Color, Flavor, Texture, and Nutritional Quality of Fresh ...

1 Critical Reviews in Food Science and Nutrition, 50:369 389 (2010). Copyright C Taylor and Francis Group, LLC. ISSN: 1040-8398. DOI: Color, Flavor, Texture, and Nutritional Quality of Fresh -Cut Fruits and Vegetables: Desirable Levels, Instrumental and Sensory Measurement, and the Effects of Processing Downloaded By: [University of California, Davis] At: 19:29 12 April 2010. DIANE M. BARRETT,1 JOHN C. BEAULIEU,2 and ROB SHEWFELT3. 1. Department of Food Science & Technology, University of California, Davis, CA. 2. USDA ARS Southern Regional Research Center, New Orleans, LA. 3. Department of Food Science & Technology, University of Georgia, Athens, GA. The color, flavor, texture, and the Nutritional value of Fresh -cut fruit and vegetable products are factors critical to consumer acceptance and the success of these products.

2 In this chapter, desirable and undesirable Quality attributes of Fresh -cut fruit and vegetable products are reviewed. Both instrumental and sensory measurements for determining these critical Quality attributes are discussed. The advantages and disadvantages of sensory and instrumental Quality measurements are described. A review of typical unit operations involved in the production of Fresh -cut products is presented. The effects of Fresh -cut processing techniques and treatments on sensory Quality , including the appearance, texture, flavor (taste and aroma) of vegetables, and fruits are detailed. Keywords Fresh -cut, fruit, vegetable, Quality , color, texture, flavor, nutrients COMPONENTS OF FRUIT AND VEGETABLE Quality 3) texture and 4) Nutritional value.

3 As consumers, these four attributes typically affect us in the order specified above, for Quality Defined example we evaluate the visual appearance and color first, fol- lowed by the taste, aroma, and texture. Kramer (1965) stated Quality is a term which denotes a degree of excellence, a high that the appearance of the product usually determines whether a standard or value. Kramer (1965) stated that: Quality of foods product is accepted or rejected; therefore this is one of the most may be defined as the composite of those characteristics that critical Quality attributes. Nutritional value is a hidden charac- differentiate individual units of a product, and have significance teristic that affects our bodies in ways that we cannot perceive, in determining the degree of acceptability of that unit to the user.

4 But this Quality attribute is becoming increasingly valued by consumers, scientists, and the medical profession. We eat with our eyes. The shape, size, gloss, and vibrant Attributes of Fruit and Vegetable Quality color of a fruit or vegetable attract us and entice us into picking it up by hand or fork. Once we are attracted by the appearance In reference to fruits and vegetables, the characteristics that and color of a product, we put it into our mouths, where the impart distinctive Quality may be described by four different aroma and taste take over. Freshness, spiciness, sweetness, and attributes 1) color and appearance, 2) flavor (taste and aroma), other flavor attributes are critical to our eating pleasure.

5 Aroma refers to the smell of a fruit or vegetable product, whereas flavor Address correspondence to: Dr. Diane M. Barrett, Dept. of Food Science & includes both aroma and taste. Once the product is placed in the Technology, University of California, Davis, CA, 95616. mouth, one can perceive the smoothness, thickness, firmness, 369. 370 D. M. BARRETT ET AL. hardness, or crispness of the fruit or vegetable material. As Flavor Aroma and Taste chewing proceeds, the perception of textural Quality changes and products generally become softer. Nutritional value is an Flavor has been defined (Anon, 1959) as: A mingled but extremely important Quality component that is impossible to see, unitary experience which includes sensations of taste, smell, taste, or feel.

6 Nutrients are critical for the growth and long-term and pressure, and often cutaneous sensations such as warmth, development of our bodies, and include both micro nutrients color, or mild pain. Flavor is typically described by aroma (odor). and macro nutrients. There are some associations between and taste. Aroma compounds are volatile they are perceived textural attributes, especially juiciness and flavor and between primarily with the nose, while taste receptors exist in the mouth the color and Nutritional composition of fruits and vegetables. and are impacted when the food is chewed. While color and appearance may be the initial Quality attributes that attract us CHEMICAL AND PHYSICAL BASIS FOR FRUIT to a fruit or vegetable product, the flavor may have the largest AND VEGETABLE Quality impact on acceptability and desire to consume it again.

7 Taste has been divided into five primary tastes sweet, sour, salty, bitter, Color and umami. Umami can be described as a taste associated with salts of amino acids and nucleotides (Yamaguchi and Ninomiya, 2000). Odors are much more diverse and difficult to classify, but Downloaded By: [University of California, Davis] At: 19:29 12 April 2010. Color is derived from the natural pigments in fruits and veg- etables, many of which change as the plant proceeds through an attempt by Henning (Gould, 1983) includes the following . maturation and ripening. The primary pigments imparting color spicy, flowery, fruity, resinous or balsamic, burnt, and foul. Quality are the fat soluble chlorophylls (green) and carotenoids Stevens (1985) stated that it is possible to classify vegetables (yellow, orange, and red) and the water soluble anthocyanins into two major groups, depending on their flavor characteristics.

8 (red, blue), flavonoids (yellow), and betalains (red). In addi- The first group of fruits and vegetables has a strong flavor that tion, enzymatic and non-enzymatic browning reactions may re- can be attributed to a single compound or group of related com- sult in the formation of water soluble brown, gray, and black pounds. Bananas with isoamylacetate, onions with characteristic colored pigments. The enzymes involved in browning reac- sulfide compounds, and celery, with distinctive phthalides are tions include polyphenol oxidase, which catalyzes the oxida- examples of this group. The second group of fruits and veg- tion of polyphenolic compounds, and phenylalanine ammonia etables includes those whose flavor is determined by a number lyase, which catalyzes the synthesis of precursors to phenolic of volatiles, none of which conveys the specific characteristic substrates.

9 Aroma. Examples in this group include snap beans, muskmelons, The chlorophylls are sensitive to heat and acid, but stable to and tomatoes. alkali whereas their counterpart carotenoids are sensitive to light In the evaluation of fruit and vegetable flavor, it is important and oxidation but relatively stable to heat. Carotenoids may be to consider off-flavors as well as desirable ones. These off- bleached by an enzyme called lipoxygenase, which catalyzes flavors may be produced through the action of enzymes such the oxidation of lipid compounds. Anthocyanins are sensitive to as lipoxygenase or peroxidase, which form reactive free rad- both pH and heat, while the flavonoids are sensitive to oxidation icals and hydroperoxides that may catalyze the oxidation of but relatively stable to heat.

10 Betalains are heat sensitive as well lipid compounds. When these reactions occur, the result may (Clydesdale and Francis, 1976). be the development of undesirable flavors described as rancid, Appearance is determined by physical factors including the cardboard, oxidized, or wet dog. However, there are instances size, the shape, the wholeness, the presence of defects (blem- of enzyme-catalyzed reactions that result in desirable flavors. ishes, bruises, spots, etc.), finish or gloss, and consistency. Size For example, hydroperoxide lyase catalyzes the production of and shape may be influenced by cultivar, maturity, production typical tomato flavors (Anthon and Barrett, 2003).