胡柚汁益生菌发酵挥发性风味特征

利用筛选到的2株乳酸菌植物乳杆菌L1（Lactobacillus plantarum）和发酵乳杆菌L2（L. fermentum）对胡柚汁发酵,研究其挥发性风味成分及其变化特征。采用静态-顶空固相微萃取和气相色谱-质谱联用分析方法,测定胡柚汁经此2种乳酸菌发酵后挥发性风味物质组分和相对含量,运用主成分分析法对发酵胡柚汁样品挥发性风味成分进行分析,并采用电子鼻对乳酸菌发酵胡柚汁的香气进行检测。结果表明,胡柚汁经发酵后共鉴定出79种挥发性风味物质,其中醇类20种、烯烃类15种、烷烃类12种、酮类10种、醛类5种、酯类2种、其他类15种,挥发性风味物质分别为59、36种和35种。经乳酸菌发酵后,胡柚汁挥发性风味化合物种类均增加,并检测到了胡柚汁中未被检测到的酯类、醇类、酮类和烷烃类相对含量显著提高,醛类物质相对含量大量降低。主成分分析找出了影响4个样品特征风味组分在主成分中的差异,表明主成分分析法可实现对乳酸菌发酵胡柚汁特征风味差异性的评价。电子鼻分析表明胡柚汁经不同乳酸菌发酵后风味差异显著。研究结果揭示了胡柚汁乳酸菌饮料的风味特征并为产品质量评定等提供依据。     

Volatile organic compounds in the aril juices and seeds from selected five pomegranate (Punica granatum L.) cultivars

A study was conducted to investigate the distribution of volatile organic compounds in the juice and seed of the most popular five pomegranate cultivars (“Ek?i,” “Devedi?i,” “Hicaz,” “Kat?rba??,” and “Keben”) in Turkey. The volatile organic compounds were analyzed using solid phase micro-extraction and gas chromatography–mass spectrometry. A total of 60 volatile organic compounds, belonging to six chemical groups including aldehydes, alcohols, esters, terpenes, ketones, acids, and phenol were identified. There were 11 volatile organic compounds (1-hexanol, [Z]-3-hexen-1-ol, 1-octanol, α-terpineol, β-myrcene, limonene, [E]-α-bergamotene, β-caryophyllene, hexanal, [E]-2-hexenal, and guaiacol) common to all five pomegranate juices and seeds. Hexalin, phenylacetaldehyde, 3-methyl butanal, and methyl-(1-methylethenyl) benzene were found in seeds only. According to discriminant analysis based on Eigenvalues, volatile organic compounds recovered in the juices could be used to discriminate and classify the pomegranate cultivars. “Devedi?i” and “Hicaz” were the most promising cultivars with respect to the largest volatile organic compounds, high total soluble solid and deep red color.     

Chemical Characterization of Orange Juice from Trees Infected with Citrus Greening (Huanglongbing)

ABSTRACT: The effects due to Candidatus Liberibacter infection, commonly called citrus greening or Huanglongbing (HLB), on volatile and nonvolatile components of orange juices, OJ, were examined using GC-MS and high-performance liquid chromatography (HPLC). HLB symptomatic, asymptomatic, and control “Hamlin” and “Valencia” oranges were harvested from December to May during the 2007 to 2008 harvest season. Brix/acid levels in control and asymptomatic juices were similar but symptomatic juices were as much as 62% lower than control juices. No bitter flavanone neohesperidosides were detected and polymethoxyflavone concentrations were well below bitter taste thresholds. Limonin concentrations were significantly higher (91% to 425%) in symptomatic juice compared to control but still below juice bitterness taste thresholds. Juice terpenes, such as γ-terpinene and α-terpinolene, were as much as 1320% and 62% higher in symptomatic juice than control. Average ethyl butanoate concentrations were 45% lower and average linalool was 356% higher in symptomatic Valencia OJ compared to control. Symptomatic Valencia OJ had on average only 40% the total esters, 48% the total aldehydes, and 33% as much total sesquiterpenes as control juice. Total volatiles between control and symptomatic juices were similar due to elevated levels of alcohols and terpenes in symptomatic juice. There were no consistent differences between asymptomatic and control juices. The chemical composition of juice from HLB/greening symptomatic fruit appears to mimic that of juice from less mature fruit. The reported off-flavor associated with symptomatic juices probably stem from lower concentrations of sugars, higher concentrations of acid as all known citrus bitter compounds were either below taste thresholds or absent.     

Influence of pre- and post-harvest factors and processing on the levels of furocoumarins in grapefruits (Citrus paradisi Macfed.)

The changes in the levels of three furocoumarins such as dihydroxybergamottin (DHB), paradisin A and bergamottin in Rio Red and Marsh White cultivars of grapefruits were monitored from November to May. The levels of DHB and bergamottin in both varieties of grapefruits decreased as the season progressed except for the bergamottin in Marsh White grapefruit. Influence of growing location, processing and storage on the levels of these compounds were also evaluated. Among the varieties the highest levels of DHB (2.266 μg/ml) and bergamottin (2.411 μg/ml) were found in Flame grapefruit grown in Florida. The highest level of paradisin A was found in Rio Red grapefruit grown in California and the lowest levels were observed in Rio Red grapefruit grown organically in Texas. Hand squeezed juice contained 1.98, 1.06 and 3.03-fold more DHB, paradisin A and bergamottin, respectively as compared to processed juice. The levels of furocoumarins showed a decreasing trend in all the juices with progress of storage. Levels of furocoumarins were more in cartons container than the cans and cardboard container juices.     

Variation in Furanocoumarin Content and New Furanocoumarin Dimers in Commercial Grapefruit (Citrus paradisi Macf.) Juices

ABSTRACT: Grapefruit ( Citrus paradisi Macf.) sales and crop value have declined during the last decade. One reason is consumer concerns about possible drug interactions. Coadministered grapefruit increases the bioavailability of some medicines because it contains furanocoumarins that inhibit an intestinal enzyme (cytochrome P450-3A4 or CYP3A4) that normally metabolizes these drugs. Only drugs metabolized by intestinal CYP3A4 are significantly affected when taken with grapefruit juice, but the magnitude of the effect varies considerably between studies, indicating that there are differences in the amount of components responsible for CYP3A4 inhibition in commercial grapefruit juices. Content variation of 6,7-dihydroxybergamottin, bergamottin, and 6 furanocoumarin dimers were determined for 58 commercial grapefruit juices collected over 2 seasons. The content of 6,7-dihydroxybergamottin ranged from 0.2 to 7.7 ppm in all juices tested, and averaged 1.8 ± 0.85 ppm in the red compared with 2.9 ± 2.07 ppm for white grapefruit juices. Bergamottin content ranged from 1.6 to 7.3 ppm for all juices and averaged 3.4 ± 0.98 and 4.2 ± 1.23 ppm and in red and white grapefruit juices, respectively. Only 1 dimer varied significantly between the red and white juice types. Dihydroxybergamottin and 2 dimer compounds were significantly lower in shelf-stable or nonrefrigerated products compared with refrigerated products whereas bergamottin and 1 dimer compound occurred at higher levels in the shelf-stable products. Individual measured dimer compounds varied up to 60-fold in all juices, but the sum of all 6 dimers varied only 14-fold. The clinical significance in terms of CYP3A4 inhibition is uncertain. The presence of 3 new furanocoumarin dimers are also reported.     

Limonoids and Flavonoids in Juices of Oroblanco and Melogold Grapefruit Hybrids

Oroblanco and Melogold are hybrids obtained from pummelo and grapefruit. Limonoids and flavonoids in both juices were analyzed. Oroblanco and Melogold juices contained low concentrations of limonoid glucosides, an average of 99 and 59 ppm, respectively. However, they contained relatively high concentrations of bitter limonoid aglycones, limonin and nomilin, at levels above the limonin bitterness threshold. For comparison, limonoid glucosides in juices of grapefruit, another pummelo hybrid, were also analyzed. Limonin glucoside was the major limonoid glucoside in all juices analyzed. Nomilin glucoside and nomilinic acid glucosides were also present. Oroblanco and Melogold juices contained bitter flavonoids normally found in grapefruit and pummelo including naringin, neohesperidin and poncerin in total amount of 440 ppm in Oroblanco juice and 495 ppm in Melogold juice. They also contained several other nonbitter flavonoids found in grapefruit.     

Effect of low-temperature, high-pressure treatment on the survival of Escherichia coli O157:H7 and Salmonella in unpasteurized fruit juices

The destructive effect of high pressure (615 MPa) combined with low temperature (15 degrees C) on various strains of Escherichia coli O157:H7 and various serovars of Salmonella in grapefruit, orange, apple, and carrot juices was investigated. The three-strain cocktail of E. coli O157:H7 (SEA13B88, ATCC 43895, and 932) was found to be most sensitive in grapefruit juice (8.34-log reduction) and least in apple juice (0.41-log reductions) when pressurized at 615 MPa for 2 min at 15 degrees C. Correspondingly, no injured survivor was detected in grapefruit and carrot juices under similar treatment conditions. No Salmonella spp. were detected in a 2-min pressure treatment (615 MPa, 15 degrees C) of grapefruit and orange fruit juices. Except for Enteritidis, all four serovars tested in the present study have viability loss of between 3.92- and 5.07-log reductions when pressurized in apple juice at 615 MPa for 2 min at 15 degrees C. No injured cells were recovered from grapefruit and orange juices, whereas the same treatment demonstrated reduction in numbers of Salmonella serovars Agona and Muenchen in apple juices and to a lesser extent with Typhimurium, Agona, and Muenchen in carrot juice. The present study demonstrated that low-temperature, high-pressure treatment has the potential to inactivate E. coli O157:H7 strains and different Salmonella spp. in different fruit juices.     

Survival of Lactobacillus plantarum in model solutions and fruit juices

The aim of the work was to study the survival of Lactobacillus plantarum NCIMB 8826 in model solutions and develop a mathematical model describing its dependence on pH, citric acid and ascorbic acid. A Central Composite Design (CCD) was developed studying each of the three factors at five levels within the following ranges, i.e., pH (3.0-4.2), citric acid (6-40 g/L), and ascorbic acid (100-1000 mg/L). In total, 17 experimental runs were carried out. The initial cell concentration in the model solutions was approximately 1 × 10⁸ CFU/mL; the solutions were stored at 4 °C for 6 weeks. Analysis of variance (ANOVA) of the stepwise regression demonstrated that a second order polynomial model fits well the data. The results demonstrated that high pH and citric acid concentration enhanced cell survival; one the other hand, ascorbic acid did not have an effect. Cell survival during storage was also investigated in various types of juices, including orange, grapefruit, blackcurrant, pineapple, pomegranate, cranberry and lemon juice. The model predicted well the cell survival in orange, blackcurrant and pineapple, however it failed to predict cell survival in grapefruit and pomegranate, indicating the influence of additional factors, besides pH and citric acid, on cell survival. Very good cell survival (less than 0.4 log decrease) was observed after 6 weeks of storage in orange, blackcurrant and pineapple juice, all of which had a pH of about 3.8. Cell survival in cranberry and pomegranate decreased very quickly, whereas in the case of lemon juice, the cell concentration decreased approximately 1.1 logs after 6 weeks of storage, albeit the fact that lemon juice had the lowest pH (pH ~ 2.5) among all the juices tested. Taking into account the results from the compositional analysis of the juices and the model, it was deduced that in certain juices, other compounds seemed to protect the cells during storage; these were likely to be proteins and dietary fibre In contrast, in certain juices, such as pomegranate, cell survival was much lower than expected; this could be due to the presence of antimicrobial compounds, such as phenolic compounds.     

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.     

固相微萃取结合GC-O分析两种葡萄柚汁香气成分

固相微萃取(solid phase microextraction,SPME)-气质联用(gas chromatography-mass spectrometry,GC-MS)对白葡萄柚和红葡萄柚汁的挥发性成分进行分析,分别检测出45种和41种挥发性成分,相对含量分别为84.43%和89.16%。通过气相色谱质谱联用-嗅觉检测法(gas chromatography-olfactometry,GC-O)分析发现两种葡萄柚汁中呈现气味的化合物分别有20种和21种,白葡萄柚中香气较强的组分是3-羟基-丁酸乙酯,乙酸香叶酯和RI=1006(水果香、清香、松油),红葡萄柚中有较强气味的是2-甲基丙酸乙酯、2-甲基丁酸乙酯、反式-2-己烯-1-醇、庚醛、1-辛烯-3-醇、α-松油烯、3-羟基己酸乙酯、香芹酮和3种未知化合物(RI=971、1156、1390)。气味轮廓分析发现白葡萄柚以果香为主,红葡萄柚以木头/树叶味为主。     

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.     

Shelf Life and Quality of Freshly Squeezed, Unpasteurized, Polyethylene-Bottled Citrus Juice

Florida's chief orange and grapefruit cultivars were used to produce five freshly squeezed, unpasteurized, polyethylene-bottled juices using commercial conditions. Juices were stored at different temperatures. Shelf life depended primarily on storage temperature: ?1.7°C, 20–23 days; 1.1°C, 16–22 days; 4.4°C, 10–16 days; and 7.8°C, 5–8 days. Staleness was the primary off-flavor limiting shelf life at the three lower temperatures while spoilage with diacetyl was primarily responsible at 7.8°C. At the three lower temperatures, microbial counts generally decreased markedly during storage, while at 7.8°C, an increase was generally noted. Ascorbic acid retention after 2 wk of storage at the three lowest storage temperatures was about 91–93% for two orange juices and 86–88% for the grapefruit juice.     

A review of limonin in grapefruit (Citrus paradisi) juice,its relationship to flavour,and efforts to reduce it

Ever since limonin was first discovered in grapefruit (Citrus paradisi Macf) juice in 1965 and found responsible for significantly contributing to bitterness in the juice, a great deal of research has been directed towards understanding its role therein. Information is presented relative to limonin's chemical determination, taste threshold and content in grapefruit juice, and to relevant legislation. Also considered are (1) several factors affecting the limonin content of grapefruit juice (2) the effect of limonin content on sensory flavour in grapefruit juice (3) the interaction between the Brix: acid ratio and limonin content in affecting grapefruit juice flavour and (4) methods for reducing limonin in citrus juices generally. Finally, recommendations for future studies on limonin in grapefruit juice are reviewed.     

Comparative Effects of Three Types of Florisil Treatments on Flavanone Glycosides and Minerals of Processed Grapefruit Juice

Treatment of single-strength grapefruit juice with three types of Florisil (B-Florisil, C-Florisil, and K-Florisil) resulted in a simultaneous reduction in citric acid and bitter compounds (limonin and naringin). Ascorbic acid and sugar concentrations were not altered as a result of the treatment. Juices treated with B- and C-Florisils had high concentrations of sodium, whereas juice treated with K-Florisil had no change in sodium concentration. Elevated potassium was found in juice treated with K-Florisil, but potassium concentrations were diminished in juices treated with B- and C-Florisils in comparison to the control juice. Juices treated with all three types of Florisils had increased amounts of magnesium, iron, and silicon but phosphorus and strontium were reduced.     

杨梅干红酒的酒质优化

以离子色谱、紫外可见分光光度法和气质联用等技术对乌酥梅和荸荠品种杨梅原汁的基本成分 ,以及杨梅干红优化实验样品的Aλmax值和主要芳香成分的相对含量进行了分析和研究。结果表明 ,荸荠品种杨梅原汁的酸度和色泽特性较适合杨梅干红的酿造 ,LAVIND4 7活性酿酒干酵母是优良的主酵菌种 ,采用 3%浓度的铝离子海藻酸固定化细胞 ,于 30℃发酵可获得较好的酒色和风味。     

Inhibition of loquat enzymatic browning by sulfhydryl compounds

The effectiveness of a series of sulfhydryl compounds in inhibiting polyphenoloxidase (PPO) activity in a model system (chlorogenic acid solution) and in loquat juices was evaluated. Application of different concentrations of sulfhydryl compounds to chlorogenic acid solution and fresh loquat juice showed that l-cysteine appeared to be an effective browning inhibitor. The required concentration of l-cysteine for 90% browning inhibition depended on loquat cultivars, and ranged from 0.6 mM for “Nagasaki” to 2.0 mM for “Yukawa” or “Toi”. The difference may be due to the concentration of endogenous phenolic compounds inherent in each cultivar. The results from oxidized product analysis by loquat PPO implied that the mechanism of browning inhibition by thiols involved the formation of a thiol-conjugated reaction product.     

Sensory quality and compositional characteristics of blackcurrant juices produced by different processes

Effects of enzymatic and non-enzymatic juice pressing on key orosensory and chemical quality factors of blackcurrant juices were studied in laboratory scale using berries of five different cultivars (Mortti, Mikael, Marski, Ola and Breed15). Enzymatic processing increased the juice yield by 10–22% and the content of various phenolic compounds in juice by 4–10-fold as compared to the non-enzymatic process. Higher intensity of the mouth-drying astringency of the enzyme-aided juice was the most significant orosensory difference between the processes. Juices of different blackcurrant cultivars varied in sweetness, sourness and bitterness. The most intensive sensory attributes of the juices were sourness and puckering astringency regardless of processing method. They correlated positively with each other and were contributed by acid content and pH. In enzyme-aided juices, the contents of flavonol glycosides and hydroxycinnamic acids were associated with mouth-drying astringency, and sugar/acid ratio correlated with sweetness. These correlations were less clear in non-enzyme juices possibly due to lower content of phenolic compounds and the high content of pectin.     

Analysis of grapefruit sulphur volatiles using SPME and pulsed flame photometric detection

Sulphur volatiles are major factors in the perceived aroma of grapefruit juice, GFJ. The objective of this study was to develop a procedure to concentrate, separate, identify and quantify the major volatile sulphur compounds, VSC’s, in grapefruit juices. SPME parameters such as headspace atmosphere, fibre coating, extraction time and temperature were evaluated. High resolution capillary GC using ZB-5, DB-Wax and PLOT columns coupled with pulsed flame photometric detection, PFPD, were employed for separation and detection. Thirteen sulphur volatiles were identified including; hydrogen sulphide, sulphur dioxide, methanethiol, dimethyl sulphide, carbon disulphide, dimethyl disulphide, 2-methyl thiophene, 3-methyl thiophene, methional, dimethyl trisulphide, 3-mercaptohexylacetate, 2,8-epithio-cis-p-menthane and 1-p-menthene-8-thiol. Five additional VSC’s were tentatively identified. Canned reconstituted GFJ had more total sulphur volatiles and a greater number than fresh GFJ. Hydrogen sulphide comprised over 80% of total sulphur volatiles in fresh GFJ but only 5% in canned GFJ.     

Reduction of bitterness and acidity in grapefruit juice by adsorptive processes

By choosing an appropriate adsorbent, the bitter principles (naringin and limonin) and titratable acids could be removed from grapefruit juice in varying combinations. For example, Amberlite XAD-7 removed about 63% naringin, 85% limonin and 3% titratable acids and Deacidite-FFIP removed about 20% naringin, 8% limonin and 23% titratable acids when contacted for 1 h with grapefruit juice at the rate of 20 g (dry wt) of adsorbent per litre of juice. Such treatments, applied consecutively, would eliminate excessive bitterness and acidity from juices containing up to 2 g naringin and 36 mg limonin litre^?1 and with a total soluble solids:titratable acid ratio of < 6. The adsorbents are readily available, may be used as supplied and can be reactivated simply and economically; some of them have already been approved for use with foods, and such approval seems possible for the others.     

Endpoint Temperature, Internal Cooked Color, and Expressible Juice Color Relationships in Ground Beef Patties

Ground beef patties from A- and E-maturity carcasses and imported trimmings were cooked to 55 to 77°C. Internal patty color became less red as endpoint temperature increased. However, some patties cooked to lower temperatures turned brown prematurely. Visual evaluation of internal patty color was not an accurate indicator of patty doneness. Raw material source had little effect on internal patty color. Expressible juices from imported trimmings were less red than those from A-and E-maturity carcasses. Expressible juice became less red and more yellow with increasing endpoint temperature; however, expressible juice never “ran clear.” A more appropriate guideline would be “cook until juices lack redness.”