Our recommendation to fix white cabinets that have yellowed is to do a thorough sanding and precleaning and recoat with the following products:
- Prep clean and scuff sand for adhesion.
 - Apply Stain Blocker from GF's line. Many contractors use an oil-based or shellac-based primer.
 - Finish sand between coats.
 - Apply another coat of durable, cabinet-grade wood coatings paint, not wall paint. From General Finishes line, choose Brushable White Enamel or professional Enduro White Poly.
 - Do not apply a topcoat as that can cause yellowing.
 
This is an industry-wide issue - read this FAQ for more details about how to prevent light colored paint from yellowing and watch How To Achieve a Bright White Finish With the GF Paint System.
      
  Enduro Water-Based Conversion Varnish
  Enduro Water Based Stain Blocker Primer
  Enduro Water-Based Tintable 2K White Poly
  Enduro Water-Based Pro Series White Polyurethane
  Hard Wax Oil & Hardener
  Gel Stains
  Pro Image Flooring Topcoat
  Jen Poly Brushes
  Stir Stix
  Ultraflex Softback Sanding Sponge