Quality in brewing
- means: consistently meet the specification
- specification: which beer style? how to measure them?
- consistency: depends on scientific facts and measurements
- homogeneity: 2 row barley is more homogeneous than 6 row barley, easy to meet the quality standard
- basic rules of quality control: set-compare-fix
- establishment of specification: via human sense or instrumental analysis
- spec in/out
Quality control via sampling
- raw material: each delivery
- brewhouse operation: each batch
- unfermented wort: each batch
- yeast: each batch, every pitch
- fermenting beer: every 12 hours
- fermented beer and beer ready for filtration: each tank
- packaging material: each delivery
- beer in package: each code
- plant: number of tanks per week
- cleaning material: specific sample of material per week
Parameters in specification
- ABV: alcohol
- OG, FG: body, richness in flavor
- pH: yeast performance, hop utilization, and bitterness, microorganism growth
- beer color
- IBU
- flavor compounds
- DO2: origin of oxidation
- CO2: over carbonation?
- N2: head retention
- beer flavor: match for style?
- clarity
- head stability
- sterility: wild yeast or bacteria
Main components of contamination
- chemical
- microbiological
- physical
Anaerobic organism
- obligate anaerobe: cannot live with oxygen
- aero-tolerant organism: no need oxygen to live but can tolerate
- facultative anaerobe: no need oxygen to live but can use, brewer's yeast
Microorganism
in unpitched wort:
- obesumbacteria(Hafnia), grow with yeast and found in top fermentation
- escherichia(e-coli), originated from contaminated water
- enterobacter, cannot grow in pH 4.3 and vigorously grow in wort(not beer). produce DMS, diacetyl off flavor
in fermentation:
- pediococcus, produce lactic acid and diacetyl
- lactobacillus, produce lactic acid and diacetyl
- wild yeast, produce biofilm, super attenuation
wild yeast:
- pichia, vigorously grow in the air and produce biofilm
- candida, vigorously grow in the air and produce biofilm
- saccharomyces diastaticus, super attenuation
- torulopsis, produce precipitate, cause haze
- brettanomyces, long slow growth and give sourness, off flavor to beer
- hansenula, vigorously grow in the air and produce biofilm
Control over microorganism
- equipment design for easy cleaning
- efficient cleaning and sterilization
- sterilizing product and raw material: boiling, filtering, pasteurization
- environment against microorganism growth: low temperature(1'c), lower pH(3.5~4.5), washing yeast, pasteurization, fresh yeast
Sensory evaluation
4-vinyl guaiacol(phenolic)
- how to: 맥주 잔을 손으로 덮어 향이 맥주잔 내 가득 발산하게 한 뒤 냄새를 맡아봄.
- mainly considered as off flavor, but one of the profiles in wheat beer
- word: clove like, spicy, herbal, 치과냄새. 치과 치료 받고 우루룩하는 느낌
- origin: wild yeast, bacteria infection
- threshold: 0.2mg/L
- similar to Isobutyraldehyde, Sulphur dioxdie, Vanillin
Diacetyl
- how to: 유리잔 채로 맥주를 흔들어 향 발산시켜 냄새를 맡아봄. 인지 어려울 경우 입 안에 머금어 미끈거리는 느낌 확인
- off flavor for pale lager, not bad for ale and stout
- word: buttery, butterscotch, honey, caramel, 둥글고 들큰한 향
- origin: alpha-acetolactate, bacteria infection, lactobacillus, pediococcus
- threshold: 10-40ug/L(2,3-butanedione)
- similar to Butyric acid, Vanillin, Isobutyraldehyde
Citric acid(sour)
- how to: 입 안에 소량의 맥주를 머금고 혀를 몇 초간 굴린 후 삼킴
- when too much, considered as off flavor
- word: acidic, lemon, sour milk, 신맛. 레몬즙 맛. 피니시까지 계속 시기만 함
- origin: wrong fermentation environment, bacteria infection
- threshold: 60-170mg/L
- similar to Acetic acid, Lactic acid, Astringent
H2S(Hydrogen sulphide)
- how to: 향이 발산되게 흔들어 냄새를 맡는다
- bring freshness with low amounts, off flavor with high amounts
- word: rotten eggs, sulphidic, 썩은 달걀
- origin: by product of wrong fermentation, bacteria infection
- threshold: 4ug/L
- similar to Sulphur dioxide, Ethanethiol, Methanethiol
Oxidation(Trans-2-nonenal, T2N, Parpery)
- how to: 유리잔 채로 맥주를 흔들어 향 발산시켜 냄새를 맡아봄.
- mainly found in aging beer, produced during production and distribution, favored in high temperature
- word: cardboard, oxidized, papery, 오래된 맥주, 마분지, 골판지
- origin: oxidation
- threshold: 50-100ng/L
- similar to 2,4,6-Trichloroanisole, 2-Ethyl fenchol, Isobutyraldehyde
Lightstruck(3-methyl-2-butane-1-thiol, 3MBT)
- how to: 팔 길이 안에서 냄새를 맡는다
- exposed by sunlight
- word: skunky, sunstruck, 음식쓰레기 냄새, 구린내
- origin: distortion of the chemical structure of iso-alpha acid
- threshold: 4-30ng/L(3-Methyl-3-butane-1-thiol)
- similar to sulphur dioxide, cis-3-Hexenol, Ethanethiol
Dimethyl sulphide(DMS)
- how to: 맥주를 흔들어 향 발산시켜 냄새를 맡아봄.
- sweet corn flavor, good for certain pale lager style
- word: sweet corn, cooked vegetable, 들큰한 스위트콘, 스위트콘 통조림
- origin: imperfect malt modification(kiln), bacteria infection, S-methyl methionine and dimethyl sulphoxide
- threshold: 25ug/L
- similar to Methyl thioacetate, Ethanethiol, Dimethyl trisulphide
Acetaldehyde
- exist in every beer with low content, but off flavor with high content
- word: aldehyde-like, green apple, oil painting, 사과주 냄새
- origin: short fermentation, dissolved oxygen, pediococcus
- threshold: 5-15mg/L
Metalic
- how to: 입 안에 소량의 맥주를 머금고 혀를 몇 초간 굴린 후 삼킴. 손등에 맥주를 비벼 금속 향이 나는지 확인
- contact with metal pipe or machine, can, bottle cap or oxidation of lipids
- word: inky, blood-like, tinny, 피맛, 뒷맛이 금속맛, 메아리처럼 퍼짐
- origin: raw material, contact with metal, diatomite
- threshold: 1~2.7mg/L
- similar to Sulphitic, Citric acid, T2N
Ethylmercaptan/Ethanethiaol(Mercaptan/Methanethiol)
- how to: 유리잔 채로 맥주를 흔들어 향 발산시켜 냄새를 맡아봄.
- rotten gas, sulphur, burnt match
- word: drain, rotten vegetable, neutral gas, 하수관 냄새, 오래된 배관의 퀘퀘함
- origin: produced during conditioning, yeast autolysis
- threshold: 1ug/L
- similar to Ethanethiol, Dimathyl trisulphide, Sulphur dioxide
Butyric
- how to: 맥주 잔을 손으로 덮어 향이 발산하게 흔들어줌. 향이 묻은 손의 냄새를 맡으며 인지할 때까지 반복
- rotten flavor, baby vomit
- word: rancid, babysic, putrid, 아기 토 냄새
- origin: bacteria(pectinatus, megasphaera) infection during wort production or packaging
- threshold: 2-3mg/L
- similar to Isovaleric acid, Ethyl butyrate, 2,3-Butanedione
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