From sweet pastry fillings to savory almond-and-rice mixes, food scientists should be aware of all the unique processed versions of fruits and nuts and the applications that they work best in. Handling these often delicate ingredients with care will ensure optimal presentation as well as safety and flavor quality for the duration of that application’s shelf life.

Fruits in their natural state are around 85-95% water. The unbound portion (or “free water”) is described as its “activity” or “water activity,” and it is the water activity of the fruit that contributes to its susceptibility to bacteria or mold growth.

Depending on the finished product application, that water activity must be controlled, usually by binding the water with sugar or salt. Otherwise, processes such as pasteurization, retorting, or acidification, can be used. Those alternatives are especially recommended for products for which water is indispensable — for example, beverages or canned fruit.

Makers of clean-label and value-added beverages typically incorporate either fruit concentrate or fruit purées into their products. There are benefits and challenges to using natural ingredients such as fruit versus a flavoring or extract. Fruit purées work better in smoothie applications because they are thick and often have visible particulates, which can actually be a plus if the company selling that drink is aiming for the natural, unprocessed look. On the other hand, those particulates can cause issues during production and lead to settling in the container.

Fruit purées are often sold frozen and not thermally processed beforehand, so they must be used in products that will be pasteurized or sold as a refrigerated short shelf-life item. It also can be expensive to ship and store these items in refrigerated trucks, storerooms, and warehouses.

Purées are used frequently by the baby food industry. These are always pasteurized and sold in jars or pouches, and if blended with higher pH vegetables, they have extra acid added to ensure compliance with FDA acidified food regulations. While pasteurization can kill some of the fresh flavor notes, the macronutrients, minerals, and most vitamins are still available in the finished product.

Fruit concentrates differ from purées in that they are cooked ingredients. The cooking process evaporates the water and renders the product shelf stable. Concentrates lose many of their flavorful top notes during the heating process, so the products they’re used in — especially beverages — may have to add flavorings to bring back what was lost.

FRUIT FILLINGS

Fruit pastes consist of whole fruit that has been dried and combined with sugar to lower the water activity to less than 0.65aW so as to prevent growth of yeast and mold. They are used as a filling or binding agent in shelf-stable food products like pastries, bars, and jams. Some dried fruits, such as figs, raisins, and dates, are naturally high in sugar. That sugar binds the water within the fruit, allowing the paste to remain shelf stable while still spreadable and pliable for application.

Because dried fig, prune, raisin, and date pastes naturally contain sufficient sugar to bind water, there is no need to add extra sugar or even yeast- and mold-inhibiting preservatives to ensure microbial stability. Other fruits, like strawberries and cherries, do not have enough natural sugar to make a pliable shelf-stable dried paste. These might require either added sugar to bind free water, or preservatives and/or pasteurization to ensure the finished product can last at room temperature, even after opening.

Fruit fillings (AKA fruit “preps”) are also used in yogurt applications, layered on the bottom of a yogurt cup. A fruit prep must be pre-processed for sterility before being injected into a yogurt cup and covered up with a dairy ingredient. It must be thermally processed and properly acidified because it will be in close contact with the yogurt, which has more water and could be subject to molding if the fruit ingredient is not sterile when it goes into the cup.

Some fruit purées, such as those from prunes, work as a functional ingredient in baking. The natural sorbitol present in prunes attracts moisture, which can help prevent baked goods from drying out — especially gluten-free bakery products. When prune purée is added to a batter at as little as 1% of the total formula, it can boost caramelization and moisture in the finished product.

At prune purée percentages of 5-10%, fat can be reduced because moistness is being contributed by the added prunes. In meat and poultry marinade applications, prunes enhance moisture and flavor with less salt. In studies at the University of Arkansas, prune ingredients were shown to increase moisture at a level similar to phosphates when used in chicken marinades.

It is the sugar in dried fruit powders and dried fruit juice powders that helps nutritional bars retain moisture and stay pliable – although too much fruit powder will result in the bar not being able to hold its form in warm weather as the sugar will melt and cause the bar to turn to mush if too much fruit powder has been used.

In concentrated form, the juice of fresh prune plums is especially effective in staving off warmed-over flavor and binding moisture when used in marinades at concentrations of 1-2%. Diced prunes or prune paste are effective at binding moisture in sausages when used at 1.5-2% of the meat block.

SWEET MEETS MEAT

With culinary influences from South Asia, the Middle East, and North Africa increasingly prevalent, the inclusion of fruit flavors in savory preparations and especially the combination of fruit and meat is becoming increasingly familiar to the American palate. While dried fruits such as cherries (especially tart dried cherries), raisins, currants, and aronia berries are excellent companions to pork, game (such as venison, bison, or  duck), and beef, poultry marries well with lighter-flavored and fresh fruits. A great example is the recently launched Apple and Gouda chicken burgers from Sechler Family Foods, Inc.’s Bell & Evans line.  “There’s a gap in the market for a really great gourmet chicken burger, like one you would find hand-blended at your favorite butcher,” explains Bell & Evans owner Scott Sechler. “We knew we could create a high quality, convenient chicken burger with our 100% air-chilled chicken and state-of-the-art grinding, mixing, and freezing equipment.” Sechler notes that the goal was to have flavors come from real fruit and cheese inclusions, not through flavorings or seasoning blends. “We looked at trends, scoured our personal flavor profile favorites and knew we had to include a fruit and cheese combination — a tart, sweet-and-savory mixture checked all the boxes for a great product.”

Bell & Evans’ apple and Gouda chicken burger uses diced Granny Smith apples for a hint of tartness, some sweetness, and great texture. A pinch each of savory herbs (thyme and sage), plus the aromatic spices ginger and coriander were included.

Sechler’s team chose apple pieces large enough to experience the apple “bite” and did not dispense with the bright green Granny Smith peel, either. “The nutty, sweet flavor of the gouda cheese perfectly complements the apple and offers creamy texture without dissolving through cooking,” Sechler says. “We’re really happy with the end result and know they will be a customer favorite.” 

Some of the challenges in incorporating apples into the ground chicken base, according to Sechler, included finding the correct apple variety, one that could hold its own flavor in the blend. Then, the proper dice size that could deliver a recognizable bite and complement the meat block texture was needed. Freeze-dried fresh apple pieces were chosen to provide optimum availability, flexibility, and handling ability without compromising quality or flavor, notes Sechler. “Our apple supplier is freeze-drying the apple pieces using only natural ingredients to prevent browning — citric acid, ascorbic acid, and salt,” he explains. “All Bell & Evans products require clean ingredients.”

HOW DRY I AM

Fruits that are freeze-dried or low-moisture are designed to work as powdered flavoring components or particulate inclusions in granola blends, bakery mixes, fruity popcorn seasoning blends, dry rubs, and sauces. The process of sublimation, which involves freeze-drying fruit in a vacuum to change the water from ice to vapor, maintains the fruit’s flavor and color. Careful drying also can allow many of the water-soluble vitamins and other nutrients to remain
as well.

Another method of drying fruit involves microwave drying. These so-called micro-dried fruits are more economical, using traditional dryers for dehydrating and then finishing the drying process using low-impact microwave energy in a vacuum chamber. Microwave drying is better than other methods at preserving the natural color, flavor, and size of each piece. 

The process also allows greater control of moisture level, water activity, and particle structure of the fruit ingredients than do other drying methods. This helps ensure consistent texture and safety. Depending on the application, the fruit or vegetable piece is then right-sized and available as whole pieces, fragments, or powders, and many are available in chewy or crunchy textures.

Deciding which type of dried fruit to incorporate into a food product depends on the experience that the brand owner wants for their consumer. A granola, for example, would require higher moisture and a chewier fruit piece, whereas freeze-dried fruits work better for RTE cereals. Moreover, they will rehydrate and be similar to real fruit when milk is added. Nutritional bars may use a combination of both fruit powders and pieces to give their product a natural fruit flavor and attractive, chewy inclusions.

Seasoning blends, such as those for popcorn, chips, or crackers, may use either micro-dried flakes for more visual particulates or a freeze-dried fine powder to ensure total flavor coverage of the entire product. The food scientist can gauge which is more desirable by considering the finished application from both the consumer perspective as well as the manufacturing and food quality angle.

NUTS INCLUDED

With their balanced carbohydrate, fiber, and fat content, nuts are the perfect food for today’s keto, Paleo, and lower-carb market. Their many types and forms bring texture and functionality to a finished product, and selecting the right format can make a big difference in the end product. 

Almond flour and almond butter are nutritionally equal. Almond butter, or paste, is really just a few more spins in the grinder, resulting in the oils being released and the flour turning into a paste. Almond flour can be used in dry mixes like those for gluten-free cakes, cookies, or pancakes. It is important to carefully blend the almond flour with other dry ingredients like rice flour, fiber powders, or dried egg whites to ensure that the particulates of almond flour are separated from each other and won’t, via shaking or mixing, turn into a paste.

Nut butters or pastes have their own unique applications. They can work as a pliable base and binding agent in nutritional bars. Using too much nut butter can result in an oily nutritional bar, with oil seeping out of the package and creating oil stains. The keto diet food industry is familiar with and actually grateful for this oil seepage, seeing it as proof to their buyers that the fat is all in there and encouraging their users to keep the bars refrigerated upon arrival.

Almond flour has been especially popular in gluten-free formulations, and among nut butters, almond butter has been a well-received replacement for peanut butter for those avoiding that allergen. Both almond butter and almond flour come in blanched and unblanched versions. Blanched almond flour is favored in products that have a strong color component, such as a strawberry protein shake or yellow cake. If the final product is going to be a dark brown or blended with a date or fig paste, then unblanched, which is less expensive and higher in fiber, can be used.

Nut pastes can be combined with sugar to create mixtures used in bakery fillings like almond-filled croissants and French-style macarons. Hazelnuts are ground up with sugar and chocolate to make hazelnut spreads, a popular breakfast item in Europe.

While whole nuts and the various cut sizes and forms (blanched, slivered, diced, paste) are most commonly used, there are now fractionated nut powders whose fat is manually pressed out, leaving behind a higher protein ingredient that is 50% protein, 15 to 30% fat, and 22% fiber. Peanut protein powder is common; known as peanut flour, it has long been used to make pet treats but now is also finding its way into the high-protein snack market. Newer nut-based protein powders include almond, cashew, hazelnut, and walnut — all with their excess fat pressed out, leaving behind a dry, low-oil, higher protein ingredient. 

SHELF LIFE

Nuts that are slivered, diced, sliced, or ground into flour or paste have greater surface area exposure to oxygen. Thus, they’ll oxidize quickly if not handled properly by manufacturers and kept stored at cool or cold temperatures. Thick foil packaging also helps keep out oxygen and light, slowing down oxidation. Vitamin E and other natural antioxidants like rosemary, oregano, and licorice extracts (as well as the synthetic versions) are used as additives to slow down oxidation and extend shelf life while preventing rancidity.

Almonds are relatively low-moisture, high-oil nuts that have a long shelf life when handled appropriately. Manufacturers should store almonds at less than 65% humidity and less than 50°F for a 2-year shelf life; if the nuts are roasted, they should be stored vacuum-packed or nitrogen-flushed until used in production.

Manufacturers should make sure their finished almond-based products are packaged in foil-lined wrappers that keep out both air and light. Nuts that are caramelized in sugar, and bars that are enrobed in chocolate (sugar-free or very dark), have a longer shelf life than uncoated versions because the sugar and chocolate are protective against degrading elements like light and heat.

In their many forms, fruits and nuts can bring so much diversity to new food products, both shelf-stable and refrigerated. Their unique attributes should be recognized by food scientists and should be taken advantage of by using them in the right application and getting the maximum benefit while utilizing food technology methods like drying and pasteurization to extend their shelf life and maximize profit.

Rachel Zemser, MS, CCS, is a San Francisco-based food scientist, chef, consultant, and certified culinary scientist with more than 20 years of industry experience in shelf-stable, acidified sauces, dressings, and dairy products, as well as food microbiology, fermentation, and quality/safety plant operations. She can be reached at www.theintrepidculinologist.com. And check out her e-book, “The Food Business Toolkit for Entrepreneurs.".

GROWING TROPICALS

A number of fruits that started to become popular just a few years ago experienced sudden jumps in demand in just the past year or so. While part of that has to do with availability, for the most part it is based on consumer familiarity with these once-rare fruits and their demand for same. Some of the stand-out examples are named by Robert Schueller, director for Melissa’s World Variety Produce, Inc. “We carried jackfruit for more than 15 years, then just a couple of years ago demand skyrocketed when vegan product makers in the US learned that the texture of shredded jackfruit makes a great substitute for taco meat and pulled pork.” Schueller adds that jackfruit has been the most heavily sold tropical fruit in the US for three years running.

While jackfruit is retailed typically cut into quarters or smaller (it’s the largest fruit, with some specimens reaching 150lb. each), ingredient suppliers offer it pre-processed or as pulp, typically in freezer packages.

Another fast-rising tropical Schueller notes is rambutans. The spiny relative of the lychee became popular suddenly about two years ago. “Rambutans actually outpaced lychees in sales now, in part because they are available year-round where lychees are highly seasonal,” he explains. “The key is that the fruit is sourced from so many countries — Vietnam, Thailand, Guatemala — allowing for steady supplies.

Another fruit benefitting from year-round availability is passion fruit. “After decades of intermittent popularity, passion fruit really started to take off again just a few years ago,” says Schueller. “With sources now from New Zealand, California, and Florida it’s available for at least ten months out of the year.” The same helpful increase in availability is true for dragonfruit. Although introduced to the US in 2004, the expansion into multiple growing areas (including Vietnam, Central/South America, Israel, California, and Florida) and its designation as a “superfruit” spurred rapid growth. The spiny favorite also received added support from its natural vivid magenta hue. Yet it was the recent entry of the canary yellow version from Ecuador that gave the fruit a huge bump in the past couple of years. Unlike the delicate flavor of the other versions of the fruit, the Ecuadorian variety is delightfully rich and sweet.

Riding the wave of popular tropical fruits is sweet young (green) coconut. As Schueller points out, this type of coconut is used almost exclusively for coconut water. “Product developers are missing out, though,” he says. “The lightly sweet, custardy pulp, when puréed, can — and should — be put to great use in a number of dessert, dairy, and smoothie beverage formulations.”

SUGAR ADDED

Any finished product that contains dried fruit ingredients will have a higher sugar content than the fruit in its original form. Dehydrating increases the percentage of natural sugar in the ingredient. If water removal is the only process involved, the higher sugar finished product does not have to be listed as an “added sugar.” However, some processors prefer to also remove the skin and fiber to create dried fruit juice powders. These powders often are plated on water-soluble dextrose. A dried fruit product with skin and fiber removed will not only have a higher sugar content, but that sugar must be listed as an added sugar, even though it is natural. Too much sugar, added or naturally present, is something consumers try to avoid.

MOCK MEAT

Plant-based meat analogs have been growing rapidly and exponentially in popularity, and recent meat shortages and price increases have further driven demand. These products often are made with soy and pea proteins, but consumer concerns about allergens and additives have turned some developers toward ingredients such as jackfruit and walnuts. Jackfruit can be prepared to mimic the texture of pulled pork and does well in items such as barbecue. Walnuts, on the other hand, when ground coarsely, have a similar color and texture to ground beef and can extend or replace it in hamburgers, hamburger analogs, or fillings for items such as pastas and calzones. Neither of these examples requires excess ingredients and fillers to substitute for the meat they are meant to replace.