Study Notes for Chapter 18: Vegetables and Vegetable Preparation

Introductory Foods: Chapter 18 - Vegetables and Vegetable Preparation

Learning Objectives

18.1 Consumption Trends and Nutritive Value of Vegetables

  • Consumption Trends: Vegetable consumption has increased since 1970. The main contributors to this consumption include:

    • Potatoes
    • Tomatoes

  • It is noted that the overall consumption is still below the recommended servings.

  • Nutritive Value: Vegetables offer numerous health benefits, including potential reductions in the risk of several types of cancers and chronic diseases. Nutritional benefits include:

    • High fiber content
    • Several essential vitamins and minerals
    • Rich in phytochemicals
    • Generally low in calories

Figure 18.2 illustrates consumption levels of vegetables among males and females of various ages, showing a stark contrast against USDA-recommended consumption levels.

Types of Vegetables and Their Characteristics

Leaf Vegetables
  • Examples include:
    • Brussel Sprouts
    • Several types of lettuce and greens
    • Cabbage
    • Chinese Cabbage
    • Cactus Pads
  • Nutritional Characteristics:
    • Typically high in water content
    • Low in carbohydrates, protein, fat, and calories
    • Calcium content prevalent but bound by oxalic acid, making it less bioavailable
  • Storage Recommendations:
    • Should be refrigerated
    • Must be kept away from ethylene-producing fruits and vegetables
    • Require high humidity for preservation

Refer to Table 18.4 for detailed storage guidelines.

Vegetable-Fruits
  • Examples include:
    • Cucumber
    • Eggplant
    • Okra
    • Pepper
    • Pumpkin
    • Snap Beans (String Beans)
    • Various Squash Types
    • Several Varieties of Tomatoes
  • Botanical Classification: Despite being classified as fruits botanically, they are treated as vegetables in culinary contexts.
  • Nutritional Characteristics:
    • High water content
    • Source of Vitamin C especially in tomatoes and green peppers
    • Contain carotenoid pigments notably in pumpkins, yellow squash, and tomatoes

Refer to Table 18.5 for additional classifications.

Flowers and Stems
  • Examples include:
    • Artichoke
    • Broccoli
    • Cauliflower
    • Asparagus
    • Celery
    • Fennel
    • Kohlrabi
  • Nutritional Characteristics:
    • High in water and carbohydrates
    • Broccoli is particularly high in Vitamins A and C

Preparation Tips: For globe artichokes, a detailed preparation process includes clipping thorny tips, cutting the top and stem, removing heavy leaves, boiling with seasonings for 20 to 45 minutes until tender.

Roots, Tubers, and Bulbs

  • Roots and Tubers:

    • Examples include:
    • Beet
    • Carrot
    • Celery Root
    • Ginger Root
    • Jicama
    • Parsnip
    • Potato (the most consumed vegetable in America, differentiated into:
      • Mealy Potatoes
      • Waxy Potatoes)
    • Rutabaga
    • Salsify
    • Sweet Potato
    • Sunchoke
    • Turnips

  • Bulbs:

    • Examples include:
    • Garlic
    • Leek
    • Onion
    • Shallot

Refer to Table 18.7 for storage information on roots and Table 18.8 for bulbs.

Seeds
  • Examples:
    • Sweet Corn
    • Various Peas
    • Dent Corn (which is categorized as a grain)
  • Note: Legumes are also seeds (further discussed in Chapter 19).

Refer to Table 18.9 for additional information on seeds.

Mushrooms
  • Classification: Mushrooms are fungi and are not officially classified as vegetables.
  • Varieties: There are numerous varieties of mushrooms, not all of which are edible.
  • Storage Recommendations: Should be stored in the refrigerator and away from strong odors. Submerging in water is discouraged.

Refer to Table 18.10 for mushroom types.

Purchasing Vegetables

Economic Considerations
  • Selection for Nutritional Guidance: It's important for selections to meet the Dietary Guidelines for Americans, and households may need to reallocate budgets accordingly.
  • Packaging Options: Consider frozen, canned, or fresh vegetables, with a preference for seasonal buying to ensure quality and pricing.
  • Nutrient Cost Analysis: Generally, fruits and vegetables deliver higher nutritional value per cost than other food types.

Figure 18.11 represents food expenditures of low-income, middle-income, and high-income Americans across different food groups.

Budget Tips
  • Balancing Household Budgets: Americans can increase the intake of fruits and vegetables by adjusting expenditures, specifically reducing spending on protein foods and sweetened beverages.

Figure 18.12 emphasizes potential strategies for incorporating more produce into American diets.

Grading of Vegetables
  • Voluntary Grading: Grading is voluntary and may apply to fresh, frozen, or canned vegetables.
  • USDA Involvement: The USDA conducts grading upon the request of a food processor or grower willing to pay for the service.
  • Shield Symbols: Continuous inspection shields and grade labels provide quality assurance.

Figure 18.13 displays a USDA grading shield for products inspected continuously.

Organic Produce Considerations
  • Organic Standards: Established by the USDA in 2002; condition requirements include:
    • No conventional pesticides or synthetic fertilizers
    • No bioengineering or ionizing radiation
  • Certification: Farms must be inspected and certified to qualify as organic.
  • Terminology Clarification: "Organic" and "natural" are not synonymous concepts.

Figure 18.14 elucidates the USDA Organic shield use criteria (95% organic ingredients).

Value-Added Convenience Foods
  • Examples:
    • Peeled Carrots
    • Bagged Salad Mixes
    • Fresh-Cut Vegetables
  • Technologies: Ensure quality and safety, including modified atmosphere packaging and hermetic packaging.

Storage of Vegetables

  • Storage Life Factors: Include respiration, senescing, and loss of turgor.
  • General Storage Conditions:
    • Temperature
    • Humidity
  • Method Extensions: Possible methods to extend storage include use of vegetable oil emulsions and controlled atmospheres.

Food Safety and Preparation

Contamination Risks
  • Sources of Contamination:
    • Soil organisms
    • Postharvest handling
    • Improper storage
  • Recommendations for Safety:
    • Proper selection of produce
    • Prevention of cross-contamination
    • Ensuring thorough washing
    • Peeling green pigmentation from potatoes as they indicate solanine contamination.

Figure 18.15 illustrates effective techniques for washing produce using water to separate dirt efficiently.

Edible Portion and As Purchased

  • Definitions:
    • Edible Portion (EP): The amount of produce left remaining after cleaning, which is considered edible.
    • As Purchased (AP): The total weight or volume of produce before cleaning or preparation.
  • Refuse/Waste: Refers to the non-edible parts of vegetables, including:
    • Lettuce (weight reduction after removal of core and spoiled leaves)
    • Potatoes (weight reduction after peeling)
    • Tomatoes (core and stem removal results in weight loss).

Why Cook Vegetables?

  • Benefits of Cooking:
    • Improves palatability
    • Aids in digestion through gelatinization of starches
    • Provides flavor variety between cooked and raw form
    • Enhances utilization of proteins in dried legumes
    • Ensures food safety by destroying microorganisms (e.g., red navy beans must boil).

Plant Pigments Overview

  • Types of Pigments:

    • Chlorophyll
    • Carotenoids
    • Anthocyanins
    • Betalains
    • Anthoxanthins

  • Impact of Preparation: Vegetable preparation can negatively impact pigments and sensory desirability.

Detailed Study of Plant Pigments

Chlorophyll
  • Role: Crucial in photosynthesis, primarily found in green leaves.
  • Effects of Heat:
    • Initially enhances green color; however, excessive cooking leads to degradation into pheophytin.
    • Canning can yield pheophytin and pyropheophytin.
  • Effects of Acids:
    • Result in pheophytin formation.
  • Effects of Alkalies:
    • Converts chlorophyll to chlorophyllin, which softens texture and destroys Vitamin C and Thiamin.
Carotenoids
  • Location: Present in the chloroplasts of green leaves such as lettuce, greens, green beans, and broccoli.
  • Solubility and Stability:
    • Insoluble in water; prone to oxidation and degradation with overcooking.
  • Types of Carotenoids: Includes Carotene, Xanthophyll (yellow pigments), and Lycopene (found in tomatoes and watermelon).
Anthocyanins
  • Properties: Soluble in water, located in cell sap in vegetables and fruits, such as red cabbage, radishes, blackberries, and black raspberries.
  • Color Changes with pH:
    • Acidic conditions yield red hues; alkaline conditions yield blue.
Betalains
  • Location: Found primarily in the red root of beets and yellow in yellow cactus pears.
  • Stability Range: Stable between pH 3 and pH 7; very soluble in water (suggest peeling beets after cooking to minimize pigment loss).
Anthoxanthins
  • Examples: Common in potatoes, cauliflower, turnips, and white onions.
  • Effects of pH: Can change from colorless to yellowish in more alkaline conditions.
  • Heating Effects: Excessive heating can darken their color.
Browning
  • Type: Enzymatic browning occurs through oxidation of phenolic compounds.
  • Control Methods: Include applying lemon juice, pineapple juice, citric acid, submerging in water or saltwater, and using sulfites.
  • Specific Reaction: Cooking potatoes may cause darkening due to ferric iron and polyphenols; increase acidity in cooking water to mitigate this.
Flavor Considerations
  • Impact of Overcooking: Cooking can greatly alter the flavor profile of vegetables and influence their sensory appeal.
  • Cabbage Flavor Shifts: Mild when raw but intensifies when cooked; certain cooking methods can help mitigate strong cabbage flavors.
  • Onion Flavor Shifts: Strong when raw but becomes mild when cooked.
Texture Considerations
  • Desirable Cooking Texture: Achieving a tender-crisp texture is generally recommended.
  • Fiber Components: Include cellulose, hemicelluloses, pectins, betalains, lignin, and gums/mucilages; influenced by cooking processes.
Prevention of Nutrient Losses
  • Loss Mechanisms: Nutrients can be lost through dissolution in water or salt, chemical decomposition, mechanical loss, and volatilization.
  • Cooking Losses: Particularly affect water-soluble nutrients and fat-soluble nutrients, alongside antioxidants, influenced by food production systems.

Cooking Methods

  • Common Cooking Techniques:
    • Broiling and Grilling
    • Roasting and Baking
    • Pan-frying and Deep-Fat Frying
    • Sautéing
    • Boiling (includes blanching and par-boiling)
    • Steaming
    • Pressure Cooking
    • Microwave Cooking

Figure 18.18 depicts broccoli spears steaming in a commercial food service steamer.

Additional Cooking Considerations

  • Cooking Times: Variability based on cooking method.
  • Frozen and Canned Cooking: Specific methods for handling and cooking frozen and canned vegetables for optimal results.