Free sugars determination by HPLC in pineapple products

Free sugars have been determined by HPLC in fresh pineapple fruit, freshly extracted pineapple juice (home-made), pineapple juice concentrate (for industrial use), commercial pineapple juices and nectars. In natural samples, intermediate products and commercial juices the dominant sugar was sucrose, followed by fructose and glucose, both of which were found in similar concentrations. However, the sugar content of nectars analyzed was highly variable. The presence of maltose in nectar samples is a clear indication of the addition of sugars from corn syrup. We have found a fructose/glucose ratio close to 1, and the coefficient fructose plus glucose/sucrose close to 1, both of which are a good index of authenticity of pineapple juices.     

Survival of SA11 rotavirus in fresh fruit juices of pineapple, papaya, and honeydew melon

Survival of rotavirus in fresh fruit juices of papaya (Caraca papaya L.), honeydew melon (Cucumis melo L.), and pineapple (Ananas comosus [L.] Merr.) was studied. Clarified juices were prepared from pulps of ripe fruits and sterilized by ultrafiltration. One milliliter of juice from each fruit was inoculated with 20 microl of 1 x 10(6) PFU of SA11 rotavirus and sampled immediately (0-h exposure) and 1 and 3 h later at 28 degrees C. Mean viral titers in juices of papaya (pH 5.1) and honeydew melon (pH 6.3) at 1 and 3 h were not significantly different from titers at 0-h exposure. Mean viral titers in juices from pineapples with ripening color indices of 3 (pH 3.6) and 6 (pH 3.7) at 1-h exposure (color index 3: 4.0 +/- 1.7 x 10(4); color index 6: 2.3 +/- 0.3 x 10(5)) and 3-h exposure (color index 3: 1.1 +/- 0.4 x 10(4); color index 6:1.3 +/- 0.6 x 10(5)) were significantly lower than titers at 0-h exposure (color index 3: 5.7 +/- 2.9 x 10(5); color index 6: 7.4 +/- 1.3 x 10(5)). Virus titers in pineapple juices of color index 3 were significantly lower than titers of the virus in juices of index 6. In cell culture medium (pH 7.4), SA11 titer remained stable over 3 h at 28 degrees C. However, at pH 3.6, the virus titer was reduced to a level not significantly different from that of the virus in pineapple juice of color index 6 (pH 3.7). In conclusion, papaya and honeydew melon juices, in contrast to pineapple juice, have the potential to transmit rotavirus. Inactivation of SA11 virus in pineapple juice can be possibly attributed to low pH and constituent(s) in the juice.     

低醇菠萝汁饮料的发酵工艺条件研究

确定了制作低醇菠萝汁饮料所用菠萝发酵液的适用菌种和发酵条件。同时,采用顶空分析法检测了发酵前后菠萝发酵液中主要挥发性香气成分。结果显示,选择合适的酿酒酵母菌种在适当的发酵条件下发酵132h ,调配出的低醇菠萝汁饮料感官指标上佳,风味独特     

Analysis of sterols: a novel approach for detecting juices of pineapple,passionfruit, orange and grapefruit in compounded beverages

Direct GC/MS analysis of the hexane extracts of fruit juices provides an efficient means for demonstrating that very different sterol patterns exist in the juices of pineapple, passionfruit and the two citrus fruits, orange and grapefruit. Ergostanol and stigmastanol were found to be the sterol markers for pineapple juice, while passionfruit juice was characterised by the presence of an unidentified but unique sterol referred to as compound C. Juices of orange and grapefruit yielded very similar sterol profiles. They were readily distinguished from pineapple and passionfruit juices by a higher stigmasterol/campesterol ratio. Valencene/nootkatone response ratio in the hexane extracts was employed to aid in the differentiation of the two citrus juices. Matrix effects on the determination of sterol and sesquiterpenoid distributions were found to be insignificant. Although natural variation and absolute uniqueness of the sterol profile for each of the four fruit juices were not established due to the relatively small number of fruit samples examined, the results of several compounded beverages clearly point to the potential usefulness of sterol profiles for detecting juices of orange, grapefruit, pineapple and passionfruit in mixed drinks. © 1998 SCI.     

菠萝汁及其在加工过程中挥发性风味成分的变化

菠萝挥发性风味成分十分复杂,除受产地、品种、成熟度等因素影响外,加工时的热处理及发酵过程对香气的影响也非常明显。文中采用顶空固相微萃取(HS-SPME)技术与气相、气-质联用色谱结合,分析海南产冬菠萝鲜汁香气成分以及加热、发酵对香气成分的影响和变化。为菠萝的加工、工艺的改进、产品质量控制等提供有益资料。     

Stability of enterocin AS-48 in fruit and vegetable juices

Enterocin AS-48 is a candidate bacteriocin for food biopreservation. Before addressing application of AS-48 to vegetable-based foods, the interaction between AS-48 and vegetable food components and the stability of AS-48 were studied. Enterocin AS-48 had variable interactions with fruit and vegetable juices, with complete, partial, or negligible loss of activity. For some juices, loss of activity was ameliorated by increasing the bacteriocin concentration, diluting the juice, or applying a heat pretreatment. In juices obtained from cabbage, cauliflower, lettuce, green beans, celery, and avocado, AS-48 was very stable for the first 24 to 48 h of storage under refrigeration, and decay of activity was markedly influenced by storage temperature. In fresh-made fruit juices (orange, apple, grapefruit, pear, pineapple, and kiwi) and juice mixtures, AS-48 was very stable for at least 15 days at 4 degrees C, and bacteriocin activity was still detectable after 30 days of storage. Gradual and variable loss of activity occurred in juices stored at 15 and 28 degrees C; inactivation was faster at higher temperatures. In commercial fruit juices (orange, apple, peach, and pineapple) stored at 4 degrees C, the bacteriocin was completely stable for up to 120 days, and over 60% of initial activity was still present in juices stored at 15 degrees C for the same period. Commercial fruit juices stored at 28 degrees C for 120 days retained between 31.5% (apple) and 67.71% (peach) of their initial bacteriocin activity. Solutions of AS-48 in sterile distilled water were stable (120 days at 4 to 28 degrees C). Limited loss of activity was observed after mixing AS-48 with some food-grade dyes and thickening agents. Enterocin AS-48 added to lettuce juice incubated at 15 degrees C reduced viable counts of Listeria monocytogenes CECT 4032 and Bacillus cereus LWL1 to below detection limits and markedly reduced viable counts of Staphylococcus aureus CECT 976.     

Development and optimisation by means of sensory analysis of new beverages based on different fruit juices and sherry wine vinegar

BACKGROUND: Despite the long history of sherry wine vinegar, new alternatives of consumption are being developed, with the aim of diversifying its market. Several new acetic‐based fruit juices have been developed by optimising the amount of sherry wine vinegar added to different fruit juices: apple, peach, orange and pineapple. Once the concentrations of wine vinegar were optimised by an expert panel, the aforementioned new acetic fruit juices were tasted by 86 consumers. Three different aspects were taken into account: habits of consumption of vinegar and fruit juices, gender and age. RESULTS: Based on the sensory analysis, 50 g kg^?1 of wine vinegar was the optimal and preferred amount of wine vinegar added to the apple, orange and peach juices, whereas 10 g kg^?1 was the favourite for the pineapple fruit. Based on the olfactory and gustatory impression, and ‘purchase intent’, the acetic beverages made from peach and pineapple juices were the most appreciated, followed by apple juice, while those obtained from orange juice were the least preferred by consumers. CONCLUSION: New opportunities for diversification of the oenological market could be possible as a result of the development of this type of new product which can be easily developed by any vinegar or fruit juice maker company. © 2012 Society of Chemical Industry     

Stability of Pycnogenol® as an ingredient in fruit juices subjected to in vitro gastrointestinal digestion

BACKGROUND: The enrichment of fruit juices with concentrated polyphenolic extracts is an expedient strategy to compensate possible phenolic loss through gastrointestinal processing. Pycnogenol®, a standardised procyanidin‐rich extract from pine bark, has been proposed as a potential candidate for polyphenol enrichment of foods. In this study the effects of in vitro digestion on the phenolic profile of fruit juices enriched with Pycnogenol® were investigated. RESULTS: After in vitro digestion the level of detectable total phenolic compounds (expressed as gallic acid equivalent) was higher in both pineapple and red fruit juices enriched with Pycnogenol® than in non‐enriched commercial juices. Five phenolic monomeric compounds were identified by high‐performance liquid chromatography, namely chlorogenic acid, caffeic acid, ferulic acid, gallic acid and taxifolin, the last two being predominant. In vitro digestion of both Pycnogenol®‐enriched pineapple and red fruit juices led to a significant (P < 0.05) increase in detectable chlorogenic and ferulic acids, indicating that hydrolysis of more complex molecules occurs. On the other hand, in vitro digestion of non‐enriched juices was associated with a decrease in gallic and caffeic acids in pineapple juice and with a decrease in ferulic acid in red fruit juice. In no case did in vitro digestion increase the amount of detectable phenolic compounds in non‐enriched juices. CONCLUSION: The stability of Pycnogenol® after in vitro gastrointestinal digestion makes it a good choice for phenolic enrichment of fruit juices. Copyright © 2010 Society of Chemical Industry     

Inactivation of Escherichia coli and Listeria innocua in kiwifruit and pineapple juices by high hydrostatic pressure

Escherichia coli and Listeria innocua in kiwifruit and pineapple juices were exposed to high hydrostatic pressure (HHP) at 300 MPa for 5 min. Both bacteria showed equal resistance to HHP. Using low (0 degrees C) or sub-zero (-10 degrees C) temperatures instead of room temperature (20 degrees C) during pressurization did not change the effectiveness of HHP treatment on both bacteria in studied juices. Pulse pressure treatment (multiple pulses for a total holding time of 5 min at 300 MPa) instead of continuous (single pulse) treatment had no significant (p>0.05) effect on the microbial inactivation in kiwifruit juice; however, in pineapple juice pulse treatment, especially after 5 pulses, increased the inactivation significantly (p<0.05) for both bacteria. Following storage of pressure-treated (350 MPa, 20 degrees C for 60 s x 5 pulses) juices at 4, 20 and 37 degrees C up to 3 weeks, the level of microbial inactivation further increased and no injury recovery of the bacteria were detected. This work has shown that HHP treatment can be used to inactivate E. coli and L. innocua in kiwifruit and pineapple juices at lower pressure values at room temperature than the conditions used in commercial applications (>400 MPa). However, storage period and temperature should carefully be optimized to increase the safety of HHP treated fruit juices.     

Optimization of Tropical Juice Composition for the Spanish Market

ABSTRACT: The optimal proportions of 3 concentrate juices, passion fruit, pineapple, and banana, mixed with white grape juice were investigated by preferences mapping techniques. The objective was to establish the minimum level of each concentrated tropical juice necessary to add to a white grape juice so that it would be perceived as a mixture by consumers. A nonverbal test, analyzed by proxscal, demonstrated that decreasing an amount of concentrate juice from 4% to 1% would have no statistically significant effect on flavor recognition by consumers. Internal preference map for flavor and color acceptability revealed that a commercial mix of pineapple with white grape juice mix (used as control) was the most accepted juice, closely followed by an experimental mix of passion fruit with white grape juice. Principal component analysis revealed the importance of overall taste, overall odor, acid fruit aroma, acid taste, and pulp in the acceptability of these 3 juices.     

The formation of 2,5-dimethyl-4-hydroxy-2H-furan-3-one by cell-free extracts of Methylobacterium extorquens and strawberry (Fragaria × ananassa cv. Elsanta)

The formation of 2,5-dimethyl-4-hydroxy-2H-furan-3-one (DMHF), using the bacterial cells of Methylobacterium extorquens (strain with CABI registration number: IMI 369321) and strawberry cells (Fragaria × ananassacv. Elsanta), was studied. A combined mixture of the bacterial cell-free extract plus the strawberry extract was used as the enzymatic source. The pH of all the experimental aliquots was pH 6.0. The studied substrates were short-chain alcohols, carbohydrates and one amino acid. DMHF was analyzed by HPLC with UV detection at 280 nm. When 1,2-propanediol, 1-propanol, sucrose and fructose were used as substrates, the best production rates of DMHF were achieved, having a combined mixture of the bacterium and strawberry (minus the achenes) as the enzymic source. On the other hand, glucose, 1,2-propanediol, 2-propanol and fructose were the best substrates for the production of DMHF when a combined mixture of the bacterium and achenes served as the enzymic source. All results were obtained by comparing the production of DMHF from the strawberry extract alone and the bacterium plus the strawberry, without the achenes (in the first case) and the production of DMHF from the achene extract alone and the bacterium plus the achenes (in the second case). Moreover, the dehydrogenation activities of these three enzyme sources were determined by measuring the absorption of NADH at 340 nm. The substrate which was used for this series of the experiments was 1,2-propanediol. These results indicate the undoubted cooperation between the plant and the bacterial cells. This paper reports, for the first time, the formation of DMHF by bacterial and plant cell-free extracts.     

Prevalence, concentration, spoilage, and mitigation of Alicyclobacillus spp. in tropical and subtropical fruit juice concentrates

The presence of Alicyclobacillus in fruit juices and concentrates poses a serious problem for the juice industry. This study was undertaken to determine the (i) prevalence, concentration, and species of Alicyclobacillus in tropical and subtropical concentrates; (ii) efficacy of aqueous chlorine dioxide in reducing Alicyclobacillus spp. spores on tropical and subtropical fruit surfaces; and (iii) fate of and off-flavor production by Alicyclobacillus acidoterrestris in mango and pineapple juices. One hundred and eighty tropical and subtropical juice concentrates were screened for the presence and concentration of Alicyclobacillus spp. If found, the species of Alicyclobacillus was determined by 16S rDNA sequencing and analysis with NCI BLAST. Of these samples, 6.1% were positive for Alicyclobacillus, and nine A. acidoterrestris strains and two Alicyclobacillus acidocaldarius strains were identified. A five-strain cocktail of Alicyclobacillus spp. was inoculated onto the surface of fruits (grapefruit, guava, limes, mangoes, oranges and pineapple), which were then washed with 0, 50, or 100 ppm aqueous chlorine dioxide. Significant reductions due to chlorine dioxide were only seen on citrus fruits. A five-strain cocktail of A. acidoterrestris was inoculated into mango and pineapple juices. Microbial populations were enumerated over a 16-day period. Aroma compounds in the juice were analyzed by GC-olfactometry (GC-O) and confirmed using GC-MS. GC-O of mango juice identified previously reported medicinal/antiseptic compounds. GC-O of pineapple juice revealed an unexpected “cheese” off-aroma associated with 2-methylbutyric acid and 3-methylbutyric acid.     

Analysis of Aliphatic Organic Acids in Commercial Fruit Juices by Capillary Electrophoresis with Indirect UV Detection: Application to Differentiation of Fruit Juices

A simple, cheap, and reliable capillary zone electrophoresis (CZE) method with indirect UV detection to determine the main organic acids in several fruit juices has been developed in this work. The parameters affecting CZE separation including the chromophore reagent (2,6-pyridinedicarboxylic acid, PDC) concentration and pH in background electrolyte (BGE), temperature, and applied voltage were studied. The analytical parameters of the method as linearity, precision, and detection and quantification limits were also investigated. The proposed method was applied to the evaluation of organic acid contents of commercial fruit juices from apple, grape, mandarin, orange, and pineapple and compared with the levels allowed by European legislation. A chemometric technique such as linear discriminant analysis (LDA) was also applied to differentiate fruit juices based on CZE data. This simple and reliable developed procedure allows a rapid control of adulteration of high-value commercial fruit juices, which constitutes an important tool for authenticity texting in food industries and regulatory agencies.     

2,5-Dimethyl-4-hydroxy-3(2H)-furanone as a secondary metabolite from D-fructose-1,6-diphosphate metabolism by Zygosaccharomyces rouxii

2,5-Dimethyl-4-hydroxy-3(2H)-furanone (DMHF) is an important aroma compound found in many fruits such as strawberries and pineapples and it is also produced by the soy-sauce-fermenting yeast Zygosaccharomyces rouxii after the addition of d-fructose-1,6-diphosphate to yeast-peptone-dextrose nutrient media. Dilute DMHF solutions exhibit a strawberry-like flavor while DMHF concentrates have a caramel-like aroma. In media containing D-fructose-1,6-diphosphate as the sole carbon source, growth of Z. rouxii and formation of DMHF were not observed. Although Z. rouxii cells grew in media with D-glucose as the sole carbon source, DMHF was only produced when media were supplemented with D-fructose-1,6-diphosphate. The DMHF concentration always correlated with the yeast cell count and D-fructose-1,6-diphosphate concentration. Addition of CaCl2 (up to 50 g.l(-1)) led to a higher DMHF concentration. Addition of Na2SO3 reduced the growth of Z. rouxii and inhibited DMHF formation. The amount of DMHF formed by Z. rouxii was not significantly affected by the addition of KH2PO4. DMHF concentrations of 5 and 10 g.l(-1) partially and completely inhibited the growth of Z. rouxii cells, respectively. Only the singly labeled furanone was formed after the addition of 1-13C-D-fructose-1,6-diphosphate to the medium. However, unlabeled DMHF was formed in the presence of (13)C(6)-D-glucose. Therefore, the carbons of the furanone originate exclusively from exogenously supplied D-fructose-1,6-diphosphate as no exchange with the internal pool of D-fructose-1,6-diphosphate occurs. This implies that DMHF is a secondary metabolite of Z. rouxii formed from D-fructose-1,6-diphosphate. We assume that at least the first step of the metabolism of D-fructose-1,6-diphosphate takes place in the cell wall or membrane of the yeast.     

Heat-resistant fungi in Nigerian heat-processed fruit juices

Sixty packaged heat-processed Nigerian fruit juices consisting of 15 each of mango, orange, pineapple and tomato, were screened for the presence of heat-resistant fungi after storage at approximately 28°C for 30 days. The resulting fungal growth was purified on potato dextrose agar. Approximately 17% of all the fruit juice packages and 27% of mango and tomato juices contained heat-resistant fungi. These were identified as Paecilomyces variotii, Aspergillus tamarii, A. flavus and A. ochraceus , the latter being predominant.     

发酵前澄清处理对菠萝酒品质的影响

为探讨发酵前果汁澄清处理对菠萝酒高级醇和挥发性酯类香气成分形成的影响,利用壳聚糖对菠萝汁进行澄清处理,分别对不同澄清度的菠萝汁调整可溶性固形物为20°Bx、pH3.5,接入0.03%的活性干酵母于15℃下发酵。结果表明,菠萝汁未经过澄清处理,发酵后酒的高级醇含量达0.45 g/L左右,当果汁透光率在80%时,高级醇含量降至0.27 g/L。GC-MS检测结果表明,菠萝酒的主要香气成分是辛酸乙酯和癸酸乙酯,清汁发酵菠萝酒的辛酸乙酯和癸酸乙酯相对含量分别为28.29%和38.53%,较原汁发酵的菠萝酒分别提高了8.92%和18.45%,表明发酵前对菠萝汁进行澄清处理有利于菠萝酒香气的形成。     

Heat resistance of Neosartorya fischeri in various juices

Heat resistance of Neosartorya fischeri was studied in three different juices (apple, pineapple and papaya). The optimum heat activation temperature and time for the ascospores of the N. fischeri (growth for 30 days at 30 °C) was 85 °C for 10 min. Of the three juices tested, apple juice exhibited maximum 1/k values at 80, 85 and 90 °C (208.3, 30.1 and 2.0 min, respectively). The 1/k values for papaya juice (129.9, 19.0 and 1.9 min) and pineapple juice (73.5, 13.2 and 1.5 min) decreased with acidity and °Brix/acidity (ratio) level. The Z^* values for apple, papaya and pineapple juices were 5, 5.5 and 5.9 °C, respectively. The sterilization F values (4-log reduction) for apple, pineapple and papaya juices were 56.3, 38.0 and 7.2 s, respectively. Considering the thermal treatments commercially applied to pineapple (96 °C/30 s) and apple juices (95 °C/30 s), it is concluded that such treatments will not guarantee that less than 1 ascospore in each set of 10³ packs survive. Only the treatment applied to papaya juice (100 °C/30 s) will be sufficient because the F value is less than 30 s.     

Use of a multivariate approach to assess the incidence of Alicyclobacillus spp. in concentrate fruit juices marketed in Argentina: results of a 14-year survey

The purpose of this study was to determine the incidence of Alicyclobacillus spp. in fruit/vegetable juices (concentrated pulps and clarified and non-clarified juices) marketed in Argentina between 1996 and 2009.The presence of Alicyclobacillus was determined in a total of 8556 samples of fruit and vegetable juices (apple, pear, grape, peach, blend of juices, tangerine, pineapple, orange, mango, plum, guava, apricot, lemon, banana, kiwi, carrot, strawberry, grapefruit, and beetroot) collected in seven Argentinean provinces. Multiple factor analysis (MFA) was carried out on a data matrix that contained the percentage of positive samples, type of juice, raw material and production year.Except for kiwi and orange, Alicyclobacillus was found in juices from all the evaluated raw materials. The highest percentage of positive samples was found for beetroot, strawberry, banana, peach, mango, carrot and plum juices. The percentage of positive samples for these juices ranged from 100% to 24%.Furthermore, the application of multivariate techniques provided an insight on the relationship between the incidence of Alicyclobacillus and production variables. This approach enabled the identification of the most relevant variables that increased the percentage of positive samples among the juices, which could help in developing strategies to avoid the incidence of this bacterium.By means of hierarchical cluster analysis seven groups (clusters) of juices which showed different percentages of positive samples for Alicyclobacillus spp. were identified. This analysis showed that pineapple, peach, strawberry, mango and beetroot juices had higher rates of positivity for Alicyclobacillus than the rest of the evaluated juices. MFA analysis also showed that some clear relationships could be highlighted between the percentage of samples positive for Alicyclobacillus and five types of fruit juices (strawberry, beetroot, grapefruit, pineapple and mango). It was observed that a large proportion of juices produced in 2000, 2005 and 2008 were located in clusters with higher incidence of Alicyclobacillus spp., whereas a larger proportion of clarified concentrate juice and concentrate pulp samples showed higher probability of incidence of Alicyclobacillus in these products. Data presented in this study brings a contribution to the ecology of Alicyclobacillus in fruit/vegetable juices marketed in Argentina. This information would be useful to enhance the microbiological stability of fruit juices regarding the presence of Alicyclobacillus spp.     

OPTIMUM QUALITY PARAMETERS OF MUSCADINE GRAPE JUICES, BEVERAGES, AND BLENDS

Cold- and hot-pressed juices from black and bronze muscadine grapes were tested to determine optimum Brix/acid ratios, optimum juice level in beverages, and optimum blend ratios with other fruit juices. The optimum Brix/acid ratio, regardless of cultivar or process, was approxi-mately 30 with. an acceptable range from 25. to 35. Increased sweetness due to sugar addition was perceptible, even when balanced with addition of acid. Optimum dilution was dependent upon cultivar and process. Red hot-pressed juice was most acceptable at a 25% juice level, when Brix/acid was adjusted to 30. Optimum blends with fruit juices varied with muscadine juice color and process. Best blends were muscadine juices and commercial grape juices, orange juice, and pineapple juice. Muscadine grape-grapefruit juice blends had poor acceptability.     

Stability of black carrot anthocyanins in various fruit juices and nectars

Fruit juices (apple, grape, orange, grapefruit, tangerine and lemon) and nectars (apricot, peach and pineapple) were coloured with black carrot juice concentrate and stability of black carrot anthocyanins in these matrices was studied during heating at 70–90 °C and storage at 4–37 °C. Anthocyanin degradation, in all coloured juices and nectars, followed first-order reaction kinetics. During heating, black carrot anthocyanins in apple and grape juices showed higher stability than those in citrus juices at 70 and 80 °C. High stability was also obtained for the anthocyanins in peach and apricot nectars at these temperatures. Black carrot anthocyanins were the least stable in orange juice during both heating and storage. During storage, degradation of anthocyanins was very fast at 37 °C, especially in pineapple nectar. Refrigerated storage (4 °C) markedly increased the stability in all samples. Activation energies for the degradation of black carrot anthocyanins in coloured juices and nectars ranged from 42.1 to 75.8 kJ mol⁻¹ at 70–90 °C and 65.9–94.7 kJ mol⁻¹ at 4–37 °C.