Which one is better for preserving fruits and vegetables, PVPK30 or K17 ?

The difference in fruit and vegetable preservation performance between PVPK30 (polyvinylpyrrolidone K30) and K17 is fundamentally due to performance differences caused by differences in molecular weight and molecular structure . Considering their film-forming properties, moisture retention, stability, and practical application scenarios, PVPK30 performs better in fruit and vegetable preservation , particularly in applications requiring long-term physical protection and delayed oxidation. K17, on the other hand, is only suitable for specific needs (such as rapid penetration or low-viscosity systems). The following analysis focuses on core performance, preservation mechanisms, application scenarios, and experimental data:

1. Core Performance Comparison: K30's "High Molecular Weight Advantage" and K17's "Low Molecular Weight Limitation"

1. Film-forming property: K30 forms a tougher three-dimensional protective network

• PVPK30 :
  With a molecular weight of approximately 40,000 Da, it features longer molecular chains and a higher degree of branching, resulting in a significantly higher solution viscosity than K17 (3-5 times that of K17 at the same concentration). During film formation, it forms a dense, continuous three-dimensional network structure with a thickness of up to microns. This effectively blocks oxygen, moisture, and microorganisms, slowing the oxidative browning of fruits and vegetables (for example, the inhibition rate of enzymatic browning in apple slices can exceed 60%).
  For example , in peach preservation experiments, a 0.1% PVPK30 coating reduced fruit weight loss by 30% and increased firmness retention by 25%, surpassing a 1.0% chitosan coating.
• PVPK17 :
  With a molecular weight of approximately 10,000 Da, its molecular chains are short and its linear structure is high. The resulting film is thin and easily broken (nanometer-thick), providing only a short-term physical barrier. For example, strawberries coated with K17 showed noticeable surface wrinkling after seven days of refrigeration, while those treated with K30 remained plump.

2. Moisturizing: K30's "hydrogel effect" lasts longer

• PVPK30 :
  The pyrrolidone rings in the polymer chain form strong hydrogen bonds with water molecules. After absorbing water, it expands to form a hydrogel with a water content of 80% to 90% of its own weight . This hydrogel slowly releases water to maintain surface moisture on fruits and vegetables. For example, in grape preservation, K30 coating reduced the browning index of the fruit stem by 40%, while the browning rate of the fruit stem in the K17 treatment group was not significantly different from that in the control group.
• PVPK17 :
  Due to its low molecular weight, the hydrogel network formed after absorbing water is loose, and its water retention capacity is only 50%-60% of that of K30. Experiments showed that after 24 hours at room temperature, cherries treated with K17 experienced a 15% higher weight loss than those treated with K30.

3. Stability: K30 is more resistant to complex environments

• PVPK30 :
  It maintains a stable molecular structure in high-temperature (≤150°C), acidic and alkaline (pH 3-10), and high-salt environments, making it suitable for** high-temperature sterilization packaging or preserving high-acid/high-salt fruits and vegetables (such as pickled olives and preserved fruit). For example, in blueberry juice at pH 4.5, K30 remains stable for over three months, while K17 partially degrades within one month under the same conditions.
• PVPK17 :
  Its low molecular weight makes it susceptible to chain breakage in high temperatures or strong acid environments, resulting in poor stability. For example, K17-coated bananas stored at 50°C showed cracking after 3 days, while the K30-coated group maintained its stability for over 7 days.

2. Preservation Mechanism Comparison: K30's "Multi-dimensional Collaborative Protection" and K17's "Single Function Limitation"

1. Delaying oxidation: K30’s dual antioxidant mechanism

• Physical barrier :
  The dense film layer of K30 can reduce oxygen contact and inhibit the respiration of fruits and vegetables (for example, the respiration rate of kiwifruit is reduced by 40%).
• Chemical chelation :
  The amide groups (-CONH-) on the molecular chain can bind to the active sites of polyphenol oxidase (PPO) in fruits and vegetables, directly inhibiting enzymatic browning (for example, the browning inhibition rate for apple slices reached 60%).
  Experimental data : In the preservation of pears, the malondialdehyde (MDA) content in the K30 coating group was 35% lower than the control group, while the K17 coating group was only 12% lower.

2. Inhibit microorganisms: K30's "membrane barrier + slow-release antibacterial"

• Physical barrier :
  The K30 film layer can prevent the attachment and germination of mold spores (such as gray mold), reducing the incidence of strawberry gray mold by more than 50%.
• Slow-release antibacterial effect :
  If K30 is loaded with antibacterial ingredients (such as tea polyphenols), its three-dimensional network can slowly release the antibacterial substances and prolong the antibacterial effect (such as the inhibition rate of Staphylococcus aureus is maintained for more than 7 days).
• Limitations of K17 :
  The film layer is thin and has no sustained-release ability. It can only inhibit microorganisms in the short term (for example, the inhibition rate of yeast on the surface of cherries only lasts for 24 hours ), and the long-term effect is limited.

3. Maintaining cell structure: K30's advantage in membrane-cell interaction

• Cell membrane protection :
  K30's polymer chains can form hydrogen bonds with phospholipid molecules on the surface of fruit and vegetable cell membranes, enhancing membrane stability and reducing damage to cell membranes during cold storage (e.g., the permeability of tomato cell membranes is reduced by 20%).
• Microenvironment regulation :
  K30's water-retention properties can maintain cell turgor pressure, preventing cell shrinkage in fruits and vegetables due to water loss (for example, the cracking rate of lychee peel is reduced by 40%).

III. Application Scenarios and Experimental Data: The Universality of K30 and the Specificity of K17

1. Universal Scenarios: K30 is superior to K17 in all aspects

• Fresh-cut Fruit and Vegetable Preservation :
  K30 coating significantly extended the shelf life of fresh-cut apples and pears (up to 14 days at 4°C), while the K17 coating only extended the shelf life by 7 days.
  Mechanism : The K30 coating effectively blocks oxygen and inhibits PPO activity by 65%, while the thinner K17 coating only inhibits PPO activity by 30%.
• Berries (e.g., strawberries and blueberries) :
  K30 coating reduced water evaporation from the berries (weight loss reduced by 40%) while also creating a physical barrier to mold intrusion (gray mold incidence reduced by 50%). However, the weight loss and disease incidence of the K17-treated group were not significantly different from those of the control group.

2. Specific Scenarios: Limited Applicability of K17

• Rapid penetration requirements :
  When PVP needs to quickly penetrate into fruits and vegetables (such as a carrier of mango ripening inhibitors), K17 can complete penetration within 2 hours due to its small molecular weight and fast diffusion rate (the diffusion coefficient is twice that of K30), while K30 requires more than 6 hours.
• Low viscosity system :
  In spray-dried or emulsion-type preservatives, the low viscosity of K17 (viscosity is only 1/3 of K30 at the same concentration) can prevent the system from being too viscous and facilitate uniform coating (such as spray preservation of citrus fruits).

4. Safety and Economy: K30's Cost-Effectiveness

1. Food safety compliance

• PVPK30 :
  Complies with EU food additive standards (E1201), with monomer residues ≤ 10 ppm and heavy metal content ≤ 20 ppm, suitable for direct food contact. Its biocompatibility has been certified by the FDA and can be used in infant food packaging.
• PVPK17 :
  Although it also meets food grade standards, due to its small molecular weight, it may release trace monomers (such as N-vinyl pyrrolidone) in an acidic environment, and the long-term intake risk is slightly higher than K30.

2. Economic comparison

• Dosage Difference :
  Due to its strong film-forming properties, K30 requires only 0.1% to 0.5% concentration for preservation, while K17 requires 0.5% to 1.0% to achieve similar results. Based on a ton of fruit and vegetables, the raw material cost of K30 is 20% to 30% lower than that of K17.
• Overall cost :
  K30's long-term preservation effect can reduce energy consumption in cold chain transportation (such as reducing the refrigeration load of refrigerated trucks by 15%), further reducing overall costs.

5. Conclusion: K30 is the "optimal solution" for preserving fruits and vegetables, while K17 is only a supplement

1. Prefer K30 for your scene

• Fresh-cut fruits and vegetables, berries, and fruits and vegetables with high respiration rates (such as lychees and peaches) : require long-lasting physical barriers and antioxidant protection;
• High temperature and high humidity environment : a stable film layer that is resistant to high temperature and hydrolysis is required;
• Complex formula system : such as sustained-release preservatives loaded with essential oils, tea polyphenols and other functional ingredients.

2. Consider the K17 scenario

• Rapid penetration requirements : such as carriers of mango ripening inhibitors;
• Low viscosity system : such as spray drying or emulsion preservatives;
• Short-term preservation (≤3 days) : such as temporary protection of freshly cut fruits in supermarkets.

3. Experimental data support

In a peach preservation experiment, the weight loss rate of the 0.1% PVPK30 coating group was 18% lower than that of the K17 group, the firmness retention rate was 22% higher, and the total soluble solids (TSS) content was significantly higher after 25 days of storage. This fully demonstrates the core role of K30 in delaying the deterioration of fruit and vegetable quality.

In summary, PVPK30, with its film-forming properties, moisture retention, and stability brought by its high molecular weight, is the preferred material for fruit and vegetable preservation , while K17 should only be used as a supplementary measure under specific circumstances. In practical applications, the choice can be flexibly based on the characteristics of the fruit and vegetable (such as skin thickness and respiration rate) and the preservation goal (such as short-term protection or long-term storage).