Higher Total Acid Content Research Articles

S2O82−/CeO2 Solid Superacid Catalyst Prepared by Radio-Frequency Plasma-Assisted Hydrothermal Method

CeO2 was prepared using a hydrothermal method, modified by radio-frequency plasma in the form of glow discharge, and then the solid superacid S2O82−/CeO2 was prepared by the impregnation method. A series of properties such as pore structure was characterized by N2 adsorption–desorption experiments, surface morphology was characterized by TEM, crystal phase was characterized by XRD, and surface acidity of the catalyst was characterized by Py-IR and Hammett titration. The methyl esterification reaction of tryptophan was used to evaluate the activity of the solid superacid. The results showed that the catalyst modified by radio-frequency plasma had a larger specific surface area, more surface oxygen vacancies, smaller particle size, and higher total acid content. The yield of tryptophan methyl ester reached a higher level of 94.5% (150 °C, 1 MPa, 2 h), catalyzed by the modified S2O82−/CeO2. This work verified the feasibility of plasma technology in the field of catalytic activity enhancement of solid superacid.

Synthesis of Precursors to Ethylene Glycol via the Acid-Catalyzed Carbonylation of Formaldehyde

Methyl glycolate was synthesized as a precursor to ethylene glycol from the acid-catalyzed carbonylation of formaldehyde, followed by esterification with methanol. Homogeneous acids and different solid acids (e.g., resins and zeolites) were used as catalysts, and the effect of the solvent was examined. Afterward, a carboxylic acid protection strategy was proposed. With sulfolane and acetic acid as the mixed solvent, the solubility of CO increases, and the reaction rate can be accelerated. The rapid reaction between acetic acid and glycolic acid inhibits glycolic acid polymerization and pulls the reaction balance to promote the carbonylation reaction rate. Under the optimal solvent system (a molar ratio of acetic acid to sulfolane of 1:5) and the appropriate reaction conditions, the selectivity of the target product is higher than 85%. Solid acid catalysts with a −SO3H or −CF2SO3H functional group are supposed to be efficient in the carbonylation of formaldehyde, based on which a supported Nafion catalyst with a high surface area and total acid content was designed and synthesized. The novel supported Nafion catalyst presents a high total acid content and high Brönsted–Lewis acid ratio due to the characteristics of modified zeolite and, thus, leads to the high reactivity and very low selectivity of the by-product. A possible reaction mechanism is proposed to explain the product’s distribution by ascribing the formation of different products to different types of acid sites.

Feed Durability and Feed Quality of Concentrate Feed with Addition of Monosodium Glutamate Manufacturing by-products

This research was conducted at the Nutrition and Animal Feed Laboratory, Beef Cattle Research Institute, Grati, Pasuruan, East Java. This study aimed to determine the effect of the addition of MSG by-product on the durability and nutritional content of the concentrate. The material used in this research was concentrate, which contained several raw materials and was added with MSG by-product with several levels. The treatments applied were: Treatment A: 5 Kg Concentrate (C) + 12% MSG by product (OP); Treatment B: C + 16% OP; Treatment C: C + 20% OP; and Treatment D: C + 24% OP. Observations on variables were carried out for 4 weeks, and the data obtained were analyzed descriptively. The results showed that until the fourth week of storage, there were no differences in flavor, clumpiness, louse, and fungus in treatments A, B, C, and D. In the color of the concentrate, it was known that treatment D had a brownish color but was the darkest when compared to the other treatments and the dust produced by treatment A appears to have the highest dust. However, it was found that the total acid content in treatment D has the highest total acid content, as a result of adding the highest OP concentration and resulting in the highest total acid formation when fermentation occurs during the feed shelf life. Based on these data, it can be concluded that adding OP to the concentrate could maintain its durability and quality until the fourth week of storage in the feed warehouse.

The differences between broad bean koji fermented in laboratory and factory conditions by an efficient Aspergillus oryzae.

Broad bean paste-meju was fermented by a mixture of broad bean koji and saline; koji fermentation is an essential process for the production of broad bean paste-meju. Aspergillus oryzae was the most widely used in sauce fermentation. The purpose of this study was to research the factory adaptability of the highly efficient A. oryzae PNM003 and further evaluate the effect of fermentation conditions and fermentation strains on koji. A. oryzae PNM003 was compared with the widely used strain HN 3.042 not only in the laboratory but also in factory conditions (large scale). Results showed that the koji made with the same starter in the factory had a greater amount of fungi than that in the laboratory. Bacteria and yeast levels in HN_L koji were higher than in PN_L koji. As for fungi constitution, almost only Aspergillus survived in the end through the microorganism self-purification process during koji fermentation. As for the bacterial constitution, koji was grouped by fermentation conditions instead of fermentation starter. PN koji had higher protease activity and a higher content of total acids, amino acid nitrogen, amino acids, and organic acids in the laboratory conditions. Nevertheless, in factory conditions, PN koji and HN koji had similar indexes. As for volatile flavor compounds, koji made with the two starters in the same condition was grouped together. As for the same starter, there were more flavor compounds metabolized in the factory condition than in the laboratory condition, especially esters and alcohols. The results showed PN was a highly efficient strain to ferment koji, but the advantages were expressed more remarkably in laboratory conditions. In brief, the fermented condition had a greater influence than the fermentation starter for broad bean koji.

Comparative Assessment of Functional Components and Antioxidant Activities between Hippophae rhamnoides ssp. sinensis and H. tibetana Berries in Qinghai-Tibet Plateau.

The Qinghai-Tibet Plateau is the main production area of Hippophae rhamnoides ssp. sinensis (Rha) and H. tibetana (Tib), but studies on the types and contents of soluble sugars, organic acids, free phenolics, bound phenolics, vitamin C (VC), tocopherol (VE) and carotenoids of the two sea buckthorn berries from this region have not been reported. In this paper, we found that the soluble sugars in Rha and Tib were mainly glucose and fructose; Rha exhibited a higher content of total sugar and fructose compared to Tib. The organic acids were mainly quinic acid and malic acid; Rha exhibited a higher content of total acids and quinic acid, but lower tartaric acid and citric acid compared to Tib. Rha also possessed a higher total (free and bound) phenolic as well as total (free and bound) flavonoid content than those in Tib; twelve phenolic compounds were analyzed, among which flavonols were dominant. Catechin, isorhamnetin and quercetin were the main phenolic substances. VC and VE (γ-tocopherol (γ-VE) and δ-tocopherol (δ-VE)) were higher in Rha than Tib. The total carotenoid, lutein, β-carotene and lycopene content of Tib was remarkably higher than that in Rha. Moreover, both Rha and Tib showed good in vitro and cellular antioxidant activities, and Rha had a stronger antioxidant activity. Taken together, Rha had a higher antioxidant activity, which may be due to its higher content of phenolics, flavonoids, VC and VE.

THE WINE QUALITY DESCRIPTION OF DIFFERENT ORIGIN EVALUATED BY MODERN CHEMOMETRIC APPROACH

The main chemical parameters such as content of sugar (glucose and fructose), organic acid (total acids, malic and tartaric acids), total phenolics and the antioxidant activity in 9 dry white wines with PDO of 3 varieties (Pinot Blanc, Riesling, Sauvignon blanc) from 3 countries (Slovakia, Hungary, Austria) were studied in this work in order to identify possible differences in their quality affected by geographical origin. The wine samples were examined by the FTIR and spectrophotometry methods (TPC and DPPH). As supporting parameters, alcohol and glycerol content were used and sensory evaluation of wines was performed. For the statistical evaluation were used ANOVA and PCA methods. Austrian wines in general, were characterized by high glucose and fructose content, high TPC and antioxidant activity. Higher results of these parameters are characteristic especially for the Austrian varieties Pinot blanc and Sauvignon blanc which originated from the same wine-region in Austria. Sauvignon variety from Slovakia was characterized by higher total acid content, especially in the case of tartaric acid. Statistical evaluation was helpful to show several differences, especially in the case of PCA application. Just Riesling variety from all countries of origin was so similar that it was not possible to be strictly distinguished using PCA. Wines from Hungary (Sauvignon and Pinot blanc) showed higher content of alcohol and glycerol, as they are produced by the sugar fermentation. Wines from Slovakia were evaluated as the best samples among selected ones within their sensory evaluation.

Variation of organic acids in mature fruits of 193 pear (Pyrus spp.) cultivars

Organic acids play important roles in fruit flavor and nutrition. Here, the organic acid contents of 193 pear germplasm fruits were determined using ultraperformance liquid chromatography (UPLC). The results showed that the organic acids in pear fruit mainly included malic acid, citric acid, quinic acid, oxalic acid and shikimic acid. Correlation analysis showed that these pear cultivars could be separated into the malic acid-dominant and citric acid-dominant types. By comparing organic acid content among the different pear species, we showed that Pyrus ussuriensis had the highest total acid content, followed by Chinese sand pears (Pyrus pyrifolia), Pyrus sinkiangensis, the hybrid breeding (HB) cultivar group, Pyrus bretschneideri, Japanese and Korean (J&K) sand pears (Pyrus pyrifolia) and Pyrus communis. In addition, a positive correlation between acid content and pear fruit ripening period was detected. These fundamental data and results could greatly augment pear breeding programs and provide a comprehensive understanding of pear germplasm resources.

Multiple rounds of Aspergillus niger biofortification confer relatively stable quality with minor changes of microbial community during industrial-scale Baoning vinegar production

Vinegar is consumed worldwide as a food condiment, especially in the Chinese diet. The present study optimized the addition of A. niger biofortified-bran Qu (0.3%, 0.45%, and 0.6%) as additional starter to improve total acid content and starch utilization rate in industrial-scale Baoning vinegar production. In addition, this novel study determined the quality and microbial community changes of Baoning vinegar during three-round biofortification in industrial scale. Our results indicated that A. niger biofortified-bran Qu added at 0.6% resulted in higher total acid content and starch utilization rate of vinegar Pei. Biofortification imposed minor changes in the microbial community during three-round biofortification, and more variation was observed in fungal community than that in bacterial community. Most importantly, the quality of Baoning vinegar remained relatively stable. This information further confirmed the feasibility of multiple rounds of A. niger biofortification, and can be used to provide theoretical basis for industrial-scale production.

The PHYSICOCHEMICAL AND SENSORY CHARACTERISTICS OF PROMISING PLUM (Prunus domestica L.) GENOTYPES BRED AT FRUIT RESEARCH INSTITUTE, ČAČAK

Five plum hybrids (38/62/70, IV/63/81, 32/21/87, 34/41/87 and 22/17/87) and newly released cultivar ‘Nada’, obtained by planned hybridisation and singled out within breeding programme at Fruit Research Institute, Čačak, were assessed for the main physical (fruit and stone weight and flesh percentage), chemical (soluble solids content, total and inverted sugars content, sucrose content, total acids content, pH value of fruit juice, ratio of soluble solids and total acids content and ratio of total sugars and total acids content) and sensorial (attractiveness, taste, aroma and consistency) traits compared with the standard cultivar ʻČačanska Lepoticaʼ. Results showed that the studied plum genotypes differed significantly in all of the assessed traits. Regarding the physical features, the best results were shown by hybrid 38/62/70, which had the highest fruit weight (56.92 g) and flesh percentage (96.91%), as well as by the new cultivar ‘Nada’, for which a larger fruit was observed in comparison to the standard (45.54 g and 42.24 g, respectively). Also, ‘Nada’ had better sensorial properties such as attractiveness, taste, aroma and consistency in relation to the other promising hybrids and the standard cultivar. From the aspect of all the studied sensorial characteristics, in addition to ‘Nada’, only hybrid 38/62/70 was aligned with the standard cultivar. Out of the studied genotypes, late ripening hybrid 22/17/87 had the best values of parameters of fruit chemical composition such as the soluble solids content (17.01%), total and inverted sugars contents (12.31% and 8.96%, respectively). The highest sucrose content (3.39%), pH value of fruit juice (3.51), as well as the highest ratio between soluble solids and total acids content (43.72) and ratio between total sugars and total acids content (32.58) were found in cultivar ‘Nada’. The highest total acids content (1.42%) was recorded in hybrid 32/21/87. Compared to ʻČačanska Lepoticaʼ, the same or better results in terms of the fruit chemical composition were determined in cultivar ‘Nada’ and hybrids 34/41/87 and 22/17/87. The study revealed existence of significant correlations between individual studied parameters of the fruit physical, chemical and sensorial properties.

The Effect of Different Starter Cultures on the Fermentation of Yogurt Added with Aqueous Extract of White Oyster Mushroom (Pleurotus ostreatus)

The objective of this study was to evaluate the effect of different starter cultures on the fermentation of yogurt added with aqueous extract of white oyster mushroom (Pleurotus ostreatus) whether each starter culture respond differently. This study used a completely randomized design (CRD) with 3 treatments and 4 replications. Yogurt was made with one of the starter cultures as treatment: Streptococcus thermophilus (ST), Lactobacillus acidophilus (LA), or Lactobacillus bulgaricus (LB). Data were analyzed using analysis of variance followed by the least significant difference test. The variables tested were pH, total acid content, viscosity and total lactic acid bacteria. The results showed that yogurt made with ST had lower pH and total acid than the others. The use of LB resulted in higher total acid content. The addition of different starter cultures in yogurt did not influence viscosity. Among starter cultures, the use of LA resulted in higher total lactic acid bacteria (LAB) than the others. However, the number of LAB from different treatments were not much different (within the range of 7 log CFU/mL). It is suggested that the three starter cultures are adaptive and capable to fermenting yogurt added with aqueous extract of white oyster mushroom (Pleurotus ostreatus).

Dynamic changes of total acid and bacterial communities during the traditional fermentation of Hong Qu glutinous rice wine

Abstract Background Hong Qu glutinous rice wine (HQGRW) is brewed under non-aseptic fermentation conditions, so it usually has a relatively high total acid content. The aim of this study was to investigate the dynamics of the bacterial communities and total acid during the fermentation of HQGRW and elucidate the correlation between total acid and bacterial communities. Results The results showed that the period of rapid acid increase during fermentation occurred at the early stage of fermentation. There was a negative response between total acid increase and the rate of increase in alcohol during the early fermentation stage. Bacterial community analysis using high-throughput sequencing technology was found that the dominant bacterial communities changed during the traditional fermentation of HQGRW. Both principal component analysis (PCA) and hierarchical clustering analysis revealed that there was a great difference between the bacterial communities of Hong Qu starter and those identified during the fermentation process. Furthermore, the key bacteria likely to be associated with total acid were identified by Spearman's correlation analysis. Lactobacillus, unclassified Lactobacillaceae, and Pediococcus were found, which can make significant contributions to the total acid development (| r | > 0.6 with FDR adjusted P Conclusions This was the first study to investigate the correlation between bacterial communities and total acid during the fermentation of HQGRW. These findings may be helpful in the development of a set of fermentation techniques for controlling total acid. How to cite: Liang Z, Lin X, He Z, et al. Dynamic changes of total acid and bacterial communities during the traditional fermentation of Hong Qu glutinous rice wine. Electron J Biotechnol 2020;43. https://doi.org/10.1016/j.ejbt.2019.12.002

The early performance and fruit properties of apricot cultivars grafted on Prunus spinosa L. interstock

The present study was undertaken to determine some pomological, physical and chemical properties of five apricot cultivars from University of Novi Sad, Faculty of Agriculture, Novi Sad, Serbia—‘Novosadska kasnocvetna’, ‘Novosadska rodna’, NS-6, NS-4, and ‘Buda’—and two selections (SK-1 and SK-3) grafted on myrobalan as a rootstock, with blackthorn (Prunus spinosa L.) used as interstock. The experiment was conducted during the 2013–2017 period at the experimental field for fruit growing of the University of Novi Sad, Faculty of Agriculture. The orchard was established in 2012 with 4 × 2 m tree spacing. Phenological characteristics, yield, trunk circumference, fruit and stone size, as well as chemical properties of Novi Sad’s apricot cultivars and selections were determined. The earliest flowering onset was observed in the cultivar ‘Buda’ and the latest in the selection SK-3. In all examined cultivars and selections, fruit weight was above 60 g and ‘Buda’ was particularly distinguished by its fruit weight and stone to flesh ratio. ‘Novosadska kasnocvetna’ had the lowest yield efficiency (0.4 kg cm−2), yield per tree (4.4 kg) and per ha (5.5 t). Cultivar NS-6 and selection SK-1 were the most productive, with the cumulative yield per tree of 27.1 and 26.2 kg, respectively. The highest trunk cross-sectional area in all five experimental years was measured for the cultivar ‘Buda’ (58.1 cm2). The highest soluble solids content was detected in the cultivar ‘Buda’ (16.1°Brix), while ‘Novosadska kasnocvetna’ had the highest total acid content (1.4%). Novi Sad’s apricot cultivars and selections yield good fruit quality, which can thus serve as a very powerful source of phenolic compounds.

Esterification of oleic acid to biodiesel catalyzed by a highly acidic carbonaceous catalyst

Carbonaceous catalyst, with a variety of acid sites, was successfully synthesized by a two-step method at low temperature. The synthesized catalyst (Zr-SO3H@CMC) was characterized by elemental analysis, XRD, ICP-OES, FT-IR, BET, SEM-EDX and Boehm titration. It had high total acid content (8.45 mmol/g) for oleic acid esterification with high biodiesel yields (> 99%) at 40–90 °C. Under conditions of 90 °C, 20/1 methanol/oleic acid molar ratio, 5 wt% catalyst and 2 h reaction time, biodiesel yield of > 87% was achieved after 10 cycles of use. At lower temperatures (40, 50 and 60 °C), biodiesel yield still reached 82%, 93% and 90% after 3 cycles, respectively. The high activity of Zr-SO3H@CMC benefited from low activation energy of 24.7 KJ/mol. It shows potential application for esterification of free fatty acids or pretreatment of oils with high acid value for the green production of biodiesel.

Chemical constituents and antimicrobial activity of wood vinegars at different pyrolysis temperature ranges obtained from Eucommia ulmoides Olivers branches.

Pyrolysis is a promising approach for converting biomass to solids, liquids, and gases. Herein wood vinegars (WVs) were produced from pyrolysis of Eucommia ulmoides Olivers (EUO) branches in different temperature ranges that were labeled as WV90∼120 and WV480∼510. The yield, the physicochemical characteristics, the chemical composition, and the antimicrobial activity of the WVs were comprehensively investigated. During the pyrolysis process, as the temperature increased, the yield of the WVs increased firstly and then decreased, and WV300∼330 achieved the maximum yield of 236.79 g, accounting for 23.26% of the total amount of raw WVs. However, both the lowest pH value (2.39) and the highest total acid content (12.70%) occurred for WV270∼300. GC-MS results demonstrated that six components of WVs for WV300∼330 were phenols, ketones, aldehydes, alcohols, organic acids, and benzenes, while no clear regularity between the contents of each component and the reaction temperature was found. Thereafter, the antimicrobial activity of WVs was tested, and the results showed that the longest inhibition circle diameter of 24.50 mm for Enterobacter aerogenes was obtained for WV300∼330 indicating an excellent antibacterial activity; the overall inhibitory effects of WVs on bacteria were superior to those of plant pathogens and fungus. Therefore, WV300∼330 showed a better antimicrobial activity than that of WV270∼300 in this study. The result could be a reference for the further utilization of WVs in the field of antimicrobial development.

Effects of Different Growing Regions on Quality Characteristics, Bioactive Compound Contents, and Antioxidant Activity of Aronia (Aronia melanocarpa) in Korea

The objective of this study was to determine the effects of different growing regions on quality characteristics, total bioactive compound contents, and in vitro antioxidant activity in aronia. Aronia grown in 3 different regions (Sangjoo, Ulju, and Youngcheon) in Korea was obtained and used fresh or as a freeze-dried powder. No statistically significant differences were observed for moisture, ash, crude lipid, and crude protein contents in aronia sampled from the 3 different regions. Aronia grown in Sangjoo had the highest total acid content and the lowest sugar content and pH value. Conversely, aronia grown in Youngcheon possessed the lowest total acid content and the highest sugar content and pH value. Aronia grown in Sangjoo possessed relatively high levels of polyphenols, flavonoids, and anthocyanins, as well as high antioxidant activity in comparison with aronia produced in other regions. Aronia grown in Youngcheon scored the highest for taste and overall acceptability in sensory evaluations, which may be related to the high sugar content and pH, and the low total acidity of the fruits. It is possible that higher sugar contents and pH, and lower total acidity in the aronia grown in Youngcheon result in more preferable sensory characteristics. However, they also contain relatively low levels of total polyphenols, flavonoids, and anthocyanins, and have low antioxidant activity as measured by 2,2-diphenyl-1-picrylhydrazyl and 2,2′-azino-bis(3-ethylbenzothiazoline-6-sulfonic acid) radical scavenging assays.

Sugarcane hybrids with original low lignin contents and high field productivity are useful to reach high glucose yields from bagasse

Five sugarcane hybrids plus a reference material were evaluated according to the glucose yields obtained after alkaline-sulfite pretreatment and enzymatic hydrolysis. Sugarcane hybrids with varied original chemical compositions were used to assess how contrasting samples might influence the integrated pretreatment and hydrolysis process. The hydrolysis efficiency of six samples treated at three different chemical loads, suggested that lignin and hemicellulose removals during the pretreatment were not the single factor necessary to reach high cellulose conversion levels in the enzymatic hydrolysis step. Pretreated samples with the highest total acid contents (mainly sulfonic acids) were also the most digestible materials. The glucose yields were heavily dependent not only on the digestibility of the pretreated materials but also on the field productivity of the plants. One of the hybrids, presenting high glucan yields after pretreatment and high digestibility, produced low glucose yields because it presented very low biomass productivity. In contrast, one of the hybrids that presented low glucan yield after pretreatment, but was highly digestible and presented high biomass productivity, provided the highest glucose yields in the data set, producing 4192 and 5629 kg of glucose per hectare after enzymatic hydrolysis for 24 h and 72 h, respectively.

The effect of different position of grape clusters on the bearing shoot on production results of Cabernet Sauvignon clones

In this paper the differences were examined between clones of Cabernet sauvignon (clones ISV-F-V5, ISV-F-V6 and R5), i.e. the difference between uvological properties of grape clusters and grape berries, based on the different positions on the bearing shoot. Tests were conducted at the experimental fled of the Faculty of Agriculture “Radmilovac.” Standard ampelographic methods were used in numerous analyses of grape yield, as well as uvological properties of clones. All data were statistically analyzed and processed by the method of two-factor analysis of variance with repeated measuring of one factor (height) and Tukey HSD test. Analysis of variance showed no significant differences between clones. The best results were achieved with grape clusters positioned in the base of bearing shoot. The first positioned grape clusters on the bearing shoot had the highest share in the total grape yield, the highest amount of sugar, and the highest positioned grape clusters had higher content of total acids. The differences determined between examined clones were in regard to productivity and quality of grapes which reflected also on production value.

Assessment of nutritional parameters of native apple cultivars as new gene sources

Although there are tens of different apple varieties in Europe, only some of them were purposefully bred and selected in the past. In spite of the fact that they can have outstanding nutritional and technological properties, the majority of them are of only a local importance. The objective of this study was to show and popularize altogether 35 local apple varieties which are typical of the conditions of Central Europe. However, their genetic uniqueness represents an irreplaceable ecological wealth and for that reason these local varieties could become a new and outstanding source of nutrients and food. Today, they can be used not only for direct consumption and in food industry but also as a potential material for further breeding and selection. It was found out in our experiments that the highest content of total acids was shown by the variety ’Citronové zimní’ (6.1 g.kg−1 of fresh matter). As far as the content of pectins was concerned, the highest levels were found out in the variety ’Strymka’ (3.26% in fresh matter). Of minerals, potassium showed the highest levels in fruit; for example, the variety ’Boikovo’ contained 9.70 ppm of this element in dry matter. Peels showed approximately 7 times higher antioxidant capacity than the flesh. For example, peels of the variety ’Bernské růžové’ showed antioxidant capacity of as much as 56.65 mmol of trolox per kg of fresh matter. This paper should contribute to efforts focused on saving of genetic variability of apples and their further application both in human nutrition and a further breeding and selection under conditions of pomological and alimentary practice.

STABILITY OF YIELD AND FRUIT QUALITY IN PROMISING PEACH CULTIVARS

Yield and fruit quality (fruit weight, reducing sugar content, sucrose content and total acids content) were studied in 20 introduced peach cultivars. To evaluate the stability of those characteristics in the agro-ecological conditions of Belgrade surroundings, bi and S2di were applied. ‘Adriana’ had the highest yield and content of reducing sugars, ‘Aurelia’ the highest fruit weight, ‘Pegaso’ the highest sucrose content, and ‘Croce del Sud’ the highest total acids content. Values of bi coeffi cient indicated that ‘Sirio’ had the highest stability of yield ‘Iris Rosso’ the highest stability of fruit weight and content of reducing sugars, ‘Aurelia’ the highest stability of sucrose content, and ‘Emilia’ the highest stability of total acids content. Values of S2di, despite being relatively high, did not show any statistical signifi cance, which indicates a more signifi cant deviation from regression and unsatisfactory stability of the studied genotypes. The results of the present work confi rm that bi, being a stability parameter, is more important than S2di in heterozygous genotypes, the genotype of a majority of fruit cultivars, therefore of peach itself.

Comparison of the microbiological, compositional, biochemical, volatile profile and sensory characteristics of three Italian PDO ewes’ milk cheeses

Three batches of three Italian ewes’ milk cheeses (Canestrato Pugliese, Fiore Sardo and Pecorino Romano), which were manufactured under the Protected Denomination of Origin (PDO), were compared for microbiological, compositional, biochemical, volatile profile and sensory characteristics. After ca. 1 year of ripening, the three cheeses had a complex microbial population, composed mainly of non-starter lactic acid bacteria (NSLAB); several species of mesophilic lactobacilli and enterococci were identified. Pecorino Romano had a very high level of NaCl, 8.7±0.1% w/w. The level of pH 4.6-soluble nitrogen increased in the order: Canestrato Pugliese>Fiore Sardo>Pecorino Romano. Urea-PAGE electrophoresis showed that the hydrolysis of α s1 -casein was more consistent than β -casein. RP-HPLC profiles of the ethanol-soluble and ethanol-insoluble fractions of the pH 4.6-soluble nitrogen showed differences between the cheeses which agreed with the content of free amino acids. Glutamic acid, histidine, valine, isoleucine, leucine and phenylalanine were the free amino acids present at the highest levels in all the cheeses. Sixty-two volatile components were identified by Gas Chromatography-Mass Spectrometry analysis of steam distillates of the cheeses. The volatile profile of the three cheeses differed significantly. Esters were the main volatiles in the Canestrato Pugliese cheese but were the lowest in Fiore Sardo cheese. Ketones and alcohols were the principal class of volatile components in Fiore Sardo and Pecorino Romano cheeses, respectively. Lactones and products of the breakdown of the sulphur-containing amino acids were found at considerable levels in all cheeses, but aldehydes were present at low levels. Only 30 carboxylic acids were identified; Canestrato Pugliese had the highest content of total acids. Butanoic, hexanoic, octanoic and decanoic acids represented the 30–33% of the total carboxylic acids in the cheeses. The cheeses were subjected to descriptive sensory analysis; 19 discriminating and 2 descriptive attributes were analysed by Principal Component Analysis (PCA). The sensory characteristics of the three ewes’ milk cheeses were distinct.