Thursday, December 18, 2014

The Bone Broth Manifesto

You can head straight to the accompanying recipes for chicken bone broth or beef bone broth, or get lost in a culinary subject I'm really passionate about: the art of making bone broth or stock. I have some different ideas about making bone broth than others, in part because I love to rebel against silly rules, and also because challenging the status quo leads to all sorts of adventures...

Golden stock
that sparkles
When I think of food as medicine, or at least food with medicinal qualities, is there any other food that is both comforting and effective at promoting health as the humble bone broth? Kale might be more nutritious, but for pure joy, I think bone broth wins every time. Something about a fragrant, hearty bone broth bubbling on the stove just says 'I love you.'

What is the difference between broth, bone broth, and stock?
I'll confess that the Primal/Paleo term 'bone broth' irritates me. I can only imagine the term was created to make stock sound more appealing to the caveman aesthetic. 'Broth' to me sounds like a weaker brew, and who wants that?

There are key differences between meat stock and meat broth, although many use these terms interchangeably. Culinary professionals differentiate between the two. It is important to know the proper terminology so that you will interpret cookbook recipes correctly and get the best results from your cooking.
  • Stock is made by simmering bones, with or without meat, in water. Vegetables or other flavorings may or may not be included. Stock may be used in place of oils or fat for sauteing.(1) 
  • Broth is meat without bones simmered in water. Many of the canned and boxed chicken broth products are made without bones and are properly labeled as broth. Broth, because it is not made with bones, lacks the mineral content of stock and is not as nutritious(1).
  • Bone broth is largely a Primal/Paleo term. Bone broth can mean bones simmered in water alone, with or without meat, and with or without vegetables. The goal of bone broth is maximum nutrition. Stocks and broths are usually cooked for less time, while bone broths may be cooked for up to several days. Clarity is less important than pulling all of the gelatin, minerals, and other nutrients possible out of the bones. Bone broths are frequently opaque or creamy in appearance because of the nutrients extracted from the bones during cooking.
That said, I have found that good stock is always a welcome addition to any recipe that calls for broth. Bone broth may be used in any recipe that calls for stock or broth, though the final appearance of the dish may vary due to bone broth's opaque appearance. Bone broth is generally the healthier of the three, given its content of gelatin, collagen, bone marrow, vitamins from any vegetables simmered with the bones, and finally the minerals extracted from the bones during the lengthy cooking process. 

What makes a good bone broth?
Any bone broth recipe worth its salt will:
  • Deliver great meaty flavor, along with hints of the herbs and vegetables included in the broth.
  • Develop an appetizing golden to golden brown color and silky that says, "Eat me! Please!"
  • Contain as little salt as possible. If you are using great ingredients for your bone broth, you may find you need less salt.
  • Be flexible in its flavor so that it can be adapted for use in many different kinds of recipes. Be careful about increasing the amount of garlic or herbs in the recipe the first time you make it. A fierce garlic flavor in your bone broth may not be appetizing in recipes where garlic is not supposed to be the main attraction. Example: a mushroom risotto should feature the fresh flavors of mushrooms and not the harsh bite of garlic. Follow your individual tastes, and remember you can always increase the vegetable and herb flavors later on if they are not strong enough.
  • Make your kitchen smell amazing after an hour or two. This is an important indicator that you are cooking at the right temperature and have effectively balanced the chicken, vegetables, and savory additions that will result in a well-rounded bone broth.
  • Gel into wiggly goodness, with the right cooking time and ingredients. This is a great indicator that you were able to get enough gelatin from your ingredients. However, it is not the only indicator that you have made a wonderful bone broth.
Is there really such a thing as Jewish penicillin?
Chicken soup first received written attention in the 12th century AD, recommended by the Egyptian Jewish doctor and philosopher Moses Maimonides. At the time, little was known about how the chicken soup worked. Yet Maimonides had very specific ideas of how the soup should be prepared, recommending that "[T]he chicken or pullet can be boiled, stewed, steamed, or boiled with fresh coriander or green fennel added to the soup." For summertime use, he recommended the addition of lemon or citron juices(2). Maimonides' recipe for chicken soup describes a type of soup that we would now call chicken bone broth or chicken stock with a few aromatics added. Our beloved noodles, matzo balls, and vegetables would become a common part of the medicinal chicken soup experience later in history.

Has anyone ever done any scientific testing to confirm that bone broth really works?
An University of Nebraska study in 1993 demonstrated the in vitro specific immune-boosting effects of chicken soup. The conclusions of the study suggest that chicken soup might have an anti-inflammatory activity, which could ease symptoms and speed healing during upper respiratory tract infections.(2)

I have found no articles testing the health impacts of beef bone broth consumption. Many people just know their bodies like it, and for now, that is enough for me.

How long should bone broth cook?
Over time, I have extended my cooking time from a few hours to 24 to 48 hours. This is a matter of personal taste. Some are content to cook bone broth for shorter periods of time. You wouldn't believe the different characteristics that emerge in bone broth over a longer cooking time, however. I was shocked. It's similar to drinking a young wine versus a properly aged one. If you have not tried making bone broth over a 24 to 48 hour period, I would highly recommend trying to do so at least once. By the end of cooking, chicken bones have gone completely soft and beef bones have very little nutrition left.

I keep my stockpot going continuously for 48 hours. I usually do this over a weekend. Ages ago, when I first started making bone broth, I only cooked it for an hour! That seemed nice enough at the time, but now I know I was throwing away a lot of nutrition. Then I expanded to four to eight hours, thinking myself a daredevil. The results were tasty. It was when I started cooking for 24 to 48 hours that I discovered entirely new realms of texture and umami flavor - that hard to describe roasted taste present in soy sauce, coffee, and mushrooms.

What sort of pot should I use for making bone broth?
You can make bone broth in either a large stockpot, a crock pot, or a pressure cooker. In my personal experience, the low and slow cooking in a stockpot delivers the best flavor every time. For maximum nutrition and collagen breakdown, I prefer to cook a large batch of bone broth over 24 to 48 hours every few weeks. I get about six quarts of glorious bone broth each time.

Holy cow! Do you stay awake to stir the pot?
Nope. For me personally, using a crock pot actually requires more attention and stress than working with a stockpot. Crock pots can boil dry over an extended period of time, requiring the cook to add water periodically. Using a large stockpot over low heat with six to seven quarts of water gives me a very wide margin of error. I never need to add water, and I don't need to stir the stockpot very often, either. The ingredients tend to move around in the pot very little, and there is enough water in the pot that ingredients sticking to the bottom isn't a concern. I don't have to worry about the stockpot ever boiling dry because there is around seven quarts of water. In fact, after stabilizing the temperature right where I want it to be and keeping an occasional eye on the stockpot for the first hour, I then freely go to bed or leave the house to run short errands. I have been doing this for more than twelve years without incident.

Are you insane? You can't leave a pot on the stove overnight!
I realize this is a radical idea at first. Yet is it really so weird to let cooking go on overnight? Some people will also leave ovens on overnight for cleaning, or leave a roasting turkey unattended in the oven for a few hours whilst fighting with the in-laws at Thanksgiving. I realize you might not be comfortable doing this and you don't have to; the results will just be a bit different.

Most home cooks would use a crockpot for cooking projects that require so many hours to cook. Here's a surprise: would you believe that the instruction book for my relatively new and fancy crock pot clearly states that crock pots should never be left on without someone watching it. Seriously? I thought the whole point of a crockpot is to cook while you are not watching it, and ideally, not even at home! Depending on your specific crock pot, you may already have gone rogue in the kitchen.

This recipe uses a low heat setting for cooking (between Low and Simmer on my stove). The stockpot has six quarts of liquid at the end of cooking, much more than needed to keep the solid ingredients from any danger of scorching. You'll find the scent of the cooking bone broth is hard to ignore or forget, eliminating some of the worries of longer cooking times. Waking up to the happy scent of bone broth certainly isn't a hardship. Truly, once the base temperature in the stockpot is achieved, this approach is stunningly low maintenance. At the ideal temperature, the surface of the bone broth will barely move. You may see a few small bubbles, but otherwise there is not a lot of visible action during the bone broth process.

Easing into the idea of longer-term cooking
You could set a timer or an alarm on your phone to check the stockpot periodically as you become accustomed to the longer cooking times. Think of the stockpot as a child who is learning to stay home alone. You start low and go slow in increasing the time as your comfort level increases. However, in the end, how you make your bone broth is a very personal choice. It should be joyful. I find making bone broth to be a meditative, highly enjoyable ritual. The longer cooking time yields results that are well worth a little extra juggling, particularly given the resulting bone broth's nutrition, volume, strength, and depth of flavor. I am always surprised by how the flavors develop and condense over the extended cooking time.

Another option: turn off the burner when you step out or go to sleep, and restart it when you return. If you bring the temperature up to boiling for ten minutes, you do not need to refrigerate the bone broth between cooking periods(4). Be aware of safe storage and cooking temperatures if you do this - additional information on food safety below.

How should I store my bone broth?
You can store your bone broth in the refrigerator for three to four days. Bone broth freezes beautifully in bags and containers, lasting from two to three months(5) and leaving you well-prepared to whip up soups, pilafs, gravy, healthy bone broth beverages, and sauces with wonderful homemade flavor. Goodbye, creepy aseptic broth boxes! It's also a thoughtful gift to have on hand to drop off when friends and family get sick. Once you've had homemade bone broth, you will grumble if you ever have to use store-bought broth or stock again - particularly if you are drinking it.

Store your bone broth in the freezer in either BPA-free bags or glass containers. I have researched the best practices in storing, freezing, and reheating bone broth for your consideration.

I can quickly grab a pre-measured amount of bone broth, open the container (or cut open the bag and peel it away to remove the frozen bone broth, as if opening a banana), and set the block of frozen bone broth inside a pan over heat. In less than five minutes, I can have eight cups of bone broth thawed and ready to cook. If you store your bone broth in jars, you can jumpstart the process by allowing the containers to thaw overnight in the refrigerator.

I want to make chicken bone broth. What type of chicken should I use? 
I generally make my bone broth with a pastured stewing hen. I realize those are not always easy to find - though they are cheap and worth looking for. You can also make bone broth with:
  • One whole chicken
  • Leftover chicken carcass from a roasted chicken
  • A mixture of bones, chicken parts, and chicken pieces such as feet, backs, and wings
  • A stewing hen
  • Another combination of the above options
Is it best to use a whole chicken or just bones?
The ideal fuel for your chicken bone broth would be a whole uncooked chicken with other chicken pieces, bones, and a few pairs of chicken feet added. The very best type of chicken to use is a stewing hen - more on those later. Each part of the chicken adds unique flavor and nutrition to your bone broth. You can skip the feet - they are difficult to consider appetizing at first - but your bone broth will have less collagen and gelatin. You can add unflavored or meat-derived gelatins to boost the nutrition profile of your bone broth if you wish. Amazon.com has a nice selection of unflavored organic and kosher gelatins. My favorite brand is Great Lakes Unflavored Beef Gelatin.

I start my chicken bone broth with a whole chicken, either fresh or frozen. You can also choose to remove and store the chicken meat after simmering for 60 minutes or so. If you are using a pastured chicken, the meat will still be flavorful enough to use in soups, stews, salads, chicken jerky, and sandwiches. Stewing hen meat is not that appealing, but the tradeoff is the greater yield of broth and the price, which is often half what you pay for a four-pound roasting hen.

So what on earth is a stewing hen?
Stewing hens are 'retired' egg laying chickens. The chickens we buy for meat are usually harvested at less than a year old. However, egg laying chickens are usually a year or two older when they are 'retired.' These hens are prized for the gorgeous layer of yellow fat beneath the skin, more connective tissue, and larger bones with more marrow and other nutrients.. You may decide later you don't want all of the fat (such a shame) in your bone broth, but the extra nutrition provided by stewing hens is well worth considering.

I love talking about stewing hens to professional chefs who have been classically trained, because the broth from such hens is heavenly and more chicken-y than even pastured roasting chickens. However, you won't find stewing hens at a traditional grocery store. Ask around at farm-to-table restaurants and natural food cafes to find potential suppliers for stewing hens. Farmer's markets are also good resources.

Stewing hens often cluck in (sorry) at right around two to three pounds, and because of their scrawny size, the equipment at some meat processing facilities can't handle them. A farmer with both an egg laying and meat operation might have stewing hens on ice somewhere. Many do not advertise stewing hens because few people know about them, and thus demand is low. I've had good luck sourcing stewing hens in Amish and Mennonite communities. I have also seen these hens offered for sale online.

Note that while stewing hens are much loved for their contributions to the world of chicken bone broth, their meat is tougher and not what we are used to eating. After all, these egg layers were not spring chickens when they retired! They spent a lot of time scampering about, laying eggs. If I am using a stewing hen, I leave all of the meat in the stockpot throughout cooking and throw away the leftovers at the end. I might share a little with my dog and cats, though.

Over the past 12 years, I have paid an average of $5 per pastured stewing hen, and one stewing hen yields about 6 quarts of delicious bone broth. The economics work out well for my family.

Should I reuse leftover chicken bones from last night's roasted chicken?
By all means, hoard chicken bones and leftovers in the freezer until you are ready to make bone broth. You may also wish to scoop up any tasty juices, leftover meat, or browned bits left in the roasting pan for safe keeping. I prefer to add these items in addition to a whole chicken for bone broth.

While adding the remnants of a roasted chicken certainly adds character and helps improve the nutritional value of your bone broth, there are a few drawbacks. Chances are, you've enjoyed every single bit of the chicken skin already. (If you haven't, why not? What is wrong with you?) Making chicken bone broth without uncooked skin means your bone broth will have less gelatin and collagen. The connective tissue in chicken is a great source of nutrients, including glucosamine and chondroitin - two ingredients that are very helpful for those with arthritis. Why buy supplements when you can get the real thing in your soup bowl? However, these nutrients tend to dissolve into the meat of the chicken or into the pan during roasting and are consumed. You want everyone to enjoy all of the chicken, of course, but you may run short on gelatin when making bone broth. Adding chicken feet and/or additional chicken bones can help make up for the lost nutrients.

These additional concerns about using a previously roasted chicken depend entirely on your personal taste. A roasted chicken without herbs and spices would be extremely boring, however, some flavorings added to the roasted chicken may not transfer well to the flavor of your chicken bone broth. I'm not a fan of curry powder or tandoori spice in my everyday chicken bone broth, but others may disagree. Finally, a roasted chicken may add undesirable fats to your bone broth such as coconut oil, ghee, olive oil, or butter. Once these fats are roasted and stewed, you might not like the flavors once concentrated in your bone broth. I think these flavors detract from the overall chicken-y flavor, but others may feel differently. You can always try to rinse or briefly blanch the leftover chicken bones in a pot of boiling water before adding them to your stockpot. This may help remove unwanted flavors.

Is it worth using a whole pastured chicken for chicken bone broth?
I have a direct answer to the question above: yes, oh yes, I think it's worth it! Each part of the chicken contributes flavor and nutrients to bone broth. You get to cook and save the chicken meat for later use while enjoying the full nutritional benefits of six quarts of delicious chicken bone broth. What more could you ask for? By the time we're done with that whole chicken and 48 hours' cooking, even its bones will be soft. You will have shown that chicken that you are the boss.

Should I roast the chicken bones before making bone broth?
Roast the bones first if you like the umami flavor. I like a sweeter bone broth and do not roast the chicken bones first. If you would like to roast the bones, place them in a casserole dish and roast at 350 degrees F for 30-45 minutes. You can also choose to include the vegetables during the roasting process for extra flavor. The vegetables can also be sauteed until brown before adding them to the stockpot.

I'd like to make beef bone broth. What do I need to know?
Choosing the right type of bones is everything, but beef bone broth is easier than making chicken bone broth. If you want a bone broth that gels, be sure to select bones that have a lot of connective tissue. Beef joints have the most connective tissue. However, the cross-cut bones usually have the most marrow. I recommend using one of each type of bone to get a great balance of nutrients and gelling ability. I love finding beef bones with a little meat attached. It adds great flavor to the bone broth.

Can I make bone broth in a crockpot?
You can, and many people do, but I don't. I prefer the flexibility of using a stockpot. Here's why:

Limited space. The largest type of crock pots I've seen max out at 7 quarts. Add several pounds of meat and bones, vegetables, and other savory ingredients, and you won't have much space left for water - and thus you will make far less bone broth.

Limited temperature control.
 Crock pots usually do not have temperature gauges. Most offer three settings: Keep Warm, Low, and High - and good luck finding out what those temperature settings really mean. The manufacturer may or may not publish this data. Additionally, some crock pots claim that Low and High are actually the same temperature! How is that possible? The heat element cycles on and off at slower or higher frequencies depending on whether the setting is on Keep Warm, Low or High, respectively. Got that? Good.

Finally, in crock pots that are more than a few years old, it is normal for appliances to lose their effectiveness over time. Your crock pot's ability to maintain or cycle temperatures can be negatively affected as well. During cooking, you can check the temperature of your crock pot periodically, though admittedly this is a somewhat annoying task. Using an instant read thermometer with a probe and an programmable alarm is helpful.

Food safety. Arguably few home kitchens would survive a professional food safety inspection. We all have at least one naughty habit that we know is probably not the safest practice, but we do it anyway. Why? Because we keep getting away with it. Well-respected cookbook author Michael Ruhlman landed in a bit of trouble with food safety experts in 2011. He innocently described his practice of making small batches of broth or stock from leftover bones, leaving the finished product out at room temperature for use throughout the week. This set the Internet on fire, and the New York Times responded rather critically to Ruhlman's broth practice, citing the risk of botulism, toxins, and other food safety concerns. What is the final word on food safety with bone broth? I keep mine for three days in the refrigerator, else I freeze it. Bone broth thaws quickly on the stove in a stockpot, Dutch oven, or saucepan.

I'd rather be safe than sick, especially when I am thinking of my food as medicine. Anyone who has immune system issues needs to give these matters careful thought.

Getting the most from your ingredients. If you buy pastured meats, you likely love the taste - but the price? Not so much. Squeezing every bit of nutrition from those meats is important. Crock pots, due to the irregular nature of temperature regulation, may or may not wring every last bit of nutrition from the bone broth ingredients.

The Journal of Food Science published a fascinating article on the physicochemical properties of chicken stock. According to the research, 99 degrees Celsius/210 degrees Fahrenheit is the ideal cooking temperature for chicken stock. At this temperature - just a whisper below boiling - you'll see a bubble rise to the surface every now and then, but the stock will not be at a full boil. I was thrilled to see this news, because I had been cooking broth at this temperature for years. It seemed like a natural sweet spot for flavor development.

If you enjoy clearer bone broth, staying below the boiling point and straining the finished bone broth with cheesecloth and/or a fine wire mesh strainer is particularly important. Boiling your bone broth hard agitates the ingredients, causing more particles to be released into the water. This causes the bone broth to become cloudy. When cooked at 99 degrees Celsius/210 degrees Fahrenheit, the resulting product contained more protein, had better viscosity (the body of the broth), and was rated better by tasters than products cooked at lower temperatures(6). Collagen begins breaking down into gelatin starting around 70 degrees Celsius/160 degrees Fahrenheit. Can you achieve these temperatures in your crock pot? The answer varies, and the only way to know for sure is to check the temperature with a thermometer.

Efficiency. Some prefer to make multiple batches of bone broth from the same bones. Repeated use of the bones until the bones dissolve or crumble is a thrifty, useful practice and has a delightful French name: remouillage. Doesn't that sound fancy? However, I prefer to make one large batch of bone broth and use up every last bit of nutrition from the bones. I like this more than making frequent, smaller batches and reusing the bones. It's a personal choice. Making more bone broth in a stockpot and storing the excess bone broth in the freezer saves me lots of worry, time, and preserves more of my sanity.

Can I cook bone broth all week long in a crock pot?
If you trust the temperature of your crock pot, you can certainly make bone broth all week long. Some prefer to do this, adding leftover vegetables, meat, and bones here and there throughout the week. Unless you have two crock pots, however, this means you cannot use your crockpot for cooking meals without interrupting your bone broth. The crock pot is the Paleo cook's most time-saving tool. Particularly for families with mixed nutritional needs, I think the crock pot is extremely helpful in providing hands-free cooking for protein entrees that the whole family can share. It's also handy to be able to cook enough protein to last several nights. I recommend making one big batch of bone broth in a stockpot every few weeks, and save the crock pot for daily meal preparation. If counter space is at a premium, you might also prefer to stow the crock pot when not in use. If you have a kitchen that has fantastic amounts of unused counter space, please invite me over. I will clutter up your unused kitchen space in no time flat.

My bone broth often doesn't look or smell very meaty. 
The very best way to get amazing tasting bone broth is to use amazing ingredients, the right temperature, and delicious vegetables. First suggestion: use stewing hens or the best chicken you can afford. If you have made a batch of bone broth with a leftover chicken carcass but didn't get the flavor you want, then you might want to augment the bone broth with some additional chicken pieces - particularly chicken feet or backs. If you are reusing chicken or beef bones, be sure to add some new bones in with the old to keep the flavor bright.

How can I make my bone broth more colorful?
My mom taught me that yellow onion skins help the bone broth develop better color. Whenever I cut up onions or shallots, I stash the skins and ends in the freezer. Onion skins bring more nutrition to the party(7) in addition to adding gorgeous color to your bone broth. I mostly use the red onion skins when I make beef bone broth, but a few red onion skins tossed in with a bunch of yellow ones looks nice, too.

Other colorful foods can share their color with your bone broth: orange and red heirloom carrots, a dash of turmeric, a little bit of red cabbage, or even browning a tablespoon of tomato paste slowly in a saucepan and then stirring the paste into the bone broth. The tomato paste solution is my least favorite, because it can change the flavor of the bone broth. Going overboard with turmeric, cabbage, or any other vegetables you might wish to add - particularly if you keep a batch of broth going all week - can also change the flavor, so choose wisely. Sulfurous veggies such as broccoli, cauliflower, and Brussel sprouts can add bitter or sour flavors to bone broth.

How should I cut up the vegetables for making bone broth? 
Mirepoix is the beautiful word describing the holy trinity of savory vegetables traditionally used to flavor bone broth. The traditional French ratio of onion to carrot to celery is 2 cups diced onion to 1 cup diced carrot to 1 cup diced celery. I prefer these flavors best as they blend well together while not attracting too much attention away from the meat flavor. For making this type of bone broth, dicing the vegetables is fine. If I'm really tired, I just throw the veggies in the food processor and process until minced for a stronger vegetable flavor. Every surface area you expose in the vegetables is an opportunity for more flavor and nutrition.

What about salt? 
I only add salt to broth when I know exactly how the broth will be used. The challenge I have is that I never quite know how I will be using the broth when I make it! Thus I rarely add salt during the cooking or storage process. I have found that salting the bone broth before or during the cooking process may cause regret later. If you make a lot of bone broth, you'll eventually have a batch that just isn't as good as the others - or if you are truly unlucky, a batch might turn out so badly that you need to get rid of it. This happens, although some of these bone broths can be saved with a little know-how. If my bone broth's flavor is weak, I may need to reduce the bone broth by 25% or more to concentrate the flavor and get a better gel. Yet if I have already added the salt, and then need to cook down the broth, then the salt flavor will be too strong. What was a perfect sprinkling of salt at the beginning of cooking may now be overpowering, and that's a difficult problem to fix. If I add salt at all, I add very minimal salt and do so toward the end of cooking time. You can always add more salt later when you know exactly how you will be using the bone broth.



Why put vinegar in a bone broth recipe?
The acids in vinegar not only tenderize meat and encourage the meat to release more delicious juices, but also encourages the breakdown of collagen into gelatin(6). You won't be able to taste a few tablespoons of vinegar by the end of cooking. I prefer using apple cider or champagne vinegar. Some like to add half a lemon with the rind included. These steps are optional, but are very popular in Paleo cooking now. Be mindful that if you use a 'live' vinegar such as an apple cider vinegar with the mother included, any probiotic benefit will be destroyed during the heat of cooking.


Sources:
(1)McGee, Harold (2004). On Food and Cooking, pg. 599-600.
(2)Rosner, Fred. The Medical Writings of Moses Maimonides. (1998). Volume 3, pp 60-62.  KTAV Publishing House, Inc.
(3)Robbins, Richard A. and Rennard, Stephen I. (2000). Chicken Soup Inhibits Neutrophil Chemotaxis In Vitro. CHEST 2000; 118:1150–1157 [Author's note: CHEST is the official publication of the American College of Chest Physicians (ACCP).]
(4)McGee, Harold. Bending the Rules on Bacteria (2011). The New York Times. August 24, 2011, on page D3
(5)USDA Food Safety Fact Sheets. Chicken from Farm to Table. July 25, 2014
(6)Krasnow, M., Bunch, T., Shoemaker, C. and Loss, C. R. (2012), Effects of Cooking Temperatures on the Physicochemical Properties and Consumer Acceptance of Chicken Stock. Journal of Food Science, 77: S19–S23. 
(7)Vanesa Benítez, Esperanza Mollá, María A. Martín-Cabrejas, Yolanda Aguilera, Francisco J. López-Andréu, Katherine Cools, Leon A. Terry, Rosa M. Esteban. Characterization of Industrial Onion Wastes (Allium cepa L.): Dietary Fibre and Bioactive Compounds. Plant Foods for Human Nutrition, 2011; 66 (1): 48 DOI: 10.1007/s11130-011-0212-x