Thickeners, stabilizers, and gums are the basic texturizing ad- ditives used in fruit processing. These hydrocolloids are long- chain polymers that function as thickeners and stabilizers.
Functions of Hydrocolloids
1. Suspension of particulate matter in food products along with the regulation of crystallization.
2. Optimization of rheological properties of solid as well as liquid food products. The major parameters include flow and mouth-feel properties.
3. Stabilizers for oil and water emulsion systems.
4. Binding of dry and semi-dry products.
5. Optimized gelation to give both hard and soft gels.
6. Foam stabilization and flavor fixation.
The major sources of hydrocolloids are plant products, viz, gum exudates, seeds, and seaweeds. Products obtained by fermentation and chemically modified polysaccharides also contribute to the development of hydrocolloids for dif- ferent food applications. A variety of terms are often used to describe hydrocolloids. The terms are based either on the origin of the product or on the function for which it is being used. Three of the most common terms employed are gums, stabilizers, and hydrocolloids. The term “gum” describes a wide variety of water-soluble thickening and gelling polysac- charides (Carr 1993).
“Stabilizer” is another term used in the food industry to describe products that prevent separation of multicomponent food systems during storage. Another term that addresses both the behavior and physical characteristics of food gums is “hydrocolloids.” This term is a contraction of two terms
“hydrophilic colloid” and describes the water-loving nature and colloidal characteristics of this class of compounds (Table 12.8).
Besides use of pectin in fruit bars for texturization and in jams for gelling, newer fruit products such as structured fruits involve novel applications of state-of-art gelling agents.
Ample information is available on the mechanical properties of gelling agents such as alginates with or without other polysaccharides (Pelaez and Karel 1981). Nevertheless, for texturizing pulp or concentrated fruit juice, optimal gelling conditions such as pH of the pulp/juice concentrate is impor- tant. Calcium alginate gels have been found to be superior, causing continuity in gel formation (Wood 1975). Fruit pulps such as mango pulp have been texturized using hydrocolloids such as alginates (Mouquet et al. 1992).
The above-listed hydrocolloids are approved by FDA and are classified as either food additives or GRAS sub- stances (CDR 121.172.580–CDR 121.172.874). Their safety has been promulgated by JECFA and European Economic Community.
Emulsifiers
Emulsions are necessary for obtaining homogeneity in liq- uid foods having a tendency toward phase separation during processing/storage. Emulsifiers have lipophilic as well as hy- drophilic groups enabling the products to bring together the water and oil moieties without phase separation.
Besides phase separation, the other functions of food emul- sifiers are to enhance stability of flavors, and fats and oils by limiting the onset of rancidity. Emulsions are also used for better crumb texture in baked products due to optimal starch complexing property (Thompson and Buddemeyer 1954).
Usually, except lecithin, most emulsifiers are used in combi- nations. The important emulsifiers used widely are as follows:
r Mono- and diglycerides r Acetylated monoglycerides r Sucrose fatty acid esters r Stearoyl-2-lactylates r Propylene glycol esters r Sorbitan esters
r Diacetyl tartaric acid esters of monoglycerides (DATEM)
The FDA permits lecithin, mono- and diglycerides, and DATEM as GRAS. The other emulsifiers are approved under the standards of identity at specific levels. In fruit products, emulsifiers find applications in flavor emulsions, beverages, pie fillings, fruit desserts, and salad dressings (Mahungu and Artz 2002).
Table 12.8. Classification of Hydrocolloids
No.
Type of
Hydrocolloid Functions Sources Food Applications
1. Unmodified starch Thickener
Gelling, adhesive, and film former
Potato, cereals tapioca, and arrow root
Pie fillings Jams and jellies 2. Modified starch Bodying and gelling
Improvement of viscosity and other rheological parameters, Thermal resistance against higher as well as lower temperatures,
Modification in gelling, To improve solubility and gelling in cold water.
Products of chemical modification of natural polysaccharides
Pie fillings Canned fruits Fruit-based desserts
3. Casein Film former with cohesive and adhesive properties
Milk Edible films for packaging of
precut fruits and vegetables
4. Guar gum Stabilizer Guar beans Beverages
Water-based frozen fruit desserts
5. Gum arabic Stabilizer
Emulsifier
Exudate from genus Acacia
Beverages
Emulsifier for citrus oils and flavors
6. Carrageenan Gelation Irish moss Frozen desserts
Structured fruits
7. Pectin Gelation Fruit wastes Jams and jellies
Texturization as binder Beverages
Stabilizer Fruit bars
Fruit snacks and desserts 8. Xanthan gum Stabilizer
Gelation
Fermentation product fromXanthomonas comprestris
Beverages Puddings
Dry mixes of beverages 9. Carboxy methyl
cellulose
Thickener Stabilizer
Modified cellulose Dry drink mixes Fruit-flavored syrups
Enzymes
Enzymes are biological catalysts and proteinaceous in nature.
The use of enzymes in food processing in general and in fruit industries in particular is an offshoot of advances in fermentation/biotechnology. Enzymes, which exist within the fruits, perform a number of functions, such as softening, flavor development, ethylene biosynthesis, etc. Vegetables and fruits are also rich in oxidases, a class of enzymes, such as PPO and peroxidase, which cause browning reaction and off- flavor development, which is detrimental to the fruit quality (Whitaker 1996).
In case of fruit processing, enzymes are used mainly as processing aids aimed at specific functions, such as
r Improvement in juice extraction yields r Increment in solids recovery
r Improvement in filtration
r Removal of nonnutritional factors r Flavor enhancement
r Viscosity modifications r Anticlouding operations
r Antifouling operations for membrane concentrations.
Enzymes of commercial importance used in fruit process- ing are (a) pectinases, (b) cellulases, (c) amylases, and (d) glucose oxidase. Pectic enzymes, i.e., pectin methylesterase and polygalacturonase are used often in combination with amylases and cellulases in fruit and vegetable juice clari- fications to obtain higher juice yields and clarity. The tur- bidity/cloudiness of fresh fruit juices can be decreased with pectinase treatment due to the removal of negatively charged pectin deposits on particulate matter, which ultimately results in the coagulation of turbidity-causing materials (Yamasaki et al. 1967). Enzymatic treatment of soft fruit pulp facili- tates pressing and improves juices and anthocyanin pigment yields (Neubeck 1975). Pectin-degrading enzymes are also used to degrade highly esterified apple pectin and increase juice yields (Devos and Pilnik 1973). Amylases are often used along with pectinases to clarify juices such as banana to
obtain optimal juice yields. Similarly, application of cellu- lases also facilitates higher recovery of juices due to the degradation of cellulosic matrix. Cellulases are also used for waste treatments from fruit processing units for the devel- opment of value-added products. Glucose oxidase in com- bination with catalase is used to protect citrus juices from off-flavor development (Scott 1975) and in the prevention of enzymatic browning in frozen fruits (Somogyi 1996).
Enzymes are considered as direct food additive as per FDA.
The source organisms play an important role in the affirma- tion of GRAS status. Pectinases as well as glucose oxidase derived fromAspergillus nigerare considered as GRAS. The same holds good for-amylase and cellulase derived from A. niger.
Nutritional Additives
Nutritional additives have attained enhanced importance over the years due to the advances in product development with extended nutritional and nutraceutical values. The domains of nutritional and nutraceutical additives often overlap each other as many of the nutritional additives possess nutraceu- tical importance. Traditionally, nutritional additives are in the form of vitamins, minerals, amino acids, and fatty acids.
Consumption of conventional traditional foods used to take care of nutritional requirements subject to different culinary items consumed at different time intervals in a daily diet rou- tine. Problems have cropped up as some of these items got substituted due to consumption of new type of products in the dietary balance and inadvertently underwent imbalances, giving rise to a variety of deficiency syndromes. Food fortifi- cation had its origin in the form of addition of iodine to table salt to prevent goiter. Sodium iodide was recognized as an ef- fective means of iodization of salt. Similarly, vitamin D was supplemented in margarine, milk, and milk products. Later, a number of fortifications included vitamin B components, vitamin A, and vitamin C; trace minerals gained popularity due to the nutritional labeling.
Vitamins
Fruits are rich sources of both water-soluble as well as fat-soluble vitamins. Vitamin A precursors in the form of carotenoids are available in significant proportions in sev- eral fruits. Fruits are also rich sources of vitamin C. Certain fruits like seabuckthorn are known to be a good source of vitamin E.
The processing loss of water-soluble vitamins is significant and supplementation is required to maintain the nutritional balance. Thermally processed fruit extracts need such sup- plementations due to heavier loss of vitamins during heat pro- cessing as well as subsequent storage of the product (Kanner et al. 1982).
Vitamin C is widely used as ascorbic acid in dextro- or levo-rotatory forms as a natural antioxidant. Vitamin E (to-
copherols) is also known as a potential antioxidant. Ascorbic acid on oxidation can inhibit PPO activity by restricting the availability of molecular oxygen required for the reaction.
Fruit processing unit operations such as blanching, thermal processing, and freezing considerably reduce vitamin C con- tent. The storage losses add to the processing losses, demand- ing necessary supplementation (Kacem et al. 1987). The other functionalities include use of riboflavin-5-phosphate as a colorant.
The FDA considers vitamins as GRAS and nutritional sup- plements. Pantothenate is allowed as a food additive and requires label-mediated expression with regards to the con- centration used. Some of the commercial forms are marketed as follows:
r Vitamin A as vitamin A acetate r Thiamine as thiamine hydrochloride r Pantothenic acid as calcium pantothenate r Pyridoxin as pyridoxine hydrochloride
r Ascorbic acid as ascorbic acid, calcium ascorbate, and sodium ascorbate
r Vitamin E as tocopherol acetate,dl-␣-tocopherol Vitamin A supplementation gained worldwide publicity as many of the developing and underdeveloped countries found deficiency of vitamin A to be one of the main factors in the malnutrition of infants causing blindness or partially impaired vision. Vitamin A is usually marketed in the form of retinol acetate or palmitate and both of them are permitted for use in food.-Carotene, which is the precursor for vitamin A, could be expressed in terms of equivalent values. The commonly used unit for vitamin A is the international unit (1 IU = 0.33 g of retinol or 1 retinol equivalent). The recommended daily allowance for vitamin A is 5000 IU.
In case of-carotenes, 1 g of-carotene is equivalent to 0.167 g of retinol, 0.167 retinol equivalent, or 1.67 IU, and the RDA is the same as in the case of vitamin A. Milk and milk products had been the traditional media for the fortification of vitamin A. The other vitamins for fortification include vitamin D, E, and K besides vitamin C. Some of the salient features of different vitamins in terms of nutritional supplementation include the implications of toxicity upon excessive consumption (Table 12.9).
Minerals
Mineral supplementation had been given due consideration in fortification of several products inclusive of cereal products.
The most common minerals for fortification are Ca, Mg, and P, and minerals such as Cu, Fl, I, Fe, Mn, and Zn are usually provided as trace minerals (Table 12.10). The form of the mineral usually pertains to various salts, and the ideal salts are selected with beneficial effects in terms of bioavailability, solubility, and conformity with the food product as such.
Calcium fortification has considerable significance in infant nutrition and also lactating mothers. The adverse effects of
Vitamin Commercial Forms Units Solubility RDA Toxicity Symptoms Vit A Retinol acetate
Retinol palmitate
IU (1 IU= 0.33g retinol)
Fat soluble 5000 IU ⬎25,000 IU
Headache, nausea, sleeplessness, tenderness of bones Vit D Ergocalciferol (Vit D2)
Cholecalciferol (Vit D3)
IU 1 IU=1 mg DL␣- tocoferol acetate
Fat soluble 13 IU ⬎400–1000 IU
Calcification of soft tissues such as heart, lung, kidneys
Vit K Menadione sodium bisulfite, menadione dimethyl pyrinidole bisulfite, phylloquinone (vit K1)
mg org Fat soluble 0.5–1
g/kg body weight
Relatively nontoxic
–
Vit C l-ascorbic acid, sodium ascorbate, nicotinamide ascorbic acid complex
mg Water
soluble
60 mg Relatively nontoxic
–
Vit B com- ponents Thiamine
Thiamine hydrochloride, Thiamine nitrate
mg Water
soluble
1.5 mg Relatively nontoxic
–
Riboflavin Riboflavin, riboflavin phosphate, riboflavin butyrate
mg Water
soluble
1.7 mg Relatively nontoxic
–
Niacin Nicotinic acid, niacin, nicotinamide
mg Water
soluble
20 mg Relatively nontoxic
–
B6 Pyridoxin hydrochloride mg Water
soluble
2 mg Relatively nontoxic
– Pantothenic
acid
Calcium pantothenate, pantothenol
mg 10 mg Relatively
nontoxic
–
Folic acid Folic acid g Water
soluble
400g Low
toxicity above 400
g/day
–
B12 Folic acid g Water
soluble
6g Relatively nontoxic
–
Biotin d-biotin g or mg Water
soluble
0.3 mg Relatively nontoxic
–
Table 12.10. Minerals and Their Physiological Role
Mineral RDA Major Commercial Sources Physiological Role
K, Na, and Cl
1.1–3.3 g Na, 1.875–5.625 g K, 1.7–5.1 g Cl
Potassium chloride, potassium carbonate, sodium chloride, sodium carbonate, potassium citrate
Sodium–potassium balance is an important feature of body electrolyte balance.
Chlorides are potential cofactors.
Fe 18 mg Ferrous sulfate, ferrous lactate, ferrous gluconate
Iron constitutes an important entity as an electron carrier in oxidative phosphorylation besides being cofactor for several enzymes.
Iron also helps in assimilation of ascorbic acid and certain amino acids.
Zn 15 mg Zinc chloride, zinc oxide, zinc gluconate Cofactor in enzymatic functions
Cu 2 mg Copper gluconate, copper sulfate Cofactor for many enzymes and also plays an important role in iron metabolism and heme biosynthesis
I 150 mg Potassium iodide, cuprous iodide Has an important role in the formation of thyroid hormone.
Mn 2.5–5.0 mg Manganese chloride, manganese citrate, manganese gluconate
An important cofactor for enzymes
207
ageing result in development of osteoporosis and fragility of bones. Ranhotra et al. (1980) evaluated a number of cal- cium sources in terms of bioavailability. The various forms of calcium permitted include calcium carbonate, calcium chlo- ride, calcium citrate, ground limestone, calcium hydroxide, calcium sulfate, etc. The U.S. RDA for calcium is 1000 mg.
Along with calcium intake, it is recommended that the ratio of calcium to phosphorus be 1:1 in adults and 1:0.5 for infants.
Phosphorus is amply present in different foods and therefore is being used as nutritional additive only in some infant for- mulae. The U.S. RDA for phosphorus is 1.0 g and the usual forms of application are sodium and potassium phosphates and pyrophosphates. Magnesium is also available in abun- dance in various foods and the U.S. RDA for magnesium is 400 mg. Seelig and Haddy (1980) reported that magne- sium deficiency causes cardiovascular damage. The major sources of magnesium supplementation include salts such as magnesium carbonate, magnesium chloride, and magnesium hydroxide. Magnesium gluconate is considered by FDA as a GRAS nutritive additive.
The trace minerals are important to augment overall well being of humans and appropriate supplementation need to be carried out to avoid deficiencies. The regulations controlling nutritional additives suggest two routes, out of which pill forms constitute the first and food supplements constitute the second option. Mineral pills shall be considered as foods as long as specific claims are not made for disease resistance.
Food standards illustrate the threshold values for such sup- plementation in foods. Some of the FDA standards for the minerals in the case of adult males could be calcium 1300 mg/day, phosphorus 1250 mg/day, magnesium 240 mg/day, potassium 4500 mg/day, sodium 1500 mg/day, chloride 2300 mg/day, iron 8 mg/day, zinc 11 mg/day, copper 900g/day, iodine 150g/day, and manganese 2.3 mg/day. The recent advances with regards to mineral nutrition are to enhance the bioavailability by using appropriate crystalline forms of salts.
In the case of calcium, the carbonate salts are being struc- tured as layers and new commercial forms with improved bioavailability are available.