Effect of thermal treatment and storage on the stability of organic acids and the functional value of grapefruit juice

The effect of conventional and microwave pasteurisation on the main bioactive compounds of grapefruit juice and their stability during 2 months’ refrigerated and frozen storage was evaluated. Ascorbic acid (AA), vitamin C and organic acids were analysed by HPLC, whereas total phenols and antioxidant capacity (%DPPH) were measured by spectrophotometry. The results showed that conventional treatment led to a significant decrease in citric acid (from 1538 to 1478 mg/100 g) and AA (from 36 to 34.3 mg/100 g), whilst microwave pasteurisation preserved these compounds. Frozen storage maintained AA and vitamin C, especially in treated samples. Frozen non-treated samples and conventional pasteurised ones preserved about a 75% and 20% of the total phenols and antioxidant capacity, respectively, whilst in frozen microwave pasteurised juices this preservation was of 82% and 33%. From these results, the use of microwave energy may be proposed as an alternative to traditional heat pasteurisation in order to preserve the natural organoleptic characteristics and essential thermolabile nutrients of grapefruit juice.     

Comparison of the effects of novel processing technologies and conventional thermal pasteurisation on the nutritional quality and aroma of Mandarin (Citrus unshiu) juice

Conventional thermal pasteurisation (90 °C and 30 s), high pressure processing (HPP: 600 MPa, 4 °C and 300 s), ultrasound processing (US: 50 °C, 750 W and 36 min) and microwave processing (MW: 800 W, 80 °C and 70 s) were evaluated by examining their effects on the sensory and nutritional qualities of mandarin juice. The treated samples had <2 log CFU/mL total aerobic bacteria, which is equivalent to microorganism inactivation. Sugar and acid components were almost constant for all the treated mandarin juices, and no differences between treatments were perceptible. However, the mandarin juice treated with novel technologies maintained better colour (L*, a* and b*), nutritional value (ascorbic acid, total phenolic, total carotenoid content and phenolic components) and aroma than the thermally pasteurised one. This study showed that US, MW and HPP are good novel processing techniques to inactivate microorganisms and maintain the sensory and nutritional quality of mandarin juice.     

Influence of ultra-high pressure homogenisation on physicochemical and sensorial properties of orange juice in comparison with conventional thermal processing

The effect of different ultra-high pressure homogenisation (UHPH) treatments on physicochemical and sensorial properties of orange juice was studied in comparison with thermal pasteurisation (90 °C, 1 min). UHPH treatments consisted on combinations of two inlet temperatures (10 or 20 °C) and three pressures (100, 200 and 300 MPa). Effect of treatments was assessed on general quality parameters (colour, pH, °Brix, titratable acidity, reducing sugars and non-enzymatic browning index), particle size distribution and cloud stability. None of the UHPH treatments caused significant differences in the °Brix, reducing sugars, pH and non-enzymatic browning index with respect of fresh or pasteurised juice. Only titratable acidity was significantly lower when inlet temperature of UHPH treatments was 20 °C. UHPH treatments significantly reduced the particle size and in consequence the cloudiness and the total colour value (∆E*) increased. The overall consumer acceptability of UHPH and pasteurised juices was similar.     

High hydrostatic pressure treatment and storage of carrot and tomato juices: Antioxidant activity and microbial safety

The application of high hydrostatic pressure (HHP) (250 MPa, 35 °C for 15 min) and thermal treatment (80 °C for 1 min) reduced the microbial load of carrot and tomato juices to undetectable levels. Different combinations of HHP did not cause a significant change in the ascorbic acid content of either juice (P > 0.05). Both heat treatments (60 °C for 5–15 min and 80 °C for 1 min) resulted in a significant loss (P < 0.05) in the free‐radical scavenging activity as compared to untreated samples. HHP‐treated juices showed a small loss of antioxidants (below 10%) during storage. The ascorbic acid content of pressurized tomato and carrot juices remained over 70 and 45% after 30 days of storage, respectively. However, heat treatment caused a rapid decrease to 16–20%. Colour changes were minor (ΔE = 10) for pressurised juices but for heat‐pasteurised samples it was more intense and higher as a result of insufficient antioxidant activity. HHP treatment (250 MPa, 35 °C for 15 min) led to a better product with regard to anti‐radical scavenging capacity, ascorbic acid content and sensory properties (colour, pH) of the tomato and carrot juices compared to conventional pasteurisation. Therefore, HHP can be recommended not only for industrial production but also for safe storage of fresh juices, such as tomato and carrot, even at elevated storage temperatures (25 °C). Copyright © 2007 Society of Chemical Industry     

Effects of β‐cyclodextrin addition and farming type on vitamin C,antioxidant activity,carotenoids profile,and sensory analysis in pasteurised orange juices

The effects of organic farming, pasteurisation and addition of β‐cyclodextrin on the content of vitamin C, colour, carotenoids and antioxidant capacity of orange juices were studied. After pasteurisation at 98 °C (20 s) and subsequently storage along 145 days at room temperature (20–25 °C), the loss of vitamin C content was around 30%. The effects of the thermal process on carotenoid were clearly observed in lutein (loss of 16% for organic and traditional 8%) and especially β‐cryptoxanthin (loss of 30%). The colour changes were noticeable after the pasteurisation of orange juice and subsequent storage, with significant decreases being observed in lightness and the coordinate a*, while increases were found for coordinates b*, Hue* and chroma. The antioxidant capacity was 0.075 ± 0.01 and 0.053 ± 0.01 mMT mL^?1 for organic and conventional, respectively, with losses around 40% being found at the end of the storage period. The addition of β‐cyclodextrin caused no significant effects on the parameters under analysis. These data showed that strong thermal treatments, such as pasteurisation, adversely affect the nutritional and sensory quality of orange juices.     

Original article: Effects of continuous dense‐phase CO2 system on antioxidant capacity and volatile compounds of apple juice

The effects of different operating conditions applied to a continuous dense‐phase carbon dioxide (DPCD) system on antioxidant capacity and volatile compounds of apple juice were compared with current heat pasteurisation method. Only the microbial tests required by Italian Regulation to assure microbiological safety to ‘fruit juices and vegetables’ were performed, and DPCD‐treated (15 MPa, 35 °C, 15 min; 25 MPa, 35 °C, 15 min), heat‐pasteurised (75 °C, 15 s) and untreated apple juice samples were considered. The DPCD processing carried out at 15 MPa resulted as effective as 25 MPa in reducing microbial cells. Trolox equivalent of DPCD treated at 25 MPa (0.41 mm ) resulted significantly (P < 0.05) lower than DPCD treated at 15 MPa (0.48 mm ). Head space analysis of volatile compounds indicated the lowest decrease in apple aroma compounds (59% esters and 59% aldehydes) in DPCD treated at 15 MPa.     

Composition of volatile compounds in bovine milk heat treated by instant infusion pasteurisation and their correlation to sensory analysis

Volatile compounds in skim milk and nonstandardised milk subjected to instant infusion pasteurisation at 80°C, 100°C and 120°C were compared with raw milk, high temperature short time pasteurised milk and milk pasteurised at 85°C/30 s. The composition of volatile compounds differed between infusion pasteurisation treated samples and the reference pasteurisations. The sensory properties of skim milk subjected to instant infusion pasteurisation were described by negative attributes, such as cardboard sour and plastic flavours, which are not associated normally with fresh milk. Partial least squares modelling showed good correlation between the volatile compounds and the sensory properties, indicating the predictive and possible causal importance of the volatile compounds for the sensory characteristics.     

Are we closer to understanding why viable cells of Mycobacterium avium subsp. paratuberculosis are still being reported in pasteurised milk?

Mycobacterium avium subsp. paratuberculosis (MAP) continues to be associated with Crohn’s disease. Following work in the 1990s that suggested that statutory pasteurisation of milk (72 °C, 15 s) was insufficient to destroy MAP, the UK Dairy Industry increased the holding time to 25 s. Since then, some plants have increased the lethality of pasteurisation further with a number using 78 °C for 27 s. Despite the increase in lethality, a recent survey of pasteurised milk in England found that 10.3% of pasteurised milk samples tested positive for viable MAP. This article discusses the significance of MAP and why viable MAP might be found in pasteurised milk.     

Pasteurised,microfiltered and lactose‐hydrolysed skimmed milk with added probiotics: Development and storage stability

Recently the food industry has been attempting to innovate its products to meet consumer demands for health benefits from their food. Thus, the objective of this research was to study the combination of technologies to obtain a pasteurised, microfiltered, and lactose‐hydrolysed skim milk with an extended shelf life and with added probiotics (PMLHSP). This PMLHSP was subjected to physicochemical, microbiological and sensory evaluations, plus its shelf life was estimated at 5 °C. The viability of the probiotics in this system was also evaluated during storage at 5 °C and indicated a shelf life of about 28 days. The probiotic culture added to the microfiltered skim milk presented good viability in the product throughout refrigerated storage, with counts of above 8 log CFU/mL.     

Quality degradation kinetics of pasteurised and high pressure processed fresh Navel orange juice: Nutritional parameters and shelf life

A kinetic study of post processing quality loss was conducted after high pressure processing (600 MPa, 40 °C, 4 min) or thermal pasteurisation (80 °C, 60 s) of fresh Navel orange juice. Selection of processing conditions was mainly based on pectin methylesterase inactivation. Ascorbic acid loss, colour, viscosity and sensory characteristics were measured during storage at different isothermal conditions (0–30 °C). Increased shelf life (based on ascorbic acid retention) was achieved for high pressurised compared to thermally pasteurised juice, ranging from 49% (storage at 15 °C) to 112% (storage at 0 °C). Activation energy values for ascorbic acid loss were 68.5 and 53.1 kJ/mol, respectively, for high pressurised and thermally treated juice. High pressure processing resulted in better retention of flavour of untreated juice and superior sensory characteristics compared to thermal pasteurisation. Colour change was linearly correlated to ascorbic acid loss for both types of processing. Slightly higher apparent viscosity values were determined for high pressurised juice.Industrial relevanceApplication of high hydrostatic pressure on orange juice industry. Fresh orange juice is a product of high commercial and nutritional value due to its rich vitamin C content and its desired sensory characteristics. High Hydrostatic Pressure (HHP) is an alternative non-thermal technology that has been proposed for application on orange juice. Such a treatment denaturates enzymes and eliminates microorganisms responsible for spoilage of orange juice without detrimental effects on the sensory and nutritional quality of juice. The effect of HHP on the stability of fresh orange juice has been studied by different research groups, while orange juices processed with the new technology have already been commercially available in Japan, U.S.A., Mexico and Europe. However, a systematic kinetic approach of the effect of HHP on different quality indexes (not only microbial spoilage) immediately after processing, as well as during a long term storage of the processed orange juice is needed, in order to achieve an optimal process design and a successful application of the new technology in orange juice industry. Such kinetic data for parameters related to the quality and nutritional value of fresh orange juice were gathered in the present work providing therefore industry with useful information for the HHP stabilization of orange juice and the production of a high quality product. Due to the great benefits of HHP compared to the conventional pasteurization that emerged from this work regarding the quality, shelf life and nutritional characteristics of fresh orange juice, HHP technology is an advantageous alternative process for high valued products like orange juice.     

Flavour characterisation of fresh and processed pennywort (Centella asiatica L.) juices

The flavour characteristics of fresh and processed pennywort juices treated by pasteurisation, sterilisation and high pressure processing (HPP) were investigated by using solid-phase micro-extraction combined with gas chromatography–mass spectrometry. Sesquiterpene hydrocarbons comprise the major class of volatile components present and the juices had a characteristic smell due to the presence of volatile compounds including β-caryophyllene, humulene, E-β-farnesene, α-copaene, alloaromadendrene and β-elemene. All processing operations caused a reduction in the total volatile concentration, but HPP caused more volatile acyclic alcohols, aldehydes and oxygenated monoterpenoids to be retained than pasteurisation and sterilisation. Ketones were not present in fresh pennywort juice, but 2-butanone and 3-nonen-2-one were generated in all processed juices, and 2-nonanone and 2-hexanone were present in pasteurised and sterilised juices. Other chemical changes including isomerisation were also reduced by HPP compared to pasteurisation and sterilisation.     

Changes in the volatile composition of Spanish-style green table olives induced by pasteurisation treatment

Thermal treatment of pasteurisation is the most widely used stabilisation method for packed green table olives. In the present work, the influence of pasteurisation on the composition of volatile compounds in packed Spanish-style green table olives was studied. To this aim, two thermal processes (P1 = 85 °C for 7 min; P2 = 85 °C for 15 min) were evaluated by comparing the contents of volatile compounds in pasteurised olives with those in unpasteurised olives. Volatiles were analysed, both in olive juice and cover brine, by means of headspace solid-phase microextraction (HS-SPME) followed by gas chromatography-mass spectrometry (GC-MS). Both pasteurisation treatments caused significant increases in diverse ethyl and methyl esters and in volatile compounds derived from several chemical reactions (lipid oxidation, Maillard reaction, degradation of carotenoids). Significant differences between samples subjected to P1 and P2 were only found for 1-octen-3-ol, pentanal and 6-methyl-5-hepten-2-one in olive juice.     

Characterisation of the microflora during ripening of a Norwegian semi-hard cheese with adjunct culture of propionic acid bacteria

The microflora of a semi-hard, washed curd, Norwegian cheese with an added adjunct culture of propionic acid bacteria (PAB) was investigated throughout ripening by phenotypic and physiological tests, API test and 16S rRNA sequencing. Cheeses were made at two commercial Norwegian dairies using different milk treatments (pasteurisation versus microfiltration plus pasteurisation) and the same type of starter cultures. Microflora in the cheese varied according to different plant site, milk treatment, and ripening time. PAB dominated the microflora throughout the ripening process. Leuconostoc spp., most probably from the starter, dominated among the isolates from the cheese using microfiltered and pasteurised milk; however, after 40 weeks of ripening non-starter lactic acid bacteria specie Lactobacillus casei/paracasei and Leuconostoc spp. dominated at the dairy using pasteurised milk. Cheese made at the two plants on two subsequent days showed almost identical microflora throughout ripening.     

Effect of enzymatic treatments and microfiltration on the physicochemical quality parameters of feijoa (Acca sellowiana) juice

Feijoa fruit (Acca Sellowiana) has a short postharvest period, thus, processing is usually an alternative. The objective of this work was to evaluate the efficiency of three different commercial enzyme preparations in the extraction of feijoa juice in the yield and quality parameters. The juices with Pectinex®, Lallzyme® and Rohapect® were evaluated under three different concentrations (1, 5 and 10 U mL⁻¹) before and after the pulping process. The samples were valued for total soluble solids, pH, reducing sugars, titratable acidity and colour. The juice that showed the most promise was evaluated for the microfiltration stage and rheological behaviour and particle size distribution were measured. The three treatments with Pectinex had an increase in juice yield in 43, 55 and 60%, while the samples with enzymes Lallzyme and Rohapect had no increase in yield compared to the control. All the tested enzymes had a positive impact on the colour of the juice, improving the colour parameters. The microfiltered juice had a behaviour index value of 1,091, indicating Newtonian behaviour. The fresh juice showed values below one (0.2178), indicating a non-Newtonian and typically pseudoplastic behaviour. Among three enzymes used, Pectinex® showed the better results for physical–chemical parameters for extraction of feijoa juice.     

Phenolic acids, flavonoids, vitamin C and antioxidant capacity of strawberry juices processed by high-intensity pulsed electric fields or heat treatments

The effect of high-intensity pulsed electric fields (HIPEF) processing (35 kV/cm for 1,700 μs in bipolar 4-μs pulses at 100 Hz) on individual phenolic compounds (phenolic acids and flavonoids), vitamin C and antioxidant capacity of strawberry juice was evaluated and compared to heat (90 °C for 60 or 30 s) and fresh juice as a reference. Although strawberry juice underwent a substantial depletion of health-related compounds with storage time irrespective of the treatment conducted, ellagic acid was enhanced. HIPEF-treated strawberry juice maintained higher amounts of phenolic acids (ellagic and p-coumaric acid) and total anthocyanins than the thermally treated juices during the storage period. Regarding the antioxidant capacity, similar DPPH and ABTS values were obtained so that differences among pasteurized juices were non significant. HIPEF processing may be a technology as effective as thermal treatments not only to achieve safe and stable juices, but also to obtain juices with a high content of antioxidant compounds.     

Effects of cyclodextrin type on vitamin C, antioxidant activity, and sensory attributes of a mandarin juice enriched with pomegranate and goji berries

Abstract: The effects of the addition of cyclodextrins (CDs), β‐CD, or HP‐β‐CD (1%), on the protection of antioxidant compounds of mandarin juices enriched with pomegranate extract and goji berries juice, was studied. Juices were prepared and after their thermal treatment (98 °C, 30 s) they were stored at 4 °C during 75 d. Vitamin C content, CIE L*a*b* color, antioxidant capacity, retinol equivalents, and sensory properties were studied. Losses on vitamin C were higher (6%) for juices with β‐CD than juices with HP‐β‐CD. Retinol equivalents degradation was lower (3.4%) in juices with HP‐β‐cyclodextrins than in those treated with β‐CD. Lower losses were observed for the instrumental and sensory color intensity in juices with HP‐β‐CD addition. Finally, the antioxidant capacity was also higher in juices treated with HP‐β‐CD. Finally, the overall sensory quality of juices with HP‐β‐CD was the best one after 30 d of cold storage. Even though β‐CD addition did not cause any improvement compared with control juice (without CD addition), the benefits of adding HP‐β‐CD to this particular juice were shown in almost all parameters under study. Practical Application: The present study deals with the practical aspects of the utilization of CDs and CD‐complexes in the food industry. The molecular encapsulation of lipophilic food ingredients with CD are supposed to improve the stability of flavors, vitamins, colorants, and antioxidant activity, leading to extended product shelf life. The HP‐β‐CD treated mandarin juice enriched with pomegranate extract and juice of goji berries will have a more intense color, higher vitamin C content, retinol equivalents, and antioxidant activity during storage and shelf life than control juices, with no CD addition.     

Comparative study on antioxidant properties of carrot juice stabilised by high‐intensity pulsed electric fields or heat treatments

BACKGROUND: The effect of high‐intensity pulsed electric field (HIPEF) processing (35 kV cm^?1 for 1500 µs using 6‐µs bipolar pulses at 200 Hz) on the antioxidant features (vitamin C, β‐carotene, total phenolic compounds and antioxidant capacity) of carrot juice as well as on peroxidase activity was investigated and compared to the observed in heat pasteurised juices (90 °C for 60 s or 30 s) having the fresh juice as a reference. RESULTS: HIPEF and heat‐treated carrot juices had higher β‐carotene and lower vitamin C contents than the untreated juices immediately after processing. The antioxidant capacity of the juices was significantly modified neither by HIPEF nor by thermal treatments. POD activity decreased drastically (≥93.3%) after processing irrespective of the treatment applied. Vitamin C and β‐carotene content decreased throughout the storage following an exponential trend (R² = 0.801–0.984) with degradation rates between 1.7 × 10^?2 and 3.5 × 10^?2 day^?1. Vitamin C and β‐carotene contents were better maintained in HIPEF‐treated than in heat‐pasteurised juices throughout the storage. Total phenolic content and the antioxidant capacity of the HIPEF‐treated juice did not substantially differ from that of the thermally treated juice for 56 days. CONCLUSION: HIPEF processing may help to achieve fresh‐like carrot juices with increased amounts of health‐related phytochemicals. Copyright © 2009 Society of Chemical Industry     

Determination of insulin-like growth factor-1 and bovine insulin in raw milk and its casein and whey fractions after microfiltration and ultrafiltration

Insulin-like growth-factor 1 (IGF-1) and insulin were analysed from bovine milk during microfiltration (MF) and ultrafiltration (UF) processes using immunochemical methods. IGF-1 was found in the MF retentate and in the UF retentate. A very small fraction of IGF-1 was in the UF permeate. The results indicated that IGF-1 was present in milk as a complex molecule or bound to milk proteins. Insulin showed similar behaviour, but more insulin was found in the MF retentate than in the UF retentate. No insulin was found in the UF permeate. There were no differences in IGF-1 or insulin distribution between pasteurised or non-pasteurised milk. The stability of bovine insulin to heat treatments was also determined. The molecule was stable during pasteurisation at 65 and 72 °C, but lost some of its immunochemical activity at 90 and 135 °C.     

Comparison of dynamic viscoelastic and physicochemical properties of pressurised and pasteurised longan juices with xanthan addition

Physical and biochemical properties of pressurised and pasteurised longan juices with various xanthan additions, such as viscoelastic behaviour, colour L (lightness), −a^∗ (greenness), b^∗ (yellowness), ΔE (total different colours) and BI (Browning Index) parameters, polyphenol oxidase (PPO) activity, ascorbic acid, gallic acid, ellagic acid, total phenols and antioxidant capacity (DPPH assay) were studied. Viscoelastic determination indicated that longan juice with 0.15% xanthan addition was optimal for a fruit drink. Colour parameters showed pressurised longan juice at 500 MPa was brighter and more transparent than fresh and other processed juices. PPO was completely inactivated in pasteurised juices, whereas in pressurised juices at 300 and 500 MPa, the activities were more than 100% and 95–99%, respectively. Bioactive components including ascorbic acid were significantly reduced according to treatment severities, whereas gallic and ellagic acids were relatively stable in all processed juices. Total phenols and DPPH radical-scavenging activity decreased significantly on pasteurisation, but were stable on pressurisation.     

Properties of Orange Juice with Supercritical Carbon Dioxide Treatment

The effects of supercritical CO₂ (SC-CO₂) on the microbiological, sensory (taste, odour, and colour), nutritional (vitamin C content), and physical (cloud, total acidity, pH, and °Brix) qualities of orange juice were studied. The CO₂ treatment was performed in a 1 litre capacity double-walled reactor equipped with a magnetic stirring system. Freshly extracted orange juice was treated with supercritical CO₂, pasteurised at 90°C, or left untreated. There were no significant differences in the sensory attributes and physical qualities between the CO₂ treated juice and freshly extracted juice. The CO₂ treated juice retained 88% of its vitamin C, while the pasteurised juice was notably different from the fresh juice and preserved only 57% of its vitamin C content. After 8 weeks of storage at 4°C, there was no microbial growth in the CO₂ treated juice.