Bioactivity of volatile organic compounds by Aureobasidium species against gray mold of tomato and table grape.

Aureobasidium strains isolated from diverse unconventional environments belonging to the species A. pullulans, A. melanogenum, and A. subglaciale were evaluated for Volatile Organic Compounds (VOCs) production as a part of their modes of action against Botrytis cinerea of tomato and table grape. By in vitro assay, VOCs generated by the antagonists belonging to the species A. subglaciale showed the highest inhibition percentage of the pathogen mycelial growth (65.4%). In vivo tests were conducted with tomatoes and grapes artificially inoculated with B. cinerea conidial suspension, and exposed to VOCs emitted by the most efficient antagonists of each species (AP1, AM10, AS14) showing that VOCs of AP1 (A. pullulans) reduced the incidence by 67%, partially confirmed by the in vitro results. Conversely, on table grape, VOCs produced by all the strains did not control the fungal incidence but were only reducing the infection severity (< 44.4% by A. pullulans; < 30.5% by A. melanogenum, and A. subglaciale). Solid-phase microextraction (SPME) and subsequent gas chromatography coupled to mass spectrometry identified ethanol, 3-methyl-1-butanol, 2-methyl-1-propanol as the most produced VOCs. However, there were differences in the amounts of produced VOCs as well as in their repertoire. The EC50 values of VOCs for reduction of mycelial growth of B. cinerea uncovered 3-methyl-1-butanol as the most effective compound. The study demonstrated that the production and the efficacy of VOCs by Aureobasidium could be directly related to the specific species and pathosystem and uncovers new possibilities for searching more efficient VOCs producing strains in unconventional habitats other than plants.

Short communication: Short-time freezing does not alter the sensory properties or the physical stability of ultra-high-temperature hydrolyzed-lactose milk.

In this study, the effect of milk freezing was studied, focusing on the changes in 1% and 3% fat UHT hydrolyzed-lactose milk after slow- (-20°C) and fast-rate freezing (-80°C) for 72 h. Changes on the sensory properties were first assessed by discriminant analysis (triangle test), and then by volatile organic compounds and color analysis. The milk emulsion stability was characterized by optical centrifugation, particle size analysis, and confocal microscopy. The sensory panel was not able to distinguish the milk subjected to freezing from the control (72 h at 20°C). The volatile organic compounds and color analysis demonstrated that both freezing rates did not cause any significant changes in the milk aroma or color characteristics. The results of physical properties confirmed that short-time freezing did not lead to a distinct destabilization, except for a slight increase in the mean particle diameter at -80°C. Taking all the results together, UHT hydrolyzed-lactose milk was not significantly altered during the operation of freezing and thawing and, therefore, short-time freezing at both -20°C and -80°C can be used for milk storage without altering the product.

Effects of grazing cow diet on volatile compounds as well as physicochemical and sensory characteristics of 12-month-ripened Montasio cheese.

The aim of this study was to evaluate the effects of pasture type and cow feeding supplementation level on a 12-mo-ripened Montasio protected designation of origin (PDO) cheese, which is one of the most important PDO cheeses produced in northeast Italy. Cheeses were characterized for volatile compounds, color, mechanical variables, and sensory descriptors. Pasture type significantly affected most of the instrumental variables considered and, as a consequence, sensory properties were affected as well. Cheeses from the pasture characterized by a nutrient-rich vegetation type were higher in protein and lower in fat content. Furthermore, such cheeses, evaluated by a sensory panel, were more intense in color with a more pungent and less cow-like odor, in agreement with what found through instrumental analyses. Supplementation level resulted in less pronounced effects, limited to volatile compounds and texture properties, which were not detected by sensory analysis. The characterization of the 12-mo ripened Montasio cheese reported here is an important step for the valorization of this PDO product.

Proton transfer reaction time-of-flight mass spectrometry: A high-throughput and innovative method to study the influence of dairy system and cow characteristics on the volatile compound fingerprint of cheeses.

The aim of this work was to study the effect of dairy system and individual cow-related factors on the volatile fingerprint of a large number of individual model cheeses analyzed by proton transfer reaction time-of-flight mass spectrometry (PTR-ToF-MS). A total of 1,075 model cheeses were produced using milk samples collected from individual Brown Swiss cows reared in 72 herds located in mountainous areas of Trento province (Italy). The herds belonged to 5 main dairy systems ranging from traditional to modern and the cows presented different daily milk yields (24.6±7.9kg × d(-1)), stages of lactation (199±138 d in milk), and parities (2.7±1.8). The PTR-ToF-MS revealed 619 peaks, of which the 240 most intense were analyzed, and 61 of these were tentatively attributed to relevant volatile organic compounds on the basis of their fragmentation patterns and data from the literature. Principal component analysis was used to convert the multiple responses characterizing the PTR-ToF-MS spectra into 5 synthetic variables representing 62% of the total information. These principal components were related to groups of volatile compounds tentatively attributed to different peaks and used to investigate the relationship of the volatile compound profile obtained by PTR-ToF-MS to animal and farm characteristics. Lactation stage is related to 4 principal components which brought together 52.9% of the total variance and 57.9% of the area of analyzed peaks. In particular, 2 principal components were positively related to peaks tentatively attributed to aldehydes and ketones and negatively related to alcohols, esters, and acids, which displayed a linear increase during lactation. The second principal component was affected by dairy system; it was higher in the modern system in which cows received total mixed rations. The third principal component was positively related to daily milk production. In summary, we report the first application of this innovative, high-throughput technique to study the effects of dairy system and individual animal factors on volatile organic compounds of model cheeses. Individual cheesemaking procedures together with this spectrometric technique open new avenues for genetic selection of dairy species with respect to both milk and cheese quality.

Effects of dairy system, herd within dairy system, and individual cow characteristics on the volatile organic compound profile of ripened model cheeses.

The objective of this work was to study the effect of dairy system, herd within dairy system, and characteristics of individual cows (parity, days in milk, and daily milk yield) on the volatile organic compound profile of model cheeses produced under controlled conditions from the milk of individual cows of the Brown Swiss breed. One hundred fifty model cheeses were selected from 1,272 produced for a wider study of the phenotypic and genetic variability of Brown Swiss cows. In our study, we selected 30 herds representing 5 different dairy systems. The cows sampled presented different milk yields (12.3-43.2kg/d), stages of lactation (10-412 d in milk), and parity (1-7). In total, 55 volatile compounds were detected by solid-phase microextraction and gas chromatography-mass spectrometry, including 14 alcohols, 13 esters, 11 free fatty acids, 8 ketones, 4 aldehydes, 3 lactones, 1 terpene, and 1 pyrazine. The most important sources of variation in the volatile organic profiles of model cheeses were dairy system (18 compounds) and days in milk (10 compounds), followed by parity (3 compounds) and milk yield (5 compounds). The model cheeses produced from the milk of tied cows reared on traditional farms had lower quantities of 3-methyl-butan-1-ol, 6-pentyloxan-2-one, 2-phenylethanol, and dihydrofuran-2(3H)-one compared with those reared in freestalls on modern farms. Of these, milk from farms using total mixed rations had higher contents of alcohols (hexan-1-ol, octan-1-ol) and esters (ethyl butanoate, ethyl pentanoate, ethyl hexanoate, and ethyl octanoate) and lower contents of acetic acid compared with those using separate feeds. Moreover, dairy systems that added silage to the total mixed ration produced cheeses with lower levels of volatile organic compounds, in particular alcohols (butan-1-ol, pentan-1-ol, heptan-1-ol), compared with those that did not. The amounts of butan-2-ol, butanoic acid, ethyl-2-methylpropanoate, ethyl-3-methylbutanoate, and 6-propyloxan-2-one increased linearly during lactation, whereas octan-1-ol, 3-methyl-3-buten-1-ol, 2-butoxyethanol, 6-pentyloxan-2-one, and 2,6-dimethylpyrazine showed a more complex pattern during lactation. The effect of the number of lactations (parity) was significant for octan-1-ol, butanoic acid, and heptanoic acid. Finally, concentrations of octan-1-ol, 2-phenylethanol, pentanoic acid, and heptanoic acid increased with increasing daily milk yield, whereas dihydrofuran-2(3H)-one decreased. In conclusion, the volatile organic compound profile of model cheeses from the milk of individual cows was affected by dairy farming system and stage of lactation and, to lesser extent, by parity and daily milk yield.

Volatile compounds and sensory properties of Montasio cheese made from the milk of Simmental cows grazing on alpine pastures.

The aim of this study was to analyze the volatile compounds, physicochemical characteristics, and sensory properties of Montasio, a semicooked pressed cheese, produced from the milk of the dual-purpose Italian Simmental cows grazing on alpine pastures. A total of 72 cows grazing on 2 pastures, which differed in botanical composition (nutrient-rich pasture vs. nutrient-poor pasture), received 2 different levels of supplementation (3.0 vs 1.5 kg/head per day). The experimental cheeses were produced from whole, raw milk and ripened for 60 d. Sixty-one volatile compounds, including alcohols (11), aldehydes (6), ketones (10), lactones (2), esters (6), hydrocarbons (3), carboxylic acids (6), phenolic compounds (4), monoterpenes (7), sesquiterpenes (1), sulfur compounds (4), and amines (1), were detected. The main families in terms of relative weight appeared to be carboxylic acids, esters, and alcohols. A panel of trained assessors described the experimental cheeses as having an intense color; small and evenly distributed eyes; an intense odor and flavor of milk-sour, milk, and cow; and a tender and creamy texture. The pasture type affected the volatile fraction, particularly ketones, phenolic compounds, and terpenes, which are overall higher in nutrient-poor pastures. A slight effect on the sensory analyses, in particular the effect of the cow attribute on odor and flavor, was perceived by the panelists. The cheeses produced on nutrient-rich pasture had higher b* (yellowness) index. These results were consistent with the color evaluation of the sensory panel. In addition, the pasture affected some textural attributes (adhesivity, creaminess, and granules) as perceived by the panelists. Concentrate supplementation, which is required to meet the feeding requirements of grazing cows, had no clear effect on either the volatile compounds or the sensory properties of the cheeses. Thus, at least within levels of integration adopted, it is expected not to alter the organoleptic characteristics of this product.

Effect of the pig rearing system on the final volatile profile of Iberian dry-cured ham as detected by PTR-ToF-MS.

The volatile compound profile of dry-cured Iberian ham lean and subcutaneous fat from pigs fattened outdoors on acorn and pasture (Montanera) or on high-oleic concentrated feed (Campo) was investigated by proton transfer reaction time-of-flight mass spectrometry. In addition to the usual proton transfer ionization the novel switchable reagent ions system was implemented which allows the use of different precursor ions (H(3)O(+), NO(+) and O(2)(+)). The analysis of the lean and subcutaneous fat volatile compounds allowed a good sample discrimination according to the diet. Differences were evident for several classes of compounds: in particular, Montanera hams showed higher concentrations of aldehydes and ketones and lower concentrations of sulfur-containing compounds compared to Campo hams. The use of NO(+) as precursor ion confirmed the results obtained with H(3)O(+) in terms of classification capability and provides additional analytical insights.

Does milk treatment before cheesemaking affect microbial and chemical traits of ripened cheese? Grana Trentino as a case study.

The aim of this study was to evaluate the influence of different storage temperatures and delivery system of the milk on the microbiological and physicochemical characteristics of Grana Trentino, a long-ripened hard-cooked Italian cheese. In particular, 3 kinds of milk storage and delivery were studied: milk delivered to the dairy in the traditional manner without temperature control, milk delivered at 18°C, and milk stored at the farm and delivered at 12°C. Milk, natural whey starter, and cheeses after 18 mo of ripening were sampled for microbiological profiles, physicochemical analysis, and proteolysis evaluation, and a study of cheese volatile compounds through a solid-phase microextraction gas chromatography-mass spectrometry technique was performed. Milk microbiota was not affected by any of the treatments. At the end of ripening, free fatty acid and ester contents were significantly higher in cheeses from milk without temperature control. This was probably due to the milk delivery to the dairy in churns causing the fat globule membrane break during transport and, consequently, a greater release of fat and deeper lipolysis. Milk refrigeration at 12°C for 12h before delivery affected the distribution of nitrogen fractions in cheeses. Lower temperatures of milk storage favored a larger soluble nitrogen fraction and greater cheese proteolysis, probably caused by an enhanced plasmin activity. From this work, it is concluded that both milk temperature storage and transport system could affect cheese ripening, leading to significant differences in chemical compounds: if milk was delivered by churns, higher free fatty acid and ester content in cheeses was observed; if milk was stored at 12°C for 12h before delivery, greater cheese proteolysis was induced with consequent faster ripening.

Monitoring of sensory attributes used in the quality payment system of Trentingrana cheese.

Trentingrana is a Protected Designation of Origin (PDO) hard cheese manufactured in the valleys of Trento province (eastern Italian Alps) by several small cooperative dairies linked in a consortium. Nine months after production, wheels are delivered to a shared facility, ripened up to 18 mo, and assessed by a panel of 8 experts for 7 sensory attributes; namely, external aspect, rind thickness, paste color, texture, odor, taste, and aroma. The evaluation takes place every 2 mo on wheels sampled within each dairy. Based on the results of the assessment, dairies receive a price premium or penalty depending on a quality index, which is the weighted sum of the scores attributed to each sampled wheel. Sensory scores and quality index of 652 wheels representing 11 dairies and 10 yr of production were analyzed using a model that included fixed effects of dairy, year, and season of production, and first-order interactions between them. The coefficients of determination ranged from 0.50 (texture) to 0.66 (aroma). All factors significantly affected the studied traits, with the exception of interactions between dairy and season of production for texture and external aspect, and between year and season of production for odor. Dairy was the most important source of variation for visually assessed traits (external aspect, rind thickness, paste color, and texture) and for quality index, whereas year of production was the most important for flavor attributes (odor, taste, and aroma). The latter traits were always highly correlated among them and with the quality index, whereas correlations among visually assessed attributes, between them and flavor attributes, and between them and the quality index were more erratic. The sensory evaluation performed by the panel of experts has proven to be a useful tool to define the quality index and address the payment system of Trentingrana cheese, but it has some limitations in correctly describing the sensory profile of cheese and identifying specific defects and possible remedies.

Measuring odour emission and biofilter efficiency in composting plants by proton transfer reaction-mass spectrometry.

PTR-MS (Proton Transfer Reaction-Mass Spectrometry) is an innovative technique that allows the rapid detection of most volatile organic compounds (VOCs) with high sensitivity (sub-ppb) and by direct injection. We describe here the possible use of PTR-MS in waste managements and composting plants both for the real time monitoring of volatile emissions and, after calibration with olfactometric assessments, for the instrumental determination of odour concentration. Beside a short description of the technique, we will report on the calibration of PTR-MS data with olfactometric assessment of odour concentration showing the possibility of a relatively good estimation of odour concentration by instrumental data. We will also show how the rapid PTR-MS fingerprint can be used to visualise the overall effect of a biofilter on the VOCs concentration and to calculate the reduction of the concentration of single masses and, finally, we will provide examples of the performances of a new implementation of this technique based on a time of flight (TOF) analyser. Instead of the usual quadrupole mass filter, the TOF provides an increase of analytical information and the possibility to separate important compounds that in the quadrupole version were not or only indirectly quantifiable. In conclusion we suggest that PTR-MS analysis can be a valuable tool for the rapid and on site monitoring of odour emission and plant operation.

Xanthone 1,4-dihydropyridine derivatives with a potent selective bradycardic effect.

A series of xanthone 1,4-dihydropyridine derivatives were prepared. The compounds were evaluated for inotropic, chronotropic and calcium antagonistic properties. The tested compounds are weak calcium antagonists but exert potent selective bradycardic effects.