Sue Fishkoff is the author of "Kosher Nation: Why More and More of America's Food Answers to a Higher Authority" (Schocken, 364 pages, $27.95 ), a fascinating portrait of the kosher-food industry in the United States, where an estimated 40 percent of the country's annual $500 billion in food sales are of kosher-certified products. Since most American Jews, who make up less than 2 percent of the population, don't even keep kosher, the size of the industry may sound incredible. But with the growing sophistication and globalization of food production, and considering that even for non-Jews, kashrut certification on a product - to the extent they're actually aware of it - is perceived as a guarantee of quality, more and more food purveyors and manufacturers believe the supervision is worth the cost.

Fishkoff explains that even a seemingly straightforward package of frozen vegetables can include ingredients made in more than a dozen countries: If any of those components isn't certified kosher by a recognized international agency, then the frozen vegetables can't be either. So, mashgichim (inspectors ) regularly fan out to every part of the world to oversee fish packing, fruit canning, chemical production and grape harvesting.

In one chapter, Fishkoff accompanies a mashgiach as he visits plants in China that produce glucoamylase (an enzyme used in high-fructose corn syrup ) and rice crackers, among other items for export. China's religious restrictions mean that its citizens can't convert to Judaism or even attend Jewish services, but business is business, and in China, kosher food production is booming.

Fishkoff devotes a chapter to the startling growth in concern about insect infestation in produce, and the vast amount of time (and water ) consumed by inspectors to check romaine lettuce, among many other fruits and vegetables, for bugs; and another chapter to the near-disappearance of the kosher (as opposed to kosher-style ) deli on the American scene; and she explains why most kosher slaughterers no longer sell non-glatt meat. She also details the fall of Agriprocessors, the huge meat-packing plant in Postville, Iowa raided by federal agents in 2008 for employing illegal alien workers, and notorious for its abusive treatment of both employees and animals. Last June, the company's vice president, Sholom Rubashkin, was sentenced to 27 years in prison for a wide variety of crimes.

Fishkoff, 52, a national correspondent for the Jewish Telegraphic Agency (www.jta.org ), is also the author of the 2003 book "The Rebbe's Army: Inside the World of Chabad-Lubavitch." Haaretz spoke with her by phone from her home in Oakland, California.

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Q:Your first book was about the growth of the Chabad movement, which is a story of increasing ritual observance, and now you have written about the explosion of the kosher food industry, with a major characteristic of the story being increasing stringency and continuous discovery of new ways to keep kosher. Do you consider these as two aspects of the same story?

A: The growth of Chabad and also the increased interest in kashrut are related to a rightward march religiously. Certainly, both books are also about U.S. Jews' search for spiritual significance in ritual. That's what interests me: American Jews looking for meaning.

Q: You reached a wide range of individuals in "Kosher Nation," in many obscure locations. How did you track people down?

A: One person usually leads to the next, and one topic to the next. When I began, I knew how I wanted to approach the topic of Jewish attitudes toward kashrut, but I didn't know much about the industry itself, so I had to start with the big kashrut agencies. Once I sat down with the head guys - and they are all guys - they started to tell me their own personal stories, like what it's like to be the mashgiach at the herring harvest in New Brunswick, Canada. After that, I went to the mashgichim on the ground, and asked if I could join them as they did their work.

You know, all the interesting stuff takes place in the middle of the night. The research was fantastic fun. Sometimes in those huge factories, I felt like I was in a Hieronymus Bosch painting - with figures scurrying around, huge vats of boiling liquids and always something dripping from the ceiling.

Q: One very striking element is the lengths you go to to describe firsthand what the lives of some of these kashrut inspectors are like. For instance the yeshiva students and their boss, who work through the night each autumn to kasher a grape-processing plant in Washington State because of the especially stringent rules of kashrut related to that fruit. And the mashgichim who travel to the remotest ends of China, where the understanding of Jewish practice is so limited that one rabbi told you about being asked to certify tables and chairs by a factory owner who wanted to export to the United States.

A: I was in China only a week, but that was a part of the story that I very much wanted to have in the book. Half of the food that China exports is kosher.

Q: But in the book you make the point that very little of that consists of finished products; most of it is chemicals used for food production or raw ingredients, right?

A: Well, my research is already two years old, and since then I know of candies, including milk chocolates, being made there, as well as other snack goods, fruit rollups and even cholov Yisrael [milk that has undergone especially stringent supervision] - although that is nearly all for domestic consumption.

Also, shipping food to the Far East just for packaging happens all the time. I used the example of tuna fish as well - fish caught in one country, shipped to the U.S. for cooking and then back to the Far East for canning. That goes on all over, when you're dealing with that bulk and those kinds of profit margins.

Q: You wrote a powerful chapter on the Agriprocessors scandal. Do you think that shocking revelation of abuse, of both animals and workers, was a watershed for the kashrut community in terms of widening its concerns beyond technical issues?

A: I think it's very much on their minds. That's clear from the public statements that have [since] been made by Orthodox rabbinical authorities and the kashrut agencies themselves. But you used the word "shocking," and I have to say that I think the shock is disingenuous. Anyone who read "The Jungle" [Upton Sinclair's 1906 novel about the meatpacking industry in Chicago] knows that the entire meat industry is dirty and low-paying.

There may be those Jews who think that everything about the kosher industry is clean. But the kosher meat business also has a long history of fraud and corruption. Still, the Agriprocessors affair generated a conversation across the denominational spectrum. Within a year, the RCA [Orthodox Rabbinical Council of America] passed a resolution requiring companies to obey all secular laws, including labor laws, or risk losing their kosher certification. I think the conversation is genuine, and the issue is now part of the American Jewish agenda.

Q: What was the most surprising thing you encountered in your reporting?

A: I think the whole bugs-in-the-vegetables question was most surprising to me. I was unaware of the intense Orthodox concern about bugs in produce, and so seeing the amount of time mashgichim spend cleaning fruits and vegetables, that was amazing to me. Who knew it could be so difficult to serve a kosher fruit salad at a kosher banquet? Oh, if we could only have DDT back.

Q: You describe one woman who devotes much of her time to educating people about the spiritual dangers of ingesting produce that hasn't been painstakingly cleansed of all insects. My sense is that you find her interest obsessive, but also admire her devotion.

A: That's Freyde Ilowitz. She believes so deeply that educating Jews not to eat bugs is helping them obey Torah, and she's willing to devote her life to this. Personally, I think it's delusional to try to keep people from eating fresh produce, which is in effect what you have to do if you want to avoid ingesting any insects at all. But this is the natural outgrowth of the Torah prohibition on eating bugs that you're able to see.

Q: You mean because modern technology allows us to spot bugs we would have been oblivious to a few generations ago?

A: Yes. One man I interviewed, in Los Angeles, spoke about how technology has improved, so that leniencies that were acceptable years ago no longer are. That is, when you're able to do more, you're required to do more. Take the example of swordfish. Once, Orthodox Jews were perfectly happy to eat it, until one rosh yeshiva in 1951, Rabbi Moshe Tendler, sat down and examined the scales on the fish, and said they were the wrong kind.

Q: I was impressed with how hard the inspectors you present actually work. In Israel, restaurant owners complain that inspectors only show up on their payday. But the men you profile are not just overseeing kashrut observance, they are pitching in and doing some of the labor. Is that typical?

A: The mashgichim who I interviewed were sterling examples of the profession, yes. But you have to understand that in America, agencies are competitive, so there's built-in motivation to provide good service. In Israel, I believe they're paid by the state, no? Still, there are certainly plenty of no-goodniks in America and someone could write an interesting book about that. One deli owner I met mentioned a mashgiach who asked for $10,000 in cash, in his pocket - that mashgiach probably wouldn't have wanted me along for the ride.

Q: In the book's foreword, you describe growing up in New Jersey fairly oblivious to kashrut observance. How about today? Do you keep kosher?

A: I don't keep kosher, but I don't bring meat into my house. The more I learn about kashrut, the more interested I am in it. Now that I have seen animals being killed, I don't automatically reach for a turkey sandwich when I'm shopping.

Any good farmer would chuckle at the thought of young city folk waxing romantic about killing their animals [Fishkoff is referring to her chapter on the "New Jewish Food Movement," in which she describes various entrepreneurs with special interest in organic food, humane treatment of animals and the environmental impact of food production, and who do small-scale raising, slaughter and distribution of meat]. But I'm city folk and I saw the care that the shohet, too, gave to the act of slaughter. It was moving, as well as an acknowledgment of the human blood lust, which is why people were permitted to eat meat after the Flood, according to the story of Noah. As we sat there and cleaned these animals, it made us more aware of the cycle of life and death.

Kashrut is about recognizing this entire cycle of sunlight - to grasses and vegetables, to animals, to us, and then back to the earth. Its laws are meant to remind us that we are not alone in the world, but part of an intricate, carefully balanced network of life and death that existed before us and extends far beyond us.

David B. Green