Apples are the grapes of the North. Where wine cannot be (easily) produced, apple juice — fresh or fermented, is consumed in large quantities. Fresh apple juice is a natural alternative to soft drinks, whereas fermented apple juice — also known as cider — is a tasty alternative to beer, wine and even champagne. As it happens, apple varieties grown for their juice are distinct to those grown for eating whole. They contain more tannins (taste in the cider), more fermentable sugars, and they are more crisp (soft apples don’t give up their juice easily).
Apple pomace is the remaining solid mass after juice extraction. It should be called apple pulp, but the juice/cider industry calls apple pulp the shredded apples just before pressing. In fact, the word “pomace” is a tautology in that it denotes apples. Nevertheless, we add the word “apple” to distinguish this byproduct from other “pomaces” as the term has been borrowed by other agro-industries; there is tomato pomace and grape pomace, just to mention the most well-known pressed pulp byproducts.
Depending on the process method, apple pomace contains 8 to 14 percent sugars, which are highly digestible and contribute toward increased palatability.
The way apples are processed to extract the apple juice is of importance to the animal feed industry, which is interested in using apple pomace as an ingredient. Otherwise, the variety of cider apples is of little consequence, and the same applies to the fate of the apple juice. In brief, single-pressed apple pomace contains more sugars than double-pressed juice. The latter is produced by adding 10 percent water to the already pressed pulp, letting the mash settle for an hour and then pressing it again. The resulting juice is weak, and it is usually added to the first press, although in older times it was payment received in specie by orchard workers. Furthermore, the type of press used will affect the resulting nutrient concentration in pomace: belt/rollers leave behind more nutrients compared to hydraulic presses.
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Apple pomace is usually stored, transported and used in wet condition. A good part is used for pectin extraction, with the resulting “waste” product known as pectin-extracted apple pomace. This is a depleted product that lacks one of the most useful fiber sources, namely pectins that possess significant functional properties. Such is the case for ruminants, and also for monogastric animals raised in diets without antibiotics. The rest of this article discusses normal apple pomace with its pectin intact.
Apple pomace derived from cider apple varieties contains little if any chemicals normally used in the production of culinary apples because the outside appearance of cider apples is of little importance. Furthermore, cider apples are thoroughly cleaned before pulping and pressing, and as such, any further impurities are removed. Thus, the use of apple pomace (derived from properly tended orchards) is considered a safe ingredient to feeding in all farmed animal species. In contrast, culinary apples, usually “wasted” apples, are of secondary quality as they contain many agro-chemicals, and they are unwashed, meaning they should be used with care when picked from the grounds of orchards to be fed to animals.
Apple pomace contains everything but the juice of apples. Although it is fed in wet condition, it is the dried apple pomace that has commercial interest as a commodity. Thus, we will next examine the composition of this latter form.
First, apple pomace is a rich source of fiber, and unfortunately, a good part of this fiber is lignin (15 percent), which is of limited value. Thus, apple pomace has been traditionally fed to ruminants. Fortunately, apple pomace contains about 15 percent pectins, which is a type of fiber that is easily fermentable, yielding energy for ruminants and provides a substrate (prebiotic) for beneficial bacterial proliferation. The latter is important in monogastric animals raised in diets without antibiotics. Depending on the process method, apple pomace contains 8 to 14 percent sugars, which are highly digestible and of course contribute toward increased palatability. Apple pomace contains also small amounts of alcohol and organic acids, which further increases digestibility and palatability. Finally, apple pomace contains limited amounts of crude protein (4 percent) that are of low digestibility, perhaps due to high tannin concentration.
Wet apple pomace has a pH of 3.5 that enables its storage for some length of time without special considerations. In addition, apple pomace is a good candidate for silage making. During silage storage, however, substantial changes in chemical and nutrient composition occur. First, a significant amount of effluent is produced, and this increases dry matter concentration. Unfortunately, this effluent removes a good part of the available sugars that results in reduced energy concentration of the remaining matter. Furthermore, as cider apples are rich in fermentable sugars, silage process promotes fermentation to alcohol. This can have substantial health consequences to animals consuming large quantities of apple pomace silage. The bacterial and yeast load of silage also increases.
Ruminants can consume relatively large quantities of fresh/wet apple pomace. Their rations should be balanced based on the amount of fiber contributed by apple pomace and the need to reserve space to account for the limited protein contributions. When apple pomace is offered as silage, it should be limited according to its concentration in alcohol and organic acids to maintain health and rumen pH levels. Dried apple pomace is usually too expensive to be used as a pectin source for ruminants, mainly because dried sugar beet pulp is a less expensive alternative.
For pigs, dried apple pomace can provide a source of fibers to decrease constipation in sows and increase gut health in young pigs. The contributions in palatability and reduced pH potential remain largely unexplored. The same can be said for poultry raised in diets without antibiotics. Such a multi-faceted ingredient can be used in diets for poultry raised on a slower plane of nutrition (slow growth broilers) to decelerate their growth and provide a means of providing enough gut fill to satisfy hunger.