Editing Tempeh (section)

==Production==
[[File:Membungkus Tempe.jpg|thumb|Making tempeh by wrapping boiled soybeans in [[Musa (genus)|banana]] leaves]]
Tempeh begins with whole soybeans, which are softened by soaking, [[dehull]]ed, then partly cooked. Specialty tempeh may be made from other types of [[bean]]s, [[wheat]], or may include a mixture of beans and [[whole grain]]s.<ref name="The Book of Tempeh" /> Adding vinegar during soybeans soaking process had also been reported in tempeh industries and it had been found to influence the sensory nature of the final product.<ref>{{Cite journal |last1=Dahlan |first1=Hadi Akbar |last2=Nambu |first2=Yosuke |last3=Putri |first3=Sastia Prama |last4=Fukusaki |first4=Eiichiro |date=January 2022 |title=Effects of Soaking Tempe in Vinegar on Metabolome and Sensory Profiles |journal=Metabolites |language=en |volume=12 |issue=1 |pages=30 |doi=10.3390/metabo12010030 |issn=2218-1989 |pmc=8781261 |pmid=35050152|doi-access=free }}</ref>

The principal step in making tempeh is the [[fermentation]] of soybeans which undergo inoculation with ''[[Rhizopus]]'' spp. molds, a type of filamentous fungus most widely used for the production of tempeh. A [[fermentation starter]] containing the spores of [[fungus]] ''Rhizopus oligosporus'' or ''Rhizopus oryzae'' is mixed in.<ref>{{cite journal|journal=Tempeh.info|url=http://www.tempeh.info/starter/what-is-tempeh-starter.php|title=What is tempeh starter?}}</ref> The beans are spread into a thin layer and are allowed to ferment for 24 to 36 hours at a temperature around 30°[[Celsius|C]] (86°[[Fahrenheit|F]]). The soybeans have to cool down to allow spore germination and abundant growth of [[mycelium]]. Later, the temperature of the beans will naturally rise and rapid mold growth happens for around 4 hours. As mold growth declines, the soybeans should be bound into a solid mass by the mycelium. In good tempeh, the beans are knitted together by a mat of white [[mycelium]]. Typically, tempeh is harvested after 48 hours of fermentation with its distinguishable whitish color, firm texture, and nutty flavor. Extended fermentation time results in an increase in pH and undesirable color darkening in the tempeh.<ref>{{Cite conference|last1=Muzdalifah|first1=D.|last2=Athaillah|first2=Z. A.|last3=Nugrahani|first3=W.|last4=Devi|first4=A. F.|date=2017 |volume=1803 |issue=1|pages=020036|doi=10.1063/1.4973163 |bibcode=2017AIPC.1803b0036M|title=Colour and pH changes of tempe during extended fermentation|conference=International Symposium on Applied Chemistry |series=AIP Conference Proceedings}}</ref>
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During the fermentation process, optimal time of fermentation, temperature, oxygen, humidity, and pH levels are required to encourage the growth of the ''Rhizopus'' mold, while discouraging the growth of undesired microorganisms.<ref>{{Cite journal|last1=Nout|first1=M.J.R.|last2=Kiers|first2=J.L.|date=April 2005|title=Tempe fermentation, innovation and functionality: update into the third millenium|journal=Journal of Applied Microbiology|volume=98|issue=4|pages=789–805|doi=10.1111/j.1365-2672.2004.02471.x|pmid=15752324|s2cid=19259459|issn=1364-5072|doi-access=|url=https://research.wur.nl/en/publications/tempe-fermentation-innovation-and-functionality-update-into-the-t }}</ref> The pH level should be kept around 3-5 by adding a mild [[acidulant]] such as [[vinegar]], [[lactic acid]], or [[acetic acid]], thereby favoring mold growth and restricting the growth of spoilage microorganisms.<ref name=":03">{{Cite book|title=Tempeh production : a craft and technical manual|author=Shurtleff, William|date=1986|publisher=Soyfoods Center|others=Aoyagi, Akiko., Shurtleff, William, 1941-, Soyfoods Center (Lafayette, Calif.)|isbn=978-0933332232|edition= 2nd|location=Lafayette, CA|oclc=13002817}}</ref> Oxygen is required for ''Rhizopus'' spp. growth, but should be maintained at low levels to prevent the production of undesired microorganisms. Under conditions of lower temperature, or higher ventilation, gray or black patches of [[spore]]s may form on the surface—this is not harmful, and should not affect the flavor or quality of the tempeh.<ref name="How We Make and Eat Tempeh down on The Farm">{{cite journal|author=|journal=Mother Earth News|date=September–October 1977|url=http://www.motherearthnews.com/Real-Food/1977-09-01/Tempeh-Recipes.aspx|title=How to Make and Cook Tempeh|access-date=3 January 2013}}</ref> <!--Tempeh mushroom good clean white, if black does not mean perfect circulation.--> This sporulation is normal on fully mature tempeh. A mild [[ammonia]] smell may accompany good tempeh as it ferments, but it should not be overpowering.

Traditional tempeh is often produced in [[Indonesia]] using ''[[Hibiscus tiliaceus]]'' leaves. The undersides of the leaves are covered in downy hairs (known technically as trichomes) to which the mold ''Rhizopus oligosporus'' can be found adhering in the wild. [[Soybean]]s are pressed into the leaf, and stored. Fermentation occurs resulting in tempeh.<ref name="The Book of Tempeh">{{cite book |url=https://books.google.com/books?id=hdKzFlaqWT8C |format=PDF |title=The Book of Tempeh |first1=William |last1=Shurtleff|author-link=William Shurtleff |first2=Akiko|last2=Aoyagi|author-link2=Akiko Aoyagi |publisher=Soyinfo Center, [[Harper and Row]] |year=1979 |url-status=dead |archive-url=https://web.archive.org/web/20130819141428/http://https/ |archive-date=2013-08-19 |isbn=9780060140090 }}</ref> In particular, the tempeh undergoes salt-free aerobic fermentation.<ref name="Watanabe">{{cite journal | last1=Watanabe | first1=N. | last2=Fujimoto | first2=K. | last3=Aoki | first3=H. | title=Antioxidant activities of the water-soluble fraction in tempeh-like fermented soybean (GABA-tempeh) | journal=International Journal of Food Sciences and Nutrition | volume=58 | issue=8 | year=2007 | pages=577–587 | doi=10.1080/09637480701343846| pmid=17852485 | s2cid=45727148 }}</ref>

Tempeh made with traditional inoculation methods are also more likely to include molds of other species including ''[[Rhizopus arrhizus]]'' and ''[[Rhizopus delemar]]'' which may outcompete Rhizopus oligosporus as the dominant mold. This results in white woolly appearance and more pleasant aroma compared with tempeh made with commercial starter containing only Rhizopus oligosporus. Famously these variant tempeh are found in [[Malang]] and [[Purwokerto]] in the 1960s, because Malang is located in a cool [[plateau]], and tempeh made with ''Rhizopus oligosporus'' resulted in less compact and more alcoholic-smelling tempeh, while ''Rhizopus arrhizus'' required lower optimum temperature which made it more ideal. However the widespread use of commercial starter resulted in most tempeh in Java only containing ''Rhizopus oligosporus'', with few traditionally made tempeh outside Java still containing ''Rhizopus arrhizus'' and ''Rhizopus delemar''.<ref name="Sjamsuridzal Khasanah Febriani Vebliza 2021 pp. 1–10">{{cite journal | last1=Sjamsuridzal | first1=Wellyzar | last2=Khasanah | first2=Mangunatun | last3=Febriani | first3=Rela | last4=Vebliza | first4=Yura | last5=Oetari | first5=Ariyanti | last6=Santoso | first6=Iman | last7=Gandjar | first7=Indrawati | title=The effect of the use of commercial tempeh starter on the diversity of Rhizopus tempeh in Indonesia | journal=Scientific Reports | volume=11 | issue=1 | date=2021-12-14 | page=23932 | issn=2045-2322 | doi=10.1038/s41598-021-03308-6 | pmid=34907227 | pmc=8671487 | bibcode=2021NatSR..1123932S }}</ref>

=== Dry matter losses and yield ===
During the processing of soybeans to make tempeh there are inevitable losses of material due to the removal of the hulls and the leaching of soluble compounds during the soaking, washing and cooking stages. Hulls constitute about 8% of the dry beans and losses due to the leaching of soluble compounds equate to 12 - 17% of the dry beans. The [[oligosaccharides]], [[stachyose]], [[raffinose]] and [[sucrose]], can constitute up to 50% of the soluble materials lost.<ref name=":4">{{Cite book|last=Steinkraus|first=K.H.|title=Handbook of Indigenous Fermented Foods|publisher=Marcell Dekker|year=1996|isbn=0-8247-9352-8|location=New York|pages=7–110}}</ref><ref name=":5">{{Cite book|last1=Owens|first1=J.D.|title=Indigenous Fermented Foods of Southeast Asia|last2=Astuti|first2=M.|last3=Kuswanto|first3=K.R.|publisher=CRC Press|year=2015|isbn=978-1-4398-4480-9|editor-last=Owens|editor-first=J.D.|location=Boca|pages=1–108|chapter=Tempe and related products.}}</ref> During the fermentation there is some further loss of material due to respiration by the mold and the oxidation of compounds to carbon dioxide and water. Reported losses of dry matter during the fermentation range from 2.1 to 10%.<ref name=":4" /><ref name=":5" /><ref>{{Cite journal|last1=Sparringa|first1=R.A.|last2=Owens|first2=J.D.|date=1999|title=Protein utilization during soybean tempe fermentation.|journal=Journal of Agricultural and Food Chemistry|volume=47|issue=10|pages=4375–4378|doi=10.1021/jf981279u|pmid=10552819|bibcode=1999JAFC...47.4375S }}</ref> Hence, the overall yield of tempeh is in the range of 72-78 g tempeh per 100 g soybeans on a dry matter basis. In practical terms, this means that 100 g dry soybeans (7-9% moisture content) will yield about 170 to 210 g fresh tempeh (61-64% moisture content).<ref name=":4" />

=== Determining quality ===
Once tempeh is produced, it is divided into three categories based on its quality: good, unfinished, and inedible. Good tempeh includes [[bean]]s that are bound into a firm, compact cake by a dense, uniform, white [[mycelium]], which should permeate the entire cake; the beans should be barely visible. The odor of good tempeh should be pleasant, clean, subtly sweet or resemble the aroma of mushrooms. The entire tempeh should lift as a single, cohesive cake without crumbling when shaken gently. Unfinished tempeh has beans that are bound together loosely by a sparse white mycelium, hence it crumbles easily. Unfinished tempeh should be incubated longer unless it has been incubated more than eight hours past the recommended time. If it has been incubated for enough time and still remains unfinished, it should be discarded. Inedible tempeh has beans with foul odor, resembling strong ammonia or alcohol, indicating the development of undesirable [[bacteria]] due to excess moisture or overheating. Inedible tempeh cake is wet, slimy, and mushy with a collapsed structure. Its color is tan to brown and [[Mold (fungus)|mold]] develops in sparse patches.<ref name=":03"/>

=== Packaging ===
[[File:Tempeh 001.jpg|thumb|right|Tempeh traditionally wrapped in [[banana leaf]]]]
Food grade wrapping paper and perforated [[polyethylene]] bags are the most suitable materials for packaging tempeh. They have demonstrated good retention of the quality of tempeh and extension of the [[shelf life]] of tempeh for three days compared to fresh tempeh. Appropriate packaging is important as it provides optimum oxygen supply and temperature for inoculation and [[fermentation]] to occur during processing.<ref name=":1">{{Cite journal|last1=Santhirasegaram|first1=Vicknesha|last2=George|first2=Dominic Soloman|last3=Anthony|first3=Kelvin Kiran|last4=Singh|first4=Hasvinder Kaur Baldev|last5=Saruan|first5=Nadiah Mohd|last6=Razali|first6=Zuliana|last7=Somasundram|first7=Chandran|date=December 2016|title=Effects of Soybean Processing and Packaging on the Quality of Commonly Consumed Local Delicacy Tempe|journal=Journal of Food Quality|volume=39|issue=6|pages=675–684|doi=10.1111/jfq.12252|issn=0146-9428|doi-access=free}}</ref> Tempeh is a [[perishable food]] and must be wrapped and placed into the refrigerator or freezer immediately after incubation or other processing steps such as [[Blanching (cooking)|blanching]]. In the refrigerator or freezer, stacking of tempeh should be minimized to prevent overheating and the undesirable, gradual continuation of fermentation, both of which shorten the storage life of tempeh. Even under cold temperature, tempeh continues to [[Cellular respiration|respire]] and undergo slow [[decomposition]] from [[microorganism]]s and its natural [[enzyme]]s. Therefore, tempeh should be well cooled for at least two to five hours in a cooler before it undergoes further packaging.<ref name=":03" /> Tempeh packaged in perforated polyethylene bags is usually repacked inside another labeled, non-perforated bag for distribution, sale and easier labeling. If the tempeh is packaged in only one perforated bag, the label must be directly attached to the perforated surface with the use of government food contact approved [[adhesive]].<ref name=":1" /> It is then bulk packed in cartons and returned to the refrigerator or freezer to await shipment.<ref name=":03" />