In the realm of food processing and preservation, Vacuum Pressure Impregnation (VPI) has emerged as a groundbreaking technology to enhance the quality and prolong the shelf life of fruits and vegetables. This comprehensive guide will delve into the world of VPI for fruits and vegetables, shedding light on its principles, applications, and the transformative role it plays in preserving the freshness, taste, and nutritional value of produce, thereby contributing to sustainability, and reducing food waste.
Vacuum impregnation is a non-destructive method of introducing a solution with a specific composition to the porous matrices of fruit and vegetables. Mass transfer in this process is a result of mechanically induced differences in pressure. Vacuum impregnation makes it possible to fill large volumes of intercellular spaces in tissues of fruit and vegetables, thus modifying physico-chemical properties and sensory attributes of products.
This method may be used, e.g., to reduce pH and water activity of the product, change its thermal properties, improve texture, color, taste and aroma. Additionally, bioactive compounds may be introduced together with impregnating solutions, thus improving health-promoting properties of the product or facilitating production of functional food.
During typical vacuum impregnation the free spaces and capillaries of the material are filled due to a mechanically induced difference in pressure. The process consists of two stages: The phase of reduced pressure and the phase of atmospheric pressure. Impregnation of the material occurs as a consequence of two phenomena: hydrodynamic mechanism (HDM) and deformation relaxation phenomena (DRP), which lead to the filling of intracellular capillaries.
Before we explore the applications and advantages of VPI for fruits and vegetables, it's essential to grasp the fundamental concept behind this specialized food preservation technique. Vacuum Pressure Impregnation is a process that involves subjecting fruits and vegetables to a vacuum environment while immersing them in a solution, allowing the produce to absorb the solution, enhancing its quality, and extending its shelf life.
Before we explore the applications and advantages of VPI for fruits and vegetables, it's essential to grasp the fundamental concept behind this specialized food preservation technique. Vacuum Pressure Impregnation is a process that involves subjecting fruits and vegetables to a vacuum environment while immersing them in a solution, allowing the produce to absorb the solution, enhancing its quality, and extending its shelf life.
Reducing Food Waste and Enhancing Nutritional Value
In a world grappling with food waste and the quest for sustainable practices, VPI holds significant promise in the food industry:
1. Reducing Food Waste: VPI can extend the shelf life of fresh produce, reducing the amount of discarded fruits and vegetables.
2. Enhancing Nutritional Value: By preserving the freshness of produce, VPI helps maintain its nutritional content, contributing to healthier diets.
3. Sustainability: Reduced food waste aligns with sustainability goals by conserving resources used in production and transportation.
4. Improved Taste and Quality: VPI enhances the taste, texture, and overall quality of fruits and vegetables.
5. Export and Storage: It facilitates the export of perishable produce and enables longer storage without compromising quality.
Components of a VPI System for Food
Precision Engineering for Quality Enhancement
Key components of a Vacuum Pressure Impregnation System for food include:
1. Impregnation Chamber: The chamber, often made of stainless steel, houses the produce to be impregnated and seals them in a vacuum-tight environment.
2. Impregnation Solution: A specially formulated solution containing desired nutrients, preservatives, or flavorings.
3. Vacuum Pump: A vacuum pump creates a low-pressure environment within the chamber, facilitating the impregnation process.
4. Pressure System: A pressure system pressurizes the chamber to enhance solution penetration and absorption.
5. Temperature Control: Advanced temperature control systems ensure that the impregnation occurs at the optimal temperature for the specific product.
Applications of VPI for Fruits and Vegetables
VPI for fruits and vegetables finds applications in various areas of the food industry:
1. Fresh Produce Preservation: VPI extends the shelf life of fresh fruits and vegetables, reducing food waste and preserving quality.
2. Flavor Enhancement: It can be used to infuse produce with desired flavors, enhancing their taste and consumer appeal.
3. Nutrient Fortification: VPI allows for the addition of nutrients or vitamins, enriching the nutritional value of produce.
4. Preventing Oxidation: It prevents oxidative browning in fruits like apples and pears, maintaining their visual appeal.
5. Reducing Post-Harvest Losses: VPI helps reduce post-harvest losses in perishable fruits and vegetables, ensuring they reach consumers in optimal condition.
Advantages and Benefits of VPI for Food
Enhanced Quality, Sustainability, and Consumer Satisfaction
The adoption of Vacuum Pressure Impregnation (VPI) for fruits and vegetables offers several key advantages:
1. Extended Shelf Life: VPI significantly extends the shelf life of produce, reducing food waste.
2. Improved Nutritional Value: It helps maintain the nutritional content of fruits and vegetables.
3. Sustainability: Reduced food waste aligns with sustainability goals by conserving resources.
4. Enhanced Flavor: VPI enhances the flavor of produce, contributing to consumer satisfaction.
5. Reduced Post-Harvest Losses: It helps growers and suppliers reduce losses during storage and transportation.
Challenges and Considerations
While VPI for fruits and vegetables offers substantial benefits, challenges may include selecting the appropriate impregnation solution, optimizing process parameters, ensuring food safety, and adhering to regulatory standards. Stringent quality control measures are essential for safe and effective impregnation.
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apple cv. Jonagold (1-cm thick slices) |
ascorbic acid, citric acid, 4-hexylresorcinol, sodium chloride, calcium chloride, sodium lactate, calcium lactate and sucrose solutions |
p1 7 kPa t1 5 min t2 5 min |
effective inhibition of browning and softening of apple slices during storage by 1% ascorbic acid, 0.005% 4-hexylresorcinol, 0.5% calcium chloride, 20% sucrose in mpregnated solution |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apple cv. Jonagold (cut into 1 cm thick slices) | 10 mg/L ascorbic acid, 0.05 mg/L 4- hexylresorcinol, 5 mg/L calcium chloride and 200 mg/L sucrose | p1 8 kPa t1 5 min t2 5 min | the same effect of dipping and vacuum impregnation regarding hardness |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apple samples cv. Granny Smith (cylindrical samples (8 cm height and 2 cm diameter)) | sucrose isotonic solution | p1 50 kPa t1 10 min t2 20 min | increase of thermal conductivity |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apple samples cv. Granny Smith | CaCl2 solution (0.6%, 2.0% or 4.0% (w/w)) | p1 9.3 and 59.9 kPa t1 4 min t2 5 min | improvement of texture |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apple sticks | mass ratio of fruit:syrup was 1:17; fructose isotonic solution (14.0°–15° Brix) containing ascorbic acid (0.5% wt/wt) and dry, food-grade green apple flavoring (0.5% wt/wt) | p1 28 kPa t1 5 min t2 2.5, 5, 12.5 min | aroma enrichment |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apples cv. Granny Smith (1 cm cubes) strawberries (cut in halves) and raspberries | high methylated pectin solution preparation up to 3% (w/w) and/or CaCl2, up to 6.5% (w/w) | p1 6.6 kPa t1 2 min | limitation of loss in fruit firmness following pasteurization |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apples cv. Granny Smith and Stark Delicious | higher values of hardness, crispness, juiciness and sourness in vacuum impregnated Granny Smith apples | the solution:fruit ratio was 11:1; p1 10 kPa t1 30 min t2 5 min | higher values of hardness, crispness, juiciness and sourness in vacuum impregnated Granny Smith apples |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
button mushrooms (slice thickness was 6.5 mm with a 3 to 5 mm cap length) | 2 g/100 g ascorbic acid + 1 g/100 g calcium lactate solution; 2 g/100 g citric acid + 1 g/100 g calcium lactate; 1 g/100 g chitosan + 1 g/100 g calcium lactate solution; and 1 g/100 g calcium lactate solution | p1 6.7, 10.0, 13.3, 16.7 kPa t1 5 and 10 min t2 5 and 10 min | vacuum impregnation with ascorbic acid and calcium lactate at 6.7 kPa for 5 min and atmospheric restoration time of 5 min was the most effective to limit adverse changes of color in sliced button mushrooms |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
carrots (cv.Nantesa) slices (20-mm diameter, 10 mm thick) | chitosan (1%, w/v) dispersed inaqueous solution of glacial acetic acid (1%, w/v), at 40 °C | p1 5 kPa t1 4 min t2 2 min | improvement of sample resistance to water vapor transmission, better preservation of color and mechanical response during cold storage |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
eggplant, carrot, oyster mushroom | 33 g sucrose and 20 g calcium lactate solution in isotonic solution | p1 5 kPa t1 10 min t2 10 min | notable impact on mechanical behaviour of eggplant and carrot, no effects in oyster mushroom |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
eggplants (slices of 1 cm trick) | pectinmethyl-esterase derived from Aspergillus niger and extracted from orange and grapefruit and 4000 ppm CaCl2·2H2O | 1st method: p1 68 kPa, t1 15 min at 30 °C 2nd method: pulsed vacuum impregnation p1 85 kPa, t1 5 min release vacuum to atmospheric pressure for 1 min reapply vacuum for 5 min and release for 5 min | increase of firmness in impregnated eggplants |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
litchi cv. Rose | 502 g/kg sucrose solution containing 4.9 g/kg cysteine + 20 g/kg ascorbic acid + 0.134 g/kg 4-hexyl resorcinol and 502 g/kg sucrose solutions also contained 20 g/kg calcium lactate and 1 g/kg potassium sorbate | p1 76 kPa t1 10 min t2 10 min | samples were sensory acceptable up to 24 days |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
olive fruits cv. Domat | NaCl (3%), NaOH (1.5%) and NaOH (1.5%) + NaCl (3%) solutions | p1 68 kPa | shortening the duration of debittering process |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
papayas (cut into 4 × 2.5 × 0.5 cm pieces (length × width × thickness)) | 55% and 65% (w/w) sucrose solution | p1 5 kPa t1 10 min at 30 °C | decrease of aw |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
peaches (cut in halves) | pectin methylesterase together with CaCl2 (100 mg/L) | p1 85 kPa t1 30, 60, 90, 120 min | increase of firmness in canned peaches |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
pear (Pirus communis cv. Blanquilla) (cylinders 2 cm height, 2 cm diameter) | isotonic sucrose solution (14° Brix) containing trisodium citrate 2-hydrate, sodium L-ascorbate, ethylenediamine tetraacetic acid 2-hydrate disodium salt and calcium lactate 5-hydrate and 4-hexylresorcinol | solution: fruit ratio of 20:1; p1 5 kPa t1 5 min t2 10 min | ascorbate and calcium lactate in impregnated solution were the most effective for extending the shelf life of pear |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
pineapple (slices 1 cm thickness) | chitosan- or casinate- based film-forming emulsions | ratio of the weight of coating solution:sample: 20:1; p1 5 kPa t1 3 min t2 2 min | extension of shelf-life in pineapple-cereal system for caseinate based coating |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
rabbiteye blueberries | aqueous sucrose solutions (600 g/kg) | solution:product ratio of 1:1; p1 88 kPa | shortenning of dehydratation time in comparison with soaking at atmospheric pressure |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
strawberries (cv. Elsanta and Darselect) (cut in halves) | high methylated pectin (from Aspergillus aceleatus) containing 100 U/mL, 0.5% (w/w) CaCl2·2H2O 1% and 3% (w/w) of apple pectin | p1 1 kPa t1 5 min | limitation of structural damage during subsequent rapid freezing processes |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
strawberry slices | CaCl2 solution (1, 10, 100 mM); spermine solution (1, 10, 100 mM); spermidine (1, 10, 100 mM); putrescine (1, 10, 100 mM); | p1 16.9 kPa t1 8 min | effect of spermine and spermidine on the increase of firmness, whereas putrescine was not as effective. |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
strawberry | 65% (w/w) sucrose solution | steam blanching or microwave and osmotic dehydration at atmospheric pressure or pulsed vacuum treatments p1 5 kPa t1 5 min at 30 °C | decrease of aw |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
strawberry | 12 g/100 g trehalose solution; 0.2 g/100 g solution unpasteurized cold acclimated winter wheat grass extract as a source of AFP and 12 g/100 g trehalose and 0.2 g/100 g unpasteurized cold acclimated winter wheat grass extract | p1 86 kPa t1 5 min | improvement of freezing tolerance of strawberry |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
watercress (leaves were selected diameter 1.4 cm) | winter flounder antifreeze protein type I solution (1 mg/100 mL AFP-I ultra pure water) | p1 51, 58, 68, 85 and 101 kPa t1 5 min | smaller ice crystals in AFP-I impregnated (58 kPa, for 5 min) frozen samples |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
zucchini (slices 0.5-cm thick) | maltodextrine solution (7.5%–9%, 10%), NaCl (0%–5%) and CaCl2 (0–1000 mM) | product:solution ratio of 1:3.3; p1 2.5 kPa t1 10 min t2 30 min | improvement of solute and water gain and limitation of textural and microstructural changes |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
apples cv. (cultivar). Granny Smith (cylindrical samples (2 cm height and diameter)) | rectified grape must (hypertonic solutions: 65°, 50° and 30° Brix) and 3% (w/w) high methoxyl pectin solutions | p1 5 kPa t1 5 min t2 25 min in higher solution viscosity t2 55 min | Improvement of mechanical and structural properties of tissue, notable reduction of freezable water which could improve fruit resistance to freezing damage |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
Mushrooms (Agaricus bisporus) (cut in half) | lactic acid solution (pH 3.05) | solution: sample mass ratio of 8:1; p1 20 and 40 kPa t1 5 min t2 20, 40, 60, 120, 240, 300, 360 and 720 min | increase of the acidification degree in mushrooms |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
peppers (slices of 15 cm in length and 1 cm in width) | lactic acid solution (pH 2.70) | solution:sample mass ratio of 5:1; p1 20 kPa t1 5 min t2 10 to 30 min | increase of the acidification degree in peppers |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
Plum (cut in slices of 4 × 1 × 1 cm, weighting approximately 10 g) | 40°, 50° and 60° Brix sucrose solution | solution: sample mass ratio of 10:1; p1 20 and 40 kPa t1 10 min | new product with good visual quality and satisfactory shrinkage |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
spinach (rectangular 3.0 cm long, 0.5 cm wide and 0.06 cm thick) | 40% (w/w) trehalose solution | pulsed electric fields (580 V/cm) in combination with vacuum impregnation P1 86 kpa t1 20 min t2 150 min | improvement of freezing tolerance of spinach leaves |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
strawberry (10 mm slices) | 50% (w/w) high fructose corn syrup or 3% (w/w) high methoxyl pectin solution containing calcium and/or zinc | p1 7 kPa t1 15 min t2 30 min | Improvement of textural quality and reduced drip loss of frozen-thawed strawberries |
Raw Material | Composition of Vacuum Impregnation Solutions |
Process Parameters |
Effect |
zucchini (slices of 1.5 cm in thickness and a diameter of 2.0 cm; the average weight of each slice was 5 g) | lactic acid solution (pH 2.70) | solution: sample mass ratio of 8:1; p1 20 and 40 kPa t1 5 min t2 20, 40, 60, 120, 240, 300, 360 and 720 min | increase of the acidification degree in Zucchini slices |
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