External damage including scale loss and bruising as well as muscle fillet damage such as gaping, blood spotting, reduced translucency, reduced yield and reduced shelf life all lead to product downgrades, poor market acceptability and a reduction in value.  Rested harvesting with AQUI-S^® dramatically reduces the severity of the damage and results in consistent product quality and premium prices.

Fish at the point of sale are predominantly presented in the form of fillets or steaks. The customer therefore can only rely on the appearance of the “fillet” as the key factor to be considered in making a buying decision.  The following section outlines how stress at harvest impacts on product quality.

Blood Spotting

Blood spotting occurs in fish that have been highly active and stressed from the harvest procedure and results from blood vessels being weakened and rupturing during excessive activity, leading to pooling of the blood in the tissue. Stress increases blood viscosity, and this combined with poor bleed-out processes results in blood remaining in the muscles small vessels and capillaries. During processing this will leak into the white muscle appearing as distinct areas of discolouration, impacting on the fillets appearance and customer acceptance. This is of particular concern for value-added products and often results in a downgrading of the product.

Gaping

Gaping generally happens when the myotome (muscle block) - myocomata (connective tissue) junction is no longer strong enough to hold the tissue together, thus resulting in gaps between muscle blocks. Fillet gaping is known to be significantly reduced when the fish are harvested using rested harvest techniques. Gaping is a major issue in value-added products such as smoked or raw sashimi fish, as consumer acceptance and value are lowered.

Drip Loss

An important quality of flesh post-harvest is the ability to retain water for an extended period of time. There is little understanding on the mechanism behind fluid loss from the muscle, but it is well documented that stress at harvest has a negative impact. Water holding capacity is understandably economically important, as fluid losses cause weight discrepancies and the presence of exudates are unsightly to the buyer.

Shelf Life

Shelf life or spoilage is another key quality factor that will determine the value of the final product. Shelf life can be attributed to the action of autolysis (muscle breakdown) and consequent microbial growth in the muscle. Unstressed or rested harvested fish retain energy in the muscle which means the autolytic activity and microbial spoilage is delayed, thus extending the shelf life and maximising the period of highest product quality and edibility.