Production and Quality of White Asparagus Grown under Opaque Rowcovers

Abstract

<jats:p>Black and white plastic rowcovers were established over field-grown `Jersey Giant' asparagus <jats:italic>(Asparagus officinalis</jats:italic> L.). Spears were cut for 7 weeks. Season soil temperatures were lowest under white plastic and highest without plastic covering. Night air temperature under plastic covers was ≈ 1.4C higher than without plastic covering (control), but day air temperature was typically 10C higher under black plastic, with temperatures under white plastic intermediate. Marketable yield (t·ha<jats:sup>-1</jats:sup>) was improved with the use of plastics as was total yield <jats:italic>(P =</jats:italic> 0.05), but spear number/ha was similar in all treatments. There was no consistent treatment effect on spear diameter. Average spear weight was higher when under plastic, whereas spear length was reduced compared with uncovered spears. There were no differences among treatments in spear fiber content, but spears grown under plastic covers were higher in soluble solids content, titratable acidity, and nitrate and lower in protein, ascorbic acid, and total phenolics than uncovered spears. Quantitative differences in these constituents were also a function of whether they were from the upper, middle, or lower spear segment. Very little chlorophyll and carotenoids were produced in the absence of light, but there was a chroma (color intensity) difference between spears grown under the two plastics.</jats:p>

Textural Quality of Green and White Asparagus

“…Although asparagus spears can be produced as either green or white (etiolated or blanched), in the US, production of green asparagus has dominated over white. White asparagus is envisioned as a means of diversification since it is a product that supports a price structure two to three times that of green asparagus (Makus and Gonzalez 1991). While green asparagus is known to have higher nutritional value (Ketsa and Uthaiburt 1987), white asparagus has been cited as having a more distinctive flavor and better spear quality (Vilmorin-Andrieux 1981).…”

FACTORS AFFECTING ASPARAGUS SENSORY EVALUATION1

“…Jersey Giant asparagus plants were grown uncovered, to produce green spears, or covered, with opaque black row covers (Brovelli 1991), to produce white spears. Row covers allow asparagus to develop in darkness, thus chlorophyll is not synthesized and developing spears are white (Makus and Gonzales 1991).…”

“…Exact sensory differences, other than color, between the two types of asparagus have not been fully defined in the literature. Researchers have compared the flavor attributes of green and white asparagus (Makus and Gonzales 1991), and how these flavor attributes were affected by length of storage (King et al 1987), but these studies were limited and not conclusive.…”

“…Row covers allow asparagus to develop in darkness, thus chlorophyll is not synthesized and developing spears are white (Makus and Gonzales 1991).…”

Forcing White Asparagus in Various Substrates under Cool and Warm Regimes

“…Fresh white asparagus is rare in major U.S. markets, and there is little demand for white asparagus in the eastern United States. White asparagus usually is two to three times more expensive than green asparagus (Makus and Gonzales, 1991 ).…”