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parti-gyle
Antiquated brewhouse practice in England. First and strongest runnings become strong ale, second runnings become ordinary beer, and the last and weakest runnings become small beer. Useful technique for no sparge mashing where the last runnings is used for yeast starters.
pasteurization
The process of sterilizing by heat.
pectin
A chain of galacturonic acid that becomes gelatinous in the presence of sugars and acids.
pentosans
Pentose-based complex carbohydrates, found in barley as gums.
pentose
A group of simple sugars having five carbon molecules. Monosaccharides from the decomposition of pentosans, unfermentable by yeast. Includes arabinose and xylose.
peptidase
This proteolytic enzyme works to break large and medium-sized protein molecules into amino acids. It is less thermal stable than protease so it is denatured quickly at higher temperatures. Most effective around 122 °F (50 °C).
peptide
Short fragment of proteins consisting of between two and 30 amino acid molecules bound by peptide links. Peptides enhance the fullness of beer.
peptonization
Alternate name for proteolysis.
pH
A numerical measurement of acidity or alkalinity determined by the presence of hydrogen ions. The pH scale ranges in values from one to 14 with seven being neutral. A pH of lower than seven indicates acidity or the presence of more hydrogen ions. The lower the pH number, the higher the concentration of hydrogen ions and the stronger the acidity of the solution. Numbers above seven represent alkalinity with 14 representing the strongest alkali solution.
pH meter
An instrument with a digital display that measures, calculates and displays the pH of a solution. This device must be calibrated with a solution of known pH. A properly calibrated pH meter is more accurate than pH paper because visual comparison of color is not required.
pH paper
Chemically treated strips used to measure the pH of a solution. The strips change color in response to the acidity or alkalinity of a solution. The degree of color on the strip is compared to a standard scale to determine the level of acidity or alkalinity.
phenols
Aromatic hydroxyl precursors of tannins (polyphenols).
phenolic flavor
Can be any one or a combination of medicinal. plastic, electrical fire, Listerine-like, Band-Aid-like, smoky or clovelike aromas and flavors. Most often caused by wild yeast or bacterial contaminations. Can be extracted from grains, sanitizing residues left in brewing equipment can contribute.
phosphates
These molecules are the source of phytic acid created during malting and during decoction or step infusion mashes. They contribute to the acidulation of the mash.
phytase
An enzyme that reduces the mash pH by creating phytic acid from the phytin of the malt. This aids saccharification, wort clarification and fermentation.
pitching
Inoculating wort with a yeast starter to begin fermentation.
plato
European and American scale of gravity based on a percentage of pure sugar in the wort. A newer, more accurate version of the Balling scale. Expressed as °Plato.
polyclar
The tradename for a material used to clear beer. Consists of microscopic plastic beads that remove chill-haze by adsorption.
polymer
Chemical molecule made of the repetition of smaller basic units. Examples in brewing are polyphenols, polysaccharides and polypeptides.
polypeptide
Chain of amino acids. Includes proteins and other polymers of peptides.
polyphenols
Polyphenols are derived from the husk and are acidic precursors of tannins. These molecules can give beer an astringent taste. Polyphenol extraction can be reduced by keeping the pH of the mash between 5.0 and 5.5. Polyphenols form complexes with proteins and are the cause of chill haze.
polysaccharide
Polymers of simple sugars. Includes a range from complex sugars through dextrins, up to starches. Polysaccharides are reduced to monosaccharides by hydrolysis in mashing.
PPB
Parts per billion. 1 microgram per liter.
PPM
Parts per million. 1 milligram per liter.
precipitation
A process, involving a material coming out of solution such as in a cold or hot break.
precursor
A substance from which another substance is derived.
premium lager
A beer category made up by megabreweries. See domestic commercial.
primary fermentation
The first stage of fermentation. Initial rapid stage of yeast activity when the simple sugars in the wort are metabolized.
primary fermenter
The vessel in which primary fermentation is carried out.
priming
The process of adding sugar to beer before bottling or racking to kegs. Induces fermentation to carbonate the beer (bottle condition).
protein
Complex chains of amino acids. Proteins provide essential yeast nutrients and contribute to the body and head retention of beer. During a protein rest large proteins are broken down to amino acids and smaller soluble proteins.
protein rest
A stage of the mashing process during which complex proteins are decomposed by proteolytic enzymes (peptidase, proteinase) to progressively less complex fractions. The stability of finished beer is largely established during the protein rest. Nutrients required for proper fermentation also are developed during this process. The proteolytic enzymes become active at temperatures from 120 - 140 °F (26 - 52 °C).
proteinase
This proteolytic enzyme works to break large protein molecules down into medium-sized proteins. It is more thermal stable than peptidase so it works at higher temperatures where peptidase is soon denatured. Also know as protease.
proteolysis
The breaking up or digestion of proteins by enzymes that occurs in the mash around 122¡F/50¡C. The reduction of protein by proteolytic enzymes to fractions.
proteolytic enzymes
Peptidase, proteinase. Enzymes naturally present in barley and malt that have the power to break up proteins in the mash.
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