ 17%). A comparison with other available methods reported in the last decade is provided. The method has been applied to 19 real samples from Poland, and the results show that organochlorine pesticides (OCPs) are present in analysed honeys at levels not posing threat to human health (below 14 ng/g for sum of 4,4′-DDT and metabolites and below 5 ng/g for aldrin, endrin and lindane). To the best of our knowledge, this is the first reported application of DLLME for the determination of OCPs in honey.     

Quantitative analysis of volatiles in transesterified coconut oil by headspace-solid-phase microextraction-gas chromatography–mass spectrometry

A simple and fast headspace-solid-phase microextraction (HS-SPME) method coupled with gas chromatography–mass spectrometry (GC–MS) was developed for the analysis of volatile compounds in transesterified coconut oil by applying solvent dilution. Solvent dilution conditions (solvent type and solvent amount) and HS-SPME sampling parameters (adsorption temperature and time) were optimised through monitoring the adsorption result of the selected volatiles (octanoic acid esters) in transesterified coconut oil samples. The incubation of methanol (800 μl)-diluted oil (200 μl) sample at 60 °C for 30 min led to the best result. The method was further validated by determining the calibration linear range, correlation coefficient (R²), accuracy, precision, limit of detection and limit of quantification through spiking standards into the blank matrix consisting of coconut oil and methanol. This method may also be applicable for detection and determination of volatile compounds in other transesterified oil samples.     

Concentration of camu–camu juice by the coupling of reverse osmosis and osmotic evaporation processes

The objective of this work was to evaluate the technical feasibility of coupling two membrane separation processes, reverse osmosis (RO) and osmotic evaporation (OE), in order to concentrate clarified camu–camu juice, focusing on the vitamin C, phenolic compounds and antioxidant activity of the final product. The juice was firstly pre-concentrated by RO, reaching 285 g kg⁻¹ of soluble solids. During this step, the juice’s osmotic pressure showed to be the main factor controlling mass transfer. The juice was then concentrated by OE, reaching 530 g kg⁻¹ of soluble solids. Vitamin C, total phenolics and antioxidant activity levels of 94.6 g ascorbic acid kg⁻¹, 105.2 g galic acid kg⁻¹ and 762 mmol Trolox kg⁻¹, respectively, were achieved in the final product. The use of integrated membrane processes proved to be an interesting alternative to the concentration of thermosensitive juices, reaching concentration levels up to 7 times for camu–camu juice’s bioactive compounds.     

Optimization of low-cholesterol–low-fat mayonnaise formulation: Effect of using soy milk and some stabilizer by a mixture design approach

In the present study, the optimized mixture proportions of low cholesterol-low fat mayonnaise contained soy milk as an egg yolk substitute (10%) with different composition of xanthan gum (XG), guar gum (GG) and mono- & diglycerides emulsifier (MDG) (0–0.36% of each component) were determined by applying the simplex-centroid mixture design method to achieve the desired stability, textural and rheological properties and sensory characteristics for effective formulation process. Results revealed that the best mixture was the formulation contained 6.7% mono- & diglycerides, 36.7% guar gum and 56.7% xanthan gum. The xanthan gum was the component showing the highest effect on all the properties of mayonnaise samples. In addition, an increase of xanthan gum followed by guar gum caused greater values for the stability, heat stability, consistency coefficient, viscosity, firmness, adhesiveness, adhesive force and overall acceptance and lower value for flow behavior index. Depending on the desirable level of xanthan gum, guar gum and mono- & diglycerides, creation of low cholesterol-low fat mayonnaise with properties closely matching those of commercial ones is possible.     

Gel mechanical properties of milk whey protein–dextran conjugates obtained by Maillard reaction

The effect of Maillard reaction on the mechanical properties of whey protein isolate (WPI) heat-induced gels was evaluated. WPI and dextran (15–25 kDa) conjugates were obtained by controlled dry heating during storage at 60 °C and 63% relative humidity for 2, 5 and 9 days. Changes in browning intensity and content of free amino groups were used to estimate the Maillard reaction. A decrease in free amino groups of WPI was observed when increasing polysaccharide concentration and reaction time. An increase in both a* and b* CIE Lab colour parameters indicated the development of a reddish-brown colour, typical of the Maillard reaction. Uniaxial compression and stress relaxation tests were performed to measure the mechanical properties of mixed and conjugate gels. Maillard reaction significantly modified the mechanical properties of WPI/DX gels, and even prevented fracture when conjugate gels were subjected to 80% deformation in uniaxial compression test.     

Development of a stable hydrogel network based on agar–kappa-carrageenan blend cross-linked with genipin

Blend of food hydrocolloids, viz. agar and kappa-carrageeenan (agar/kC), was treated with the natural cross-linker genipin in aqueous medium to impart functional stability. The genipin-fixed blend exhibited remarkable stability in the wide range of pH 1–12, as well as in Ringer's solution. Ratios of the hydrocolloids and genipin in the blend as well as in the cross-linked product were optimized (agar/kC 25:75 and agar/kC/genipin 25:75:0.8, w/w) on the basis of swelling properties. Compatibilities of unmodified blend (agar/kC) and the cross-linked blend product in aqueous solution were studied by measuring apparent and intrinsic viscosities and UV absorptions. Properties of agar/kC blend and the genipin cross-linked blend in solid state were evaluated by bulk and true density, pore volume, porosity, thermogravimetric analysis (TGA), swelling ability, X-ray diffraction, degradation rate in vitro, optical microscopy, scanning electron microscopy (SEM) and rheological measurements. The cross-linked blend exhibited higher viscosity, thermal stability and swelling ability as well as low weight loss ratio compared to those of the un-modified blend. The presence of genipin in the cross-linked polymer network was confirmed by MS/MS analysis. This genipin cross-linked blend presents an immense potential for food applications and in other pH-specific applications as well.     

Determination of Nϵ-carboxymethyllysine in milk products by a modified reversed-phase HPLC method

A modified reversed-phase-HPLC method with o-phthalaldehyde pre-column-derivatisation for determination of N^ϵ-carboxymethyllysine in food samples is presented. It is shown, that the method has to be modified if applied to milk products, including specific modifications in sample preparation and chromatographic separation conditions. The increased selectivity of a double endcapped RP 18 phase is necessary for reliable separation of N^ϵ-carboxymethyllysine in hydrolysates of complex products like cheese. With a detection limit of 0.5 pMol the method shows high sensitivity and a very good reproducibility (s=2.81%). In total, several different milk products (n=50) as well as fresh, processed and ripened cheese samples (n=50) were analysed. The highest amounts of N^ϵ-carboxymethyllysine were found in a whey cheese (1016 mg/kg protein), evaporated milk (1691 mg CML/kg protein), coffee cream (613 mg CML/kg protein) and cocoa milk (413 mg CML/kg protein). N^ϵ-carboxymethyllysine could not be detected in UHT milk, fresh, processed and ripened cheese. The results show that N^ϵ-carboxymethyllysine can give valuable information on lysine damage in severely heat-treated milk products and in products, with added sugar, pre-damaged constituents or stabilising agents. ©