by Ben Jankowski (Brewing Techniques - Vol. 6, No.3)
Sheltered from the diseases common to Northern Hemisphere hopyards, the fields of New Zealand support a carefully nurtured family of hops raised on a “clean, green” ethos that few other growers can offer.
New Zealand is often perceived as a nation in harmony with its enviroment. Non-nuclear and extremely conscious of its ecosystem, the country supplies produce to consumers in the northern hemisphere during the winter and hops for breweries large and small throughout the year.
Though it may not be widely known, New Zealand has been at the forefront of hop development for more than 30 years. In 1972, New Zealand released the world’s first commercial triploid hops (bred New Zealand-style to contain alpha-acid levels of 10%). Progress continued in the 1980s with the development of triploid cultivars derived from noble aroma hops. Though New Zealand represents only about 0.5% of the world’s total hop production, the diversity of its hop selection matches that of much larger producers; New Zealand growers offer no fewer than eight varieties, including two certified organically grown varieties (see the box, “An Island Apart from Pests and Pollution”).
New Zealand hops are also free of aphids and common diseases such as downy and powdery mildew, and they are impervious to Verticillium wilt. These factors, coupled with a growing season at the opposite end of the calendar (September–March) from the northern hemisphere, provide a hedge against occasional Northern Hemisphere crop failures and make New Zealand hops an attractive alternative for brewers in 11 countries to date.
Hops Colonize the South Pacific
No hops are indigenous to the South Pacific; New Zealand hops were first brought to both the north and south islands by British settlers in the mid-19th century. These immigrant hops included Green Bine (Fuggle), Bumford (an old English Golding), Cluster (Grape, English Colgate), and Golding (1). Most of the plantings were originally used for home brewing by the settlers. Later, German immigrants to the south island brought their hops from the fatherland to the new country’s farms. Evidence suggests that Spalt was one of these varieties (2), but the lineages of other hops are not known.
As commercial brewing developed in New Zealand, farmers began to plant hops as a cash crop. Most of this activity centered in the Nelson region of the south island, where the valleys are ringed by hills and mountains that offer protection from harsh weather conditions (see map). The region boasts a mean annual temperature of 52 °F (11 °C), an annual rainfall of 55 inches (139.7 cm), and more than 2,400 hours of sunlight a year — ideal conditions for hop production. Initially, hop farmers supplied local breweries only, but by the beginning of the 20th century New Zealand was exporting hops to Ireland, England, and Germany. The stouts of Guinness and the India pale ales of Allsopp and Inde Coope breweries were made with “kiwi” hops (3,4).
The Evolution of New Zealand’s Hop Breeding Program
American influences: By the close of the 19th century, it had become evident to hop farmers that yields of the original European varieties were unsatisfactory. Some speculated that these hops had adapted poorly to the growing conditions of the southern hemisphere. To remedy the problem, California Late Clusters from the Russian River Valley were introduced in 1923 (5). Interestingly, California’s Russian River area lies on the same latitude north of the equator as Nelson does to the south. So popular were these new immigrant hops that by the 1930s “Cali” hops, as they came to be known, made up nearly all the hop acreage in the Nelson region. To this day, the majority of New Zealand’s hops have an American heritage.
Threats of disease provide a turning point: Unfortunately, Cali Clusters were susceptible to black root rot (Phytophthora citricola). By the close of World War II, this disease was serious enough to threaten the survival of the New Zealand hop industry. In some areas, up to one-quarter of the plants had to be replanted annually (7). At the behest of national breweries, hop growers and the New Zealand government, the state-run Department of Scientific and Industrial Research (DSIR) stepped in to remedy the problem.
The solution to the black root rot problem is credited to plant geneticist Dr. Rudy Roborgh. He noted that many of the original European hops brought by the settlers were resistant to the black root rot and reasoned that they could be cross-bred with the Cali Clusters. Tests were performed in which male hop plants from the hedgerows were cross-bred with the female Clusters. These experiments yielded hop plants that were immune to black root rot and that had inherited the best traits from both parents. In 1960, First Choice and Smoothcone cultivars were commercially released. Calicross, a cultivar bred from a female Cluster and a male Fuggle-derived seedling, was released in 1961. All of these hops had an alpha-acid content ranging from 8 to 10%. Gradually, Cluster fields were replanted with these more resilient offspring.
Seedless, high-alpha varieties: The next experiments performed at the DSIR research station were inspired by the demands of New Zealand brewers. By the early 1960s, highly hopped lager beers were winning favor over the less hoppy bitters, milds, and pale ales formerly produced. This trend toward hoppy lagers stimulated a worldwide demand for more alpha-acids per hop. At the same time, brewers recognized the economy of buying hops that contained fewer seeds. Hop seeds contributed nothing to the flavor profile, yet brewers were paying for the extra bulk; in some cases, hop seeds comprised up to 10% or more of each cone’s weight. Clean, seedless hops with high alpha-acid levels were therefore the preferred choice among brewers. More alpha-acid per unit of hops meant smaller quantities were required, which translated to reduced purchasing and storage costs. Flavor profiles of beers remained the same, in part thanks to the large-scale breweries’ use of blending processes to keep the taste constant.
Dr. Roborgh and DSIR set breeding objectives to coincide with brewers’ demands. Among these objectives were yields in excess of one ton of dried hops per acre, reduced seed content, and an alpha-acid content of 10% or more (8). To create seedless varieties, they genetically engineered existing hop strains to alter the plants’ chromosome patterns in ways that would result in sterile, non-seed-producing plants.
The first triploids. The early cross-bred hops were diploid in nature: they possessed 20 chromosomes, 10 from each parent. Roborgh used colchicine treatment* to chemically alter the diploids (using Smoothcone and First Choice), creating a hop with 40 chromosomes, known as a tetraploid. These female tetraploid hops were then open pollinated with diploid males. Seeds from this union were extracted from the female plants in 1962 and raised during the growing season of 1965/1966. The resulting plants were triploid in nature — as confirmed by microscopic examination of the root tip cells in 1970 (8).
In triploids, two-thirds of the genetic contribution of the seedling comes from the mother. Thus, the probability of finding a higher yielding type with chatacteristics very similar to that of the mother plant is increased (9). In addition, researchers knew that the seed content would be minimal (less than 2% by weight) in triploid plants; the odd number of chromosomes in triploids renders plants virtually sterile and seedless without affecting their yield or flavor. In 1972, these new high-alpha (12–13%), near-seedless cultivars — the world’s first commercial triploids — were released for growing. They included Green Bullet and Harley’s Fulbright, derived from Smoothcone, and Sticklebract, derived from First Choice.
*Colchicine is a poisonous alkaloid extracted from the autumn crocus plant. It suppresses cell division by inhibiting mitosis, often after some or all chromosomes have been replicated. Hop researchers induce this polyploidy by stripping a 1-Ft hop bine of foliage and “painting” it with a mixture of colchicine and water in a 50% solution.
Following their commercial release, the high-alpha triploids were widely embraced by New Zealand breweries. An additional high-alpha variety named Super Alpha joined the ranks of the super bittering hops in 1976.
Despite the hops’ popularity with brewers, it became obvious in the following years that the new varieties endangered the financial well-being of the hop farmers. High-alpha hops meant less acreage and reduced earnings. Many farmers could not subsist by growing hops, and 23 hop farms were converted to other uses in the early to mid-1980s. After the advent of triploid hops, New Zealand’s total hop acreage declined by half.
High-alpha hops with aroma: Beginning in 1975, researchers at the DSIR research station recognized that though high-alpha hops were the cornerstone of the New Zealand hop industry, triploid aroma varieties needed to be explored.
Accordingly, Dr. A.A. Frost, and later Dr. Ron Beatson, initiated a program to combine “noble” aroma hops with tetraploids in an effort to produce higher alpha triploids with the aroma of the mother plant.* It was assumed that the aroma hops would augment the high-alpha hops grown by farmers. In 1988, NZ Hallertau Aroma was released. This hop has an alpha range from 7 to 13%, with an average of about 8%. This telease was followed by NZ Pacific Hallertau in 1994, which is a Hallertauer Mittelfrüh-derived triploid that averages between 5% and 6% alpha acid. Saaz-derived and Tettnanger-derived triploids have also been released, though so far they lack major commercial customers.
*Willamette hops, released in the United States in the mid-1970s, were the first commercial triploid aroma hops.
“Kiwi” Hops Invade the Rest of the World
In response to decreased hop usage within New Zealand (thanks to the success of the high-alpha breeding program), the Nelson-based New Zealand Hop Marketing Board began resoliciting the export trade in the early 1980s. Through their efforts, New Zealand’s hop economy has stabilized, and 85% of the country’s hops are now being exported around the world, with primary markets in Asia, Europe, and the United States.
New Zealand’s place as a valued hop exporter appears to be secure thanks to both its natural geography (not least of which its Southern Hemisphere harvest schedule) and its stated commitment to a fresh, consistent product. Quality is safeguarded by the Hop Research Centre in cooperation with the Marketing Board, which is subject to ongoing internal and external checks. As a certified export organization, the Board is required to monitor hops from farm to brewery and to be able to trace all hop shipments to the farm on which the hops were grown. An onsite lab monitors alpha-acid values. To ensure quality control within its own organization (especially for the certified organically grown varieties), the Marketing Board has been quality control-accredited by a government overseeing agency.
At harvest time, all hops undergo an annual routine: The first hops harvested are NZ Hallertau Aroma, followed by NZ Pacific Hallertau, Pacific Gem, Super Alpha, Southern Cross, Sticklebract, and Green Bullet. Hops are indirectly kilned with hot air at the farm, baled, and sent to the Marketing Board’s cooperatively owned processing center in Richmond. Because of the varied alpha-acid content of identical hops grown on different farms, all hops of the same variety are blended to ensure a uniform alpha-acid level consistent with customers’ specifications. Leaf hops are then extruded through a Type 90 pelletizer designed by Amandus Kahl Nachf of Germany (almost all New Zealand hops are pelletized, though the Marketing Board will ship whole hops if an order is large enough). As with hops grown elsewhere in the world, much of the New Zealand crop is contracted to various breweries in either short- or long-term futures.
This unusually high level of control and uniformity is possible among New Zealand hop producers because of the small size of the industry. The country’s hop production has stabilized to include 26 growers on 22 farms. Most of the farms are family-owned, and a few are cooperatives.
New Varieties, Secure Supplies, Organically Grown
The future of New Zealand hop farming remains secure and even promises to expand in the near future. Continued research with triploid aroma hops has already produced Saaz-derived and Tettnanger-derived hops, with other noble aroma types to follow. North American brewers continue to regard New Zealand hops as a hedge against possible crop failures in the Northern Hemisphere, and the near-organic growing environment and high-alpha capabilities are additional attractions. Craft brewers are also beginning to enjoy the benefits of New Zealand hop varieties as more brewers become interested in brewing true organic beer with certified organically grown hops (see box, “New Zealand’s Niche in America”). The future of New Zealand hops is green, indeed.
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