Many liquids have been called “liquid gold” (that is, something very valuable and desired). Honey has been called “liquid gold” since at least On the Nature of Things by Lucretius (99 B.C.-55 B.C.). Honey began to be called “liquid gold” in American newspapers since at least 1925.
 
Maple syrup has been called “liquid gold” since at least 1910 and 1960.
     
 
Google Books
Miscellany Poems:
The First Part
By John Dryden
London: Printed for Jacob Tonson
1702
Pg. 342:
THE FOURTH ECLOGUE.
POLLIO.
Pg. 344:
The knotted Oaks shall show’rs of Honey weep,
And through the matted Grass the liquid Gold shall creep.
(From On the Nature of Things by Lucretius, 99 B.C.-55 B.C.—ed.)
 
3 April 1925, The Evening Tribune (San Diego, CA), pg. 17, col. 3:
HONEY AND APPLES
TOOTHSOME DISH
Honey and apples—both the food of the gods, and rightly, too, for what is more tempting than the liquid gold of honey or the rich blush of a ripened apple.
 
9 October 1930, Seattle (WA) Daily Times, pg. 18, col. 7 ad:
Yakima Valley Pure Honey
Cover hotcakes with this liquid gold for real flavor.
 
OCLC WorldCat record
Honey, nature’s liquid gold
Author: Peter Scott; George Lowe; Roger Climpson; Alan Lake; Australian Honey Board.; All authors
Publisher: Australia : John Bushelle Productions [production company] : Australian Honey Board [sponsor], 1970.
Edition/Format:   Film : Film Visual material : English
Summary:
Shows the life of a beehive and the production of honey, then the modern collection, processing and marketing of honey in Australia.
 
OCLC WorldCat record
Robbing the bees : a biography of honey, the sweet liquid gold that seduced the world
Author: Holley Bishop
Publisher: New York : Free Press, ©2005.
Edition/Format:   Book : English
Summary:
“Honey has been waiting almost ten million years for a good biography. Bees have been making this prized food-for centuries the world’s only sweetener-for millennia, but we humans started recording our fascination with it only in the past few thousand years. Part history, part love letter, Robbing the Bees is a celebration of bees and their magical produce, revealing the varied roles of bees and honey in nature, world civilization, business, and gastronomy.” “To help navigate the worlds and cultures of honey, Bishop-beekeeper, writer, and honey aficionado-apprentices herself to Donald Smiley, a professional beekeeper who harvests tupelo honey in the Florida panhandle. She intersperses the lively lore and science of honey with lyrical reflections on her own and Smiley’s beekeeping experiences. Its passionate research, rich detail, and fascinating anecdote and illustrations make Holley Bishop’s Robbing the Bees a sumptuous look at the oldest, most delectable food in the world. Book jacket.”—BOOK JACKET
     
OCLC WorldCat record 
The honey trail : in pursuit of liquid gold and vanishing bees
Author: Grace Pundyk
Publisher: New York : St. Martin’s Press, 2010.
Edition/Format:   Book : English : 1st edView all editions and formats
Summary:
The Honey Trail is a global travel narrative that looks at different aspects of how honey and bees are being affected by globalization, terrorism, deforestation, the global food trade, and climate change.—from publisher descritpion
 
LewRockwell.com
March 28, 2013
Raw Honey: Liquid Gold in Your Pantry
by Daisy Luther
When selecting foods for your stockpile, the most budget-friendly, space-conscious way to do it is by selecting items that multitask. This criteria places honey high on your “to-buy list”. Tess Pennington of Ready Nutrition lists honey as one of the top SHTF sweeteners to store.
 
Honey is indeed nature’s sweetener, but don’t write it off as just a condiment. The sticky sweet substance is far more than something to stir into your tea or spread on your toast.