Isolation of Saccharomyces cerevisiae strains producing higher levels of flavoring compounds for production of "cachaça" the Brazilian sugarcane spirit

In Brazil, spontaneous fermentation and open vessels are still used to produce cacha?a (the Brazilian sugarcane spirit) and this fermentation is characterized by mixed cultures with continuous succession of yeast species. This work shows the development of a methodology for isolation of yeasts, particularly Saccharomyces cerevisiae, used in the production of cacha?a. According to the proposed strategy, the strains were selected for their ability to adapt to stress conditions encountered during fermentation of the sugarcane juice such as high sucrose concentration; high temperatures and high alcohol concentration; for their capacity to flocculate; and for their higher fermentative ability. For strains with such characteristics, specific procedures were employed to select for 5,5,5-trifluoro-DL-leucine (TFL) and cerulenin-resistant strains, since these characteristics are related to a higher capacity of production of the flavoring compounds isoamyl alcohol and caproic acid, respectively. The effectiveness of such a selection strategy was documented. Taken together, the results obtained present the development of a new strategy to isolate yeast strains with appropriated characteristics to be used in the cacha?a industry. Moreover, the results obtained offer an explanation for the great variability in terms of chemical composition found in products obtained even in a single distillery.     

The Effect of the Electric Field on Lag Phase, β-Galactosidase Production and Plasmid Stability of a Recombinant Saccharomyces cerevisiae Strain Growing on Lactose

Ethanol and ??-galactosidase production from cheese whey may significantly contribute to minimise environmental problems while producing value from low-cost raw materials. In this work, the recombinant Saccharomyces cerevisiae NCYC869-A3/pVK1.1 flocculent strain expressing the lacA gene (coding for ??-galactosidase) of Aspergillus niger under ADHI promoter and terminator was used. This strain shows high ethanol and ??-galactosidase productivities when grown on lactose. Batch cultures were performed using SSlactose medium with 50?g?L^?1 lactose in a 2-L bioreactor under aerobic and microaerophilic conditions. Temperature was maintained at 30?°C and pH?4.0. In order to determine the effect of an electric field in the fermentation profile, titanium electrodes were placed inside the bioreactor and different electric field values (from 0.5 to 2?V?cm^?1) were applied. For all experiments, ??-galactosidase activity, biomass, protein, lactose, glucose, galactose and ethanol concentrations were measured. Finally, lag phase duration and specific growth rate were calculated. Significant changes in lag phase duration and biomass yield were found when using 2?V?cm^?1. Results show that the electric field enhances the early stages of fermentation kinetics, thus indicating that its application may improve industrial fermentations?? productivity. The increase in electric field intensity led to plasmid instability thus decreasing ??-galactosidase production.     

Effect of pretreatments and retort process on characteristics and sensory quality of edible bird’s nest beverage

Edible bird ’ s nest (EBN) flakes were pretreated using sodium alginate (AG) in the presence of different divalent cross-linking agents before retorting at different temperatures (118 and 121 °C). Protein was the dominant component (58.61 g 100 g⁻¹, wet weight basis), followed by carbohydrate (24.38 g 100 g⁻¹, wet weight basis). Fourier transform infrared spectra (FTIR) showed the interaction between 1.0 g 100 mL⁻¹ AG with protein as induced by cross-linking agents including 0.5 g 100 mL⁻¹ calcium chloride, 1.0 g 100 mL⁻¹ calcium lactate or 1.0 g 100 mL⁻¹ magnesium chloride. Those alginate gels formed in beverage (EBNB) could withstand retorting at both temperatures. All pretreated EBN yielded EBNB with higher hedonic liking scores than control and non-retort process. Pretreatment of ENB using 1.0 g 100 mL⁻¹ AG and 1.0 g 100 mL⁻¹ calcium lactate before retorting at 121 °C rendered safe ready-to-drink EBNB with high hedonic liking score of all attributes.     

Effect of temperature and substrate on Pef inactivation of Lactobacillus plantarum in an orange juice–milk beverage

The inactivation kinetics of Lactobacillus plantarum in an orange juice–milk beverage treated by Pulsed Electric Fields (PEF) were studied. Experimental data were fitted to Bigelow and Hülsheger kinetic models and Weibull frequency distribution function. Results indicate that both Hülsheger model and Weibull function fit well the experimental data being Accuracy factor values (Af) closer to 1 and Mean Square Error (MSE) closer to 0. The parameter of the Weibull model can be considered as a kinetic indicator as it expresses the microorganism's resistance to treatment by electric pulses. An increase in temperature favoured the inactivation of L. plantarum by PEF as reflected by a decreased in value. Under the same conditions to those studied by other authors we reached less inactivation of L. plantarum in the beverage used in this study than in substrates with a simpler composition.     

Effect of a β-agonist on meat quality and myofibrillar protein fragmentation in bulls

Three experiments were conducted to study the effect of cimaterol on meat quality and myofibrillar protein fragmentation of the Longissimus dorsi muscle. In two experiments (Experiments 1 and 2), conducted with 16 double-muscled Belgian white-blue bulls and 15 Charolais bulls, respectively, half of the animals received 60 μg cimaterol daily per kg liveweight in the diet, during 135 and 93 days, respectively. In a third experiment, 46 normal Belgian white-blue bulls received no or 4 ppm cimaterol in the diet for 246, 127 or 71 days on average. A withdrawal period of 6 days was always applied for cimaterol-treated animals. Ultimate pH, colour and waterholding capacity were not significantly affected. The effect of cimaterol on moisture content was variable, while protein content was increased and fat was reduced. Warner-Bratzler shear force values were increased by cimaterol P < 0·05 in Experiments 2 and 3 and P = 0·07 in Experiment 1). The lower tenderness cannot be explained by differences in sarcomere length or hydroxyproline content. Myofibrillar protein fragmentation was lower when cimaterol was fed, suggesting that cimaterol may reduce myofibrillar protein degradation via a lower activity of the proteolytic enzymes. Length of cimaterol administration only exerted minor effects on meat quality.     

Effect of γ-irradiation on the sensory quality of moist beef biltong

Moist beef biltong (mean moisture content = 46.7% and a_w = 0.919) was vacuum packaged and irradiated to target doses of 0, 2, 4, 6, and 8 kGy. Thiobarbituric acid reactive substance (TBARS) measurements and sensory difference and hedonic tests were performed to determine the effect of γ-irradiation on the sensory quality of the biltong. TBARS values only increased significantly (P < 0.05) if biltong was irradiated to at least 8 kGy, indicating a low degree of lipid oxidation. This can be attributed to the low fat content (on average 1.53%) of the biltong used in this study, as well as irradiation under vacuum conditions. All irradiated samples could be discriminated (P < 0.05) from non-irradiated biltong, but none was rated as less acceptable. Dissipation of volatiles before tasting (by exposing the product to aerobic conditions before consumption), a low degree of lipid oxidation and liking of distinct ‘irradiation flavours’ possibly all attributed to the flavour of irradiated biltong not being regarded as unacceptable compared to controls. Biltong irradiated at 2 and 4 kGy was however liked significantly more (P < 0.05) than other samples, indicating that slight, non-oxidative irradiation-induced flavour changes may contribute to flavour development in the usually more bland moist beef biltong. Although lean moist beef biltong can thus be irradiated to doses up to 8 kGy without adversely affecting the sensory acceptability, low dose irradiation (4 kGy) is most feasible to optimise the sensory quality.     

Effect of feeding a Saccharomyces cerevisiae fermentation product to Holstein cows exposed to high temperature and humidity conditions on milk production performance and efficiency—A pen-level trial

The objective of this study was to evaluate the effect of feeding a Saccharomyces cerevisiae fermentation product (SCFP) on milk production efficiency of Holstein cows naturally exposed to high temperature and humidity conditions. The study was conducted in 2 commercial farms in Mexico from July to October 2020 and included 1 wk covariate period, 3 wk adaptation, and 12 wk data collection. Cows [n = 1,843; ≥21 d in milk (DIM) and <100 d carried calf] were enrolled and assigned to the study pens (n = 10) balanced for parity, milk yield, and DIM. Pens were fed a total mixed ration diet either without (CTRL) or with SCFP (19 g/d, NutriTek, Diamond V). Milk yield, energy-corrected milk (ECM), milk components, linear somatic cell score, dry matter intake (DMI), feed efficiency (FE; Milk/DMI and ECM/DMI), body condition score, and the incidence of clinical mastitis, pneumonia, and culling were monitored. Statistical analyses included mixed linear and logistic models accounting for repeated measures (when applicable; multiple measurements per cow within treated pens) with pen as the experimental unit and treatment, time (week of study), parity (1 vs. 2+), and their interactions as fixed and pen nested within farm and treatment as random effect. Parity 2+ cows within pens fed SCFP produced more milk than cows within CTRL pens (42.1 vs. 41.2 kg/d); there were no production differences between groups of primiparous groups. Cows within SCFP pens had lower DMI (25.2 vs. 26.0 kg/d) and greater FE (1.59 vs. 1.53) and ECM FE (1.73 vs. 1.68) than cows within CTRL pens. Milk components, linear somatic cell score, health events, and culling were not different between groups. At the end of the study (245 ± 54 DIM), SCFP cows had greater body condition score than CTRL (3.33 vs. 3.23 in the first parity; 3.11 vs. 3.04 in 2+ parity cows). Feeding Saccharomyces cerevisiae fermentation products to lactating cows exposed to high temperature and humidity conditions improved FE.     

Effect of water activity on sugar crystallization and β-carotene stability of freeze-dried mango powder

Storage water activity (a_w) affects the stability of freeze-dried food. The sugar crystallization and storage stability of β-carotene in freeze-dried mango powder was investigated following storage under various relative vapor pressures (11.3-80.9%). Sugar crystallization was revealed by the loss of sorbed water in the water sorption experiment. However, the sorption isotherms showed unclear divergence between the experimental and predicted values. X-ray powder diffraction and scanning electron microscopy were used to confirm the crystallization. The results showed that increased a_w resulted in higher sugar crystallization. The loss of β-carotene was monitored by high-performance liquid chromatography with a diode-array detector and fitted to a first-order reaction. The rate constant decreased as a_w increased up to 0.43, due to the collapse of the mango powder. An increase in the rate constant above this value of a_w coincided with pronounced sugar crystallization. Choosing the appropriate value of a_w for storage can prevent sugar crystallization and enhance β-carotene stability in freeze-dried fruit powder.     

Effect of thermal and high-pressure processing on the nutritional value and quality attributes of a nectarine purée with industrial origin during the refrigerated storage

The application of hydrostatic high pressure on an industrial line of nectarine (Prunus persica L.) purées was assessed in comparison with the traditional thermal treatment of pasteurization. Changes after thermal processing (85 °C, 5 min) and after high-pressure processing (HPP: 450 or 600 MPa for 5 or 10 min) and during the refrigerated storage (60 d) of an industrially produced nectarine purée were evaluated. Conventional heat pasteurization as well as HPP showed similar microorganisms' inactivation and maintained the microbial stability of purées until the end of the refrigerated storage (60 d). In general, thermally treated purée and HP-treated purée at 600 MPa showed more intense color changes after processing than the other treatment. In addition, thermally treated purée showed more intense color changes during storage than HPP. The highest carotenoids extractability was found in those purées treated at the lowest high-pressure-treatment intensity and holding time (450 MPa/5 min), but at the end of the storage (day 60), no differences in individual or total carotenoid levels were found between the purées. HPP at 600 MPa/10 min showed the highest polyphenols content after the treatment and during the storage. At day 0, significantly higher values were found of total antioxidant activity in purée HP-treated at 450 MPa/10 min than in untreated purée; while at the end of the storage, HP-treated purée at 600 MPa/10 min had the highest antioxidant activity. Hydrostatic high-pressure application in the industrial line of nectarine purée presented some advantages compared to the thermal treatment; however, some of the changes found were lessen during the storage period. In addition, more studies need to be carried out for HP-treatment intensity optimization.     

Effects of mediums on fermentation behaviour and aroma composition in pure and mixed culture of Saccharomyces cerevisiae with Torulaspora delbrueckii

The nutrient status and composition in mediums have a significant effect on yeast metabolism and phenotypic characteristics in wine fermentation. In this study, the effects of three frequently used mediums, including synthetic grape juice (SGJ), grape juice without grape pericarp and seeds (GJ) and grape must with grape pericarp and seeds (GMPS), on yeast fermentation behaviour and aroma compounds produced by pure and mixed culture of Saccharomyces cerevisiae T73 with Torulaspora delbrueckii TD20 were investigated after alcoholic fermentation. The results showed that high fermentation activities and cell population were always found in GJ medium irrespective of inoculated approach. More esters and higher alcohols were produced in GMPS medium fermented by pure S. cerevisiae, while SGJ medium had increased levels of fatty acids. Consistent with previous literatures, the mixed fermentation of T. delbrueckii and S. cerevisiae produced more acetate esters and fatty acids than the pure culture of S. cerevisiae, while this enological trait was only found in SGJ and GJ, not in GMPS. Our results highlighted that more attention should be paid to the fermentation medium when evaluating the enological and aromatic properties of selected yeasts used in industrial winemaking. In this regard, the combined use of GJ and GMPS medium might be a suitable choice.     

Role of precursors on the kinetics of acrylamide formation and elimination under low moisture conditions using a multiresponse approach – Part I: Effect of the type of sugar

The effect of type of sugar on the kinetics of acrylamide formation and elimination reactions was investigated under low moisture conditions using equimolar asparagine–sugar model systems, heated at temperatures between 120 and 200 °C. The monosaccharides glucose and fructose and the disaccharide sucrose were selected to study this effect. A mechanistic model was used as a basis for multiresponse modelling of the different responses measured (acrylamide, glucose, fructose, sucrose, asparagine, aspartic acid and melanoidins). In spite of the higher acrylamide yield per mol initial asparagine for sucrose over fructose to glucose, the kinetic parameters estimated for acrylamide formation revealed that the type of sugar, monosaccharide or disaccharide, had only a limited effect on this reaction. The corresponding activation energy, however, was significantly lower in case the disaccharide sucrose was added. An opposite trend was observed for the acrylamide elimination rate constant, being significantly higher for the system with sucrose, whereas the temperature dependence of this rate constant remained unaffected by the type of sugar available under the reaction conditions considered.     

Microbial quality, and effect of cooking on survival of Salmonella, in Kokariç

A special preparation from the small intestine of lamb, called kokariç, is widely consumed in Turkey. In this study, Salmonella was not isolated from raw kokariç. Conventional ways of cooking, except precooking, destroyed Salmonella in artificially contaminated kokariç. The microbial quality of cooked kokariç bought from street sellers was not safe for public health consumption because of environmental contamination.     

Effect of γ-irradiation on physical quality attributes and identification properties of different sauces

Gamma-irradiated (0, 1, and 10 kGy) ketchup (KTP), barbeque sauce (BBQ), and sweet chili sauce (SWC) were identified using photostimulated-luminescence (PSL) and thermoluminescence (TL) analysis and characterized for physical properties like Brix, consistency, and color. PSL-based screening showed negative results for all nonirradiated samples, while intermediated results were found for irradiated samples. Routine density separation method for mineral extraction provided better TL results; however, alkaline and acid hydrolysis could ease the process with acceptable results. A slight decrease in consistency of all the samples was observed. Brix of KTP remained unchanged, while increase of same was obvious in BBQ and SWC following irradiation. The Hunter L* value of the γ-irradiated sauces decreased except SWC samples, and the a* and b* values showed a general increase compared to the non-irradiated samples. The studied methods have potential to successfully identify and characterize the irradiated sauces for technical and regulatory requirements.