In this era of high technology, it is a rare industry that does not make use of the unique, novel and diverse properties of water-soluble gums or hydrocolloids, many of them derived from seaweeds. The use of these water-thickening, emulsifying and gelling agents has become established in all types of industries ranging from foods, pharmaceuticals, cosmetics, paper, textiles, and petroleum to the new glamor industry called “biotechnology.” As new and wider diversities of properties are developed, the range of applications will broaden over the years. Nowhere is this more apparent than in the food industry, where new products continue to be the life-blood of all successful companies. And nowhere is this more appreciated than in the seaweed-extract industry, which has been responsible for much of the innovative technology leading to the increased use of these hydrocolloid materials (Glicksman, 1969).

Utilization of seaweed hydrocolloids in the food industry

Fruits serve as a source of energy, vitamins, minerals, and dietary fiber. One of the barriers in increasing fruit and vegetables consumption is time required to prepare them. Overall, fruit bars have a far greater nutritional value than the fresh fruits because all nutrients are concentrated and, therefore, would be a convenience food assortment to benefit from the health benefits of fruits. The consumers prefer fruit bars that are more tasted followed by proper textural features that could be obtained by establishing the equilibrium of ingredients, the proper choosing of manufacturing stages and the control of the product final moisture content. Fruit bar preparations may include a mixture of pulps, fresh or dried fruit, sugar, binders, and a variety of minor ingredients. Additionally to the conventional steps of manufacturing (pulping, homogenizing, heating, concentrating, and drying) there have been proposed the use of gelled fruit matrices, dried gels or sponges, and extruders as new trends for processing fruit bars. Different single-type dehydration or combined methods include, in order of increasing process time, air-infrared, vacuum and vacuum-microwave drying convective-solar drying, convective drying, and freeze drying are also suggested as alternative to solar traditional drying stage. The dehydration methods that use vacuum exhibited not only higher retention of antioxidants but also better color, texture, and rehydration capacity. Antioxidant activity resulting from the presence of phenolic compounds in the bars is well established. Besides this, fruit bars are also important sources of carbohydrates and minerals. Given the wide range of bioactive factors in fresh fruits that are preserved in fruit bars, it is plausible that their uptake consumption have a positive effect in reducing the risk of many diseases.

Developments and trends in fruit bar production and characterization.

A dried fruit or vegetable has a water content in the range 4% to 7%, and has a water activity of 0.4. Substantially all of the cells of the dried product are undamaged. An air drying process is gentle and contains four phases, during which the temperature of the drying air is maintained at 60° C. In a first phase the relative humidity of the drying air is allowed to rise to between 50% and 55%, and is maintained substantially constant at this value during a second phase by maintaining exchange of the drying air with fresh air substantially constant. In a third phase of the process, the relative humidity of the drying medium is permitted to decrease relatively rapidly until the fourth phase commences, at which stage the relative humidity is permitted to asymptotically approach a predetermined relative humidity value. During the drying process, excessive temperature differences and relative humidity differences between the temperature and relative humidity, respectively of the drying medium and the product are avoided in order to minimize damage to the cellular structure of the product.

Dried product and a drying process

Various protein fractions were prepared from non-germinated and germinated soybeans utilizing a combination of calcium chloride and sodium alginate solutions as extractant. Germination tended to improve the nutritional quality of the protein products as measured by protein efficiency ratios (PER of standard rat bioassay). PER values of proteins containing sodium alginate were reduced significantly, which was attributed to inhibition of pepsin proteolysis. Only 30 percent of the trypsin inhibitor activity in raw soybeans was eliminated during germination for three days. Vitamin C content increased from 0 to 25 mg per 100 g (dry basis) during germination.

Germinated soybean protein products: Chemical and nutritional evaluation

Apple pulp and reconstituted grapefruit juice were provided as texturized alginate gels at concentrations of 5–96%, after pH adjustment. The resulting products had appreciable mechanical integrity even at very high pulp or juice concentration. Their texture, judged by compressive strength, strain at failure, and deformability modulus was improved considerably by dipping in calcium lactate solution. The original pH of the fruit could be restored by a dip in a citric acid solution without adverse effects on texture.

Alginate Texturization of Highly Acid Fruit Pulps and Juices

Acceptance of new food resources may be achieved by simulation of traditional foods. Sodium alginate gels may be used to produce a desirable fruit-like texture useful as a base for fabricated nutrient-controlled foods. A two-step gelation process has been used to produce fruit-like textured products. These products can be flavored as desired and utilized without further processing to simulate fresh fruit pieces, or they may be either frozen and thawed, or freeze dried and rehydrated without loss of desirable texture. The freeze-dried materials rehydrate rap idly and when incorporated into food products such as yogurt, the rehydrated material compares favorably with rehydrated freeze-dried fruits or currently available commercial fruit yogurts.

A simulated fruit gel suitable for freeze dehydration

A simulated fruit gel suitable for freeze dehydration has been developed. The fabricated gel system consists primarily of alginate molecules crosslinked by calcium ions. Static compression tests or compression tests using the Instron Universal Testing Machine were used to characterize the mechanical properties of crosslinked gels having different compositions. It has been observed that incorporation of additional components such as pectin, gelatin, or sucrose to the calcium alginate system modified the textural characteristics of the crosslinked gels. Some hypotheses explaining the effect of added components on gel structure and texture are presented. Comparison of the results obtained from sensory and instrumental methods of texture measurement showed that if the instrumentally measured mechanical properties of two gel samples are different by 20% or more, sensory panelists could differentiate between the two samples at a high level of statistical significance.

Fabrication, characterization, and modification of the texture of calcium alginate gels

This invention provides a process for preparing a dehydrated banana which comprises slicing the fruit of a ripe banana along its length from 1 to 3 times to form lengthwise peeled banana slices having the carpel region exposed along their length, contacting the slices with steam to increase the temperature of the interior of the slices up to about 85°C to 95°C and maintaining that temperature for about 1/2 to 4 minutes, and dehydrating said steam blanched slices at a temperature from 50°C to 65°C to reduce the moisture content of the banana slices to less than about 20%. The slices are contacted with steam before they are substantially discolored due to enzymic discoloration. The product obtained thereby retains a substantial portion of the characteristic cellular structure of the banana, is substantially free of enzymic discoloration, has a water activity of less than about 0.6, and is rehydratable to yield a product with an appearance, texture, color, aroma and flavor similar to that of fresh ripe banana pulp. The dehydrated product retains those properties for at least 3 months under normal storage conditions.

Dehydrated banana product

This invention provides a process for preparing a dehydrated banana which comprises slicing the fruit of a ripe banana along its length from 1 to 3 times to form lengthwise peeled banana slices having the carpel region exposed along their length, contacting the slices with steam to increase the temperature of the interior of the slices up to about 85*C to 95*C and maintaining that temperature for about 1/2 to 4 minutes, and dehydrating said steam blanched slices at a temperature from 50*C to 65*C to reduce the moisture content of the banana slices to less than about 20%. The slices are contacted with steam before they are substantially discolored due to enzymic discoloration. The product obtained thereby retains a substantial portion of the characteristic cellular structure of the banana, is substantially free of enzymic discoloration, has a water activity of less than about 0.6, and is rehydratable to yield a product with an appearance, texture, color, aroma and flavor similar to that of fresh ripe banana pulp. The dehydrated product retains those properties for at least 3 months under normal storage conditions.

Nancy N. R. Luh

Papers

A simulated fruit gel suitable for freeze dehydration

Fabrication, characterization, and modification of the texture of calcium alginate gels

Dehydrated banana product

Process for dehydrating bananas and banana product