Improving the Utilization of Isomaltose and Panose by Lager Yeast Saccharomyces pastorianus

Approximately 25% of all carbohydrates in industrial worts are poorly, if at all, fermented by brewing yeast. This includes dextrins, β-glucans, arabinose, xylose, disaccharides such as isomaltose, nigerose, kojibiose, and trisaccharides such as panose and isopanose. As the efficient utilization of carbohydrates during the wort’s fermentation impacts the alcohol yield and the organoleptic traits of the product, developing brewing strains with enhanced abilities to ferment subsets of these sugars is highly desirable. In this study, we developed Saccharomyces pastorianus laboratory yeast strains with a superior capacity to grow on isomaltose and panose. First, we designed a plasmid toolbox for the stable integration of genes into lager strains. Next, we used the toolbox to elevate the levels of the α-glucoside transporter Agt1 and the major isomaltase Ima1. This was achieved by integrating synthetic AGT1 and IMA1 genes under the control of strong constitutive promoters into defined genomic sites. As a result, strains carrying both genes showed a superior capacity to grow on panose and isomaltose, indicating that Ima1 and Agt1 act in synergy to consume these sugars. Our study suggests that non-GMO strategies aiming to develop strains with improved isomaltose and panose utilization could include identifying strains that overexpress AGT1 and IMA1.

Organoleptic, Sensory and Biochemical Traits of Arabica Coffee and their Arabusta Hybrids

Coffee as a cash crop, reduces food insecurity by providing regular incomes and is a major foreign exchange earner in more than fifty tropical countries where it is grown either as Arabica (Coffea arabica) or Robust (Coffea canepora). In Kenya which grow some Robusta but mostly Arabica coffee, the production has been declining, mainly because world coffee prices have plummeted to about 5 USD for a 650Kg of un-hulled beans per acre. The only way world prices are likely to increase and benefit the small-scale farmers, is by improving the cup quality and enabling these countries to sell their coffee in specialty markets. This review, underscores the importance of analyzing and estimating organoleptic, sensory and biochemical compounds diversity in Arabica coffee, since these are the factors that determine cup quality. In an attempt to do so, the chapter presents experimental data that analyzed various sensory and organoleptic traits of Arabica coffee and their Arabusta hybrids that proves that tremendous genetic diversity exists in coffee genotypes grown in Kenya and it is possible to utilize this genetic variation to improve cup quality.

Anthocyanins and Anthocyanin-Derived Products in Yeast-Fermented Beverages

The beverages obtained by yeast fermentation from anthocyanin-rich natural sources (grapes, berries, brown rice, etc.) retain part of the initial pigments in the maturated drink. During the fermentation and aging processes anthocyanins undergo various chemical transformations, which include reactions with glycolytic products (especially pyruvate and acetaldehyde) or with other compounds present in the complex fermentation milieu (such as vinylphenols obtained from cinnamic acids by means of a yeast decarboxylase) yielding pigments which can be more stable than the initial anthocyanins. Overall, these compounds contribute to the organoleptic traits of the mature product, but also to the overall chemical composition which make the yeast fermented beverages important sources of dietary antioxidants. In this review, we focused on the studies regarding the changes underwent by anthocyanins during yeast-mediated fermentation, on the approaches taken to enrich the fermented beverages in anthocyanins and their derived products, and on the interrelations between yeast and anthocyanin which were of relevance for obtaining a high-quality product containing optimum amounts of anthocyanin and anthocyanin-derived products.

Characteristics of Polish Unifloral Honeys IV. Honeydew Honey, Mainly Abies Alba L.

Summary Coniferous honeydew honey, mainly Abies alba was characterised. Samples chosen for the study had organoleptic traits characteristic for the variety: greenish, opalescence tone of brown colour, mild, sweet flavour with pleasant, slightly resinous aftertaste and aroma as well as electrical conductivity over 0.95 mS/cm. To define composition and physicochemical parameters of the variety, contents of water and total sugars were determined. In addition various carbohydrates were identified and their contents were assessed as well. These were: fructose, glucose, sucrose, maltose, turanose, trehalose, isomaltose, malezitose. Other examined parameters related to honey quality were: free acidity, pH, the content of 5-hydroxymetylofurfural (HMF), the main amino acid - proline, and the activity of α-amylase enzyme (Diastase Number). The following properties were proven to be characteristic for this variety: high electrical conductivity with the average value of 1.14 mS/cm, ranging from 0.96 to 1.32 mS/cm; content of monosaccharides lower by few percent in relation to other honey varieties (from 58.2 to 67.4 g/100 g; on average 62.0 g/100 g) and a higher content of disaccharides and trisaccharide - melezitose. The presence of this sugar confirms that a considerable part of the honey was produced from honeydew. The average value of melezitose was 3.2 g/100 g, ranging from 0.9 to 5.9 g/100 g. Also, the results of the pH measurements were slightly higher than in other honey varieties (from 4.23 to 4.99; on average 4.63). The colour value in mm Pfund ranged from 74 to 105, with the average of 93.

Phenolic Compounds in Merlot Wines Obtained Through Different Technologies in Iaşi Vineyard, Romania

Obtaining red quality wines depends on the raw matter composition and also on the extraction technology, used in the processing of grape and must. Thus, two methods of maceration-fermentation on lees (classical and in rotating tanks), two thermal methods (thermomaceration and microwave maceration) and two methods rarely used industrially in wine-making (cryomaceration and ultrasound maceration) were experimented. Even in the years with less than favorable climatic conditions, from Merlot grape variety one obtained for the most part, legally speaking, quality wines (with the exception of microwave macerated and cryomacerated wines, which had only 21-22 g/L non-reducing extract. In regard to alcohol content, all obtained samples had more than 11% vol. The obtained Merlot wines were rich in glycerol (8-9 g/L), fact that favorably influenced their organoleptic traits. Total phenolic content had values between 1,97 and 2,86 g/L for the Merlot wines obtained through macerationfermentation and thermomaceration. Ultrasound maceration did not favor phenolic extraction from grape skins and the obtained wines were poor in anthocyans and tannins (0,94-1,1 g/L). In regard to the maceration technology used, free anthocyans were found in variable proportions in wines, between 77 and 91%. The sum of acylated anthocyans participation percentages was between 8,8 and 22,7%, and the ratio between the acetylated and cumarilated participation percentages registered small values, varietyspecific, between 1,1 and 2,8.