Ear­li­er this week, Sue Fishkoff wrote about watch­ing a goat slaugh­tered and peo­ple who only keep kosher on hol­i­days. She is the author of Kosher Nation: Why More and More of America’s Food Answers to a High­er Author­i­ty.

The most fas­ci­nat­ing work of kosher food man­u­fac­tur­ing takes place in the mid­dle of the night. That’s when fac­to­ries shut down their lines for kash­er­ing, when ovens are blast­ed with blow­torch­es and boil­ing water is run through miles of pipes and in and out of huge stain­less steel vats.

That’s when the mash­giachs, or kosher super­vi­sors, start work in indus­tri­al kitchens and ban­quet halls, clean­ing bugs from pounds of let­tuce, cel­ery and oth­er fresh produce.

And that’s when the flour for Man­is­che­witz kosher-for-Passover matzah begins its jour­ney from west­ern Penn­syl­va­nia to the company’s $15 mil­lion man­u­fac­tur­ing facil­i­ty in Newark, NJ.

Matzah is impor­tant to Man­is­che­witz. The 120-year-old com­pa­ny makes a wide range of kosher prod­ucts, but it was found­ed in 1888 to pro­duce kosher-for-Passover matzah on a new assem­bly line for­mat, and matzah is still cen­tral to its mis­sion. Like most eth­nic kosher food man­u­fac­tur­ers, Manischewitz’s busiest sea­son is Passover. Fifty per­cent of its busi­ness involves kosher-for-Passover food. Accord­ing to one sur­vey, 24 per­cent of Amer­i­can non-Jew­ish con­sumers bought a Man­is­che­witz prod­uct dur­ing the pre­vi­ous year; most of them bought matzah.

Passover matzah is the most labor-inten­sive kosher prod­uct in the world. As one of two sacra­men­tal foods required at the seder table, along with wine, its pro­duc­tion is care­ful­ly con­trolled to ensure that water only comes into con­tact with the flour for less than 18 min­utes. Longer than that and, accord­ing to rab­binic author­i­ties, leav­en­ing might begin. That would mean it can­not be eat­en at all dur­ing the eight-day Passover holiday.

In indus­tri­al pro­duc­tion, the flour must be watched by a mash­giach from the time the wheat is milled until water is intro­duced to the flour dur­ing the mix­ing process. At that point the dough remains under even clos­er super­vi­sion to make sure it is com­plete­ly baked in less than 18 minutes.

A Man­is­che­witz Passover matzah begins its life in a wheat field in one of the mid-Atlantic states. The exact loca­tion is a trade secret. Red win­ter wheat is the pre­ferred vari­ety for unleav­ened bread because it is low-pro­tein; pro­tein in the dough pro­duces air pock­ets that cause it to rise dur­ing baking.

The wheat is har­vest­ed and brought to anoth­er undis­closed loca­tion, a fam­i­ly-owned flour mill in rur­al west­ern Penn­syl­va­nia where it is stored for up to three weeks before being ground into flour. A sin­gle wheat ker­nel moves through the grind­ing and sift­ing process in about 20 min­utes. The milled flour is kept utter­ly dry in mois­ture-resis­tant bins, until it can be trans­ferred to a tanker truck for the three-hour jour­ney to Newark.

I spent a morn­ing with Rab­bi Yoel Lowen­stein, mash­giach at the flour mill, as he met a fresh­ly washed tank truck that pulled up at the mill short­ly before dawn. He crawled inside the enor­mous steel tank with a flash­light to check for mois­ture. Run­ning his hand along the curved sides, he peered at the floor and felt care­ful­ly under the jagged met­al rim. Then he crawled back out and climbed the stairs to the load­ing plat­form. The truck pulled up under­neath the plat­form, and Lowen­stein watched as close to 50,000 pounds of flour was pumped at high speed into the intake valve atop the tanker. At one point he leaped down and scooped out a few plas­tic bags of flour, which the dri­ver had to car­ry to Newark where it would be checked for mois­ture levels.

When the tanker was full, Lowen­stein stretched plas­tic wrap over the 18-inch valve open­ing to seal it tight, replaced the heavy met­al hatch, and closed it with yel­low Ortho­dox Union plas­tic seals. He placed sim­i­lar seals on the dis­charge valves, from which the flour will be pumped out. The seals can only be removed by anoth­er mash­giach after the truck arrives at the Newark plant. If even one seal is com­pro­mised dur­ing the jour­ney, so is the flour’s integri­ty. Once, a truck car­ry­ing Passover flour to Newark got a flat tire, and the impact blew out one of the seals. The entire 50,000-pound load was reject­ed by Manischewitz.

After the flour arrives in Newark, it is stored in a large out­door silo for no longer than a few days. Then it’s pumped into the plant for mix­ing and bak­ing, a pro­ce­dure that is timed to the sec­ond. Rab­bi Yaakov Horowitz, long­time head rab­bi at Man­is­che­witz and a world­wide author­i­ty on Passover pro­duc­tion and kosher food, guid­ed me around the plant, point­ing out the state-of-the-art matzah bak­ing line he helped design. In the mix­ing room, he showed off the dou­ble ket­tle sys­tem import­ed from Israel. Flour is dumped down a chute into one ket­tle, then water is added through a thin yel­low tube and the mix­ture is agi­tat­ed until it forms a sticky dough that is extrud­ed onto a con­vey­or belt to begin its short run to the ovens.

Batch­es of dough are mixed up and dropped every minute for 14 min­utes. Then an alarm sounds, the ket­tles are rotat­ed auto­mat­i­cal­ly, and the first ket­tle is thor­ough­ly cleaned while the sec­ond ket­tle repeats the process.

Before each batch of dough hits the con­vey­or belt, a mash­giach mon­i­tor­ing the mix­ing grabs an egg-sized amount called chal­lah, mean­ing tithe,” and throws it in a bin for lat­er dis­card­ing, accord­ing to Jew­ish law. The rest of the dough moves over and under a series of met­al rollers that press it into thin­ner and thin­ner sheets, until the dough is a quar­ter of an inch thick. A final per­fo­rat­ing roller scores it into matzah-sized squares, and adds tiny holes to ensure a thor­ough bake.

The dough hits the 700-degree oven between 11 – 14 min­utes after the flour and water are first mixed. The legal lim­it is 18 min­utes, but the com­pa­ny gives itself some wig­gle room. If the sys­tem breaks down and the dough does not reach the oven in time, it must all be thrown out and the entire line tak­en apart and re-kashered.

When the hot, baked matzah emerges from the oven, it moves through a roller coast­er con­vey­or belt to cool, is cel­lo­phane wrapped into pack­ages and boxed by hand, two pack­ages per box. The box­es are stacked and moved out for delivery.

Man­is­che­witz usu­al­ly begins mak­ing Passover matzah in ear­ly August, and pro­duces Passover matzah through Feb­ru­ary. Dur­ing the height of the Passover pro­duc­tion sea­son, one or two truck­loads of flour arrive at the Man­is­che­witz plant every day, about four hun­dred thou­sand pounds a week. The amount of matzah pro­duced is mind-bog­gling, close to 76 mil­lion sheets per year. Fif­teen or so full-time mash­giachs are employed to watch over every aspect of this enor­mous undertaking.

While mak­ing Passover matzah is a par­tic­u­lar­ly del­i­cate oper­a­tion, sim­i­lar sto­ries take place behind the scenes of every kosher food man­u­fac­tur­er. Of all the things I wit­nessed dur­ing my 18 months research­ing this book, noth­ing matched this work for its ener­gy, inten­si­ty, and sheer enor­mi­ty of scale.

Sue Fishkoff’s new book, Kosher Nation: Why More and More of America’s Food Answers to a High­er Author­i­ty, is now avail­able. She has been blog­ging all week for the Jew­ish Book Coun­cil and My Jew­ish Learn­ings Vis­it­ing Scribe series.