Effect of enzymatic mash treatment and storage on phenolic composition, antioxidant activity, and turbidity of cloudy apple juice

Analytical characterization of flavan-3-ol-rich apple juices produced with the innovative spiral filter press technology

The retention of flavan-3-ols and other phenolic compounds during apple juice production at pilot plant scale (200 kg, cv. Boskoop) was investigated. An oxygen-excluding spiral filter press and a conventional decanter were used with and without pectinase mash treatment. Phenolic compounds were comprehensively identified and quantitated by RP-UHPLC and HILIC, both coupled to DAD-FLD and DAD-ESI(-)-QTOF-HR-MS/MS. These techniques combined with using a NIST cocoa flavan-3-ol standard allowed for the first time an individual quantification of flavan-3-ol fractions (DP 1-7) in apple juices. Spiral filter-pressed juices were exposed to less oxidation and exhibited four times higher total phenolic compound levels than decanter-made juices (1016 vs. 262 mg/L). Apple juices derived from pectinase-treated mashes had lower total phenolic compound levels than their non-treated counterparts. However, those made by spiral filter press still retained significantly higher concentrations (780 vs. 104 mg/L). Flavan-3-ols were especially well retained by spiral filter press processing, reaching unprecedentedly high concentrations of up to 713 mg/L. A 280 mL serving of non-treated spiral filter-pressed juice would therefore suffice to provide the daily intake of 200 mg flavan-3-ols, equaling the dose of cocoa flavan-3-ols associated with an authorized European health claim for healthy blood flow.

Analysis of the Polyphenolic Composition of Vaccinium L. Extracts and Their Protective Effect on Red Blood Cell Membranes

The blueberry fruit of the genus Vaccinium, including high blueberry, low blueberry, and wild bilberry, is consumed for its flavor and medicinal properties. The purpose of the experiments was to investigate the protective effect and mechanism of the interaction of blueberry fruit polyphenol extracts with the erythrocytes and their membranes. The content of polyphenolic compounds in the extracts was determined using the chromatographic UPLC-ESI-MS method. The effects of the extracts on red blood cell shape changes, hemolysis and osmotic resistance were examined. Changes in the order of packing and fluidity of the erythrocyte membrane and the lipid membrane model caused by the extracts were identified using fluorimetric methods. Erythrocyte membrane oxidation was induced by two agents: AAPH compound and UVC radiation. The results show that the tested extracts are a rich source of low molecular weight polyphenols that bind to the polar groups of the erythrocyte membrane, changing the properties of its hydrophilic area. However, they practically do not penetrate the hydrophobic part of the membrane and do not damage its structure. Research results suggest that the components of the extracts can defend the organism against oxidative stress if they are delivered to the organism in the form of dietary supplements.

Effect of Storage Conditions on the Stability of Polyphenols of Apple and Strawberry Purees Produced at Industrial Scale by Different Processing Techniques

During a food product's life, storage conditions affect its composition of nutrients, bioactive compounds, and sensory attributes. In this research, strawberry and apple purees were selected as a model to examine how the storage of various purees industrially produced with different technologies affect the bioactive phenolic compounds, color, and sensory attributes. Specifically, fruit products processed on an industrial scale by different technologies including freezing, thermal treatment (mild and standard), and high-pressure processing were studied, as well as storage for up to 12 months at -20, 4, and 24 °C. In strawberry puree, storage conditions had a stronger impact on phenolic compound levels, particularly on anthocyanins, whereas in apple puree, the initial processing techniques exerted a greater influence than storage conditions, mainly caused by the hot or cold crushing processes. In general, proanthocyanidins were the major phenolic group and the most stable during storage, while anthocyanins were the group most affected by both processing and storage. Apple flavonols and dihydrochalcones were quite stable, while strawberry ellagitannins suffered higher degradations during storage. Through our analysis, it is found that during storage, the stability of polyphenols in each fruit is different, and processing and storage can be either detrimental or even beneficial. The selection of the ideal storage conditions (time and temperature) is a key factor to maintaining the polyphenol content in sensitive fruits such as strawberries. However, storage conditions are in some cases more important to minimizing the polyphenol losses than how the product is processed.

Selection of Enzymatic Treatments for Upcycling Lentil Hulls into Ingredients Rich in Oligosaccharides and Free Phenolics

In this study, the comprehensive chemical characterization of red lentil hulls obtained from the industrial production of football and split lentils was described. The lentil hulls were rich in dietary fiber (78.43 g/100 g dry weight with an insoluble to soluble fiber ratio of 4:1) and polyphenols (49.3 mg GAE/g dry weight, of which 55% was bound phenolics), which revealed the suitability of this lentil by-product as a source of bioactive compounds with recognized antioxidant and prebiotic properties. The release of oligosaccharides and phenolic compounds was accomplished by enzymatic hydrolysis, microwave treatment and a combination of both technologies. The key role played by the selection of a suitable enzymatic preparation was highlighted to maximize the yield of bioactive compounds and the functional properties of the lentil hull hydrolysates. Out of seven commercial preparations, the one with the most potential for use in a commercial context was Pectinex^® Ultra Tropical, which produced the highest yields of oligosaccharides (14 g/100 g lentil hull weight) and free phenolics (45.5 mg GAE/100 g lentil hull weight) and delivered a four-fold increase in terms of the original antioxidant activity. Finally, this enzyme was selected to analyze the effect of a microwave-assisted extraction pretreatment on the yield of enzymatic hydrolysis and the content of free phenolic compounds and oligosaccharides. The integrated microwave and enzymatic hydrolysis method, although it increased the solubilization yield of the lentil hulls (from 25% to 34%), it slightly decreased the content of oligosaccharides and proanthocyanidins and reduced the antioxidant activity. Therefore, the enzymatic hydrolysis treatment alone was more suitable for producing a lentil hull hydrolysate enriched in potential prebiotics and antioxidant compounds.

The impact of ultrasound-assisted thawing on the bioactive components in juices obtained from blue honeysuckle (Lonicera caerulea L.)

Ultrasound (US) assisted thawing of blue honeysuckle berry was utilized in order to reduce the losses of bioactive components (ascorbic acid, anthocyanins, phenolic acids, iridoids, proanthocyanins) and increase the extraction efficiency during juice processing. It was analysed whether it was more beneficial to apply US (alone or with enzymatic treatment) to the frozen state, until reaching the cryoscopic temperature or thawed state. Both the US and enzymatic treatment significantly increased the extraction efficiency, extract content, acidity and the content of iridoids and chlorogenic acid in juices, especially if the US was applied to 50 °C. It was probably due to a higher extractivity by the greater damage of the tissue and detexturation. Enzymatic treatment due to long heating contributed to a higher degradation of anthocyanins, ascorbic acid and proanthocyanidins, which are more heat-sensitive. The results of the study mainly indicated the possibility of including ultrasound-assisted thawing in the fruit processing before pressing the juices. This may replace costly enzymatic treatment.

Effects of acidified blanching water and pectinase enzyme pretreatments on physicochemical properties and antioxidant capacity of Carica papaya juice

The high pectin content in papaya (Carica papaya) causes the juice extraction to be difficult and results in a low yield. This study aims to determine the effect of acidified blanching water and pectinase enzyme pretreatments on the yield, physicochemical properties, and antioxidant activities of the papaya juice. For acidified blanching treatment, papaya cubes (3 cm³ ) were blanched in water containing 0%, 0.5%, 1.5%, and 2.5% w/v citric acid at 95℃ for 2 min. For enzyme treatment, a pectinase enzyme (10, 20, and 30 ppm) was added to the homogenous papaya puree and incubated at 45℃ (200 rpm) for 60 min. The enzyme reaction was stopped by pasteurization at 74℃ for 2 min. The puree was filtered, and the juice was pasteurized at 74℃ for 7 min. All pretreated papaya juice were analyzed for physicochemical properties (color, clarity, viscosity, pH, total soluble solids [TSSs], total carotenoid content, total phenolic content [TPC], and total flavonoid content [TFC]), and antioxidant activities (2,2-diphenyl-1-picrylhydrazyl [DPPH] and ferric reducing antioxidant power [FRAP] assay). Both pretreatments improved the clarity of papaya juice, and was significantly greater after pretreatment with pectinase enzyme. The TPC and antioxidant activities of papaya juice were conserved and maintained by acidified blanching at 1.5% (w/v) citric acid. Increased concentrations of pectinase enzyme significantly reduced the TPC and total carotenoid content. Pretreatment with pectinase enzyme up to 20 ppm does not significantly reduce the TFC and antioxidant activities. Acidified blanching and pectinase enzyme pretreatments have an impact on extraction of papaya fruit juice while retaining the nutritional composition of the juice. PRACTICAL APPLICATION: Papaya (Carica papaya) is a fruit with great nutritional values but is highly perishable and prone to postharvest loss. Juice has become a more cost-effective and convenient option for preserving the fruit. However, since papaya is a pectin-rich fruit, the extraction of juice using mechanical pressing is difficult due to the bonding of juice to the pulp in the form of a jellied mass, which results in juice with low yield. Using acidified blanching and pectinase enzyme to clarify the juice not only increases the yield but also retains the nutrient composition of the juice.

Preliminary Study on Ultrasonic Ageing Zhenjiang Vinegar Mechanism Based on Maillard Simulation System

In this study, ultrasonic technology was used to treat Zhenjiang vinegar, and the effects on the physicochemical characteristics of Zhenjiang vinegar were investigated. The influences of ultrasound time and power on the number of induced hydroxyl radicals and superoxide radicals were also investigated. Besides, the novel simulation system of the Maillard reaction was built to research the effects of different ultrasonic times and power treatment on Zhenjiang vinegar. The results show that, under the conditions of ultrasonic treatment, the changes of Zhenjiang vinegar physiochemical index, such as color, reducing sugar, and amino acid, are consistent with those of natural ageing. In addition, ultrasound can produce a cavitation effect and cracking water molecules to produce hydroxyl radicals and superoxide radicals, so as to achieve the ageing effect of vinegar.

Effect of 1-Methylcyclopropene (1-MCP) and Storage Atmosphere on the Volatile Aroma Composition of Cloudy and Clear Apple Juices

The effects of 1-methylcyclopropene (1-MCP), storage atmosphere (controlled (CA) or regular (RA)), and juice processing (clear or cloudy) on the volatile aroma compounds from McIntosh and Honeycrisp apples following 4-month storage were studied. All the major esters, aldehydes, and total volatile content from McIntosh juice were significantly affected by the two-way interaction between harvest maturity and 1-MCP treatment (p ≤ 0.01), as well as harvest maturity and storage atmosphere (p ≤ 0.001). In McIntosh juices, a remarkable reduction of all types of esters, aldehydes, most alcohols, and total volatile compounds was found when juices were prepared from 1-MCP-treated apples. In Honeycrisp, significant differences in the level of esters and the total volatile aroma was caused by storage atmosphere and juice processing techniques (p ≤ 0.001), but not by 1-MCP treatment. As compared to clear juices, cloudy juice samples from Honeycrisp had a considerably higher content of total volatiles, esters, and aldehydes.

Effect of the apple cultivar on cloudy apple juice fermented by a mixture of Lactobacillus acidophilus, Lactobacillus plantarum, and Lactobacillus fermentum

This study aimed to evaluate the fermentation performance of a mixture of Lactobacillus spp. in cloudy apple juices from nine cultivars. The results showed that cultivar influenced most the properties of the fermented cloudy apple juice. The fermented cloudy apple juices made from Changfu had the highest viable bacterial count and acetic acid contents (6.37 × 10⁸ CFU/mL and 2.67 mg/mL, respectively). It also had higher sensory score, second only to Huaniu. The highest total sugar consumption, utilising fructose, glucose, and sucrose (33.07 mg/mL), was seen with Golden Delicious. Qinguan fermented cloudy apple juice had the highest contents of lactic acid (6.74 mg/mL) and total esters (921.36 μg/L); d-limonene also detected in this fermented cloudy apple juice. Of the nine cultivars examined in this study, Changfu, Qinguan, and Golden Delicious were the most suitable for producing fermented cloudy apple juice with better taste, higher viable count and more intense aroma.

Interactions of Anthocyanins with Pectin and Pectin Fragments in Model Solutions

Anthocyanins determine the color and potential health-promoting properties of red fruit juices, but the juices contain remarkably less anthocyanins than the fruits, which is partly caused by the interactions of anthocyanins with the residues of cell wall polysaccharides like pectin. In this study, pectin was modified by ultrasound and enzyme treatments to residues of polysaccharides and oligosaccharides widely differing in their molecular weight. Modifications decreased viscosity and degrees of acetylation and methylation and released smooth and hairy region fragments. Native and modified pectin induced different effects on the concentrations of individual anthocyanins after short-term and long-term incubation caused by both hydrophobic and hydrophilic interactions. Results indicate that both pectin and anthocyanin structure influence these interactions. Linear polymers generated by ultrasound formed insoluble anthocyanin complexes, whereas oligosaccharides produced by enzymes formed soluble complexes with protective properties. The structure of the anthocyanin aglycone apparently influenced interactions more than the sugar moiety.

Protein and polyphenols involved in sediment formation in cloudy litchi juice

Sedimentation is a major issue in juice production. This paper aims to study the mechanisms of precipitate formation during the storage of cloudy litchi juice. The sediment concentration, relative turbidity, and ζ potential were analyzed. The supernatant and sediment were separated to determine the contents of proteins and phenolics. The results showed that the amount of sediment increased during the storage. In addition, the total protein and total phenolic content in the supernatant decreased, whereas the glutelin and total phenolic contents in the sediment increased significantly (p < 0.05). Moreover, our results showed that the amounts of procyanidin B₂ and quercetin-3-O-rutinose-7-O-rhamnoside in the supernatant decreased noticeably. However, these two substances could not be detected in the sediment. In summary, the formation of sediment from litchi juice is mainly caused by the slow denaturation of proteins and the oxidation of procyanidin B₂ and quercetin-3-O-rutinose-7-O-rhamnoside.

Haze in Apple-Based Beverages: Detailed Polyphenol, Polysaccharide, Protein, and Mineral Compositions

Producers of apple-based beverages are confronted with colloidal instability. Haze is caused by interactions between molecules that lead to the formation of aggregates. Haze composition in three apple-based beverages, namely, French sparkling cider, apple juice, and pommeau, was studied. Phenolic compounds, proteins, polysaccharides, and minerals were analyzed using global and detailed analytical methods. The results explained <75% (w/w) of haze dry mass. Polyphenols, represented mainly by procyanidins, were the main compounds identified and accounted for 10-31% of haze. However, oxidized phenolic compounds were probably underestimated and may represent a high proportion of haze. Proteins were present in all of the samples in proportions of <6% of haze except in two apple juice hazes, where they were the main constituents (18 and 24%). Polysaccharides accounted for 0-30% of haze. Potassium and calcium were the main minerals.

Production, purification and biochemical characterization of an exo-polygalacturonase from Aspergillus niger MTCC 478 suitable for clarification of orange juice

Polygalacturonases (PG) represent an important member of pectinases group of enzymes with immense industrial applications. A fungal strain Aspergillus niger MTCC478 was used for the production of polygalacturonase both under submerged and solid-state fermentation condition. Further its production was optimized under solid-state fermentation condition with media comprising of wheat bran and tea extract. Purification of an exo-PG was achieved by acetone precipitation (60-90%) and CM-cellulose column chromatography revealing 15.28-fold purification with a specific activity of 33.47 U/mg protein and 1.2% yield. A relative molecular mass of purified PG was approximately 124.0 kDa. The pH and temperature optimum was found to be 4 and 50 °C, respectively. The k cat and K m value for degradation of PGA by the purified enzyme was found to be 194 s-1 and 2.3 mg/mL, respectively. Cu2+ was found to enhance the PG activity while Ag+ completely inhibited the enzyme activity. The application of the purified PG in orange juice clarification was elucidated.

Application of Freezing and Thawing in Apple (Malus domestica) Juice Extraction

The paper presents the results of the research on the impact of enzymatic liquefaction, freezing and thawing on the efficiency of juice pressure extraction from apple pulp and quality of the obtained juices. The research was conducted using three types of pretreatment prior the pressing: crushing and enzymatic liquefaction in temperature of 25 °C, crushing and enzymatic liquefaction in temperature of 45 °C and crushing followed by freezing and thawing of the pulp. The study included three varieties of apples. The juice was obtained using a laboratory basket press. It was determined that the pretreatment of the pulp as well as the varietal characteristics of the fruits have a significant impact on the efficiency of the pressure extraction process. The enzymatic treatment of the pulp, irrespective of the temperature at which it was conducted, significantly increased the efficiency of the process. No effect of the temperature (25 or 45 °C) of enzymatic treatment on the efficiency of the pressure extraction process was found. Pretreatment of the pulp based on freezing and thawing contributes to the increase of efficiency of pressing in the case of two apple cultivars, that is, Idared and Red Delicious. It was showed that total phenolic content, antioxidant activity, the soluble solids content and juice acidity (pH) depend on the pretreatment of the pulp and the varietal characteristics of apples. Following the application of pretreatment of the pulp, an increase was observed in the content of polyphenols and in the antioxidant activity of the juices obtained.

Enhanced production of pectinase by Aspergillus terreus NCFT 4269.10 using banana peels as substrate

Aspergillus terreus NCFT4269.10 was implemented in solid-state (SSF) and liquid static surface fermentation (LSSF) for biosynthesis of pectinase. Amongst various substrates, like, mustard oil cake, neem oil cake, groundnut oil cake, black gram peels, green gram peels, chickling vetch peels/grass pea peels wheat bran, pearl millet residues, finger millet waste, broken rice, banana peels (BP), apple pomace (AP) and orange peels, banana peel (Musa paradisiaca L.; Family: Musaceae) was most suitable for pectinase biosynthesis (LSSF: 400 ± 21.45 Uml⁻¹; SSF: 6500 ± 1116.21 Ug⁻¹). Optimization of process parameters using one-variable-at-a-time method revealed that an initial medium pH of 5.0 at 30 °C and 96 h of incubation along with mannitol, urea, ammonium persulfate and isoleucine have positive influence on pectinase production. Further, K⁺ (1 mM), Riboflavin (10 mg 100 ml⁻¹) and gibberellic acid (0.025 %, w/v) supported in enhanced pectinase production. Banana peels and AP at a ratio of 9:1, moisture content of 90 % with 2 % inoculum size were suitable combinations for production of pectinase. Similarly, 96 h of soaking time with 0.1 M phosphate buffer (pH 6.5) is essential for pectinase recovery. Purification to electrophoretic homogeneity revealed 1.42 fold purification with 8.08 % yield and a molecular weight of 24.6 kDa. Scaling up of various fermentation parameters and supplementing BP as the substrate for pectinase production with better recovery could make it promising for different industrial exploitation.

Application of decolourized and partially purified polygalacturonase and α-amylase in apple juice clarification

Polygalacturonase and α-amylase play vital role in fruit juice industry. In the present study, polygalacturonase was produced by Aspergillus awamori Nakazawa MTCC 6652 utilizing apple pomace and mosambi orange (Citrus sinensis var mosambi) peels as solid substrate whereas, α-amylase was produced from A. oryzae (IFO-30103) using wheat bran by solid state fermentation (SSF) process. These carbohydrases were decolourized and purified 8.6-fold, 34.8-fold and 3.5-fold, respectively by activated charcoal powder in a single step with 65.1%, 69.8% and 60% recoveries, respectively. Apple juice was clarified by these decolourized and partially purified enzymes. In presence of 1% polygalacturonase from mosambi peels (9.87 U/mL) and 0.4% α-amylase (899 U/mL), maximum clarity (%T_660nm = 97.0%) of juice was attained after 2 h of incubation at 50 °C in presence of 10 mM CaCl₂. Total phenolic content of juice was reduced by 19.8% after clarification, yet with slightly higher %DPPH radical scavenging property.

Cardiac electrophysiological alterations in heart/muscle-specific manganese-superoxide dismutase-deficient mice: prevention by a dietary antioxidant polyphenol

Cardiac electrophysiological alterations induced by chronic exposure to reactive oxygen species and protective effects of dietary antioxidant have not been thoroughly examined. We recorded surface electrocardiograms (ECG) and evaluated cellular electrophysiological abnormalities in enzymatically-dissociated left ventricular (LV) myocytes in heart/muscle-specific manganese-superoxide dismutase-deficient (H/M-Sod2^−/−) mice, which exhibit dilated cardiomyopathy due to increased oxidative stress. We also investigated the influences of intake of apple polyphenols (AP) containing mainly procyanidins with potent antioxidant activity. The QRS and QT intervals of ECG recorded in H/M-Sod2^−/− mice were prolonged. The effective refractory period in the LV myocardium of H/M-Sod2^−/− mice was prolonged, and susceptibility to ventricular tachycardia or fibrillation induced by rapid ventricular pacing was increased. Action potential duration in H/M-Sod2^−/− LV myocytes was prolonged, and automaticity was enhanced. The density of the inwardly rectifier K⁺ current (I_K1) was decreased in the LV cells of H/M-Sod2^−/− mice. The AP intake partially improved these electrophysiological alterations and extended the lifespan in H/M-Sod2^−/− mice. Thus, chronic exposure of the heart to oxidative stress produces a variety of electrophysiological abnormalities, increased susceptibility to ventricular arrhythmias, and action potential changes associated with the reduced density of I_K1. Dietary intake of antioxidant nutrients may prevent oxidative stress-induced electrophysiological disturbances.

Antioxidant property and storage stability of quince juice phenolic compounds

The aim of this study was to characterise, in depth, 11 quince cultivars to provide data for their industrial processing into high-quality juices. Polyphenolic composition analyses (identification and quantification), soluble fraction of procyanidins, antioxidant capacity assays and cluster analysis were measured. A total of 19 kinds of polyphenolic compounds were the following in the juices: before and after 6 month of storage time at 4 and 30 °C. Large variations in polyphenolic compounds content were found as affected by quince cultivar. The total phenolics determined by UPLC ranged from 4045 mg to 721 mg/100 mL of juices, and was high correlated with antioxidant activity. During 6 months of storage a significant change was observed in the content of polyphenols, especially in procyanidins (37% and 55%, respectively). This result may be useful for the juice industry as a starting point for the development of tasty quince juices with high levels of bioactive compounds.

Chemometric classification of apple juices according to variety and geographical origin based on polyphenolic profiles

To characterize and classify apple juices according to apple variety and geographical origin on the basis of their polyphenol composition, the polyphenolic profiles of 58 apple juice samples belonging to 5 apple varieties and from 6 regions in Shaanxi province of China were assessed. Fifty-one of the samples were from protected designation of origin (PDO) districts. Polyphenols were determined by high-performance liquid chromatography coupled to photodiode array detection (HPLC-PDA) and to a Q Exactive quadrupole-Orbitrap mass spectrometer. Chemometric techniques including principal component analysis (PCA) and stepwise linear discriminant analysis (SLDA) were carried out on polyphenolic profiles of the samples to develop discrimination models. SLDA achieved satisfactory discriminations of apple juices according to variety and geographical origin, providing respectively 98.3 and 91.2% success rate in terms of prediction ability. This result demonstrated that polyphenols could served as characteristic indices to verify the variety and geographical origin of apple juices.

Interaction between plant polyphenols and the erythrocyte membrane

The purpose of these studies was to determine the effect of polyphenols contained in extracts from apple, strawberry and blackcurrant on the properties of the erythrocyte membrane, treated as a model of the biological membrane. To this end, the effect of the substances used on hemolysis, osmotic resistance and shape of erythrocytes, and on packing order in the hydrophilic region of the erythrocyte membrane was studied. The investigation was performed with spectrophotometric and fluorimetric methods, and using the optical microscope. The hemolytic studies have shown that the extracts do not induce hemolysis at the concentrations used. The results obtained from the spectrophotometric measurements of osmotic resistance of erythrocytes showed that the polyphenols contained in the extracts cause an increase in the resistance, rendering them less prone to hemolysis in hypotonic solutions of sodium chloride. The fluorimetric studies indicate that the used substances cause a decrease of packing order in the hydrophilic area of membrane lipids. The observations of erythrocyte shapes in a biological optical microscope have shown that, as a result of the substances' action, the erythrocytes become mostly echinocytes, which means that the polyphenols of the extracts localize in the outer lipid monolayer of the erythrocyte membrane. The results obtained indicate that, in the concentration range used, the plant extracts are incorporated into the hydrophilic area of the membrane, modifying its properties.

Individual astringency responsiveness affects the acceptance of phenol-rich foods

Sensory responses greatly vary between individuals, and individual sensory experiences influence eating behaviour. Three groups responding differently to phenolic astringent stimuli (Low Responding, LR, n=20, Medium Responding, MR, n=37 and High Responding, HR, n=20) were identified from a population of 77 subjects, based on the maintenance vs fluctuation of salivary characteristics after repeated stimulation of the masticatory and taste/somatosensory systems. The effect of LR, MR and HR status on perceived astringency and liking for phenol-containing apple, grape and carrot juices spiked with increasing tannic acid (TA) concentrations was examined. TA induced a greater increase of perceived astringency in HR, compared to MR and LR subjects. A decrease in liking for spiked juices was found in HR and to a lesser extent in MR and LR subjects. No significant differences were found comparing MR and LR groups for both astringency intensity and liking data. Liking for and familiarity with 37 food items, as well as preference for 14 phenol-rich foods and beverages, each paired with a less astringent counter-product, were also examined. An internal preference map was computed on liking scores and product subgroups were identified. An effect of LR/HR status was found for two food subgroups consisting of coffee without sugar, tea without sugar, raw chicory and milk chocolate, tea with sugar, coffee with sugar. LR subjects rated the products with the most astringency higher and those with the least astringency lower than did HR subjects. LR subjects also rated their familiarity with highly astringent products higher than did HR subjects. Thus, individual differences related to the physiological salivatory response to oral stimulations affect responses to astringent stimuli and can influence the overall acceptability of phenol-rich food items.

Aspergillus carbonarius polygalacturonases purified by integrated membrane process and affinity precipitation for apple juice production

Aspergillus carbonarius, when grown by submerged and solid-state fermentation, produces different molecular forms of polygalacturonase (PG; EC 3.2.1.15), among them a 42 kDa PG with a high specific activity of 7000 U/mg protein. When the enzymes were purified by integrated membrane process (IMP) and alginate affinity precipitation (AAP), the two processes concentrated different forms of the enzyme. The AAP process selectively purified and concentrated the high active PG whereas the IMP yielded different PGs and also amylase and protease. Evaluation of the AAP enzyme preparations for apple juice preparation under conditions usually employed commercially demonstrated that the high activity PG did not result in good juice clarity. With IMP processed enzymes, juice yields and clarity were similar to that obtained with commercial PG from A. niger.